BI 2060 V091 IMPACTS FROM AQUACULTURE Kaiser part three; Impacts Chapter 13: Aquaculture...

BI 2060 V09 1

IMPACTS FROM AQUACULTURE

Kaiser part three; ImpactsChapter 13: Aquaculture

Simultaneously with a stagnation or reduction in the output from fisheries on wild fish stocks in recent decades (from reasons treated in chapter 12), theproduction of marine species in aquaculture (mariculture) has increased.

While this may be an answer to the increasing demand for protein worldwide,it has also created new problems for marine ecosystemes and natural stocksof resource species. In Europe and North America the problems have first andforemost been connected with the production of anadromous salmonids (Atlanticsalmon and trout, and several species of Pacific salmonids). Shortly, the problemsmay be grouped in:

1. Problems connected with escapees and their genetic effects on wild stocks2. Problems connected with escape and competition with wild stocks3. Problems connected with transfer of disease and parasites to wild stocks4. Problems connected with the use of marine fish as feed for farmed fish5. Problems connected with local environmental effects of the farming industry

These aspects are also enlightened by other lecturers in the BI2060 course.

BI 2060 V09 2

Kaiser part three; ImpactsAQUACULTURE

Note almost linear growth 1950-2000

BI 2060 V09 3


I the year 2000 the world production in aquaculture (including plants) was ca one third of the outtake from natural stocks. This proportion has increased in the last decades.

The clearly biggest producer is China.Other asian countries are also well represen-ted on the list.

Aquatic plants included

BI 2060 V09 4


The number of persons employed in fisheries and aquaculture have been more than doubled on a world basis since 1970. Both the total increase and the rate ofincrease have been similar in the two industries.

Numbers of persons employed doubled since 1970

BI 2060 V09 5


The proportionfrom finfish of thetotal aquacultureproduction has increased muchfaster than othergroups since 1970.

BI 2060 V09 6


NB! Greenland has a smallhuman population!

BI 2060 V09 7


HOW IS SEAFOOD FROM AQUACULTUREPRODUCED?

BI 2060 V09 8


Below, a typical seawater pen forfish production. Excess feed sinks tothe bottom under the pen and create a milieu of decomposing materialsif not brought away by water currents.

Seawater pens are exposedto strong natural forces and have therefore been placedin relatively sheltered areas.However, the locations mustalso allow a sufficient waterexchange in the pens. Pen wreckage and fish escapesare not uncommon problems.

BI 2060 V09 9

Kaiser part three; Impacts AQUACULTURE

Pen wreckage and excess feed problems in coastal waters have resulted in researchand development of ocean-based fish farming plants. Pilot plants have been dispatchedboth in the North Atlantic and in the Gulf of Mexico. The idea is to avoid local pollutionby excess feed, and to reduce the wave strain by lowering the pens below the surface.

Ocean pens

BI 2060 V09 10


Landbased fishfarms often use recirculated water. Among the advantagesare better insurance against poisonous algae blooms, bad weather and predators (like seabirds and marine mammals).

BI 2060 V09 11


Fish produced in tanks and pens often show physical signs of their captive life. A very common sign is fin erosion due to small living space and constant wear by contact with the tank or pen walls.

The high density of individuals makes way for infections and contagious diseases.

Oxygen deficiency during critical embryonic development stages have been shown to cause physical deformations (skull- and spine deformations).

In Atlantic salmon, weared and rounded fins is one of the criteria for identification of escaped farmed fish.

Solea solea (sole) with damaged tail fins caused by attempts to bury themselves on the tank bottom.

BI 2060 V09 12


Java has an extensive production of shrimps. The cultivation takes place insmall ponds in glennes cleared by deforestation of the coastline. Similar conditions are found other places in the world. Mangrove forests have also been removed to secure space for shrimp production (with bad results inall aspects).

Air photo of Javanese coastline

BI 2060 V09 13


(a) Dried sea horse (a small fish) is a highly appreciated medicine in China. Under the danger of overexploiting the natural stocks, aquaculture production of seahorses has become a lucrative business e.g. in New Zealand. (b) Similar conditions are valid for popular aquarium fishes (here: Clown fish, which naturally lives on coral reefs and was threatened by over-exploitation).

