Maine lobstermen have brought in fewer pounds of lobster this year – only slightly over half of what was landed last year. That’s still 50 million pounds, so it is still an incredible amount of lobsters. But, the lower catch level this year has many lobstermen and scientists wondering why they are seeing this decline.

To say that the marine ecosystem is complex is a vast understatement. So, to point to a single reason for the lower catch this year is not realistic. There are so many different factors impacting what is landed that it is difficult to untangle them in an effort to study the “why.”

Reproduction is one of the keys to replenishing the population, so it is logical to look at how many baby lobsters are being born each year. Going back further, you can look at the number of eggs that are produced. Female lobsters carry their eggs on their bellies and are known as “berried” females because these black shiny eggs look like blackberries. The rate that the eggs develop depends highly on temperature – warmer temperatures mean eggs develop more quickly. It can also mean that a female lays fewer eggs in some cases. In this way, warming ocean waters may be contributing to fewer eggs.

It is what happens next, however, that is critical to survival. Once the eggs hatch, the larvae are easy targets for hungry predators. For every egg, maybe 1 in 10 survives to become an adult lobster. There are three larval stages before the lobster settles and becomes the crawling, insect-like crustacean we recognize. Once it settles, it can hide more easily and can also use its hard pointy shell as defense.

In addition to surviving predation, lobster larval survival also depends on food. And, this is a bit of a mystery. Try dissecting a larval lobster stomach and discerning what it ate for breakfast. Even the best microscopes don’t make it easy. Some new research, however, is helping to solve this mystery. Scientists from the Bigelow Lab are using DNA techniques to identify exactly what those tiny larvae are eating. This could help them to understand any shifts in the larval diet that could affect their survival.

This work is a partnership with the University of Maine’s Darling Marine Research Center, the University of Southern Maine and New Hampshire Fish and Game. It brings a lobster scientist, Rick Wahle (Darling Marine Lab) together with Bigelow’s David Fields, a copepod (lobster larvae food) expert, and Pete Countway, a molecular biologist from right here in Brunswick. The project began when these scientists noticed that both the copepod and larval lobster populations were decreasing. They also noticed that there were fewer “recruits” – new legal-sized lobsters. All of this led to the question of how these might be linked.

This work is just getting underway, so there are many more questions to answer. The group plans to continue to build on this summer’s initial data by doing further DNA sequencing to look at exactly what is being eaten. They’ll also be doing feeding

experiments to see what kind of food larvae prefer and testing out how well they survive with different amounts of food.

The causes of the drop in catch this year may or may not have to do with larval diet and could have more to do with any of the other myriad factors. Nonetheless, this research will help scientists to better know the habits of these little critters that grow up to be a part of our state’s most valuable fishery

Comments are not available on this story.

filed under: