Aqua-Fpe - All Fact Sheets Combined -AIT

8/12/2019 Aqua-Fpe - All Fact Sheets Combined -AIT

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COLLEGE OF FISHERIES

MINDANAO STATE UNIVERSITY MAIN CAMPUS

MARAWI CITY

INTRODUCTION TO AQUACULTURE

Compiled by

Prof. Madid A. Sheik, M.Sc.

Aquaculture maybe defined as the rearing and breeding of aquatic organisms in confined condition which is more or

less controllable by man. In the Philippines the main groups of organisms used for aquaculture are !" #infish $ %&.

Milkfish, tilapia, carp, catfish' (" Crustaceans $ %&. Prawn, Crab, )iant #reshwater Shrimp' *" Mollusks $ %&. +yster,

Mussel' and " Seaweed $ %&. %ucheuma.

-ased on the type of water used aquaculture may be classified as follows

a" #reshwater aquaculture $ It uses freshwater supplied by spring, stream or rier, rain, deep well, or lake.

/he species cultured are tilapia, carp, catfish, mudfish, giant freshwater shrimp and otherfreshwater species using ponds, cages or pens.

b" -rackishwater 0or coastal" aquaculture $ It uses the combination of freshwater and seawater and usually

located in the mangroe areas where rier flows and mi&es with the tidal water. Milkfish, black

tiger prawn, crab, tilapia and other species are widely cultured in brackishwater ponds.

c" Mariculture 0or sea farming" 1 It is usually located in protected coastal areas and uses only sea water.

It cultures some fishes like lapulapu, samaral, kitang and other species in fish cages and fish pens.

+ysters and mussels are farmed in protected areas while seaweed like %ucheuma are cultured

e&tensiely in shallow sandy areas. Pearl farming is also a type of mariculture.

Classification of aquaculture production methods

!. %&tensie method $ /he rearing of organisms with minimal stocking density using natural feed andminimal water e&change.

(. Semi1intensie method $ /he rearing of organisms at moderate stocking density, giing supplemental

feed with fertili2er and with partial water e&change.

*. Intensie method $ /he rearing of organisms with high stocking density, using artificial feed and high

water e&change rate and ma&imum aeration system.

/he types of fish feeds commonly used are a" 3atural food 0like plankton"' b" Supplemental food 0like rice bran,

home1mi&ed feeds" and c" Artificial feed 0like commercially processed fish feeds such as fish pellets"

4efinitions of some commonly used terms in aquaculture

Aeration $ /he process by which air and other gases in a medium are renewed or e&changed.

-enthos $ +rganisms that lie on or in the bottom of the ocean or bodies of fresh water from the water5s

edge down to the greatest depth' or organisms that attach or rest on the bottom or liing in

the bottom sediments.

4etritus $ +rganic debris from decomposing plants and animals.

%ndemic $ Species of fish that are peculiar to an area.%&otic fish $ #ish species that are introduced from other areas and not indigenous to a gien region

6ybrid fish $ /he offspring of fishes of two different species.

Carniorous fish $ #ish that feed on meat or another fish.

6erbiorous fish $ #ish feeding on plants.

+mniorous fish $ #ish that feed on both plant and animal.

-reeder $ Matured fish that is kept for use as parent stock in the production of fry and fingerling.

)raid $ Pregnant or ripe fish or ready to spawn.

Spawner $ )raid female fish that is ready to lay eggs.Monose& culture $ 7aising a single se& organism in a pond to preent breeding.

Monoculture $ /he raising of only one species of organism in the same pond or compartment.

Polyculture $ /he raising of two or more species of fish in the same pond which are usually compatible

or do not harm each other nor compete for food and space.Plankton $ /iny plants and animals which drift with the current and most of which sere as food of fish.

Phytoplankton consists of plant planktons while 2ooplankton consists of animal planktons.8ab1lab $ 3ame gien to a comple& of aquatic plants which includes algae, bacteria, proto2oans, and

diatoms. /his forms dense mat on the bottom of ponds and seres as food of young milkfish.

8umut $ )reen filamentous algae that seres as food of milkfish.

Salinity $ /he measure of the amount of salt in the water.

/urbidity $ A cloudy condition of water, usually caused by impurities but most often the result of wae

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action stirring up bottom sediments.

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Brief descri!i"# "f s"$e $%&"r %'(%c()!(re s*s!e$s i# !+e P+i)ii#es,

A .Milkfish culture

Milkfish or -angus which can grow in either salt water or freshwater is cultured mainly in brackishwater pondsand in fish pens in lakes like 8aguna 8ake, /aal 8ake and 8ake -uluan 0in Mindanao".

/he brackishwater pond is tide dependent. /he milkfish farm consists mainly of nursery, transition and rearingponds.

/he usual production method is e&tensie and semi1intensie.

/he stock fry comes from fry collectors.

9sually it takes *1 months of culture in rearing pond to grow them into market si2e.

Most milkfish ponds apply monoculture although some also try polyculture with prawn.

/he harested fish is sold mainly in local market.

-. Prawn culture

Sugpo or the -lack /iger Prawn is cultured mostly in brackishwater ponds under semi1intensie system. Some

howeer, apply the intensie method using pumps for water supply and paddle wheel for aeration and apply

commercial feeds. /he prawn farm consists mainly of grow1out ponds and haresting canals.

/he stock prawn larae or postlarae are produced by commercial hatcheries.

It takes months to grow the postlarae into market si2e prawn. /he harested prawns are sold mainly in the e&port market.

Prawn farming is capital intensie but also highly profitable.

C. /ilapia culture

/he species used is 3ile tilapia. 3ew hybrids are recently introduced for bigger and faster production.

/he fish is cultured mostly in floating fish cages and in freshwater fishponds.

/he common method applied is semi1intensie or intensie using commercial feeds.

/he stock fry or fingerlings are supplied mostly by hatcheries.

/he harested tilapia is sold mainly in the local market although there is demand in the foreign market.

4. +yster culture

/he oyster farm is located in shallow protected and flat coastal areas with clean water and free from heay waes.

It uses as oyster attachments rocks, corals, bamboo stakes and other materials

/he oyster feed on plankton. /he product harested is sold in the local market.

%. Mussel farming

/he mussel farm is located in protected and flat coastal areas with clean water and free from heay waes.

It uses bamboo or wooden stakes as attachment.

/he mussel feed on plankton. /he harested product is sold in the local market.

#. Seaweed farming

/he seaweed farm is located in protected and flat sandy coastal areas with clean water and free from heay waesand strong current.

/he starter stocks are tied in ropes in long line or floating rafts.

/he harested seaweed is sold to processing plants that in turn sold their products in the e&port market.

/he Philippines is the world5s leading producer of %ucheuma seaweed, And the biggest contiguous area of

seaweed farms can be found in /awi1tawi, particularly in the shallow areas of Sitangkay.

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INTRODUCTION TO AQUACULTURE ENGINEERING

A good background knowledge on the principles and practices of aquaculture planning and

implementation is ery essential for a successful aquafarm pro:ect. /he time and energy which would be

spent in the planning and designing would mean money saed and problems minimi2ed.

Many newly deeloped adances in the technology of aquaculture hae made significant

improements in aquaculture practices which hae resulted in the deelopment of new techniques,

particularly in the intensie forms of aquaculture and the aquaculture systems in natural waters. -esides

the traditional forms of aquaculture using ponds, the use of tanks, cages and enclosures or pens in natural

inland bodies of water and shallow marine coes are recent aquaculture systems that hae e&panded

aquaculture production. /hese recently improed technologies are clear indications of the blending of

biology skills, engineering know1how and practical skills which make the arious enironments faorable

for fishfarming actiities.

/he potentials for the further deelopment of aquaculture industry in the country are high. /here

are still large areas of mangroe swamps and tidal mudflats that can be suitable sites for deelopment into

fishponds, besides the large areas of lakes and swamplands that could be good sites of freshwater

fishponds, pens or cages.

8ikewise, the present production rate of the e&isting aquafarms can be increased easily with better

engineering and the use of improed technology of management. 6oweer, some e&isting engineering

problems of the fishponds in the coastal areas need to be soled to really improe production. /hese

ma:or engineering problems can be classified into three categories, as follows

!. Problems due to climate and hydrology

/he type of rainfall, occurrences of typhoons, and preailing tidal characteristics in the

fishpond location can influence the nature of construction of fishponds in such area. ;here rains

are strong and seere and where typhoons or tidal waes are frequent, the fishpond structures need

to be bigger and more firm. Also, areas with high tidal ranges will require bigger dikes and sturdy

water control structures.

(. %nironmental influences

/he factors of the enironment that influence the engineering of fishponds include the

following nature of soil, egetation, eleation of site, topographic characteristics, aailability of

freshwater supply and occurrences of pollution.

*. %ngineering specific problems

/hese are the site specific problems that are encountered during actual construction or after the

construction of the fishpond. /hese may include the following a" Shifting of management system

from one species to another or from monoculture to polyculture, b" Imbalanced cut and fill, c"

4esign of water control structure, and d" 8eakages and seepages.