Trading dried sea horse in ChinaClown fish inaquarium

BI 2060 V09 14


PRODUCTION OF MOLLUSCS AND SHELLFISH

In Norway, blue mussle production based on natural settling on hanging ropes has been an interesting enterprise for many local grunders. The professional skills did not always match the enthusiasm, and a lot of bankruptsies were seen.Poisoning by algae, and seabird predation have caused substantial problems in many areas along the Norwegian coast.

Blue mussel is easy to cultivate. Production is based on natural settlingand natural feed in form of plankton.

Productionplants found along most ofthe coast.

BI 2060 V09 15


Aquaculture production of crustaceans has no long tradition in Norway. The typeof shrimp production which are so successful in asia is for natural reasons not soviable and competitive i Norway. Nevertheless; in the last decades there has beensome activity in production of species with a particularly good market price (lobster).

As usual, when low production costs and high market value are the incentives foran industry, experiments with imported species have also been tried for lobster (i.e. american lobster in Norway). The american lobster show better growth than the European, but is also more aggressive and will have some advantages if allowed to compete for habitats.

American lobster imported for intensive production in containment has escaped from captivity, and has been observed at large on several locations along the coast. The danger for the European lobster is a reality.

PRODUCTION OF MOLLUSCS AND SHELLFISH

BI 2060 V09 16


WHAT EFFECTS DO INTENSIVE PRODUCTION SYSTEMS FOR SEAFOOD HAVE ON NATURAL

ECOSYSTEMS?

BI 2060 V09 17


Intensive production of mussles on hanging ropes often leads to organic stress at the sea bottom below the plant. As usual with this type of pollution, this may often lead to a dominance of a few opportunistic species (here the polychaete Schistomeringos loveni),and a corresponding reduction of the species diversity. Even if the absolute effect may vary with the general richness of nutrition, the difference between the bottom right belowthe ropes and the adjacent areas is very clear (cf graphs above).

Bunnforurensing under skjelloppdrett-redskap

BI 2060 V09 18


Problems connected with escapes and genetic Problems connected with escapes and genetic introgression into natural populationsintrogression into natural populations

Species under domestication will inevitably undergo genetic changes, both intended and unintended, while in captivity.

Intended genetic changes occur when stocks are bred to enhance certain genetictraits which are advantageous for e.g. high production and captive life.

Unintended genetic changes are due to characteristics of the captive environmentitself. Also, the usually small captive populations are much more unstable with respect to gene frequencies and will rapidly loose genetic variability.

Both types of genetic change will probability mean disadvantages to wild populations if the escaped specimens are allowed to interbreed with wild relatives. It has been documented that such introgression is taking place in Atlantic salmon in Norway.The unwanted effects will increase with the number of generations the fish has been under domestication, and with the magnitude of the introgression (i.e. the number of escapees per generation or in total).

BI 2060 V09 19


Basic population geneticsBasic population genetics

Hardy-Weinbergs lawHardy-Weinbergs law says that in a statistical ideal population of diploid individuals,the proportion of the genotypes for single-locus traits are determined by the allele frequencies at the locus according to the binomial formula. Such a population is said to be in Hardy-Weinberg equilibrium. Both allele frequencies and genotype proportionsare then stable over generations. If the population for some reason has been brought out of H-W equilibrium, one generation of panmixia (random mating) is enough to reconstruct the H-W equilibrium.

The H-W law rests on 5 specific assumptionsThe H-W law rests on 5 specific assumptions:1. Panmixia (random mating)2. No mutation (can be relaxed in short term)3. No random genetic drift (i.e. very large population) 4. No gene flow from other populations (with different allele frequencies)5. No selection (neither natural nor artificial)

BI 2060 V09 20


FF SF SS N qF qS 2

Obs. 35 50 15 100 .60 .40 0.677

Exp. (36.0) (48.0) (16.0) 100.0

This is how to test if a population is in Hardy-Weinberg equilibrium( kji-kvadrat Goodness-of-fit test )

HW genotype proportions acc. tothe binomial formula:

(f+s)2 = f2+ 2fs + s2

where f and s are frequencies ofallele F and S, respectively, andthe genotypes are FF, SF og SS.NB! These are frequencies; to get numbers, multiply by N.

