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DMR Lobster Surveys Give Picture of The Future

Many fishermen depend on the Maine Fishermen’s Forum to reconnect with friends and colleagues and get caught up on the latest happenings in lobster management and science. Though the Forum was cancelled this year due to the pandemic, it has held some of its annual seminars through virtual online events. On April 7, the Maine Department of Marine Resources (DMR) Bureau of Marine Science staff presented their annual update on the state of the lobster fishery.

Kathleen Reardon, DMR lead lobster biologist, presented an overview of the 2020 lobster season during which Maine lobstermen landed 96 million pounds of lobster, a 5% decline from the previous year. In 2016, a record-breaking 132 million pounds of lobster were landed in the state. Reardon noted the impact that the COVID-19 outbreak had on the lobster fishery last year as well as DMR’s sampling activities. Lobstermen fished less often than in previous years. “There were 40,000 trips in 2020, down 15% from 2019 and down 26% from 2016,” she said. Pounds per trip increased sharply in June and July, then stabilized as the year progressed to rates comparable to previous years.

DMR conducts five surveys throughout the year to monitor the different life history stages of lobster from larvae to adults. “This helps us see changes before they are seen in the catch,” explained Reardon. Robert Russell gave an overview of the annual lobster settlement survey to find newly settled lobsters. This survey monitors the number of tiny lobsters, which are as small as a thumbnail, to help predict what future catches may look like. DMR divers operating from fishing vessels conduct one-meter-square samples of the seafloor at 40 sites along the coast. The survey was begun in 1989 by Lobster Institute director Rick Wahle. “In 2015, all regions ticked up to the 20-year time series and that uptick may be showing up in other surveys,” Russell said. The 2020 samples revealed a smaller decline in juvenile settlement among the lobster zones compared to 2019, with the exception of Zone E, which saw a small increase in settlement. Overall, settlement rates remain near the 20-year average. “Peak settlement appears to be moving east,” Russell said.

Questioned about the settlement data, Russell noted that juvenile lobsters prefer water temperatures around 12oC (53.6oF). As the temperature in deeper areas of the Gulf creep up into that range, more habitat has become available for juvenile settlement. More areas of formerly chilly eastern Maine are becoming suitable so more young are surviving there. “But what comes next?” Russell asked rhetorically, referring to the steadily increasing average temperature of the Gulf of Maine.

There are two surveys that look at trends in sublegal lobsters, those too small to be legally landed in the fishery. Although the spring inshore trawl survey was canceled last year, the fall survey did take place and its results indicate that the average catch of sublegal lobsters continues to decrease, as it has each year since 2015. DMR staffer Becca Peters noted that the decline occurs in all size groups.

The ventless trap surveys also show that sublegal sized lobsters are down sharply in eastern Maine waters compared to 2019 while sublegal catches in midcoast and western Maine were similar to 2019. The past five years have shown a distinct downward trend in eastern and midcoast Maine with little change in western Maine.

At-sea sampling aboard commercial lobster boats in 2020 was also curtailed by the pandemic, but samplers were deployed on lobster boats from July to October. “Overall the sublegal catch per trap appears to be down,” said DMR’s Matt Davis. He noted that the sublegal catch in each lobster zone peaked between 2013 and 2017. The catch per trap has dropped during each of the past five years except in zones D and F. The sharpest drops occurred in Zones A, B and C during that time period.

The number of lobsters showing signs of lobster disease was also low throughout the coast last year. However, Davis cautioned that the low rate could be due to the fact that samplers were not operating in May and June. The disease is most prevalent among lobsters at that time prior to the molting season.

In addition to these long-term monitoring programs, DMR completed a three-year study of the size at which female lobsters reach maturity and produce eggs last year. A previous study took place from 1994 to 1998. Given the increased warmth experienced in the Gulf of Maine since then, researchers wanted to know what effect the warmer water may have had on female lobsters. The project collected more than 1,200 female lobsters from throughout the coast and conducted a suite of measurements. “We found that there has been a decrease in size in all three regions,” DMR lobster scientist Jesica Waller said. “We want to do this more frequently to track potential changes as the Gulf continues to change.” When asked whether there is a connection between the smaller size at maturity and age of the female lobsters, Waller explained the difficulty in getting an accurate age for a lobster. “They don’t have any growth rings. We really don’t know,” she said. Davis added that the decrease in size is alarming. “We’ve seen this big change in eastern Maine in recent years. More sampling took place in western Maine in earlier years so they saw these changes first there,” he explained.

Building on its longstanding study of larval lobster abundance in Boothbay Harbor, DMR will be conducting a broader study this summer in the Gulf of Maine and Georges Bank. From June to September researchers will take samples in set transects inshore and offshore. The study goal is to assess larval abundance and seasonal timing. “Some areas have historical data already but others have never been sampled,” Waller said. Understanding the abundance of lobster larvae will add to understanding of how the warmer Gulf of Maine is influencing lobster populations in the two areas.

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