SELECTION OF FISHPOND SITE

In enturing into any aquaculture enterprise a lot of time, effort and financial inestments are

needed. -ecause of this a proper ealuation and study is necessary in selecting the site where such

aquaculture pro:ect is proposed.

/he criteria or factors to be considered in the selection of fishpond site are the following

!. ;ater Supply and


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(. /ype of Soil $ /he type and nature of the soil is an important consideration in selection for

both brackishwater and freshwater fishpond sites. Areas with clay soil contribute to natural

fertility and yield good egetation growth. Clay soil also seres as good building material for

linings and dikes of ponds. Sandy, rocky and graelly soils are not as desirable. /hey are

more permeable 0the ponds will leak" and can not be as readily used for construction. /hesesoils are also generally less fertile and yield poor egetation growth.

*. =egetation $ =egetation is another important consideration in assessing sites for aquaculture.

6eaily forested areas with large trees would be difficult and e&pensie to deelop. /he type

and igor of the egetation will gie good clues as to the soil condition and frequency of floods.

It may also indicate fertility for proper growth of potential food organisms on the site.

. 3atural #ertility $ /he natural fertility of the site is dependent on nutrients and food organisms

occurring in the water as well as the soil nutrients. /he nature of the e&isting upland or

wetland and aquatic egetation, fauna and flora may be used as an indirect method to

determine this quality.

>. /opography and 4rainage 1 /he topography and drainage of the site are important factors in

the cost of site deelopment. )enerally, flat area with a slope of about * percent is consideredideal for deelopment. 6ighly sloping areas will require large e&caations and, therefore,

e&pensie to deelop yet this will allow only a ery limited space for the ponds to be

constructed. 8ikewise, undulating areas or those with rough terrain also require grading and

filling, 3arrow alleys also belong to this category. #urthermore, wide flat areas that cannot bedrained would be difficult to manage as the stock cannot be easily collected.

?. 3atural Protection@%&posure $ A ery common ha2ard now a1days is the occurrence of floods

in fishpond areas especially if the watershed area is deoid of the necessary forest coer. /his

has to be properly e&amined and necessary contingency measures should be incorporated in the

design of the structures of the farm.

;atershed is the ridge of highland draining towards the lower lands. /he bigger is the area of thewatershed the greater the olume of the run1off. /he factors that affect run1off are a" 4uration of

rainfall, b" Intensity and distribution of rainfall in the area, c" Si2e and shape of the watershed, d" ;ater

retention capacity of the watershed, and e" /opography and geology of the watershed.

. %conomic and other Considerations $ /he other factors that hae to be considered are

a" Accessibility and transport facilities to site'b" Aailability of seed supply or resource to be cultured'

c" Presence of market outlets, and

d" Indigenous skilled manpower

e" Pattern of land and water usef" Peace and order situation

Tide %s S"(rce "f W%!er f"r Br%c-is+.%!er Fis+"#ds

/he brackishwater fishponds are primarily dependent on tide. )ood knowledge of tidal

characteristics in the site is ery important in determining its suitability for brackishwater fishponds. /he

height of the tide and its range determine the sufficiency of water, height of dikes, eleation of pond

bottom and water gates, si2e of gate opening, construction cost and others. /he depth of water in pond to

be maintained is determined by the height of incoming tide and height or eleation of pond bottom based

on 2ero tidal datum. ;heneer possible, the aailable tidal range must be able to fill the ponds by graity

to the specified depths. In relation to tide ground eleation, this depth should allow the most economical

construction 0least cut and fill" of pond which would hae an ideal pond eleation. /he eleation of pond

bottom is considered ideal if it enables draining of the pond almost any day of the year and floods it with

seawater to the desired depth within fie days or less during the critical spring tides. /he critical springtides usually occur in the Philippines during the months of #ebruary, March and April.

/he /idal Phenomenon $ /he periodic rising and falling of the water surface of the oceans, seas,

bays, mouths of riers, etc. as a result of the graitational attraction of the moon and sun on the earth isknown as tide or astronomical tide.

/he * types of astronomical tides in the ocean a re

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!. Semi1diurnal tide $ It has a cycle of about one1half a tidal day.

(. 4iurnal tide $ It has only one high water and one low water per tidal day.

*. Mi&ed tides $ Characteri2ed by haing a large inequality of either the high or low water

heights, with two high waters and two low waters usually occurring each tidal day.A mi&ed tide is either predominantly semi1diurnal or predominantly diurnal.

/he sources of tidal information $

!. /ide /able $ Published by the goernment through the -ureau of Coast and )eodetic Surey, this

contains the compilation of tables of predicted time and height of high and low waters each day

of the year for the tide stations of the country. /his is based on many years of obserations using

different tide instruments and statistical ealuation. /he Philippines' has ? tide stations, namely

a" San #ernando, 8a 9nion, b" Manila, c" 8egaspi City, d" Cebu City, e" 4aao City, and f" Bolo,

Sulu

(. Actual tide gauging 0measurement" and@or prediction for the specific area using the tidal

differences and constants of the tide table.

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SITE SURVEYING

E#/i#eeri#/ S(r0e* E'(i$e#!

/he principal equipment for field surey work are composed of the engineer5s transit, leels,

magnetic compass, sureying tape, leeling rod, and range poles.

Me%s(re$e#! "f Dis!%#ces

4istances in surey work are measured in either ertical or hori2ontal plane. =ertical distances or

differences in eleation in fish farm planning are usually determined by the use of leel instruments and

leel rods. 6ori2ontal distances are determined in arious ways depending on the accuracy desired.

Among the aailable methods are Pacing, /aping, and the Stadia Method. A pace is the normal length of

a step or stride of an indiidual. Pace #actor 0P.#." is defined as the ratio of the measured distance and

the number of paces made by an indiidual to coer the measured distance. /apes, on the other hand, are

used for direct measurements of hori2ontal distances. -ut the quick way of measuring distance is by the

stadia method. /he measurement of distance by stadia uses the transit or leel instruments, haing

telescope proided with stadia hairs and leeling rod. /he stadia hairs are equidistant from the hori2ontal

cross hair.

Me%s(re$e#! "f A#/)es %#d Direc!i"#s

/he direction of any line is measured in terms of angle between the line and some reference line,

usually the 3orth1South line in the compass. /he instruments used to measure angles are compass,

transit, tapes, plane1table alidade, and se&tant. Angles and directions may be e&pressed in different ways,

namely, a" bearing, b" a2imuth, c" interior angles, d" deflection angles, and e" angles to the right. Among

these, the first two are commonly used in fish farm surey. -earing is the angle that is referred from the

3orth and South, whicheer applies. It can neer be greater than DE. /he a2imuth of a line is a

clockwise angle measured from a reference direction usually north.

Me%s(re$e#! "f Are%s

Aailable methods used in computing areas are the a" planimeter method 1 where boundaries of

the farm are plotted to scale and area is determined by the use of planimeter, b" double1meridian1

distance method $ where area is calculated from the coordinates of the farm, c" trape2oidal rule, and d" by

plotting the boundaries to scale and diiding the tract into regular geometric figures 0such as triangles,

rectangles, or trape2oids", scaling the dimension of these figures and computing their areasmathematically. Among these methods, the trape2oidal rule and the last method of subdiiding into

regular geometric figures are easily understood.

T""/r%+ic S(r0e*

/opographic sureys are conducted on the farm site to determine the nature of the ground relief

or its characteristics, such as differences in eleation, location and measurement of boundaries, physicalfacilities and others. A topographic map proides the basic hori2ontal and ertical controls in the

planning and design of the fishpond. It determines the direction of water moement, locations of water

control structures, olume of earthwork and others.


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POND DESIGNING AND LAYOUT

/he designing criteria in the deelopment of aquaculture farm should be based on the following

!. Planned management method 1 /he establishment and structure should create an enironment in

which the production of aquatic organisms can be improed in quantity and quality.

(. -iological considerations 1 /he enironmental conditions best suited to the growth of the

cultured species should be clarified.*. )eneral features of the area 1 #lood, typhoon ha2ards, area contours and other geographical

features must be considered.

. %conomic and administratie requirements 1 /he economic and administratie requirements

should be gien due consideration from the engineering point of iew.

/he important principles of pond designing are the following

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c" #or small ponds with oblong or rectangular shapes, the long a&is should be parallel to the

preailing winds to take adantage of wind aeration.

/here are adantages of large ponds. It has less construction cost per unit area of water' it takes

up less space per unit area of water' more sub:ect to wind action, therefore, less susceptible to o&ygendeficiency' and more conducie to rotation with rice or terrestrial crops.

/here are also adantages of small ponds. It is easier and quicker to harest' it can be drained and

refilled more quickly' it is easier to treat diseases and parasites' less sub:ect to dam and dike erosion by

wind' and if for any reason all or part of the stock in one pond is lost, it represents less of a financial loss.

4esirable ratios 0in percent" of the different ponds in a fish farm

!. -reeding pond 1 D.(> 1 ! G

(. 3ursery ponds 1 ( 1 * G

*. #ingerling ponds 1 > 1 !D G

. 7earing ponds 1 F! 1 D G

>. +thers 1 ( 1 > G

P"#d Arr%#/e$e#!s %#d L"c%!i"#s,

/he pond units should be arranged in such a way that the breeding ponds are usually close to the nursery

ponds and the fingerling ponds.

3ursery ponds 1 About ( ft 0.> 1 .> ." deep. /his must be a series of small ponds whose area

and number shall be determined by the number of rearing ponds and the frequency of

breeding of the species cultured.

7earing ponds 1 /he si2e and layout of the rearing ponds depends on the fish population

management system to be adopted, as a one stage production process 0! rearing pond only" or a

two or more stages production process 0( or more rearing pond series". It has a depth of about .>

$ !.(> m.

;ater Control Structures 1 /he water control structures of a fish farm consist of the following

!. ;ater gates, dams, pipes and canals for water supply and d rain age'

(. 8eees or perimeter dikes for protecting the farm land from floods as well as for retaining

pond water'

*. 4ikes for partitioning indiidual ponds.

Pond 4rainage 1 Pond drainage will be achieed smoothly by a ditch system. A principal ditch

and seeral secondary ditches all terminate in a gate situated in the deepest part of the pond

bottom. Attached in a gate is a screen that shall preent the fish from escaping, and a series ofsmall wooden boards which regulate the water leel.

Pond si2e 1 /his depends largely on the layout of the ground and the slope or topography of the area.Pond depth $ /he pond must be deep enough to aoid the inasion of emergent egetation and

shallow enough to allow submerged plants to grow and deelop. )enerally, a rearing pond is

D.> to !.(> m. or !.> m. deep. Carp nursery ponds hae a depth of D.> to .> m. /he dike height

at ate site must be equal to the water depth plus D cm. for clearance.

FARM LAYOUT

An effectie farm layout is the arrangement of all the fish farm facilities and structures in a

proposed site based on the physical features of the area as well as the requirements of farm

management. Ma&imum adantage should be taken of topographical features of the site. /his

basic principle intends not only to economi2e on the cost of earthwork in construction, but also to

presere soil fertility and present a better enironment for immediate operation of the farm.)enerally, for a !D to >D ha. pond system, a si2e of to > ha. for indiidual rearing ponds would

be desirable.

/he simplest form of pond layout is that of a single compartment. More recently, improed

layouts consisting of multiple combinations of compartments hae come to general use.

THE SUITABILITY OF LAYOUT FOR CULTURED SPECIES


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Pond layouts may be grouped into !" conentional' (" radiating' *" modular or progression' and

" multiple stock@harest pond system. All of these, howeer, are intended for milkfish production and in

general maintain shallow water that is required by fish food called Hlab1lab. 6oweer, combination of

deep water for plankton production and shallow water for lab1lab production is also being practiced.

/he differences between the conentional and radiating type of layout is the presence of much

longer canal and secondary dikes in the former than the latter. /he short supply canal of the radiatinglayout is desirable from the iewpoint of economy in dike construction. It also seres as catching pond.

#or most of the layouts, the space occupied by the partition and canal dikes is appro&imately !D percent

that is e&ceeded when large dikes are constructed.

/he traditional shrimp pond usually has shallow depth of water of D toD cm. with one inlet

water gate at one end and one outlet gate in the other end. /he production is usually (> to D kg@ha@yr.

/his traditional pond is modified by constructing larger ditches, higher dikes and increasing water depth

to !DD to !>D cm. and hence, the si2e of pump. -y doing so, production has increased by (DD to *DD

kg@ha@yr.

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DESIGN OF FISH FARM GATE SYSTEM

T+e E)e0%!i"# "f P"#d B"!!"$ %#d F%r$ G%!es

/he bottom eleation of fishponds is the primary consideration in the design and is determinedbased on the design tide cure. Primary consideration should be gien to both the biological needs of the

cultured species and construction aspect such as the minimum and ma&imum water leel to be maintained

in the pond and adequate flow of water into the ponds. 8ikewise, to be economical, the eleation of pond

bottom should strike a balance between the e&caation or filing work and the tidal range.

/he eleation of the other structures such as gates, canals and dikes are also based on the design

tide cure and these should fit properly to the water management and operational requirements of the

ponds.

C"$"#e#!s "f W%!er C"#!r") G%!es

a" #loor $ /he floor seres as the foundation of the structure and its eleation for main gates

must be lower than the pond bottom eleation and as low or slightly lower than the lowest tide in the

site, hence, the main gate which rests on a prepared foundation support will not be e&posed eenduring e&treme low tides.

b" Apron 1 /his is the broadened and e&tended part of the floor and also generally rests on the

foundation piles, which are made of seasoned bamboo or wood drien at D.* m. interals into

the soft soil with the butt end up /he apron seres as protection to scouring and future seepage

of water at the gate5s sides.

c" Cut1off walls $ Cut1off1walls are proided at both ends of the gate floor to preent seepage and

undercutting of water within the gate5s foundation. /hey e&tend down into the soil at a

minimum of D.?D m. and are an integral part of the gate5s foundation. ;ooden sheet piles may

be used as e&tension of concrete cut1off1walls in order to reach deeper depths at reduced cost.

d" Side or -reast ;alls $ Side walls define the water way in addition to their being retaining wall.

)rooes for flashboards and screens are built on these walls. /he top of these walls are as high

as the top of the dike.e" -uttress $ /his is built against the side walls to support or reinforce it. It also helps in

reducing seepage flow along the side walls.

f" ;ing walls $ ;ing walls proide the transition from the water way into the main canal in

addition to retaining the earth at both sides of the gate. /his transition improes the condition

of the flow by proiding a controlled flow from one bed material to another.

g" -ridges or catwalks $ /hese are reinforced concrete slabs or thick wooden planks that connect the side walls. At least two catwalks are proided, at each end of the gate.

h" #lashboards $ Slabs or flashboards are generally wooden planks, (.> to > cm thick and *D cm.

wide inserted into grooes. /hey are used to control the amount of water flowing through the

gate.

i" Screens $ Screens are usually made of bamboo strips or of fine polyethylene meshes attached

to a wooden rectangular frame that fit into the grooes. /he screens are used to preent the e&itof the cultured fish and the entry of predators into the ponds.

:" Pillars 1 In wooden gates, these are ertical supports where wooden walls are nailed. /hey are

placed at regular interals so that they form a framework for the gate itself.

k" -races 1 In wooden gates, these wooden members held or fasten two or more pillars together

or in place. /hey keep the opening of a gate rigid.

M%i# G%!e

/he main gate links the pond system to the source of water. It regulates the e&change of water

between the pond system and the tidal stream or sea. Instead of wood, it should be made of concrete for

effectie control and to last longer. /he main gate is usually situated at the central side of the proposedfishpond facing the source of water. /he following proides some information needed in the design of

the main gate.

a" /he floor eleation of the main gate should be lower than the lowest pond bottom eleation

desired inside the pond system. It should also be as low or slightly lower than e&treme low

tides.

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b" /he height of the main gate depends upon the highest tide and flood and should be the same as

the eleation of the main dike which is also dependent upon the tidal fluctuation, floods and other

factors in the area.

c" Main gates may hae single, double, or triple or een quadruple or more openings. /heopening of the main gate depends upon the area to be flooded. )ates should not hae too wide

opening so that they would be difficult to manage. +ne to !.( m. wide per opening has beenfound appropriate for easy handling of wooden slabs and screens. %&perience shows that a

single opening of !.D m. for a concrete main gate could flood a !D to !> ha. pond system in a

milkfish farm in two or three successie high tides. /his opening, howeer, does not

necessarily apply to shrimp farm because of the difference in water depth requirement between

shrimp and milkfish. -ased on the computation done a gate with three openings and !.( m.

wide each would fill an !!.*> ha. shrimp farm to a minimum depth of one meter in two

consecutie tide cycle. #or much larger areas and deeper ponds, a double or triple opening

gate of proper width may be constructed at one or more spots along the perimeter dike.

d" /here must be a separate grooe for the slabs and screens. It may be necessary to hae four

pairs of grooes' two pairs for slabs and two pairs for screens 0one at each end" depending

upon their use.

e" /he wings should be properly designed to proide easy current flow. /he best angle of flare

should be >E towards the outside. /his angle may not be necessarily the same for both ends

of the gate.

f" /he gate foundation must be rigid and stable. It must be able to carry the whole weight when

the gate is fully constructed. /here are two designs of gate foundations in use $ one has the

floor and apron of gate resting on a combination of piles and layers of boulders and grael.

/he other one uses piles alone to strengthen the foundation that supports the structure.

g" Cut1off walls and aprons must be proided. /hey must be wide enough to include portions

susceptible to scouring and under1cutting of water.

h" Adequate reinforcements against sidewise pressure must be proided. Spacing of steel bars

should not e&ceed D cm. center to center. /he si2e of ertical bars should be !( to !* mm.

and !D mm. for hori2ontal bars.

