Big claws: Good for lobster sex life, potentially fatal in the fishing season

Between Arendal and Grimstad, researchers tagged 100 lobsters with acoustic transmitters. With the help of numerous stationary receivers, they were able to track the lobsters’ movements during the fishing season.

“How lobsters move around indicates something about their personality. Are they cautious or are they risk-takers? There are advantages and disadvantages to both of those traits”, says marine scientist Even Moland.

It turned out that lobsters with a big crusher claw were more likely to end up in a crab pot.

Female lobsters appreciate a big one

Marine scientists have previously shown that yes, size does matter in the world of lobsters. “Paternity tests” have shown that lobsters with a big crusher claw in relation to their body length had more offspring in a lobster reserve.

“The very thing that makes male lobsters a hit with the ladies, turns out to be potentially fatal to them in the fishing season”, says Even Moland.

Typical “real” males

Moland believes that both of these things may be the result of the famous male overconfidence.

“This is typical alpha male behaviour. This kind of lobster takes bigger risks. It explores more, and it may also prevent other lobsters from entering the pots.

“He then gets to have the bait all to himself, which makes him feel great”, says Moland.

A trait that is advantageous in natural selection therefore appears to be a disadvantage during the crab fishery.

Walkers walk on by

The researchers also found a common denominator in the lobsters that survived the fishing season without being caught.

“Lobsters with a bigger home range were less likely to be caught”, explains Moland.

The home range is the size of the area the lobster moves around during a month. The size of the part of the sea floor that it calls “home”. Why should that matter?

“We actually expected the opposite to be the case. That more active lobsters would be at greater risk of being caught”, says the scientist.

“Our interpretation is that more sedentary lobsters are exposed to a pot that happens to be near them for a longer period. Proximity to the pot leads to a higher risk of being caught.”

Unnatural selection

The new results show that pot fisheries can select for certain types of individuals. Not just for physical traits, but also behaviour, or what the scientists compare to personality.

The lobster fishery is intensive. In the area with these 100 tagged lobsters, we recorded almost 5,000 crab pot days during the fishing season. 

“Our findings suggest that the fishery could affect the development of the lobster as a species. That knowledge is useful for the future management of the species.”

Scientific reference

Even Moland, Stephanie M. Carlson, David Villegas‐Ríos, Jørgen Ree Wiig, Esben Moland Olsen (2019). Harvest selection on multiple traits in the wild revealed by aquatic animal telemetry. Ecology and Evolution
Link: https://doi.org/10.1002/ece3.5224