Skinny cod and grey seal reveals troubling changes to food web in the Baltic Sea

JUNE 11, 2019

by Stockholm University

The prime predators of the Baltic Sea at the top of the food web are losing weight, according to a new study that links the deteriorating health of gray seals and cod with changes in bottom-living crustaceans, isopods and amphipods.

"It is important that you understand how the food web works when managing a fishery. It is not enough to manage how the fish and fisheries are changing. The availability and quality of food is at least as important," says Lena Bergström, researcher at the Department of Aquatic Resources at the Swedish Agricultural University.

In a collaboration between several universities, the authors of the study examined how the health and abundance of certain species has changed over two decades in the Bothnian Sea and the Baltic Proper. They investigated seal, cod, herring, sprat, isopods, amphipods and zooplankton, species that all occur at different levels in the Baltic Sea food web. The system is complex and several species can be both predators and prey. For example, herring eats zooplankton and some bottom fauna while the herring itself is eaten by cod and seal.

Shrinking habitats for bottom-living animals

The study primarily shows that there are links between the health of both cod and seal with the availability of bottom-living animals. Regarding the seals, the connection is indirect through that the herring it eats is influenced by the availability of the bottom-living animals. In both cases, there is a link to climate change and eutrophication.

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Cod and haddock 'may vanish' from Scotland's west coast

Cod, herring and haddock could migrate away from Scotland's west coast waters because of warming sea temperatures, according to researchers.Scientists at the Scottish Association for Marine Science (Sams) predict the cold water species will vanish from the west coast by the year 2100.

The researchers suggest the fish are already nearing "edge of their temperature tolerance range".

However, they add that global warming will see other species replace them.

Cod, herring and haddock are commercially important species to Scotland.

The researchers at Sams, which is near Oban and part of the University of the Highlands and Islands, warn that climate change could lead to the fish moving away to colder waters further north.

'Sustainable fisheries'

But over the forthcoming decades these species would "gradually be replaced by more abundant communities" of saithe, hake and whiting, the scientists said.

They said that from 1985 to 2013 the population of saithe and hake had increased four-fold off Scotland's west coast.

Sams research has been published in the journal Scientific Reports.

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Cod and haddock go north due to warming UK seas, as foreign fish arrive

Our seafood diet must adapt, say scientists, as climate change forces some favourites to colder waters and threatens others

Robin McKie

Saturday 2 September 2017 21.30 BSTLast modified on Saturday 2 September 2017 22.00 BST

Britain must prepare itself for invasions of growing numbers of foreign sea creatures attracted by our warming waters, a new report has warned. Some newcomers could have devastating effects, others could be beneficial, say the researchers.

Examples provided by the team include slipper limpets that could destroy mussel and oyster beds. By contrast, new arrivals such as the American razor clam and Pacific oyster could become the bases of profitable industries for British fishermen.

The team’s research also stresses that Britons will have to change their ideas about the seafood they eat as favourites will disappear from UK waters. Haddock and cod are being forced polewards as ocean temperatures rise, while flatfish like sole and plaice have nowhere suitable to go. At the same time, cuttlefish and sardines are being caught in rising numbers and are destined to become the fish of the future for Britain.

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Scientists search for regional accents in cod

Date: October 6, 2016

Source: University of Exeter

Fish may have regional accents and communicate differently in different parts of the world, according to fish expert Steve Simpson, Associate Professor of Marine Biology and global change.

Professor Simpson, who has listened to the vocalisations of fish using sophisticated underwater listening equipment, has identified variations in the "voices" of cod from America and Europe.

Different 'dialects' have been found in many animals, from songbirds to sperm whales. Simpson is now exploring whether vocal fish, including cod and haddock, living in different areas around Britain could have localised accents because they gather in the same spawning grounds generation after generation.

Prof. Simpson's research into bioacoustics and the "soundscape" of Britain's seas has so far focused on the impact of maritime noise pollution on fish. His group has shown that fish become stressed by noise, make bad decisions when feeding and faced with predators, and that early development is impacted by noisy conditions. He fears noise pollution from maritime construction, speed boats and ships could affect their ability to attract mates, where their vocal behaviour is key to reproductive success.

"Seawater is hundreds of times denser than air, so underwater sounds travel much faster and further. We have found that fish on coral reefs are susceptible to noise pollution, but we are yet to study the effects in our own waters, which are some of the busiest shipping areas in the world.

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Pacific cod may have learned to hunt seabirds, research indicates

Yereth Rosen

Alaska Dispatch News

November 9, 2015

You could call it revenge on the birds.

While many marine birds are well known for their skills at diving into the sea to pluck out fishy meals, there is now solid evidence that some Pacific cod have turned the tables on the avian species.

