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Did The North Atlantic Fisheries Collapse Due To Fisheries-induced Evolution?


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Author Topic: Did The North Atlantic Fisheries Collapse Due To Fisheries-induced Evolution?  (Read 264 times)
Bianca
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« on: June 04, 2009, 08:07:15 am »








The Atlantic cod has, for many centuries, sustained major fisheries on both sides of the Atlantic. However, the North American fisheries have now largely collapsed.

A new article provides insights into possible mechanisms of the collapse of fisheries, due to fisheries-induced evolution.



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« Last Edit: June 04, 2009, 08:09:56 am by Bianca » Report Spam   Logged

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Bianca
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« Reply #1 on: June 04, 2009, 08:12:37 am »










                   Did The North Atlantic Fisheries Collapse Due To Fisheries-induced Evolution?






ScienceDaily
(May 26, 2009)

— The Atlantic cod has, for many centuries, sustained major fisheries on both sides of the Atlantic.

However, the North American fisheries have now largely collapsed. A new article from scientists at the University of Iceland and Marine Research Institute in Reykjavik provides insights into possible mechanisms of the collapse of fisheries, due to fisheries-induced evolution.

Cod fishing is of highest intensity in shallow water in Iceland and it selects against genotypes of cod adapted to shallow water. The new PLoS One article reports a significant difference in Darwinian fitness (relative survival rate) between shallow-water and deep-water adapted cod. The shallow-water fish have only 8% of the fitness of deep-water fish. This difference can lead to rapid elimination of shallow-water fish in only a few generations with drastic effects on the population and the fishery.

Using molecular population genetics, the authors reports steep changes in the frequency of genotypes at a single genetic locus with depth: a gradient of nearly one half percent drop in frequency per meter. The genotypes at the locus are directly related to behavioral types that select deep vs shallow water habitat by genotype.

"There is no direct targeting of specific genotypes. Instead the intense selection results from the interaction of fish that select their habitat by genotype and fishermen choosing to fish in the preferred habitat of the fish," said Einar Arnason, professor of population genetics and lead author.

In addition to the molecular results, the study also demonstrates that the length and age at which the fish become mature have decreased. So-called "probabilistic maturation reaction norms" show that the length at which there is a 50% probability of becoming mature, has, on average, decreased nearly one centimeter per year. The changes observed very likely are evolutionary genetic changes and not simply plastic phenotypic responses to the environment. They are comparable to changes that preceded the collapse of northern cod at Newfoundland.

This finding further supports the hypothesis of an imminent collapse of Icelandic cod due to the intense fisheries-induced selection. The cod fishery at Iceland is one of the world's few remaining cod fisheries. The study appears to have met all criteria for concern that this fishery is threatened.

"Can anything be done to avert collapse?" the authors ask. A strategy that would remove selection pressures against shallow-water adapted fish would seem to be the answer. The authors speculate that immediate establishment of large no-take reserves might be the right strategy by relieving selection pressures on all genotypes.

The findings provide general lessons for population and conservation genetics that anthropogenic changes in habitat can lead to intense selection even if the mortality is non-selective in the habitat in which it occurs. The study highlights the importance of applying Darwinian principles and evolutionary thinking to fisheries and conservation science.

The study was funded by grants from the Icelandic Research Fund and resources from the Marine Research Institute and the University of Iceland. Specimens were obtained during Marine Research Institute Surveys. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.


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Journal reference:

1.Árnason et al. Intense Habitat-Specific Fisheries-Induced Selection at the Molecular Pan I Locus Predicts Imminent Collapse of a Major Cod Fishery. PLoS ONE, 2009; 4 (5): e5529 DOI: 10.1371/journal.pone.0005529
Adapted from materials provided by Public Library of Science, via EurekAlert!, a service of AAAS.
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 MLA Public Library of Science (2009, May 26). Did The North Atlantic Fisheries Collapse Due To Fisheries-induced Evolution?. ScienceDaily. Retrieved June 4, 2009, from



http://www.sciencedaily.com­ /releases/2009/05/090526202809.htm
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Bianca
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« Reply #2 on: June 04, 2009, 08:16:01 am »











                                    Excessive Bycatch Of Cod Undermines Moratorium:



                          Cod Bycatch Was At Least 70 Per Cent Higher Than Target Levels






ScienceDaily
(May 7, 2009)

— Cod bycatch was at least 70 per cent higher than target levels on the southern Grand Banks near Canada, holding back recovery of one of the world’s best known fisheries following its spectacular collapse and closure in the early 1990s.

