October 22, 2020 — The following was released by the Atlantic States Marine Fisheries Commission:
The 2020 American Lobster Benchmark Stock Assessment presents contrasting results for the two American lobster stock units, with record high abundance and recruitment in the Gulf of Maine and Georges Bank stock (GOM/GBK) and record low abundance and recruitment in the Southern New England stock (SNE) in recent years. The GOM/GBK stock is not overfished nor experiencing overfishing. Conversely, the SNE stock is significantly depleted with poor prospects of recovery. Stock status was assessed using the University of Maine Stock Assessment Model for American Lobster (UMM, Chen et al. 2005), a statistical catch-at-length model that tracks the population of lobster by sex, size and season over time.
“On behalf of the American Lobster Board, I want to applaud the members of the Technical Committee and Stock Assessment Subcommittee for their exceptional work on the 2020 Benchmark Stock Assessment Report,” stated Board Chair Dan McKiernan from Massachusetts. “This assessment made a notable advancement in considering the impact of changing environmental conditions on lobster population dynamics.”
Extensive research has highlighted the influence of the environment on American lobster life history and population dynamics. Among the critical environmental variables, temperature stands out as the primary influence. Further, its range is experiencing changing environmental conditions at some of the fastest rates in the world. Therefore, considering these environmental influences is vital when assessing the lobster stocks and was a focal point of this stock assessment. Environmental data time series included water temperatures at several fixed monitoring stations throughout the lobster’s range, average water temperatures over large areas such as those sampled by fishery-independent surveys, oceanographic processes affecting the environment, and other environmental indicators such as lobster prey abundance.
Environmental time series were analyzed for regime shifts, which indicate a significant difference in the lobster’s environment and population dynamics from one time period to another. Regime shifts can change a stock’s productivity, impacting the stock’s level of recruitment and its ability to support different levels of catch. Temperature time series were also analyzed to quantify the effect of temperature on survey catchability of lobster and correct trends in abundance estimated from surveys by accounting for temperature-driven changes in catchability through time.