IMPACTS

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IMPACTS FROM AQUACULTURE
Kaiser part three Impacts Chapter 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), the production of marine species in
aquaculture (mariculture) has increased. While
this has been said to be the answer to the
increasing demand for protein worldwide, it has
created new problems for marine ecosystemes and
natural stocks of resource species. In Europe and
North America the problems have first
and foremost been connected with the production
of anadromous salmonids (Atlantic salmon and
trout, and several species of Pacific salmonids).
Shortly, the problems may be grouped in 1.
Problems connected with escapees and their
genetic effects on wild stocks 2. Problems
connected with escape and competition with wild
stocks 3. Problems connected with transfer of
disease and parasites to wild stocks 4. Problems
connected with the use of marine fish as feed for
farmed fish 5. Problems connected with local
environmental effects of the farming industry
These aspects are also enlightened by other
lecturers in the BI2060 course.
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Note almost linear growth 1950-2000
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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
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Numbers of persons employed doubled since 1970
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 of increase have been similar in the
two industries.
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The proportion from finfish of the total
aquaculture production has increased much faster
than other groups since 1970.
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NB! Greenland has a small human population!
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HOW IS SEAFOOD FROM AQUACULTURE PRODUCED?
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Below, a typical seawater pen for fish
production. Excess feed sinks to the bottom under
the pen and create a milieu of decomposing
materials if not brought away by water currents.
Seawater pens are exposed to strong natural
forces and have therefore been placed in
relatively sheltered areas. However, the
locations must also allow a sufficient
water exchange in the pens. Pen wreckage and
fish escapes are not uncommon problems.
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Ocean pens
Pen wreckage and excess feed problems in coastal
waters have resulted in research and development
of ocean-based fish farming plants. Pilot plants
have been dispatched both in the North Atlantic
and in the Gulf of Mexico. The idea is to avoid
local pollution by excess feed, and to reduce the
wave strain by lowering the pens below the
surface.
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Landbased fishfarms often use recirculated water.
Among the advantages are better insurance against
poisonous algae blooms, bad weather and
predators (like seabirds and marine mammals).
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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.
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Air photo of Javanese coastline
Java has an extensive production of shrimps. The
cultivation takes place in small 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 in all aspects).
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AQUACULTURE
Trading dried sea horse in China
Clown fish in aquarium
(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).
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AQUACULTURE
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.
Production plants found along most of the coast.
Blue mussel is easy to cultivate. Production is
based on natural settling and natural feed in
form of plankton.
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PRODUCTION OF MOLLUSCS AND SHELLFISH
Aquaculture production of crustaceans has no long
tradition in Norway. The type of shrimp
production which are so successful in asia is for
natural reasons not so viable and competitive i
Norway. Nevertheless in the last decades there
has been some 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 for an
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.
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WHAT EFFECTS DO INTENSIVE PRODUCTION SYSTEMS FOR
SEAFOOD HAVE ON NATURAL ECOSYSTEMS?
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Bottom pollution below mussle plants
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 below the ropes and the adjacent
areas is very clear (cf graphs above).
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NON-GENETIC IMPACT FROMA QUACULTURE
"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 todays 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
and unethical 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.
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GENETIC IMPACTS FROM AQUACULTURE
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Problems connected with escapes and genetic
introgression 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 genetic traits which are advantageous for
e.g. high production and captive
life. Unintended genetic changes are due to
characteristics of the captive environment itself.
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).
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Basic population genetics
Hardy-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 proportions are 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
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)
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HW genotype proportions acc. to the binomial
formula (fs)2 f2 2fs s2 where f and s
are frequencies of allele F and S, respectively,
and the genotypes are FF, SF og SS. NB! These are
frequencies to get numbers, multiply by N.
Suppose a population of diploid organisms and a
locus with two alleles F and S, which can
combine into genotypes FF, SF and SS. We draw a
sample of N100, and count the numbers of the
different genotypes (table below).
This is how to test if a population is in
Hardy-Weinberg equilibrium ( kji-kvadrat
Goodness-of-fit test )
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
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 DF1 corresponds to P 0.414
(not significant) as looked up in a chi-squared
table.
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Looking once more at 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
errors are small in practical use of the
theorem. Populations in captivity, on the other
hand, often deviate rather strongly from these
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 stock was 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.
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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.
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• Question How large genetic effect can be
  expected in a situation where escaped
• farmed fish interbreed with wild populations?
• Answer It will depend on the actual situation
  (case-by-case). The determining
• factors will be
• Proportion of farmed fish immigrants breeding
  locally each generation
• Number of generations with such immigrations
  impact
• If and how strongly the trait is selected for
  or against in the farmed population
• The initial genetic difference for the trait
  between farmed and wild fish
• The strength of local natural selection
  affecting the trait under study

To enlighten the effect of the various factors,
one can perform what-if analyses by 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 program PopG.exe
by Joe Felsenstein, or P14G.exe by J. Mork (see
next slide).
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Simulation of evolution (change of allele
frequencies) in a population by means of the
interactive Windows program PopG.exe by Joe
Felsenstein (sample screen dump).
Simulation software 1
Example of PopG simulation
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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).
Simulation software 2
Example of P14g.exe simulation
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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
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 populations allele
frequencies.
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Simulation model
A wild population contains 1000 specimens From
the wild population, 10 individuals is sampled to
form a captive stock 10 generations goes
by The captive stock starts to give off
escapees to the wild population, amounting to 10
of the wild population each generation Question
1 How different have the two populations become
in 10 generations? Question 2 What happens
genetically during this introgression? Question
3 How efficient is natural selection in
hampering the genetic changes?
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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 (30)
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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 simulations show 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.
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GENETIC IMPACT FROM AQUACULTURE
Genetic effects of immigration (without local
selection)
After 10 generations with genetic drift After 10 generations with genetic drift After 10 generations with genetic drift After 10 generations with genetic drift
qF qS N (number)
Wild 0.500 0.500 900
Farmed 0.000 1.000 100
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.
qF0.
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.
Effect of immigrations (no local selection)
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GENETIC IMPACT FROM AQUACULTURE
Genetic effects of immigration (with local
selection)
We insert the farmed populations Ne and allele
frequencies, and simulates a situation with 10
farmed fish immigration into the wild population
each generation (see table at left for model
input).
Start situation Start situation Start situation Start situation
qF qS N (number)
Wild 0.500 0.500 900
Farmed 0.000 1.000 100
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).
Effect of immigration (with local selection)
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GENETIC IMPACT FROM AQUACULTURE
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.

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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 less nable to ascend small
  rivers, and 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.

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GENETICALLY MODIFIED ORGANISMS (GMO)
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Simulation of the introgression of a genetically
modified organism (GMO) into a natural population
In the development of genetically modified
organisms, genes are spliced into the
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
transmission. 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 SLIDEgt
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Simulation model
A wild population contains 1000 specimens A
contained stock of genetically modified organisms
of the same species as the wild population gives
off 1 individual per generation to the wild
population. Due to the genetic modification, the
escapees have some 20 fitness advantage compared
to wild specimens due to, e.g. better disease
resistence. Question What is the fate of the
modified gene in the wild? Will it disappear or
proliferate?
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Simulation of introgression of a GMO into natural
population
Assume a GMO which leaks one individual from
its containment each generation, and a natural
population of Ne1000 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.
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END OF IMPACTS FROM AQUACULTURE