Information provided to WWF-Canada also said that European Union boats were responsible for the largest proportion of the overrun in bycatch.

Excessive bycatch of cod has undermined a moratorium imposed in 1994, peaking in 2003, when bycatch amounts were estimated to be over 80 per cent of the remaining cod stock.

WWF pushed for a 2008 cod recovery strategy that included setting a bycatch reduction target of 40 per cent for southern Grand Banks cod at the September 2007 annual meeting of the Northwest Atlantic Fisheries Organization (NAFO).

The 40 per cent target was equivalent to a fishing mortality of 420 tonnes, estimated to be the maximum the population could withstand to still have some chance of recovery. Unofficial 2008 fishing year statistics however show a total of 713 tonnes of bycatch, with EU boats taking 444 tonnes – with these figures taking no account of what is believed to be considerable amounts of misreporting and illegal fishing.

Before the results of the 2008 fishing year became available, NAFO stated in a press release that they had “adopted a resolution to implement its commitment to an ecosystem-based fisheries management approach”, an approach contradicted by NAFO increasing the total allowable catches (TACs) for fisheries with high levels of cod bycatch. Evidence of an increase in young cod in the population was also ignored.

“Cod and other fish stocks can never recover as long as NAFO refuses to see the urgency of the bycatch problem and acknowledge that voluntary measures are not working,” said Dr. Robert Rangeley, Vice President Atlantic, WWF-Canada. “If NAFO’s Scientific Council starts working on solutions at their June meeting then it will be the responsibility of the Fisheries Commission, in September, to impose strict management measures that will give cod recovery a chance.”

WWF is now calling on NAFO to take steps that will benefit the ecosystem health and the fisheries of the Grand Banks. This is entirely consistent with the Ecosystem management approach adopted in the newly revised NAFO Convention.

Measures should include the adoption of an effective recovery plan for southern Grand Banks cod that sets long-term recovery goals, immediate bycatch reduction targets, gear-based solutions and closures to protect spawning and nursery areas. The adopted measures will need to be backed by monitoring and enforcement, to be effective.

Defining and Estimating Global Marine Fisheries Bycatch, a paper co-authored by WWF for the journal Marine Policy, recently estimated that global bycatch – defined as unused and unmanaged catch – constitutes more than 40 per cent of the global reported catch.


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Adapted from materials provided by World Wildlife Fund.
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 MLA World Wildlife Fund (2009, May 7). Excessive Bycatch Of Cod Undermines Moratorium: Cod Bycatch Was At Least 70 Per Cent Higher Than Target Levels. ScienceDaily. Retrieved June 4, 2009, from



 http://www.sciencedaily.com­ /releases/2009/05/090502102740.htm
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« Reply #3 on: June 04, 2009, 08:21:26 am »










                                             Cod In A Sweat: Some Like It Hot!






ScienceDaily
(Apr. 29, 2006)

— Scientists at CEFAS (UK) have found that the migration pattern of wild cod is much less restricted by environmental temperature than laboratory studies suggest.

Previously, research in the lab indicated that the preferred temperature range of cod was between 11-15ºC. However scientists following movements of wild cod equipped with electronic tags that record depth and temperature have found that whilst some fish prefer deeper cooler waters, others tagged at the same time prefer to swim in shallower habitats in the Southern North Sea where summer temperatures are consistently above 17ºC. Dr Julian Metcalfe presented the latest results of the EU-funded CODYSSEY project at the Annual Meeting for the Society for Experimental Biology on April 3.