Sec"#d%r* %#d Ter!i%r* G%!es

/hese proide the control of water to and from the main canal and into the different pond

components such as catching ponds, rearing ponds and nursery ponds. /hese structures are usually madeof wood and can be treated with coal tar for durability. Single or double opening made of reinforced

concrete or hollow blocks can also be used but it is sometimes too e&pensie. Considerations in theplanning and designing of secondary and tertiary gates are the same as those of the main gate e&cept that

their respectie eleations are dependent upon the eleation of the canal bed where they are being

constructed. /he usual eleation of the flooring of these gates aboe the canal is D.!> m. /he flooring

eleation of the farthest gate from the main gate should be checked against the design tide cure to insure

that it still is capable of filling the pond within the prescribed time. /he width of opening may ary from

D.? to !.D m. ;ing walls can be proided but some e&isting designs, especially the wooden gates, do not

hae these structures. Anti1seep boards at the side of the gate is also a good feature.

C()0er!s "r Pies

/hese structures coney water across dikes, roads, and similar embankments. A recent innoation

for a smaller and less e&pensie gate is the use of culerts or pipes made of concrete hollow blocks. /heymay or may not hae wing walls but they are likewise proided with slabs and screens and are een more

effectie for water control in a fishpond. /he conduit section may be circular or square in shape.

THE DESIGN OF DI1ES2 PONDS AND CANALS

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13/63

MAIN OR PERIMETER DI1E

/he function of perimeter dikes is to retain water for use in the fish farming operation as well as

to protect the farm ponds, fish crops and other farm facilities from destruction by floods and tidalinundation.

8ocation of Main 4ike $

/he perimeter dikes of a coastal fish farm are usually built along the rier banks, on the seaward

side or in certain spots that are ulnerable to flooding. In locating the dike, a belt of mangroes of (D m

from a rier bank, and !DD m wide from seashore must be left for the purpose of protecting the dikes

against waes and currents and absorption of wae energy and for flood control and conseration of the

enironment.

/he path of dike must aoid the following

a" Crossing of streams or creeks that hae substantial rate of flow'

b" Areas of e&tremely poor soil which result in high construction cost' and

c" Areas near an actiely eroding line of riers or coasts.

Cross1Section of Main 4ike $

/he cross1section of dikes is described by the crown or top width, height, side slope and the

bottom width or base. In some cases berm and core or puddle trench are also proided. /he cross1section

of the perimeter dike should be designed to a" preent oer1tapping at high tide combined with a

ma&imum flood height from the rier system' and b" preent failure due to slips and seepage.

4etermination of 4ike 6eight

/he height of the dike should be aboe the highest tide and flood that occur in the site. /he

design flood leel is based on the ma&imum flood water that was obsered in the locality to recur within

!D to !> years.

/he design height of dike should be proided with a free1board after shrinkage and settlement of

D.* to !.D m aboe the highest water leel. /he recommended allowance for shrinkage and settlement are

as follows

Allowance for structure

Condition and settlement 0G" 1111111111111111111111111111111111111111111111111111111111111111111111111111 111111111111111111111111

!. Poor material and poor methods and practices in construction !>1*D

(. Soil e&ceptionally high in organic matter D or more

*. Compacted by construction equipment >1!D

111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111

/he total height of the main dike aboe the ground leel can be computed by the following formula

06at1)s" J Mf J # ;here 6m K height of the main dike

6m K 11111111111111111111111111 6at K highest astronomical tide

! $ 0GS" )s K eleation of the ground surface

111111111 Mf K ma&imum flood leel

!DD # K allowance for freeboard

GS K percent shrinkage and settlement

Side slopes, Crown and -ase

/he appropriate side slope of dike is !! for clay soil and dike height up to *.D m.

Side slope of (! 0hori2ontal to ertical" is used for height greater than .D m and een flatter if locatedalong seashore and being sub:ect against wae action. /he proision for a berm 0single or both sides" is

also desirable for additional stability. /he berm should slope towards the dike wall to trap eroded soil

particles during rains. It also seres as small ditch that coneys runoffs towards the outlet gate especially

when acidity of e&posed dike is a management problem.

!*


14/63

/he top width or crown of the dike used as roadways should be preferably .D m. If not used as

roadway the desirable minimum crown for main dike is at least (.D m.. /he base 0without a berm" is

computed in accordance with the width of crown and side slope using the following formula

b K / J (02d" ;here b K width of base, m. 2 K hori2ontal alue of side slope / K width of crown, m. d K height of dike, m.

Cross1Sectional Area and =olume of 4ike

/he cross1sectional area of dike is estimated using the following formula

0b J /" 0b J /"

A K 11111111111111 0h" = K 1111111111111 0h"08"

( (

;here A K cross1sectional area of dike, mL

= K olume of dike, m

8 K length of dike, m.

8eakage and seepage 1 %ffectie measures for preenting leakage include the following

a" Minimi2ing the amount of seepage flow through proper compaction, core trenching embedding

ertical plastic membrane inside dike, coering dike wall with concrete bricks, riprapings, etc.b" Minimi2ing destruction by crustaceans by desalini2ing and drying out the embankment soils.

SECONDARY AND TERTIARY DI1ES

/he secondary and tertiary dikes are smaller than the main dikes. Secondary dikes are usually

proided on both sides of the canals and should be able to contain the mean high water springs. /ertiary

dikes are partition dikes that separate the ponds and should be able to contain the desired water leels in

the ponds.

Side slope, crown and base of secondary and tertiary dikes 1 /he top width of secondary and

tertiary dikes are narrower than the perimeter or main dike. /op width of ! to ( m are common for the

secondary dike and een less than one meter for the tertiary dike.

/he side slope is usually !!. Side berms in secondary dike may be proided if there is e&cess

soil in order to reduce the cost of hauling. Puddle trench in the dike base is proided when necessary.

/he computation of the width of base is done in the same way as in the perimeter or main dike.

TYPES OF PONDS AND POND BOTTOM

Production ponds are designed independent of each other by proiding each with indiidual watersupply and drainage gates. ;ithin the compartment pond bottoms are designed to further fit the

enironmental requirement of cultured species. /he whole bottom should slope towards the drainage gate

to facilitate remoal of water. /his sloping bottom can be modified and improed by proiding bottom

ditch within the pond running along and close to the base of the dike. /his ditch collects and leads the

water to the catching pond where the drainage gate is also located. In this scheme, a slope diide is

proided at the center of the pond. #or much larger compartments, a middle ditch connecting the

peripheral ditch may be proided.

Ponds designed purposely for shrimp culture usually hae two separate gates $ supply 0inlet" and

drainage 0outlet" gates. Peripheral canals are proided mainly to sere as shelter for the shrimp' to

increase the pond bottom surface area' and to hae better water circulation. #acilitating drainage is onlysecondary in the purpose. 6ence, more canals or bottom platforms are sometimes proided.

!


15/63

WATER CANALS OR CHANNELS

;ater from the outer sea is drawn into the fishpond at the specified rate and time through the

canal and discharged into the outer sea also through the same canal. 6ence it sere the purpose of

supplying and draining water to and from the ponds.

Ninds of ;ater Channel

a" Main water supply canal $ /his starts from the main gate and usually traerses the central portion

of the fish farm. /he si2e of the main canal should consider the emergency discharge of water

from the entire fish farm and surrounding area during heay rain.

b" Secondary water supply canal $ /his seres the portions where main canal cannot reach. It starts

from the main canal and traerses the inner portion of the fishpond. It is usually constructed in

large fishpond areas and is smaller than the main canal.

c" /ertiary canal $ /his is the canal that usually supply water in the nursery and transition ponds.

-ecause of the small si2e, it is sometimes said to be a part of the nursery pond system. /he

tertiary canal may be modified to sere as catching ponds. 9sually the bed width is !.D to !.> m.

d" 4iersion canal $ /he purpose of this canal is to protect the farm from being flooded with runoff

water coming from the watershed It should hae the capacity to carry at least the peak runofffrom the contributing watershed for a ten1year frequency storm. /he slope of the diersion canal

should be such that the water flows toward the drainage area or around the fish farm to a

conenient and prepared outlet.

e" 4rainage canal 1 A separate drainage canal is recommended in intensie culture, especially of

shrimps, in order to effect flow1through system. /his is usually located at the other side of the

pond, opposite and parallel to the supply canal, if proided.

Cross1Section of Canal -ed

/he cross1section of the canal is generally of trape2oidal shape with side slope of !! for the

alluial clay soil. /he depth of the main canal ranges from the leel of mean higher high water for mi&edtide or mean high water to the mean lower low water and the secondary canals from the designed pond

water leel to the mean tide leel. /he lower limit of the water canals depends on the range of tide.

)enerally, a smaller tide range requires a lower canal bed.

!>


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CONSTRUCTION OF A FISH FARM

CONSTRUCTION ACTIVITIES2 EQUIPMENT2 AND METHODS

A. P7%1C+3S/79C/I+3 AC/I=I/I%S

A.!" Programming of actiity and staffing of the pro:ect

/he purpose of pro:ect programming is to hae a clear flow on how the pro:ect will be implemented, the

starting and completion time for a gien amount of work, and labor force. /his is done by estimating the amount of

labor force aailable and their daily output in order to determine the number of days a piece of work can be finished.