Suppose a population of diploid organismsand a locus with two alleles F and S, which can combine into genotypes FF, SF and SS. We draw a sample of N=100, and count the numbers of the different genotypes (table below).

Expected numbers of the three genotypes under H-W equilibrium are found by putting the estimated allele frequencies in the sample into the binomial formula. The number of degrees of freedom (DF) in this test is the number of different genotypes minus the number of different alleles (i.e. DF = 3 – 2 = 1). The calculated chi-squared with DF=1 corresponds to P = 0.414 (not significant) as looked up in a chi-squared table.

BI 2060 V09 21


Looking closer on the underlying assumptions for the H-W law:1. Panmixia (random mating)2. No mutation (can be relaxed in short term)3. No random genetic drift (i.e. infinitely large population) 4. No gene flow from other populations (with different allele frequencies)5. No selection (neither natural nor artificial)

No natural population fullfills all these assumptions, but some may come so close that the error sources are small in practical use of the theorem.

Populations in captivity, on the other hand, often deviate rather strongly fromthese assumptions, particularly numbers 1, 3, and 5 in the box above. This means that allele- and genotype frequencies can change over few generations. This has been documented e.g. for farmed salmon in Norway. Even if the original brood stockwas taken from wild stocks (9-10 generations ago), there are today clear changes in allele frequencies and reduced genetic variability compared to wild salmon. At the same time, selection programs for certain traits such as growth, sexual maturation and behaviour have been undertaken and changed the gene pool accordingly.

BI 2060 V09 22

Kaiser part three; Impacts AQUACULTURE

The introgression situation in Atlantic salmon in Norway

A rule of thumb in quantitative genetics says that the offspring will perform approx. at the average of the parents phenotypic value for traits with a reasonable degree of heritability.

Hence, if escaped farmed salmon interbreed with wild relatives, the offspring from each crossing will peform intermediate between farmed fish and wild fish. This will apply to traits like growth, age at smoltification and -maturation, aggressivity and other traits with known (and quite high; 0.3-0.5) heritability. The inheritance of genetically based behaviour traits do not differ from that of other quantitative traits.

Because wild salmon stocks probably, during many generations of natural selection, have been genetically adapted to their home rivers, hybrid offspring will probably be inferiour to natives with respect to fitness in a specific habitat. Natural selection will act to "clean up" the stock, but as long as the stock is not on or near its K (carrying capacity), the introgression will tend to reduce the total fitness and productivity of the native salmon stock.

If the introgression is acute and massive, and/or is repeated over many generations, it will affect the evolutionary potensial of the Atlantic salmon as a species. Norway has a particular international responsibility for management of salmon because Norwegian rivers hold, by far, the largest part of th total gene reservoir (gene pool) of the Atlantic salmon.

BI 2060 V09 23


Question:Question: How large genetic effect can be expected in a situation where escapedfarmed fish interbreed with wild populations?

Answer: Answer: It will depend on the actual situation (case-by-case). The determiningfactors will be:

1. Proportion of farmed fish immigrants breeding locally each generation2. Number of generations with such immigrations impact 3. The genetic basis for the trait under change (number of genes affecting the trait)4. If and how strongly the trait is selected for or against in the farmed population 5. The initial genetic difference for the trait between farmed and wild fish6. The strength of local natural selection affecting the trait under study

To enlighten the effect of the various factors, one can perform ”what-if” analysesby means of computer simulations. Starting with the simplest situation; a single-locus polymorphism with two alleles A and B in a diploid organism, one can follow the change in allele frequencies over generations using the software programPopG.exe by Joe Felsenstein, or P14G.exe by J. Mork (see next slide).

BI 2060 V09 24


Simulation of evolution (change of allele frequencies) in a population by meansof the interactive Windows program PopG.exe by Joe Felsenstein (sample screen dump).

