Lobster settlement index shows changes

First published in Landings, March, 2014.

Maine lobstermen know that there are a lot of lobsters on the bottom. Whether due to warmer water or the decades-long conservation efforts of lobstermen, Homarus americanus has been turning up in traps in unprecedented numbers during the past several years.

But, as stock brokers are quick to tell potential investors, past performance is no guarantee of future returns. What lobstermen find in their traps today is not necessarily what they will find in those same traps in coming years.

Carl Wilson, lobster biologist at the Department of Marine Resources (DMR), refers to data gathered from the American Lobster Settlement Index as he speaks. The settlement index (http://www.umaine.edu/marine/people/sites/rwahle/ALSIPage.htm) is a collaborative monitoring program that generates annual data on the density of newly settled lobsters in nursery areas along the New England and Atlantic Canada coasts. It provides researchers with a sense of how many lobsters are in a specific year class, important information for assessing future abundance of the stock. The index has been funded in Maine by the DMR since 2000 and the surveys conducted by DMR researchers since 2005.

“We now have three years of declining settlement in most areas,” Wilson explained. “With three years of poor settlement there’s a good chance this lack of lobsters will work its way through the population.” Typically a Gulf of Maine lobster requires roughly seven years to reach legal size, although that rate of growth will vary based on environmental factors. So, it is likely that the diminished number of young lobsters that began three years ago will begin to show up in landings in four years’ time.

DMR uses data other than the settlement index to assess what’s going on with the state’s most valuable marine species. Each year since 2000 a trawl survey is conducted in the spring and the fall from Kittery to Calais. The survey gives scientists a good understanding of what is flourishing and what is disappearing from Maine’s coastal waters. In addition, each summer dozens of sea samplers go out on lobster boats to categorize all the lobsters caught by that boat in a given day. They measure each lobster, determine the sex, note if the lobster is V-notched or bearing eggs, and molt status. DMR also conducts a ventless trap survey each year. Vented and ventless lobster traps are stationed at 138 sites along the coast. The ventless trap survey gives researchers data on the abundance and size of lobsters during that season.

“All the different monitoring programs layer on each other,” Wilson said. “We are seeing lobsters at or near their highest levels ever.” So what’s going on?

“We are at unheard of abundance levels now, beyond the wildest dreams of those fishing in the 1980s or 1990s. But here it is, three years’ data [showing decline from the settlement index],” he continued. “It’s time to have a conversation about this.”

Wilson also expressed concern about a drop in the number of lobstermen V-notching female eggers and returning them to the water. One of the items that sea samplers note from traps sampled is the number of V-notched versus non-V-notched lobsters. “In 2008 the percentage of V-notched egg-bearing lobsters was 80%,” Wilson said, referring to sea sampler data. “That was the peak. The percentage has declined to 60% in 2013. That’s still a high number but a sharp decline from the peak.” V-notching female lobsters has been a long-standing voluntary practice among Maine lobstermen. That practice became a matter of policy back in 2001, when it was made a condition of Atlantic States Marine Fisheries Commission (ASFMC) Area 1 lobster management plan. The ASMFC lobster management plan has one primary objective: to increase egg production in females.

“V-notching protects females and can contribute to the reproductive success of the population. More eggs in the water means more chances of having lobsters,” Wilson noted. “Combine this [the decline in V-notched lobsters] with the pattern of decline in lobster settlement and there are two freight trains coming.”

It may be that the astonishing abundance of lobsters right now has led some lobstermen to think V-notching is no longer necessary. It might also be that the thousands of pounds of lobsters handled in a day by a lobsterman or his stern man make the few seconds needed to notch a female lobster problematic. Whatever the reason, the pattern causes Wilson concern. “Lobstermen were participating in V-notching when the population was increasing. But if in the future there are less and less lobsters, there may be less incentive for them to V-notch,” he said.

No one has a crystal ball to predict exactly what Maine lobstermen will be seeing in their traps in five years’ time. Yet the data suggest that the day is coming when lobstermen may want to take Wilson’s advice and begin “to have a conversation about this”.