In assessing the aailability and quality of manpower in the icinity of pro:ect site, considerations are gien

to the quantity and e&perience of skilled workers, time of aailability 0year round or seasonal", rate and condition of

payment, and working arrangements preailing in the locality. -ased on the aboe a proposed program of workshould be prepared. 8ikewise, a schedule of construction actiities shall also be prepared.

A.(" Procurement@stockpiling of materials

/he purchase and stockpiling of materials should also be accomplished according to the construction

schedule. Costs should be weighed against aailability and transport of materials under different climatic

conditions. Some materials like grael, sand, cement, lumber, and bamboo poles should be purchased and

transported to the pond site during dry weather. /ransporting them at this time is easier and cheaper. -ambooshae to be purchased during dry season to get good quality poles. Some equipment like the cement mi&er, hollow

blocks machine, ibrators, steel cutters, and water pumps should be acquired or leased at the proper time. All these

will require cash flow which should be indicated in the construction schedule.

-. MAI3 C+3S/79C/I+3 ;+7NS

/he actual construction of a fish farm can be diided into four ma:or operations, namely !" Site clearing, ("

;ater control structures construction, *" %arthwork, which inoled the construction of dikes and canals, and "

Pond leeling.

!. SI/% C8%A7I3)

Initial clearing begins where the main dike and main gate are to be located. #ull scale clearing then continues

as the construction of main gate proceeds. /he entire area of the fishpond site should be cleared of all grasses, trees,

roots and stumps. All cleared materials should be thoroughly remoed from the site of work. Site clearing can be

accomplished by any or combination of the following methods

a" 9nderbrushing $ In underbrushing, egetation including nipa trees and shrubs of less than !D cm indiameter are cut with the use of bolo. /his is done by manual labor and the work begins as soon as the

foundations of the main dike and the main gate hae been established.

b" ;ithering 0+ptional" 1 ;ithering is to kill the trees by filling up the pond with water. It has been found

that mangroe trees, specially the group of 7hi2ophora, usually die out when their trunks are constantly

soaked with water at a depth of more than D.> m for a period of to ? months.

c" #alling $ #alling is simply cutting down big trees left after underbrushing. /he falling operation shouldcommence when the tree bark begins to peel, but before the leaes and branches fall. /he prerequisite of

falling is to dry and harden the ground, which can be done by keeping the water table of the entire pond

area at D.* to D.> m below the surface for a period of ! to * months, depending on the weather conditions.

%ither manual or mechanical method, or a combination of both, can be employed for falling. A chain saw

is effectie in falling big trees and cutting logs. It is a fast method and economical to use.

d" 9prooting of stumps 1 Complete remoal of tree stumps and root system embedded in the soil is done by

manual labor or by the use of small machines.

(. C+3S/79C/I+3 +# ;A/%7 C+3/7+8 S/79C/97%S

/6% C+3C7%/% )A/%

/he main gate is constructed ahead of the main or perimeter dike to allow time for curing of concrete and hae

it used while the main dike is being completed. All the materials needed should be in the site prior to construction.

4uring construction, the design specifications must be followed particularly in the construction of gate foundation,

!?


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the proisions against undercutting of water, the spacing and si2e of reinforcements against side and bottom

pressures, and the proper mi&ture and curing of the concrete or brick 0or concrete hollow block".

Construction begins by preparing the site. /he e&act location is measured and staked out. %nough working

space of ! to ( m around the gate foundation should be proided. A reference point for checking the eleations ofgate flooring, heights, soil e&caations and others must be established. A temporary but strong dike capable of

withstanding tidal water pressure must be constructed to enclose the site and working space. %ntrapped water insidethe site is remoed manually or by pumping.

a" /he gate foundation $ /he site of gate is e&caated to D.? m deep from the reference point. 7emoal of

roots, stumps and mud or soft soil is done, if any. %&caation should include the portion where the toes of the gate

will be constructed. /he spacing and lengths of bamboo base, mangroe or wooden piles that support the structure

should be obsered. A common practice by fish farmers is to drie two lengths of piles ertically the *1m length isdrien at one1meter interal while the shorter 0one to two1meter" length is drien (> to *D cm apart within the longer

piles. 8eae at least (> cm of the pile head aboe the soil surface. /his e&posed ends should be in leel.

In some designs, wooden planks with pointed ends measuring > cm & !> cm & !FD cm are also used in addition

to bamboo piles. /hese planks are drien side by side along the centerline of side and wing walls and both ends of

aprons. /hese planks e&tend the depth of concrete cut1off or toe walls and further help in preenting undercutting of

water.

-oulders are laid about (D cm thick between the piling to form a floor. )rael layer of > m thick is spread on

top of the boulders, and then compacted. /he e&posed ends of the piles should be leel with the surface of thegrael layer.

b" #orms and reinforcing bars $ After the foundation, the forms for the slab or flooring and toes are constructed.

/he reinforcing bars are laid as planned. /he initial pouring of mi&ed concrete along the footing is done to keep in

place the ertical reinforcements for side and wing walls including collars. /he reinforcements for catwalk or

bridges are also installed. ;hile installing the reinforcements, the forms for walls, bridges and collars are being

prepared.

/he forms are properly set and should be rigid to stand the weight of poured concrete and to aoid bulging of

sides. /he reinforcement bars should be centered within the forms. /he forms are spaced apart to hae a finished

concrete wall of at least !> cm.

c" Concrete mi&ture, pouring and curing $ Concrete mi&ture should be in proportion of !(

0cementsandgrael" for all concrete works. If concrete hollow blocks are used 0for small main and secondary

gates", the mi&ture should be ! 0cementsand". Prior to pouring of concrete mi&ture, the water that has seeped into

the gate construction site should be drained out. /hen pouring of mi&ture follows continuously until completed.Saltwater should not come in contact with the concrete while still wet.

Allow the concrete to set in and harden for ( to days before remoing the forms. Plastering the surface may

be done as necessary. Plastering mortar of !* 0cementsand" ratio should be applied at a thickness of ? to !D mm.

Continuous curing of the concrete structure should be done for (F days. Curing is done by coering it with :ute sack

or similar materials and sprinkling freshwater to make it moist throughout the day for the whole curing period.

Soil backfilling of e&caated areas is done to hae a finished ground surface around the structures. Propercompaction between walls of the structure and ad:acent soils should be obsered. /he temporary dike may be

remoed after *D days. Condition the structure by letting tidal water come in and out of the gate.

/6% ;++4%3 )A/%

/he wooden gates hae much shorter life span than concrete. /his is preferred for reasons of economy or when

initial capital is limited. /he use of wooden gate can be resorted to until such time that there is capital to replace it

with concrete. /he parts, shape, height and inner dimensions of wooden gates are also similar with concrete. /hey

are, howeer, easier and faster to construct.

/he woods are planed to hae smooth edge and surfaces. /o prolong the life of the wood, thick coating of coal

tar or other similar wood preseraties is applied. Some gate builders mi& coal tar and cement and the mi&ture is

painted in two coatings to the materials, then left under the sun for drying.

/he foundation may not be as strong as in concrete gate. %&caate the site according to desired eleation.

-amboo base or mangroe piles are drien to support the structure if needed.

/he arious parts of the gate such as the walls, flooring, cut1off walls, anti1seep board are separately nailed tothe respectie braces, pillars or supports. /his is done outside the site. /he component units 0side walls, flooring,

cut1off wall, etc." are then assembled together by using galani2ed nails, or bron2e nails, if aailable, to form the

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gate after the preparation of the foundation. In some cases, the whole gate unit is already assembled outside the site

and :ust lifted and placed properly on top of the site, but sometimes the finished gate is quite heay.

/he walls and flooring of the gate are tightly nailed side by side. ;ater tightness improes the moment the

wood is soaked in water and e&pands. 6oweer, there are also water sealant compounds that further insure watertightness.

After installing the gate, the space between the e&caation and walls are mud1packed by soil blocks arranged in

layers. /hen the soil is allowed to dry and harden. Conditioning the gate is done by allowing tidal water in and out

of the pond. Checking for seepage is also being done at this time.

*. C+3S/79C/I+3 +# P%7IM%/%7 +7 MAI3 4IN%

/he most important component of the fishpond system is the dike enclosing the entire pond area. /he perimeter

dike is the first dike to be constructed to free the area from the danger of floods. /he utility of the pond system will

depend on the strength and lifetime of the perimeter dike. Construction may be done by manual method with light

implements and by using heay equipment.

/6% % m wide by D.>1!.D m deep along the center path of themain dike. /he e&caated trench is then backfilled to the same ground leel with new soil which is wet enough to

be puddled by feet or compacted by a wooden mallet or tampering deice. /he importance of puddle trench is well

recogni2ed but sparingly practiced probably due to the added cost. Although costly, it cuts a lot of water

management problems in the future.

