How old is that lobster in the sea? It's now easier to find the answer
Lobster age matters to managing healthy stocks, but can be hard to estimate
Researchers in England believe they've cracked the code of understanding lobster age, a finding they say could someday help lead to a more sustainable fishery.
Unlike fish, which have tiny stones in their ears with rings that can be counted to determine age, or deer, which can be aged by their teeth, there isn't a decisive way to tell how old a lobster is.
Fishers often estimate the age of lobsters based on their size.
But Martin Taylor, who is an associate professor in the school of biological sciences at the University of East Anglia and one of the authors of a new study on lobster aging, said that's not a very accurate method.
"Lobsters have got very different growth rates among individuals. So individual A might grow very, very rapidly and then individual B might grow very, very slowly.... So it's really almost impossible to age lobsters currently."
Other methods, such as examining proteins in a lobster's brain, or growth rings in its eye stalks, cannot be used on a living lobster.
Taylor and the research team have developed a DNA-based method of pinpointing the age of younger lobsters to within 1.6 months. The study was published in the journal Evolutionary Applications.
The researchers obtained lobsters raised from eggs so they would know their exact age. They then took tissue samples from the lobsters' claws and measured DNA methylation, which is known to decrease with age.
They used that data to build a model to estimate the age of wild lobsters, most of which were estimated at between 40 and 55 months old, or about 3.5 to 4.5 years old.
"We've demonstrated the sort of proof-of-concept that we can do it. But the thing is, lobsters live for a very, very long time," Taylor said.
The known-age lobsters in the study were only up to 51 months old, or just over four years. But European lobsters — the type examined in the study — can live for 70 or more years, and American lobsters can live longer, possibly even a century.
"If we catch a lobster and we want to age it that's 70 years, then we're extrapolating a long way beyond our known age range, so it starts to become much more difficult to be certain," Taylor said.
The researchers hope to expand their study to include older, known-aged lobsters.
Why age matters
The research could one day lead to the creation of a device that could be used on lobster fishing boats to check the age of an individual, Taylor said.
"The ultimate goal might be that you can take catch and ... take a small DNA sample and almost instantly sequence it and say, 'Okay, well, this one's very, very young. We shouldn't keep that....' We're a long way from that at the moment, but it's not an impossibility."
In the meantime, Taylor said, the DNA technique could be used to gain a better understanding of the age of lobster stock and stock health, and manage it more sustainably.
"An unhealthy age structure leads to a less resilient fishery. So if you've got lots of old individuals or lots of young individuals in the fishery, then they're less able to be resilient to environmental change, for instance."
Fraser Clark, an assistant professor in the department of animal science and aquaculture at Dalhousie University, said calculating age in crustaceans is difficult and sometimes controversial.
"At meetings I've been at whenever there's an approach that's been suggested, it causes not outright fights, but minor discussions of very differing views," he said.
Clark said the study is "interesting" and it's "fun" to age lobsters, but the team's data on age estimates for wild lobsters was very variable, so "they've got a bit of work to do."
He added that lobster age is not necessarily the best tool to manage the fishery for sustainability.
"Knowing the age may or may not help us know whether or not they are reproductively active. But the size is a very easy metric that the industry uses now to determine whether or not there's a legal catch."