Fishery Resource and Stock

Takashi Matsuishi At SERD, AIT, Thailand 24Feb-14Mar, 2014

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Resource

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Resource

Things that human do NOT use : things, garbage

Things that human use: resource

Fish: good for use / not good for use

Fishery Resource

Aquatic Animals and Plants

which is good for fishery

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Categories of Resource

Environmental Resource

Non Renewable Resource

Renewable Resource

Environmental Resource

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Water, Air, etc

It circulate as it is.

Usage: Use it without pollution or contamination

Stock

Non-Renewable Resource

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Finite Resource

Resource that does not renew itself at a sufficient rate for

sustainable economic extraction

Oil, Gas , metal ores

Usage: Use it as small as possible to use it longer

Stock

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Renewable Resource

Resource which can fill up again with the passage of time,

either through biological reproduction or other naturally

recurring processes.

Fish, Forest, Crops, Animal husbandry

Usage: Use as much as its reproduction

Stock

Reproduction

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Fishery Resource is a Renewable Resource

Reproducible

Unlimited sustainable Use

May deplete if the usage is wrong

Stock

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Resource and Stock

Resource

a stock or supply of materials or assets

Stock

a supply of goods or materials available for sale or use

(Concise Oxford Dictionary)

CONFUSING

If resource is gathered for use,

it is called Stock.

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The unit of stock

Stock : the population that made same population

dynamics

Species / population / sub-population etc.

Genetic definition: Mendelian population with a same

gene pool（Numachi1974)

Stock

= the object of stock assessment

= the object of fishery management

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Stocks of Walleye Pollock around Japan

Sea of Japan

Catch (2009)

15,000t

Nemuro

Catch (2009)

9,500t

Pacific

Catch (2009)

169,000t

Okhotsuku

Catch (2009)

26,000t

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Walleye Pollock

J-stock P-stock

Cat

ch (

1000t)

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Stock Identification

Morphological Method

Proportion, number of bones

Morphometric / Meristic

Character

Ecological Method

Difference of Spawning

season, Spawning area,

Length composition

Mark-Recapture Method

Confirm the existence of

mixture

Fishery Condition

Consistency of the catch

trends

Genetic Method

Test the samples are from

same Mendelian Population

Genetic difference made by

mutation

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Example of Herring around Hokkaido

Hotta, Matsuishi, Sakano, Kanno, 1999, Nissuishi

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Japanese Sand Smelt

Suzuki, Kobayashi, Matsuishi, Numachi (2000) Nissuishi

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Property of stock

The stock will described in the item

Habitat Area / Fishing Ground

Morphological Features (Body Length, Pictures, Colour)

Ecological Features (Prey, Predator)

Life History (Age at Maturity, Longevity)

Composition

Sex composition

Length composition

Age composition

Sex ratio

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Sex ratio

Ratio of male to female.

Basically it is near One for fish.

If the behaviour of the fish is different in sex, the sex ratio

in a certain fishing ground would not be one

If the growth of the fish is different in sex, the sex ratio in

a certain fishery with length dependent selectivity would

not be one.

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Statistical test of that the sex ratio

Number of male : n1(≥5)

Number of female: n2 (≥5)

If

then the sex ratio is significantly different from one.

(p<0.05, chi-square test)

It is difficult to test that the sex ratio is EQUAL to

one. You may find some difference from one if you

collect more samples.

84.305.0,12

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2

212

0

nn

nn

Age determination

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Methods of Age determination

In captivity

The growth speed may different to the wild situation

Mark- Recapture Method

Can not estimated absolute age

Length Composition

Difficult to determine the older age

Can not estimated absolute age

Age Character

Labourious but accurate and precise

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Age Characteristics

Scale

Otolith

vertebra

Fin ray

Shell

Scale of

Rosy seabass http://www.pref.niigata.jp/norin/chiiki/suikai/joho/dayori/9gou/akamutu.htm

Otolith of Kichiji Rockfish http://hnf.fra.affrc.go.jp/H-jouhou/seika/hnf98008.html

Shell of Abalone http://www.pref.kyoto.jp/kaiyo/kenkyu-koborebanashi-awabinenrei.html

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Age composition

A stock contains many year class or cohorts

Age composition is the relative abundance of the year

classes at a certain year

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Walleye Pollock Pacific Ocean

Biomass displayed by Year Class

http://abchan.job.affrc.go.jp/digests19/details/1913.pdf

Bio

mas

s (1

000t)

Year

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Dominant Year Class

a year class that predominates in the fishery, often

continuing over several years

It appears frequently in Herring, Walleye Pollock etc

It may be difficult to the appearance of the dominant class

just after the appearance when the young fish are not

targeted for fishery.

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Catch at age

Catch at age is the number of fish caught by year by age.

It is not a age composition of the stock, because the catch

at age is the result of fishery with selectivity

Age based population estimation method (eg. VPA) uses

Catch at Age

Catch at Age is often calculated from Length

Composition and Age length Key

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Length Composition

Length composition / Length frequency distribution

In Stock / In Catch fish

It reflects stock status

If exploitation is too strong, the frequency is moved to small side

If dominant year class is appeared, the length composition has a peak

Peaks sometimes represents year class

In younger age, it is clear

In older age, it is not clear because of the slow growth

In Crastacetean, the peak reflects the molting age

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0

500

1000

1500

2000

2500

8 10 12 14 16 18 20 22 24 26 28 30 32 34 36

Cat

ch in

Num

ber

Body Length

Age Composition of Yellowback seabream Dentex tumifrons

Akamine(2007) P5

How to measure the body length

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Fish Measurement Board

Fish Length

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Age – Length Key (ALK)

Key matrix to convert catch at length to catch at age

Procedure

1. Making ALK

Get sample

Measure length, and aging (e.g. 20 fish for each length class)

Make ALK

2. Length Composition

Get many measurement (e.g. 1000) and get length composition

Estimate total # fish caught (Total Catch / average weight)

Make catch at length table from length comp. and total # catch

3. Calculate Catch at Age by using ALK

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Simple example of ALK

Virtual data

BL (mm)

ALK

1 2 3

[80-100) 100% 0 0

[100-120) 20% 70% 10%

[120-140) 0 20% 80%

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Catch at Length

BL (mm)

Length Composition

Catch at Length

[80-100) 30% 3,000

[100-120) 50% 5,000

[120-140) 20% 2,000

合計 100% 10,000

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Calculation of catch at age

BL(mm) Age

Total 1 2 3

[80-100) ALK 100% 0 0 100%

#fish 3000 0 0 3,000

[100-120) ALK 20% 70% 10% 100%

#fish 1000 3500 500 5,000

[120-140) ALK 0 20% 80% 100%

#fish 0 400 1600 2,000

Total 4000 3900 2100 10,000

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Size Category Composition

Size Category Composition: a kind of size class decided in

market or middleman to classify the fish size for sale

Example: Size Category of Sea Bream in Nagasaki, Japan

You can convert the size category to age composition if

you make the age category key

3S 2S S M L

-15cm 15-20 20-30 30-40 40-

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Summary

Fishery Resource is Aquatic Animals and Plants which is good for fishery

Fishery resource is a renewable resource.

Stock is an unit of fishery management.

Various method of stock identification

A stock has its sex, length and age composition.

Chi-square test is used for test the difference of sex ratio.

Age determination is conducted from various age character (scale, otolith, shell etc)

Length composition will be converted to age composition by using ALK