Construction of main dike proper follows. /he stakes set for the si2e of dike guide the proper arrangement or

piling of soil blocks that are taken from higher grounds and are being transported by flatboats or rafts. +ther

methods of transporting soil blocks are by the line system and sliding system. In the line system, workers form a

!F


19/63

single line. %ach worker is positioned at ! to ( m apart. /he line e&tends from the source of soil to the dike

construction site. Soil blocks are relayed to each man until it reaches the piler. /he sliding system applies when the

source of blocks is close to the site. /he worker throws the block on the board letting the soil slide down to the base

of the dike. Among these methods, the use of flatboat is considered the best.

/he piler of blocks sees to it that they are tightly placed end to end. Compacting each layer of soil blocks by

feet or tamping deise is recommended. /here must be proper placement of dike until it is finished. /he proper sideslope must also be obsered in the piling of blocks. /he base and top width stakes as well as a side slope model

seres as guide in checking the correctness of side slope.

/he height or eleation of the top of dike should also be checked, if done according to specifications. It is

important to hae uniform eleation of top of dike in eery compartment. /o accurately measure this, a !(1mm

transparent plastic hose, (> to *D m long, is filled with water. +ne end is held by a man at the starting point whilethe other end is held by another man. /he water leel at the two ends of the hose must be the same. /his leel is

properly marked and is checked against the finished eleation of the top of dike. /he same procedure is done in

subsequent stretch of station of (D to (> m until the entire length of dike is coered. /he plastic hose with water is

also used in laying out the bed slope of canals of a fish farm.

/eam work ersus indiidual work in dike construction $ Some construction workers group themseles as a

team in working. /he team is usually composed of four members, each with distinct functions $ the soil piler, the

soil block digger, raft or flatboat pusher, and the carrier. /he carrier receies the soil blocks transported andunloaded by the boat pusher at the site, and passes them to the piler.

+ther workers prefer to work indiidually. %ach worker is proided with flatboat and does the digging,

transporting and piling. It is claimed that one skilled worker with flatboat can finish a dike with si2e of ? to cu.m

in ? to F hours, compared to *.> cu.m only for each member in the team work.

C+3S/79C/I+3 +# S%C+34A7O A34 /%7/IA7O 4IN%S

Construction of secondary and tertiary dikes follows the same procedure as in construction of perimeter dikes.

Puddle trench is also recommended to be included in the construction. /he dikes may hae berm to accommodatee&cess soil from the pond and to decrease soil erosion and water turbidity after a heay rainfall. /his berm is also a

good working space during repair of dike leaks or seepage rather than doing repairs by staying on the crown.

C+3S/79C/I+3 +# ;A/%7 CA3A8S

;ater canals are constructed following the same procedure as in dike construction. Canal bottom is, howeer,

e&caated deeper than the pond bottom and secondary gates if the channel or canal is purposely designed for fillingand draining the fishpond.

. P+34 8%=%88I3)

Pond leeling is the final step in fishpond construction. Some operators pay little attention to pond leeling and

think that construction of fishpond is finished after the main and the secondary dikes hae been constructed. +ne of

the ma:or reasons for low pond productiity is due to rough or poorly leeled pond bottom.

8eeling the pond :ust after the dikes are constructed is quite e&pensie. It is adisable to wait for two to three

years until the root systems of the trees hae partially decayed before leeling is started. /his will lessen the capitaloutlay. Partial leeling may be done :ust after enclosure, but e&caation should be limited only to portions where

there are no trees. /he soil e&caated should be dump in low portions that cannot be drained. After two to three

years, final leeling can be completed.

After a topographic surey has been made, the pond bottom eleations should be determined. 8ikewise, the

olume of soil to be cut and the portions to be filled should be marked out by stakes. A simple method of pond

leeling is done by using the tidal water. /he procedure is as follows -ring the water down to the desired pond

eleation and place a bench mark to identify it. -eside the bench mark, place another stake about .> cm wide, (.>cm thick and ( m long, marked from D to !DD cm. /he 2ero mark of the gauge should be leel with the bench mark.

/he gauge indicates the depth of water and seres as a leeling guide during filling of low spots and in cutting soil

from high places.

!


20/63

C+88%)% +# #+7%S/7O A34 %3=I7+3M%3/A8 S/94I%S

MI34A3A+ S/A/% 93I=%7SI/O $ MAI3 CAMP9S

MA7A;I CI/O

REVIEW MATERIALS IN FOREST PRODUCTS ENGINEERING

by Forester Deborah C. Achas

NOTES IN WOOD STRUCTURE AND IDENTIFICATION

C+%r%c!eris!ics "f C"$$erci%))* I$"r!%#! W""ds

/hroughout history, the unique characteristics and comparatie abundance of wood hae made it a natural

material for homes and other structures, furniture, tools, ehicles, and decoratie ob:ects. /oday, for the

same reasons, wood is pri2ed for a multitude of uses.

All wood is composed of cellulose, lignin, hemicelluloses, and minor amounts 0>G to !DG" of e&traneous

materials contained in a cellular structure. =ariations in the characteristics and olume of these

components and differences in cellular structure make woods heay or light, stiff or fle&ible, and hard or

soft. /he properties of a single species are relatiely constant within limits' therefore, selection of woodby species alone may sometimes be adequate. 6oweer, to use wood to its best adantage and most

effectiely in engineering applications, specific characteristics or physical properties must be considered.

/he gradual reduction in use of old1growth forests in the Philippines has reduced the supply of large clear

logs for lumber and eneer. 6oweer, the importance of high1quality logs has diminished as new

concepts of wood use hae been introduced. Second1growth wood, the remaining old1growth forests, and

imports continue to fill the needs for wood in the quality required. ;ood is as aluable an engineering

material as eer, and in many cases, technological adances hae made it een more useful.

/he inherent factors that keep wood in the forefront of raw materials are many and aried, but a chief

attribute is its aailability in many species, si2es, shapes, and conditions to suit almost eery demand.

;ood has a high ratio of strength to weight and a remarkable record for durability and performance as a

structural material. 4ry wood has good insulating properties against heat, sound, and electricity. It tends

to absorb and dissipate ibrations under some conditions of use, and yet it is an incomparable material for

such musical instruments as the iolin. /he grain patterns and colors of wood make it an esthetically

pleasing material, and its appearance may be easily enhanced by stains, arnishes, lacquers, and other

finishes. It is easily shaped with tools and fastened with adhesies, nails, screws, bolts, and dowels.

4amaged wood is easily repaired, and wood structures are easily remodeled or altered. In addition, wood

resists o&idation, acid, saltwater, and other corrosie agents, has high salage alue, has good shock

resistance, can be treated with preseraties and fire retardants, and can be combined with almost any

other material for both functional and aesthetic uses.

H%rd.""ds %#d S"f!.""ds

/rees are diided into two broad classes, usually referred to as hardwoods and softwoods. /hese names

can be confusing since some softwoods are actually harder than some hardwoods, and conersely some

hardwoods are softer than some softwoods. #or e&ample, softwoods such as longleaf pine and 4ouglas1fir

are typically harder than the hardwoods basswood and aspen. -otanically, hardwoods are Angiosperms'

the seeds are enclosed in the oary of the flower. Anatomically, hardwoods are porous' that is, they

contain essel elements. A essel element is a wood cell with open ends' when essel elements are set

one aboe another, they form a continuous tube 0essel", which seres as a conduit for transporting water

or sap in the tree. /ypically, hardwoods are plants with broad leaes that, with few e&ceptions in the

temperate region, lose their leaes in autumn or winter. Most imported tropical woods are hardwoods.

-otanically, softwoods are )ymnosperms or conifers' the seeds are naked 0not enclosed

(D


21/63

in the oary of the flower". Anatomically, softwoods are nonporous and do not contain essels.

Softwoods are usually cone1bearing plants with needle1 or scale1like eergreen leaes.

S!r(c!(re "f W""d

/he fibrous nature of wood strongly influences how it is used. ;ood is primarily composed of hollow,elongate, spindle1shaped cells that are arranged parallel to each other along the trunk of a tree. ;hen

lumber and other products are cut from the tree, the characteristics of these fibrous cells and their

arrangement affect such properties as strength and shrinkage as well as the grain pattern of the wood.

B%r-2 W""d2 Br%#c+es2 %#d C%$3i($

Cross section of white oak tree trunk0A" outer bark 0dry dead tissue", 0-" inner bark 0liing

tissue", 0C" cambium, 04" sapwood, 0%" heartwood,

0#" pith, and 0)" wood rays.

A cross section of a tree shows the following well1defined features 0from outside to center" bark, which

may be diided into an outer corky dead part 0A", whose thickness aries greatly with species and age of

trees, and an inner thin liing part 0-", which carries food from the leaes to growing parts of the tree'

wood, which in merchantable trees of most species is clearly differentiated into sapwood 04" and

heartwood 0%"' and pith 0#", a small core of tissue located at the center of tree stems, branches, and twigsabout which initial wood growth takes place. Sapwood contains both liing and dead tissue and carries

sap from the roots to the leaes.

