Catsharks May be More Vulnerable to Overfishing Than Previously Thought

It's important to understand shark populations as they continue to be harvested and as their numbers continue to decline. Now, scientists have announced that shark populations in the Mediterranean are highly divided, which may have important implications for conservation efforts.

In order to better understand shark populations in the Caribbean, scientists used genetic techniques. They investigated the population structure of the small-spotted shark, Scyliorhinus canicula, also known as the catshark. This particular species is common throughout Europe and has been eaten since ancient times. It's often caught for sport and can be seen in rock pools at low tides.

In this case, the scientists found evidence of isolated populations in the Mediterranean, but no population division was found between catsharks around the North East Atlantic and British Isles. During the last ice age, about 20,000 years ago, ice sheets occupied much of this region, which means that catsharks probably didn't survive in this area. This, in turn, indicates that the region had to be recolonized, and that there is very little genetic differences between the catsharks then and the ones of today.

The findings also highlight the differences in the movements of male and female catsharks, which is an increasingly common finding among sharks.

"It makes a lot of sense," said Andrew Griffiths, one of the researchers, in a news release. "Females may want to stay in areas that are good for laying eggs, but males are often the dispersing sex, perhaps taking risks to increase how much they reproduce."

So what does this mean? It shows that catsharks in the Mediterranean Sea move and migrate much less. This, in particular, may have important implications for conserving and managing sharks more widely. Not only that, but it suggests that the sharks may be more vulnerable to overfishing than previously thought.

The findings are published in the journal Royal Society Open Science.