The practice came to light a few years ago when seafood workers in Dutch Harbor noticed that some of the cod they were processing came with extra features -- partially digested birds in the fish stomachs.

Scientists from the Alaska SeaLife Center and University of Alaska have now examined remains of 74 birds collected from cod stomachs in 2011 and have some findings described in a study published online in the journal Marine Ornithology.

The bird remains come from cod caught in the Aleutian Islands region, off Cape Sarichef in Unimak Pass, using trawl and pot gear. The fish were processed at the UniSea plant in Dutch Harbor; the plant froze the bird remains and sent them to the scientists for analysis.

There have been other known cases of big fish eating small seabirds elsewhere in the world, the new study says, and past surveys by the National Oceanic and Atmospheric Administration have turned up, in very rare instances, bits of birds inside cod. In one case, a NOAA researcher found a murre foot in a cod stomach.

But the evidence from Dutch Harbor appears to be the first documentation of Pacific cod making a practice of eating birds, said study co-author Tuula Hollmen, science director at the SeaLife Center and an associate professor at the University of Alaska Fairbanks' School of Fisheries and Ocean Sciences.

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Warming waters are destroying the New England cod population

OCTOBER 30, 2015

by Eric Hopton

   

Supplies of cod, once the lifeblood of the New England fishery and a key species in the local ecosystem, have collapsed. Despite the best efforts of fishermen and fishery managers, attempts to reverse the devastating decline were too little and too late and the Gulf of Maine cod industry is done for.

Cod populations have failed to adapt to the ocean warming, and today stock levels are only 3 to 4 percent of what is needed for a sustainable fishery. Even when cuts to the numbers of fish landed and strict quota limits were introduced in 2010, the decline accelerated, leaving both fishermen and fisheries managers puzzled and disappointed.

Now, a new report in the journal Science offers an explanation. The steady pace of warming caused by global climate change was exacerbated by changes in the position of the Gulf Stream and by climate oscillations in the Atlantic and the Pacific oceans. With this triple assault on local water temperatures, no amount of stock management was going to help.

“Managers kept reducing quotas, but the cod population kept declining,” said Andrew Pershing, Chief Scientific Officer of the Gulf of Maine Research Institute (GMRI). Pershing was the lead author of the study and added: “It turns out that warming waters were making the Gulf of Maine less hospitable for cod, and the management response was too slow to keep up with the changes.”

Waters too hot for cold water cod

The researchers found the root of the problem was that increasing water temperatures reduced the number of new cod produced by spawning females, and it also led to fewer young fish surviving to adulthood.

Previous models used by fishery managers over the last decade to set quotas did not take into account the impact of rising temperatures. As a result, even though fishermen stuck to the big reductions in quotas, they were still unknowingly taking more fish than the population could sustain.

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North Sea cod back on the menu, marine body says

25 September 2015 

North Sea cod has been taken off the Marine Conservation Society's (MCS) list of fish to avoid eating.

The UK charity had previously said cod should not be eaten because stocks were only slightly above sustainable levels.

But it says it can now be eaten as an occasional treat following a recovery in numbers and having been removed from its red list of endangered fish.

Samuel Stone, from MCS, said the announcement was a "milestone", but fishing levels still needed to reduce.

The MCS said cod levels may never fully recover to their peak numbers of the 1970s and early 1980s.

There were now nine endangered stocks, which need "some of the attention that North Sea cod has had", it added.

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Gurnard and chips, please: warmer seas change UK fish stock as cod head north

Marine experts say we will soon have to get used to eating hake, mullet and other species as coastal waters heat up

Robin McKie, science editor

The Observer, Saturday 2 August 2014 13.05 BST

Cod and chips could soon become a dish of the past, as Britain's waters become ever warmer. Marine experts have warned that rising sea temperatures are transforming the makeup of fish stocks in our coastal waters.

Where cod and haddock once thrived, sea bass, hake, red mullet and anchovies are now being caught in rising numbers. If Britain wants sustainable fisheries round its shores, it will have to turn to these for the fish suppers of the future, they add.

"We are going to have to be much more flexible about the fish we eat as our coastal waters continue to warm," said Professor Richard Lampitt of the National Oceanography Centre, Southampton.

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Fisherman finds large red dildo in cod he has just caught

A fisherman was baffled after he found a massive dildo inside a cod he had just caught.

Bjoern Frilund, 64, was pleased to have reeled in the six kilogram fish while on a boat near Eidsbygda, in Norway.

But his happiness soon turned to dread when he inspected the cod further and saw it contained a large red vibrator.

‘I was astonished. I had never seen anything like this before,’ he told The Local.

‘We have a kind of multi-coloured octopus in Norway, maybe the cod thought this was one of these and ate it.’