6eartwood is formed by a gradual change in the sapwood and is inactie. /he wood rays 0)", hori2ontallyoriented tissue through the radial plane of the tree, ary in si2e from one cell wide and a few cells high tomore than !> cells wide and seeral centimeters high. /he rays connect arious layers from pith to bark

for storage and transfer of food. /he cambium layer 0C", which is inside the inner bark and forms wood

and bark cells, can be seen only with a microscope.

S%.""d %#d He%r!.""d

Sapwood is located between the cambium and heartwood . Sapwood contains both liing and dead cells

and functions primarily in the storage of food' in the outerlayers near the cambium, sapwood handles the

transport of water or sap. /he sapwood may ary in thickness and number of growth rings. Sapwood

commonly ranges from to ? cm 0!1!@( to ( in." in radial thickness. In certain species, such as catalpaand black locust, the sapwood contains few growth rings and usually does not e&ceed ! cm 0!@( in." in

thickness.

Gr".!+ Ri#/s

In most species in temperate climates, the difference between wood that is formed early in a growing

season and that formed later is sufficient to produce well1marked annual growth rings. /he age of a tree at

the stump or the age at any cross section of the trunk may be determined by counting these rings.

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Def"r$%!i"# E'(%!i"#s

%quations for deformation of wood members are presented as functions of applied loads, moduli of

elasticity and rigidity, and member dimensions. /hey may be soled to determine minimum required

cross1sectional dimensions to meet deformation limitations imposed in design.. Consideration must be

gien to ariability in material properties and uncertainties in applied loads to control reliability of the

design.

A4i%) L"%d

/he deformation of an a&ially loaded member is not usually an important design consideration. More

important considerations will be presented in later sections dealing with combined loads or stability.

A&ial load produces a change of length gien by

PL AE

where Qis change of length, 8 length, A cross1sectional area, % modulus of elasticity 0%8 when grain

runs parallel to member a&is", and P a&ial force parallel to grain.

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W""d Preser0%!i"# %#d Se%s"#i#/

3* F"res!er De3"r%+ C5 Ac+%s

Pes!s !+%! D%$%/e W""d

9nder proper use conditions, wood can gie centuries of good serice. -ut under unfaorable conditions,

wood may readily be damaged and destroyed by fungi, insects, and marine borers. /hese pests can attackin many ways, using the wood for food or shelter. Consequently, wood must be protected to insure

ma&imum serice life when used under conditions faorable to these pests.

W""d6I#+%3i!i"# F(#/i

;ood decay, mold and most sapwood stains, are caused by fungi. /hese fungi feed on liing or deadwood. /he many fungi that deelop on or in wood can be diided into two ma:or groups, depending on

the damage they cause

R wood1destroying fungi 0decay fungi",

R wood1staining fungi 0sapstaining fungi, mold fungi".

-oth of these fungi groups produce spores 0analogous to tiny seeds", which are distributed by wind and

water. /he spores can infect moist wood during storage, processing and use.

All fungi that grow on wood hae certain basic requirements

R #aorable temperature 1 usually ranging between >D degrees and D degrees #. /he optimum is

about D degrees to F> degrees #. ;ood is basically safe from decay at temperatures below *> degrees #

and aboe !DD degrees #.R Adequate moisture 1 #ungi will not attack dry wood 0i.e. wood with a moisture content of !

percent or less". 4ecay fungi require a wood moisture content 0M.C." of about *D percent 0the generallyaccepted fi3er s%!(r%!i"# "i#!of wood". /hus, air dried wood, usually with a M.C. not e&ceeding !

percent and kiln dried wood with a M.C. of !> percent or less can usually be considered safe from fungal

damage.

R Adequate o&ygen 1 #ungi cannot lie in water saturated woodR #ood source 0wood itself".

W""d Des!r"*i#/ F(#/i

-oth the sapwood and heartwood of most tree species are susceptible to decay. 4ecay fungi may grow in

the interior of the wood or appear on wood surfaces as fan1shaped patches of fine, threadlike, cottonygrowths or as rootlike shapes. /he color of these growths may range from white through light brown,

bright yellow, and dark brown. /he spore1producing bodies may be mushrooms, shelf1like brackets, or

structures with a flattened, crustlike appearance. #ine, threadlike fungal strands grow throughout the

wood and digest parts of it as food. In time, the strength of the wood is destroyed. 4ecay will stop whenthe temperature of the wood is either too low or too high or when the moisture content is drier than the

fungi5s requirements. 6oweer, decay can resume when the temperature and moisture content become

faorable again.

;ood decay fungi can be grouped into three ma:or categories

R brown rot,

R white rot, and

R soft rot.Br".# r"! 6 #ungi which cause brown rot are able to break down the cellulose component of wood for

food, leaing a brown residue of lignin. -rown1rotted wood can be greatly weakened een before decay

can be seen. /he final stage of wood decay by the brown rots can be identified by

R dark brown color of the wood

R e&cessie shrinkage

R cross1grain cracking, and

R the ease with which the dry wood substance can be crushed to powder.

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-rown1rot fungi are probably the most important cause of decay of softwood species used in aboeground

construction in the Philippines. -rown1rot, when dry, is sometimes called dry rot5. /his is a poor term,

because wood must hae moisture and will not decay when it is dry. A few fungi that can decay relatiely

dry wood hae water1conducting strands that are able to carry water from damp soil to wood in lumber

piles or buildings. /hese fungi can decay wood that otherwise would be too dry for decay to occur. /heysometimes are called the dry rot fungi5 or water1conducting fungi5.

W+i!e r"! 6 ;hite1rot fungi, which break down both lignin and cellulose, hae a bleaching effectwhich may make the damaged wood appear whiter than normal.

S"f! r"! 6 Soft rot fungi usually attack green 0water1saturated" wood 0high M.C.", causing a gradual

softening from the surface inward that resembles brown rot.

T+e W""d6S!%i#i#/ F(#/i

S% s!%i#i#/ f(#/i 6 /hese fungi penetrate and discolor sapwood, particularly of the soft wood

species. /ypical sapstain, unlike staining by mold fungi, cannot be remoed by brushing or planing.

Sapstain fungi may become established in the sapwood of standing trees, sawlogs, lumber and timbers

soon after they are cut and before they can be adequately dried. Strength of the wood is little affected, but

the wood may not be fit for uses where appearance is important 0such as siding, trim, furniture and

e&terior millwork that is to be clear1finished". Southern pine beetles often carry blue stain fungi into trees.

/his can cause the wood of infected trees to be stained before they are cut.

M")d f(#/i 6 /hese fungi first become noticeable as green, yellow, brown or black fu22y or powdery

surface growths on softwoods. #reshly cut or seasoned stock, piled during warm, humid weather, may be

noticeably discolored in > to ? days or less. As with sapstains, molds do not reduce wood strength,

howeer, they can increase the capacity of wood to absorb moisture, thereby opening the door to attack

by decay fungi.

C+e$ic%) S!%i#s

Chemical stains may resemble blue or brown stains, but are not caused by fungi. /hese stains result from

chemical changes in the wood during processing or seasoning. /he most important chemical stains are the3r".# s!%i#s that can downgrade lumber for some uses. /hey usually can be preented by rapid drying at

relatiely low temperatures during kiln drying.

I#sec!s

Seeral kinds of insects attack liing trees, logs, lumber and finished wood products for food and@orshelter. /hese pests include arious termites, ants, and beetles.

Ter$i!es 1 /ermites use wood for food and shelter and are the most destructie of all wood insects. Ants

cannot use wood for food, but they are often confused with termites because the two look somewhat

similar. 6oweer, there are seeral distinct differences in their physical appearance. Ants hae elbowed5

antennae' termites do not. Ants hae narrow waists whereas termites5 bodies are broad. Ants5 wings hae

few eins and the hind wings are smaller than the front wings. -oth pairs of termite wings are similar inshape and si2e and hae ery small eins.

/ermites are diided into three ma:or groups.

R Subterranean or ground1inhabiting termites

R 4rywood /ermites

R 4ampwood /ermites

Subterranean Termites - /hese termites attack wood products in buildings and other wood productsthroughout most of continental 9nited States, but most damage occurs in the warm, southern coastal

regions along the Atlantic +cean and )ulf of Me&ico. At certain seasons of the year, winged males and

females are produced by the termite colony. /hey swarm, mate, lose their wings, and attempt to begin a

new colony in the soil. /ermites build tunnels through earth and around obstructions to get to a source offood 0either sound or decaying wood". /hey also require a constant source of moisture $ usually obtained

from the soil.

/he presence of subterranean termites may be noted by

R the swarming of winged, ant1like insects and the discarded wings obsered after swarming

R earthen shelter tubes built oer masonry or other foundations to a source of wood

R the presence of white workers when termite shelter tubes are broken open

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R the hollowed1out condition of badly infested wood products

Drywood Termites - 4rywood termites are found naturally only in 6awaii, Puerto 7ico, and in a narrow

strip of land e&tending from southern California and /e&as to #lorida and along the Atlantic coast to

=irginia. After swarming, drywood termites enter cracks and creices in dry, sound wood. In e&caatingtheir galleries, they occasionally discharge oal1shaped fecal pellets through temporary openings in the

wood surface. /he ability of the drywood termite to lie in dry wood surface. /he ability of the drywoodtermite to lie in dry wood without direct contact with the soil increases its menace. 6oweer, it

reproduces slowly and does not destroy wood as quickly as the subterranean termite.