"We have found that cod in the northeast Atlantic repeatedly experience abrupt temperature changes of up to 8ºC, suggesting that temperature may not be so crucial in constraining the movements and distribution of adult cod", explains Dr Metcalfe, "However this doesn't mean that climate change won't impact the numbers or distribution of cod populations since there may be other environmental factors such as prey distribution that could be affected by a rise in sea temperatures".

This work is from a large EU-funded project called CODYSSEY which aims to identify key environmental forcers of horizontal movements of cod. To date the programme has tagged and released over 2500 wild-caught cod across the North Sea, Barents Sea, Baltic Sea Faeroese waters and Icelandic waters. Seventeen percent of these tags have so far been returned. In the future the researchers plan to study other key species of interest to UK and EU fishermen.



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Adapted from materials provided by Society for Experimental Biology, via EurekAlert!, a service of AAAS.
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 MLA Society for Experimental Biology (2006, April 29). Cod In A Sweat: Some Like It Hot!. ScienceDaily. Retrieved June 4, 2009, from



http://www.sciencedaily.com­ /releases/2006/04/060430004644.htm
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« Reply #4 on: June 04, 2009, 08:28:18 am »









                                             Ice Age Imprint Found On Cod DNA






ScienceDaily
(Nov. 14, 2007)

— An international team of researchers, led by the University of Sheffield, has demonstrated how Atlantic cod responded to past natural climate extremes. The new research could help in determining cods vulnerability to future global warming.

With fishing pressures high and stock size low, there is already major concern over the current sustainability of cod and other fisheries. The new findings show that natural climate change has previously reduced the range of cod to around a fifth of what it is today, but despite this, cod continued to populate both sides of the North Atlantic.

The researchers used a computer model and DNA techniques to estimate where cod could be found in the ice age, when colder temperatures and lower sea-levels caused the extinction of some populations and the isolation of others.

The computer models used to estimate ice-age habitats suitable for cod were developed by Professor Grant Bigg, Head of the University of Sheffield's Department of Geography. These climatic analyses were combined with genetic studies by US researchers at Duke University and the University of California, and ecological information prepared by colleagues at the University of East Anglia and the Institute of Marine Research in Norway.

On land, plants and animals (including humans) are known to have moved further south when the northern ice sheets reached their maximum extent around 20,000 years ago. Similar migrations must have happened for plankton and fish in the sea.

But there were two added complications: firstly, greatly reduced sea levels meant that many shallow and highly productive marine habitats around Europe and North America ceased to exist. Secondly, the ice-age circulation patterns in the North Atlantic caused the temperature change between tropical and polar conditions to occur over a much shorter north-south distance, reducing the area suitable for temperate species -- such as cod.

The new analyses included these effects, together with other environmental and ecological information, in order to estimate where it was possible for Atlantic cod to reproduce and survive.

The results indicated that the ice-age range of Atlantic cod extended as far south as northern Spain, but the total area of suitable habitat was much more restricted. Nevertheless, populations of cod continued to exist on both sides of the North Atlantic. These findings were confirmed by genetic data, based on over a thousand DNA analyses of present-day cod populations, from Canada, Greenland, Iceland and around Europe.

Professor Bigg said: "This research shows that cod populations have been able to survive in periods of extreme climatic change, demonstrating a considerable resilience. However this does not necessarily mean that cod will show the same resilience to the effects of future climatic changes due to global warming."

The journal article 'Ice age survival of Atlantic cod: agreement between palaeo-ecology models and genetics' is published online in the journal Proceedings of the Royal Society B on 14 November 2007.


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Adapted from materials provided by University of Sheffield, via EurekAlert!, a service of AAAS.
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 MLA University of Sheffield (2007, November 14). Ice Age Imprint Found On Cod DNA. ScienceDaily. Retrieved June 4, 2009, from



http://www.sciencedaily.com­ /releases/2007/11/071113195129.htm
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« Reply #5 on: June 04, 2009, 08:30:36 am »










           Type Of Plankton -- Food Source For Many Fish -- Has Ability To Survive Climate Change






ScienceDaily
(Oct. 6, 2008)

— Queen's researchers have found that the main source of food for many fish - including cod - in the North Atlantic appears to adapt in order to survive climate change.