The fisherman now seems to have got over the shock of discovering the dildo after posing happily with it in his hand.

http://metro.co.uk/2014/04/12/fisherman-finds-large-red-dildo-in-cod-he-has-just-caught-4697054/

Changing food source bodes ill for whales, cod

By Doug Fraser

dfraser@capecodonline.com

November 25, 2013

WOODS HOLE — A marine ecosystem expert is warning that the effect of changes in water temperature and plankton blooms may have ripple effects up the food chain.

"We believe that the changes in the timing of warming events have affected plant and animal reproduction," wrote oceanographer Kevin Friedland of the Northeast Fisheries Science Center in Woods Hole in an ecosystem advisory released last week.

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North Sea cod stocks 'on road to sustainability'

By Roger Harrabin, Environment analyst

North Sea cod stocks are on the road to sustainability, according to Marine Stewardship Council (MSC) research.

The body, which certifies whether fish are caught through good practice, says it is too soon to tell exactly when the North Sea fishery will meet its mark.

But a spokesman said on current trends, it would be ready for certification within years rather than decades.

Stocks would still be in recovery then, James Simpson said, but they would have passed an acceptable level.

MSC certification is determined by the state of the stocks, the environmental impact of the fishery, and if there is a management system in place to maintain sustainability if circumstances change.

The latter two were already in place, Mr Simpson said.

“This is really great news”James Simpson, Marine Stewardship Council

"This is really great news," he said. "We have done an assessment of the entire inshore industry and it's clear that cod is on the way back."

The recovery was thanks to strict catch limits aided by a massive public campaign for sustainable fish, he said.

Barrie Deas, the chief executive of the National Federation of Fishermen's Organisations, which represents fisherman in England, Wales and Northern Ireland, told Radio 4's Today programme it was a "dramatic turnaround".

Continued and video

Bycatch slows recovery of Grand Banks Cod

Halifax, Nova Scotia: After decades of little hope in what was once one of the world’s major fisheries, Atlantic Cod is showing signs of recovery on the Grand Banks off the coast of Canada. But WWF is warning that fisheries managers must not rush to reopen the cod fishery that has been under moratorium since 1994.

The Atlantic cod population on the Grand Banks, southeast of Newfoundland, is showing the early signs of improvement, according to a report by the Northwest Atlantic Fisheries Organization’s (NAFO) scientific council in 2010.

But although the current course for recovery of southern Grand Banks cod is positive, it is still just 21 per cent of what is considered to be a sustainable level for the stock.

Ahead of the annual meeting of NAFO on September 19th in Halifax, Nova Scotia, WWF is warning that fisheries managers must first finalize the promising interim cod conservation plan developed by NAFO over the past year.

“It’s an encouraging sign after decades of seeing little-to-no recovery of a cod population that was once a central part of the region’s fishing industry”, says Dr. Bettina Saier, Director of Oceans Program at WWF-Canada. “But this ongoing ecosystem recovery is at risk if NAFO doesn’t reduce the amount of allowable cod bycatch.”

Small window of opportunity
This small window of opportunity for the cod rebuilding strategy to make a difference could easily be lost to the high amount of cod caught as bycatch in other fisheries.

The bycatch of Grand Banks cod increased from 600 tonnes in 2006 to 1100 tonnes in 2009. Reducing bycatch by 50 percent is the key to cod recovery, combined with protection of habitats and other ecological important areas such as spawning and nursery grounds.

NAFO has demonstrated leadership by protecting coral and sponge habitats and seamounts, but they have fallen behind on their 2006 international commitments to protect other vulnerable marine ecosystems, such as spawning grounds, as called for by United Nations General Assembly (UNGA) resolutions.

A scientific study published in July 2011 showed that Atlantic cod off Nova Scotia are recovering from their dramatic collapse two decades ago — and that the ecosystem is recovering with them. This is a good indicator for the future of fisheries on the Grand Banks.

Collapse of the Grand Banks cod fishery
The Newfoundland Grand Banks, off the east coast of Canada, used to be famous as supporting some of the world’s most productive fisheries. Small boats caught sustainable amounts of cod for hundreds of years.

But as fishing methods advanced in the 1950s with the introduction of larger, new factory trawlers and warnings from scientists of the dangers of over-fishing went unheeded, eventually the amount of cod in the area reached record lows.

A total fishing moratorium was enforced, throwing about 40,000 people out of work and shattering the livelihoods of local fishing communities.