Dampwood Termites 6 4ampwood termites are a serious pest along the Pacific Coast. /hey do not require

contact with the soil, but do need wood with a high moisture content.

A#!s

Carpenter ants may be black or red. /hey usually lie in stumps, trees, or logs, but often damage poles ar

structural timbers set in the ground. %leated portions of buildings, such as windowsills and porch

columns, are susceptible to damage. Carpenter ants use wood for shelter not for food. /hey usually prefer

wood that is naturally soft or has been softened by decay. /he galleries are large, smooth and, unlike

those of termites, are free of refuse and powdery wood. Mounds of sawdust indicate their presence.

Bee!)es

Powder Post or Lyctus Beetles 6 Powder post beetles attack both freshly cut and seasoned hardwoods and

softwoods. /hey attack the sapwood of ash, hickory, oak, and other hardwoods.

Adults lay eggs in the wood pores. /he larae burrow through the wood, making tunnels form !@!?1 to

!@!(1inch in diameter, packed with a fine powder. after a laral period 0from a few months to a year, or

longer 1 depending on the species" and a much shorter pupal stage, newly formed adults chew holes

through the wood surface and emerge to lay eggs for another brood. Signs of damage by powder post

beetles are

R small round !@!?T holes in the surface of the wood made by emerging adults, and

R fine powder that falls from the wood.

Anobiid beetles 6 may attack softwoods in damp and poorly entilated spaces beneath buildings.

%liminating the source of moisture will cause the colony to slowly die out.

Roundheaded Borers 6 A longhorn beetle, commonly known as the old house borer, damages seasoned

pine timbers. /he larae bore through the wood. +er many years their tunneling can weaken structural

timbers, framing members, and other wooden parts of buildings. Contrary to its name, the old house borer

most often infests new buildings. It is found in the %astern and )ulf Coast States. 8arae reduce sapwood

to a powdery or sawdustlike consistency. /hey may take seeral years to complete their deelopment.

;hile working in the wood, they make a ticking or gnawing sound. ;hen mature, the adult beetle makes

an oal emergence hold about !@ inch in diameter in the surface of wood.

Flatheaded Borers 6 #latheaded borers infest lie trees as well as recently felled and dead, standing

softwood trees. /hey can cause considerable damage in rustic structures and some manufactured products

by mining into sapwood and heartwood. /ypical damage consists of rather shallow, long, winding

galleries that are packed with fine powder. Adults are often called metallic wood1boring beetles because

of their color. /hey are about *@ inch long, with wing coers usually rough, like bark.

M%ri#e B"rers

%&tensie damage is done to submerged portions of marine pilings, wharf timers, and wooden boats by a

group of animal organisms known collectiely as marine borers. In the 9nited States they are especiallyactie in the warm waters of the Pacific, )ulf, and South Atlantic coasts. 9ntreated timbers can be

destroyed in less than a year.

/he ma:or marine borers are the s+i."r$ and +")%d mollusks 0related to the clams and oysters", and

the cr(s!%ce%# 3"rers 0related to the crabs and lobsters".

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CONTROL OF PESTS THAT DAMAGE WOOD

If wood is to be used where it will be sub:ect to pest attack, it must be protected. /his protection can be

achieed by

R control of moisture content

R use of a wood that is naturally resistant to the pestsR chemical treatment

In addition, mechanical barriers 0such as metal termite shields and caps on pilings, poles and posts" are

sometimes used, but are usually ineffectie.

M"is!(re C"#!r")

/he moisture content of liing trees and the wood products obtained from them may range from about *D

percent to more than (DD percent. Much of this moisture must be remoed for most uses. )reen5 lumber

usually is dried

R to preent stain and decay

R to reduce damage by insects,

R to reduce uncontrolled dimensional change 0shrinkage",

R to reduce weight and increase strength, and

R to prepare the wood for treatment with chemical preseraties.

/he amount of water in wood 0its moisture content" is usually e&pressed as a percentage of its oen dry

weight. /he moisture is measured by

R the oendrying method1a small sample of wood is weighed, dried, and reweighed until it has

reached a constant weight when sub:ected to temperatures of (!( degrees 1 ((D degrees #.

R the electrical method 1 use of a moisture meter that measures moisture by electrical resistance./imber or logs stored for a long time before processing can be protected from fungi and insects by

R keeping the logs submerged in a pond of water

R keeping them under constant water spray

/he water reduces the o&ygen content and temperatures necessary for growth of fungi.

Se%s"#i#/ "r Dr*i#/ 6 /he moisture content of wood is reduced byR air drying in a yard, shed or pre1drier

R drying in a kiln, retort or by radio frequency

/he most efficient and most widely used system is kiln drying. It offers better control of air moement,

temperature and drying rate than air drying. Although kiln drying is more e&pensie in terms of capital

inestment and energy cost, it is much faster and proides more uniform and better quality drying. 9nless

lumber is properly stacked and protected, air drying may result in surface checking, end cracking,

warping, staining and discoloration due to weathering. %en after being well1seasoned, wood may again

reach a moisture leel faorable to pests if e&posed to rain or prolonged high humidity and faorable

temperatures.

S!"r%/e %#d H%#d)i#/

/o aoid pest induced degrading of lumber during storage or handling, you should

RConert logs into lumber as quickly as possible.

R4ry the lumber as quickly as practical, een after pressure treatment with a preseratie chemical, to

preent degrading 0surface checking, and end cracking".

R8ocate air1drying yards and sheds on well1drained sites with good air circulation, and keep the yards

free of weeds.

R Practice good sanitation by remoing debris or rotted wood which seres as source of fungal

infection and insects.

R Inspect stored wood products often. /ermites, for e&ample, may inade untreated stacked lumber if

it remains undisturbed for long periods.R Aoid rough handling of treated wood. Chipping, gouging, or splitting can e&pose unprotected

interior wood and allow attack by decay fungi.

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Use "f N%!(r%))* Resis!%#! W""d

/he sapwood of all natie tree species and the heartwood of most species hae a low natural resistance to

decay. 6oweer, the heartwood of some species is quite resistant. %&amples are the heartwood of old1

growth bald cypress 0limited supply", cedar, redwood, and post oak. /hey are resistant but definitely not

immune to attack by decay fungi and insects. -lack locust and resinous southern pine heartwood, called

fatwood5 or lighterwood5 is also highly resistant to decay. 9nfortunately, some naturally resistant woods

are e&pensie or unaailable in commercial quantities 0i.e. chestnut" or in dimensions needed. -ecause of

high costs for labor and materials, the ariable and undependable resistance of these species should

preclude their use for most high ha2ard construction applications.

C+e$ic%) C"#!r")

/he proper application of chemical preseraties can protect wood from decay and stain fungi, insects

and marine borers, thus prolonging the serice life of wood for many years. /he effectieness of

preseratie treatment depends on the chemical formulation selected, method of application, proportion

of sapwood to heartwood, moisture content of the wood, amount of preseratie retained, depth of

chemical penetration and distribution. Sapwood of most commercial species accepts preseraties muchbetter than heartwood, and softwood species are generally more receptie to impregnation than the

hardwoods. Preseratie treatment by pressure is usually required for most wood products used for

structure and other applications e&posed to high risk of attack by fungi, insects or marine borers.

T*e "f Preser0%!i0es;ood preseraties fall into three broad categoriesR creosote and creosote solutions,

R oilborne preseraties, andR waterborne preseraties.

Creosote and Creosote Solutions6 Creosote, and oily byproduct of making coke from bituminous coal, is

widely used as a preseratie for such products as railroad ties, large timbers, fence posts, poles, and

pilings.

Ad0%#!%/es,

7 to&ic to wood1destroying fungi, insects, and some marine borers,

R low olatility,

R insolubility in water,

R ease of handling and application.Dis%d0%#!%/es,

R dark color,

R strong odor,

R oily, unpaintable surface,

R tendency to bleed or e&ude from the wood surface,R should not be used in homes or other liing areas because of to&ic fumes.

Oilborne Preseraties 6 /hese chemicals are generally insoluble in water. /hey are usually dissoled inpetroleum or other organic solents in order to penetrate wood. 7esearch deelopments hae recently

made aailable oilborne preseraties formulated as water1 in 1oil emulsions or dispersions in water.Ad0%#!%/es,

R to&ic to fungi, insects and mold,

R can be dissoled in oils haing a wide range in iscosity, apor pressure and color,

R low solubility,

R can be glued depending on the diluent or carrier, andR ease of handling and use.

Dis%d0%#!%/es

R can leae an oily, unpaintable surface, depending on the carrier,

R for some applications proides somewhat less physical protection to wood than creosote,

R should not be used in homes or other li

Aqua-Fpe - All Fact Sheets Combined -AIT

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