Billions of Calanus finmarchicus, a plankton species, which are just a few millimetres in size, live in the waters of the North Atlantic where the research was carried out.

It showed they responded to global warming after the last Ice Age, around 18,000 years ago, by moving north and maintaining large population sizes and also suggests that these animals might be able to track the current change in habitat.

The effect of global climate change on the planet's ecosystems is one of the key issues scientists are currently focussing on and the research has been published in Proceedings of the Royal Society B, a publication of the national academy of science of the UK and the Commonwealth, today.

One of the main predicted effects of climate change is a forced shift in species' distribution range.

The study leader, Dr Jim Provan, from Queen's School of Biological Sciences, said the discovery that that a species has a feature which helps it cope with global warming is a rare example of good news.

"Our results, in contrast to previous studies, suggest that the species has been able to shift its distribution range in response to previous changes in the Earth's climate, and thus 'track' the effects of climate change, a feature which may be of crucial importance in its survival.

"The genetic variability of the species - the tendency of the genetic make-up of a population to vary from one individual to another - has remained high, which is good news, and suggests that these animals might be able to track the current change in habitat resulting from global warming and maintain viable population sizes.

"If the species couldn't, it might become extinct and thus threaten the fish species that depend upon it for food.

"It might be a rare example of news that may not be doom-and-gloom with respect to climate change, but it doesn't mean that we don't have to keep watching what happens."

Previous work on the species had indicated a serious drop in numbers and decreases in population size may be reflected in decreases in genetic variability.

This can compromise the adaptive potential of the populations for the future and possibly result in extinction.

As a result of the Queen's findings the team is planning further work to see how the study applies to rapid global warming over the last few decades.


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Adapted from materials provided by Queen's University Belfast, via EurekAlert!, a service of AAAS.
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 MLA Queen's University Belfast (2008, October 6). Type Of Plankton -- Food Source For Many Fish -- Has Ability To Survive Climate Change. ScienceDaily. Retrieved June 4, 2009, from



 http://www.sciencedaily.com­ /releases/2008/09/080924075311.htm
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« Reply #6 on: June 04, 2009, 08:33:14 am »








The eastern Baltic cod stock has increased since 2005 and is now higher than ever during the last decade.



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« Last Edit: June 04, 2009, 08:34:25 am by Bianca » Report Spam   Logged

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« Reply #7 on: June 04, 2009, 08:36:28 am »










                     Fisheries Management And Environmental Conditions: Win-win For Baltic Cod






ScienceDaily
(Oct. 24, 2008)

— Politics have played a critical role in the increase of the cod stock in the Baltic Sea, but environmental conditions are equally important. Only the synergies from these two factors have resulted in a stock increase that exceeds the sums of both factors.

These are the preliminary results from an ongoing analysis at Stockholm University (Department of Systems Ecology, Baltic Nest Institute at Stockholm Resilience Centre). The study is highly relevant for the management decision on Baltic cod, which will be taken by the Council of Ministers on October 27th 2008.

According to scientists at the International Council for the Exploration of the Seas (ICES), the eastern Baltic cod stock has increased since 2005 and is now higher than ever during the last decade. Researchers at Stockholm University analyzed whether this increase is a result of management actions reducing the fishing pressure or improved environmental conditions resulting in higher reproduction.

Model simulations show that neither reduced catches alone, nor higher reproduction, could explain the increase. Each factor only explained 25% of the total increase. Synergies between both factors were necessary for the current increase in the Baltic Sea cod stock.

"This analysis clearly illustrates the importance of management actions but it also underlines the non-linear dynamics in nature and the challenges involved in ecosystem management," says Henrik Österblom at Baltic Nest Institute and one of the authors behind the study.

Does this mean that the Baltic cod stock is safe now?