Example of PopG simulation

BI 2060 V09 25


Screen dump of simulated evolution (change of allele frequencies) in a population by means of the interactive DOS program P14g.exe by J. Mork, NTNU. (Sample screen dump).

("Screen-dump" fra dataprogrammet P14.exe (J. Mork, TBS). X-akse: antall generasjoner, Y-akse: frekvens allel F). Kurven viser10 uavhengige simuleringer av alleltap som følge av disruptiv seleksjon (heterozygotens er lavere enn homozygotenes).Simuleringen er gjort med genetisk drift 'innkoblet'.

Example of P14g.exe simulation

BI 2060 V09 26


Assume that we are studying a local stock of Atlantic salmon with an effective population size (Ne) of 1000 individuals, which receives escaped farmed salmon each generation. The farmed salmon origins from the wild stock, but genetic drift has lead to allele frequency differences between the farmed and the wild fish over time, because the Ne of the farmed brood stock has been only 10 individuals in 10 succeeding generations.

First, we will look at what is expected to happen over time in the two groups; immigrant (donor) and resident (recipient), respectively, as an effect of random genetic drift. Thereafter, given the new genetic characteristics of the two groups, we will look at the effect over time of an immigration of escaped farmed fish each generation on the wild population’s allele frequencies.

Simulation of an introgression of escaped farmed fish into a wild stock

First: The effect of random genetic drift in captivity and in the wild

BI 2060 V09 27


Genetic drift in the captive stock (the immigrant). Assume that the culture has lasted for 10 generations, and that the Ne has been 10 individuals each generation. The stock origined with a wild stock with the same genetic characteristics as the one playing the role as resident (recipient) in the following simulations. The change in farmed fish allele frequencies can be simulated (below are shown the outcome from ten independent simulations).

Ten independent simulations with the given parametres resulted in the loss of one of the two alleles in three out ten cases (33%)

BI 2060 V09 28


Genetic drift in the wild salmon population (recipient). Assume an effective size (Ne) of 1000 individuals. During 10 generations the allele frequencies will be affected by genetic drift, but to a much lesser degree than in the donor population because of the much larger Ne. Below are shown outcomes from ten independent simulations.

10 independent simulationsshow that the changes in allele frequencies due to random genetic drift over 10 generations are consider-ably more moderate in the large wild stock than in the small captive stock. In the follwowing simulations the allele frequencies in the wild stock will, for sake of simplicity, be regarded as constant.

BI 2060 V09 29

Kaiser part three; Impacts GENETIC IMPACT FROM AQUACULTURE

From the 10 outcomes on previous slide we use, again for sake of simplicity, one of the three outcomes where one of the alleles was lost, i.e. qF=0.

After 10 generations with genetic drift

qF qS N (number)

Wild 0.500 0.500 900

Farmed 0.000 1.000 100

If we put these parametres into the program P14g.exe, and simulates a continued evolution in many generations, we see that the escaped farmed fish eventually will change the wild population in its own direction. During only 10 generations the frequency of the F allele will have changed from 0.50 to 0.25.If this regime continues, also the wild stock will loose its F allele (i.e. half of its total genetic variability) in about 30 generations . The graph to the right shows the outcome of 5 simulations. They gave more or less the same end result.

Genetic effects of immigration(without local selection)

Effect of immigrations(no local selection)

BI 2060 V09 30


Start situation

qF qS N (number)

Wild 0.500 0.500 900

Farmed 0.000 1.000 100

We insert the farmed population’s Ne and allele frequencies, and simulates a sitiation with 10% farmed fish immigration into the wild population each generation (see table at left for model input).

A simulation of this scenario with the P14g.exe program showed that after 40 generations, the continuous immigration of farmed fish (which lacked the F allele) had resulted in the loss of this allele also in the wild population (cf graph to the right).

In this simulation, a ”self-cleaning” local selection force which favoured the F allel in the wild stock was included, with fitness coefficients shown in the graph heading (graph).