Smart Fishing Initiative
Since 2005, WWF has been involved with NAFO with the goal of recovering the Grand Banks ecosystem. WWF’s Smart Fishing Initiative works with every level of the fishing industry to reform commercial marine fisheries towards long-term sustainability - where seafood is harvested in a way that sustains and protects the marine environment, the species within it, and the people who depend on them.

http://wwf.panda.org/wwf_news/?201689/Bycatch-slows-recovery-of-Grand-Banks-Cod

Selective Trawl Catches Norway Lobster but Allows Cod to Escape

ScienceDaily (Aug. 29, 2011) — Researchers from DTU Aqua in Denmark have decoded the behaviour of Norway lobsters and cod and used the results to develop a selective trawl. This so-called SELTRA-trawl ensures that fewer cod end up as by-catch in the Norway lobster fishery in the Kattegat.

Despite the fact that the cod fishery in the Kattegat is subject to strict fishing quotas, a substantial amount of cod have ended up as by-catch in the Norway lobster fisheries. But after July 15, 2011, more cod have escaped the lobster trawl. From this date, the Danish Ministry of Food, Agriculture and Fisheries has decided, that all Norway lobster fishing in the Kattegat is to be conducted using a selective trawl, called the SELTRA-trawl.

"The Norway lobster population in the Kattegat is doing well, and the Norway lobster fishery is the most economically important fishery in the Kattegat. In 2010 alone, 1700 tonnes of Norway lobsters were caught here. The cod population, on the other hand, has declined severely in the last 20-30 years. If it had not been possible to reduce the by-catch of cod by implementing the SELTRA-trawl, the Norway lobster fishery would have to be reduced significantly in order to protect the cod," says senior research scientist Niels Madsen from the National Institute of Aquatic Resources (DTU Aqua) in Denmark. He has been in charge of developing and testing the SELTRA-trawl during a project funded by the Ministry of Food, Agriculture and Fisheries and the EU.

The cod escapes
A trawl is a funnel-shaped net, which distends when it is pulled after a vessel. When it is pulled along the bottom of the sea, it catches Norway lobsters and bottom-dwelling fish on its way. The catch then falls back towards the rearmost end of the trawl and ends up in the so-called codend.

The challenge for the researchers at DTU Aqua has been to design a trawl that selectively catches Norway lobsters while letting cod and other unwanted by-catch escape through the meshes. Norway lobsters are relatively small, and a small mesh size is thereby required to retain them in the codend. These small meshes also retain fish the size of or larger than the Norway lobsters which is the reason that previously there has been a great deal of by-catch when fishing Norway lobsters.

The researchers came up with the idea of replacing the traditional round codend with a codend shaped like a square box. This square-shaped box proved to be more stable in the water enabling the researchers to take advantage of the cods' and Norway lobsters' behaviour.

When using this codend, the researchers discovered that the Norway lobsters were passive and preferred the bottom part of the codend, while the cod were more active and had a preference for the upper part of the codend and tried to swim against the current to escape.

Based on the knowledge of the differences in behaviour, the researchers at DTU Aqua created the so-called sorting box that has a larger mesh size and is placed in the front end of the SELTRA-trawl allowing the cod to escape. Thereby, they had come up with the basic idea for the SELTRA-trawl.

To be placed on the fishermen's own trawl
In order to keep the costs of the SELTRA-trawl relatively low, the SELTRA-trawl was developed to be added to the fishermen's own trawl:

"The fishermen fishing for Norway lobsters has their own trawl already, and all they need to do is to place the seven meter long SELTRA-trawl with the sorting box and the square codend instead of the rearmost part of their own trawl. In this way, the fishermen do not have to buy a complete new trawl," explains Niels Madsen.

Testing the trawl
Project SELTRA was initiated in 2005 and completed in the end of 2008. Since then, the SELTRA-trawl has been tested in the Norwegian company SINTEF's flume tank at the North Sea Science Park in Hirtshals.

"Through the co-operation with the Danish Fishermen's Association, fishermen and net makers we got ideas on how to design the SELTRA-trawl, so that it is convenient and useful for the fishermen and easy to construct for the net makers," says Niels Madsen.

The SELTRA-trawl has been used on commercial fishing vessels in the so-called closed areas in the Kattegat. The closed areas are areas, in which the Danish Ministry of Food, Agriculture and Fisheries has prohibited cod fishing in order to protect spawning cod.

"In some places in the closed areas, the fishermen have been required to use the SELTRA-trawl when fishing for Norway lobsters. The fishermen, who have now used the SELTRA-trawl for a couple of years, say that they have not experienced significant reductions in the amount of Norway lobsters that they catch," says Niels Madsen and continues:

"Furthermore, the SELTRA-trawl has proved to allow the main part of the cod to escape. During the development work and the following tests we have seen up to 90 % of the cod escape from the SELTRA-trawl."
http://www.sciencedaily.com/releases/2011/08/110829084325.htm