Preserving large females could prevent overfishing of Atlantic cod

Sep 26, 2012

Cod are among Sweden's most common and most popular edible fish and have been fished hard for many years. One consequence is the risk of serious changes in cod stocks, reveals research from the University of Gothenburg, Sweden.

In overfished areas, there is often a shortage of large and old cod, and the fish become sexually mature at a younger age. Researchers have feared that this change may have impacted on the fish's health, physiological ageing and reproductive capacity.

In a recently published study, a research group from the University of Gothenburg working with the Swedish University of Agricultural Sciences therefore looked into the health and ageing of male and female cod.

"We measured various aspects of oxidative stress, a condition in the cells that can lead to , antioxidant capacity, which protects against oxidative stress, and telomere length," says researcher and Helen Nilsson Sköld.

Telomeres are repeated that protect the ends of . The length of these telomeres and the rate at which they get shorter are closely linked to health and ageing. The researchers compared the health of cod in the Öresund, Skagerrak and Kattegat. Cod in the Öresund have been protected from trawling since 1932 and so stocks include larger and older fish, but cod in the Skagerrak and Kattegat have been seriously overfished.

"Our results show that older males generally have shorter and a reduced antioxidant capacity," Helen Nilsson Sköld explains. "However, we didn't see the same pattern among – there were no signs of physiological ageing in the age span we looked at for the females (two to eight years)."

The researchers were surprised to see such marked . Although older males were fatter and seemed less stressed than younger males, the females were generally in better shape than the males.

"Our theory for why the males age and are more stressed during spawning is that they have to compete for territory and mates. This stress seems to be more acute among the younger males."

The researchers were unable to find any signs of the overfished stocks of the Skagerrak and Kattegat being less healthy than the Öresund population. A key factor in this context is that larger fish produce a much higher number of eggs – it can vary from half a million to five million depending on the size of the .

"Our study also shows that large older females are healthy and don't seem to have aged physiologically," Helen Nilsson Sköld adds. "The conclusion is that it's important to look after the large older females, as they produce many more eggs than younger ones. A conservation strategy of this kind would be ideal in the Skagerrak and the Kattegat."

Explore further: Salmon forced to 'sprint' less likely to survive migration

More information: Gender differences in health and aging of Atlantic cod subject to size selective fishery, bio.biologists.org/content/ear… 30/bio.20121446.full

add to favorites email to friend print save as pdf

Related Stories

New discovery: Plaice are spotted (on the inside)

Feb 22, 2010

Have you seen a spotted plaice? Probably. However, marine biologist Helen Nilsson Skold at the University of Gothenburg is the first person to research the spotted insides of plaice.

British cod stocks rebounding

Oct 22, 2007

Researchers say cod stocks around Britain have rebounded enough to permit small catches in the North Sea, The Times of London reported Saturday.

North Sea cod and herring under threat

Jun 26, 2006

European scientists say cod and herring populations in the North Sea are not reproducing enough, jeopardizing the Norwegian fishing industry.

Recommended for you

Genetically tracking farmed fish escaping into the wild

17 hours ago

European sea product consumption is on the rise. With overfishing being a threat to the natural balance of the ocean, the alternative is to turn to aquaculture, the industrial production of fish and seafood. ...

France fights back Asian hornet invader

20 hours ago

They slipped into southwest France 10 years ago in a pottery shipment from China and have since invaded more than half the country, which is fighting back with drones, poisoned rods and even chickens.

Tide turns for shark fin in China

20 hours ago

A sprawling market floor in Guangzhou was once a prime location for shark fin, one of China's most expensive delicacies. But now it lies deserted, thanks to a ban from official banquet tables and a celebrity-driven ...

Manatees could lose their endangered species status

Aug 19, 2014

About 2,500 manatees have perished in Florida over the last four years, heightening tension between conservationists and property owners as federal officials prepare to decide whether to down-list the creature to threatened ...

User comments : 0