Genetic effects of immigration(with local selection)

Effect of immigration(with local selection)

BI 2060 V09 31


Genetic effects of introgression (with or without local selection)

Simulations like those shown above leave little doubt that an introgression of farmed fish into wild populations may result in clear genetic changes. Such a one-way geneflow from a donor to a recipient will have as result that:

• The recipient will be more and more like the donor genetically• If the donor is genetically altered and has lost genetic variability, this will eventually also apply to the recipient population • If such regimes goes on for extended time, the genetic diversity and evolutionary potential of the wild stocks will be impaired.• Selection will have a certain self-cleaning effect on the wild stock, but selection can only work through increased mortality and therefore lead to reduced natural productivity. If the farmed fish are genetically modified organisms, they will transfer their genetic material to the wild stocks according to the same genetic principles.The consequences of this for natural populations, species and ecosystems can be very unfortunate, and international nature management authorities generally agree that such situations must be avoided.

BI 2060 V09 32

Kaiser part three; Impacts

NON-GENETIC IMPACTS FROM AQUACULTURE

Escaped farmed fish compete with wild fish on spawning grounds• It is known from Atlantic salmon in Norway that farmed, fish because of growth advantages, may outcompete their smaller wild relatives in the fight for spawning redds in the rivers.

The hybrid offspring may be physically less fit for life in nature• The offspring from introgression into wild stocks can, because of larger body size, be unable to ascend small rivers. In this way they may represent ”useless” production from the human point of view.

In Norway, fish farms are "hatching sites" for salmon lice• When the wild salmon return from the sea phase, they are exposed to an unnatural high consentration of sea lice in coastal waters. Not being treated for the problem, they will struggle with infections which can be decimating for the wild stocks.

BI 2060 V09 33

Kaiser part three; Impacts

NON-GENETIC IMPACT FROMAQUACULTURE

"CONVERSION EFFICIENCY"Salmon farming has been a huge economic success in Norway. Introductory problems, mostly i form of disease, have found their solutions, and some believe that this industry has an almost unlimited growth potential.

However; ther is one very apparent limitation to growth which cannot be overlooked: In today’s situation the feed used to produce salmon is taken from other marine resources (in form of fish meal from tobis, herring, capelin and other industry species). The problem is that these resource species themselves are limited in size. Actually, some of them show clear signs of overexploitation, and may therefore give limited output in the relatively near future.

It has often been held that todays’ salmon industry is not sustainable: It is energetically inefficient ethically bad to use species high up in the food chain as feed for salmon; if salmon farming shall be continuously growing, the industry must change to use feed species from lower trophic levels in the food chain, that being plants or animals.

BI 2060 V09 34


Simulation of the introgression of a genetically modified organism (GMO) into a natural population

In the development of genetically modified organisms, genes are spliced intothe individuals’ genome in order to enhance specific traits (e.g. growth rate).

During the process, marker genes are used to track the incorporation. For this, it has been common to use a gene that gives resistence towards antibiotics or pesticides, and hence the incorporation of the new gene can easily be traced by common bacteriological techniques (inoculation on treated agar gels).

If such a GMO is allowed to introgress into natural populations, it can lead to an uncontrolled spreading of antibiotic resistance in nature by horizontal gene transformation.

The entire process; escape rates, gene flow, local selection and introgression rates can be simulated with software like that demonstrated on this course (PopG.exe and P14g.exe). NEXT SLIDE>

BI 2060 V09 35


Simulation of introgression of a GMO into natural populationAssume a GMO which ”leaks” one individual from its containment each generation, and a natural population of Ne=1000 which is the recipient of such leakages.

The simulation on the graph to the right shows the introgression when the GMO is given a 20% better fitness than wild relatives relative to planticides, due to its resistence against drugs. Typically, the frequency of the GMO gene increased from zero to fixation in the wild population in only ~50 generations.

BI 2060 V09 36


BI 2060 V091 IMPACTS FROM AQUACULTURE Kaiser part three; Impacts Chapter 13: Aquaculture...

Documents

Transcript of BI 2060 V091 IMPACTS FROM AQUACULTURE Kaiser part three; Impacts Chapter 13: Aquaculture...