"A similar increase of the cod stock in the early 1990’s was rapidly nullified by unsustainable catches. But we are, now in a window of opportunity to re-build the cod stock. If only the management plan decided last year is followed and illegal catches are controlled, the future of the Baltic cod looks better than it has for a long time," according to Olle Hjerne, marine ecologist at Stockholm University.

What will happen if the environmental conditions change?

"As climate change continues, environmental conditions for cod will be affected. Research on cod in other seas has underlined the importance of high stock levels for its capacity to cope with environmental change. Climate change will thus underline the importance of adaptive management," according to Thorsten Blenckner, Baltic Nest Institute.


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Adapted from materials provided by Stockholm University, via AlphaGalileo.
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 MLA Stockholm University (2008, October 24). Fisheries Management And Environmental Conditions: Win-win For Baltic Cod. ScienceDaily. Retrieved June 4, 2009, from



http://www.sciencedaily.com­ /releases/2008/10/081020095843.htm
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« Reply #8 on: June 04, 2009, 08:39:04 am »










                             Scientists And Fishermen Join Forces To Track Celtic Sea Cod






ScienceDaily
(Dec. 2, 2008)

— A joint project between the Irish fishing industry and scientists from the Marine Institute in Galway to track stocks of cod in the Celtic Sea is starting to yield interesting results.

Funded with monies administered under the Bord Iascaigh Mhara (BIM - the Irish Sea Fisheries Board) National Development Plan over the last two years, 4,063 cod have been tagged and released in the Celtic Sea by Institute scientists working aboard commercial fishing vessels from Dunmore East. The project is designed to study the growth and migration of both the inshore juvenile component and the offshore adult spawning component of the stock.

“To date around 10% of the tagged fish have been returned by a combination of fishermen, anglers and processors from Ireland, UK, Spain and France,” said Macdara Ó Cuaig, a scientist with the Fisheries Science Services team of the Marine Institute. “What makes this project such a success is that every fish that is recaptured and reported adds its own piece of information to the jigsaw and helps us get a better understanding of the stock. This start-stop data is helpful in understanding the behaviour of the fish but does not provide information on where the fish has been at in between. To inform us on the fish activity in-between release and recapture a number of large fish (>50cm) were fitted with an electronic tag.”

These electronic Data Storage Tags (DTS tags), are surgically inserted into the gut cavity of the fish. The tags record time, temperature and depth of the environment surrounding the fish while it is at sea. Each DST tag deployed to date has been set to measure temperature and depth every four minutes for a period of up to two years. Once retrieved, they can yield valuable information about the behaviour of the fish over time by comparing the data recorded by the DST with known temperature and depth data for the area. This allows the scientists to calculate where the fish has been between the release and recapture position, which in turn builds an accurate picture of the migration patterns and associated growth of the stock.

“While the recapture of DST tagged cod to date has provided some interesting data, the amount of information can be limited if the fish is recaptured shortly after release,” explains Macdara. “However, a fish reported to us last month with a conventional tag not only confirmed the rapid growth associated with Celtic Sea cod, but also has the unique distinction of being caught three times and released twice. This fish was originally released in Waterford Estuary on the 6th May 2007 when he was 23 centimetres long with an estimated weight of 120g. He was then caught and released again around St Patrick’s Day this year by our tagging vessel up river above Dunmore East. At that time the fish was 47 centimetres long and weighed over a kilo. He was finally caught and reported by a local on the 26th August at a length of 56 centimetres, weighing a hefty 1.9 kilos, sixty miles south of Hook Head.”

The fact that this fish had grown 33 cm in fifteen months highlights the fact that Celtic Sea cod have high growth rates—in this case an almost nine-fold increase in weight in the first ten months since its initial release, followed by a slower but still significant increase over the next five months to 1.9 kilos.

“This fish had a total of a sixteen-fold increase in weight in just fifteen months!” said Macdara. “This demonstrates the potential yield possible from the Celtic Sea cod stock.”



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Adapted from materials provided by Marine Institute - Foras na Mara.
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http://www.sciencedaily.com­ /releases/2008/11/081119084535.htm
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