Preserving large females could prevent overfishing of Atlantic cod

September 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: North Sea cod and herring under threat

More information: Gender differences in health and aging of Atlantic cod subject to size selective fishery, bio.biologists.org/content/early/2012/07/30/bio.20121446.full

Related Stories

North Sea cod and herring under threat

June 26, 2006

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

British cod stocks rebounding

October 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.

New discovery: Plaice are spotted (on the inside)

February 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.

Recommended for you

Genomes uncover life's early history

August 24, 2015

A University of Manchester scientist is part of a team which has carried out one of the biggest ever analyses of genomes on life of all forms.

Rare nautilus sighted for the first time in three decades

August 25, 2015

In early August, biologist Peter Ward returned from the South Pacific with news that he encountered an old friend, one he hadn't seen in over three decades. The University of Washington professor had seen what he considers ...

Why a mutant rice called Big Grain1 yields such big grains

August 24, 2015

(Phys.org)—Rice is one of the most important staple crops grown by humans—very possibly the most important in history. With 4.3 billion inhabitants, Asia is home to 60 percent of the world's population, so it's unsurprising ...

Study shows female frogs susceptible to 'decoy effect'

August 28, 2015

(Phys.org)—A pair of researchers has found that female túngaras, frogs that live in parts of Mexico and Central and South America, appear to be susceptible to the "decoy effect." In their paper published in the journal ...

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.