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Crustaceans, which are highly susceptible to the effects of climate change, are critical for food security worldwide. Yet, management rarely evaluates the performance of alternative regulatory strategies under climate‐driven life history change. This limits the development of climate‐ready management plans, undermining fisheries sustainability. We compared the performance of alternative minimum legal size (MLS) regulations under shifts in growth and maturity for American lobster in the Gulf of Maine, the most valuable single‐species commercial fishery in the United States. Across the life history change scenarios examined, increasing MLS improved status indicators, while decreasing MLS eroded status indicators for spawning stock biomass, legal abundance, landings, and exploitation rate. Our results demonstrate that protecting the lobster stock by increasing MLS improves fishery output, highlighting that conservation and industry goals can be complementary. This study exemplifies the utility of MLS as a conservation measure for crustacean fisheries under climate change. [ABSTRACT FROM AUTHOR]

Management of marine species often relies on biological reference points (BRPs): threshold and target indicators that trigger management actions. These BRPs are usually based on the biology of the species and rarely consider environmental effects. Under climate change, this is problematic as many biological/physiological relationships are assumed temporally static. This spurious assumption can lead to inaccurate management practices. To combat this problem, recent research highlights the importance of developing temporally dynamic BRPs. This paper sees the development of a dynamic BRP calculator to inform management of levels of spawning biomass necessary to sustain the desired future levels of recruitment given forecasted climate scenarios. We test this calculator on American lobster (Homarus americanus) of the Gulf of Maine and Georges Bank. Results for lobster indicate a temperature-driven, but complex, spawning biomass/recruitment relationship. Increased warming scenarios appear to yield overall higher recruitment per spawning biomass and dynamic BRPs calculated under these scenarios reveal that smaller population levels can sustain management-desired recruitment levels. This study highlights the importance of developing dynamic BRPs for fisheries management in a changing environment. [ABSTRACT FROM AUTHOR]

Crustacean species are socioeconomically and ecologically crucial across the world. For crustaceans, as ectotherms, anthropogenic climate change threatens to significantly alter key life history characteristics, such as size at maturity and growth rate. Because crustaceans are difficult to age, length data are used in assessments of crustacean stocks; however, climate-induced changes in maturation and growth can greatly influence the performance of size-structured stock assessment models. We coupled individual-based and size-structured models for American lobster (Homarus americanus) off northeastern North America in the Gulf of Maine--to conduct a novel sensitivity analysis of the effects of maturity and growth-related input parameters on model outputs. For this analysis, we used a bottom-up approach (with parameters shifted independently) and a top-down approach (with parameters shifted jointly as they were predicted to be influenced by climate change). We found that our American lobster stock assessment model is resilient to relatively extreme shifts in biological input parameters. For size-structured modeling in assessments of crustacean stocks, we recommend the expansion of sensitivity analyses to include evaluation of the influence of climate-driven changes on input parameters based on time-varying life history traits. [ABSTRACT FROM AUTHOR]

Functional stock-recruitment relationships (SRRs) are often difficult to quantify and can differ over space. Additionally, climate change adds to the complexity of recruitment dynamics. This paper's aim was to incorporate spatial heterogeneity and environmental effects on productivity in SRRs with American lobster in the Gulf of Maine (GOM) as a case study. GOM lobster recruitment has substantially increased since the mid-2000s,  due to improved survival rates of pre-recruits and increased spawning stock biomass (SSB). GOM bottom water temperatures have increased at a rate of 0.2ºC per decade, which caused lobster settlement area to expand and improved survival rates. We first estimated local SSB using bottom trawl survey data and a geostatistical model. Using estimated SSB, recruitment data from a ventless trap survey, and an interpolated bottom water temperature field, we developed modified Ricker stock-recruitment models accounting for spatial heterogeneity and temperature impacts with varying coefficient generalized additive models. Results showed that temperature significantly impacted recruitment. Changes in temperature mediated productivity differed between the eastern and western GOM. Our study demonstrated that the incorporation of spatial heterogeneity and environmental effects impacts our understanding of SRRs. These methods can be applied to other species to understand recruitment dynamics influenced by climate change. [ABSTRACT FROM AUTHOR]

Stock assessments for a majority of the world's fisheries often do not explicitly consider the effects of environmental conditions on target species, which can raise model uncertainty and potentially reduce forecasting quality. Model-based abundance indices were developed using a delta generalized linear mixed model that incorporates environmental variability for use in stock assessment to understand how the incorporation of environmental variability impacts our understanding of population dynamics. For this study, multiple model-based abundance indices were developed to test the incorporation of environmental covariates in a length-structured assessment of the American lobster (Homarus americanus) stock in the Gulf of Maine – Georges Bank on the possible improvement of stock assessment quality. Comparisons reveal that modelled indices with environmental covariates appear to be more precise than traditional indices, but model performance metrics and hindcasted fishery statuses revealed that these improvements to indices may not necessarily mean an improved assessment. Model-based abundance indices are not intrinsically better than design-based indices and should be tested for each species individually. [ABSTRACT FROM AUTHOR]

Simulation-based assessment tools coupled with large-scale and consistent monitoring efforts contribute to the overall success of the Atlantic sea scallop (Placopecten magellanicus; ASC) fishery on the North American east coast. However, data from the Northern Gulf of Maine (NGOM) are usually excluded from the assessment because limited monitoring effort and an overall lack of information regarding the growth of ASCs in this region have led to large uncertainty of fine-scale dynamics. The objectives of this study are to determine if ASC growth varies spatially and/or temporally across the NGOM and if the variation in growth can be explained in part by variability in bottom temperature and bottom salinity. To achieve these objectives, ASC shells have been continually collected through a partnership between the University of Maine and Maine Department of Marine Resources since 2006. Individualistic ASC length-at-age curves are developed to evaluate small and large scale spatio-temporal variabilities. In comparison to ASC growth on Georges Bank and in Southern New England, it appears that ASCs in the NGOM are growing at a similar rate yet have the potential to grow to a larger size. No clear spatio-temporal trends in ASC growth are identified in the NGOM. However, our analysis reveals that bottom temperature and bottom salinity may be influencing inter-annual variabilities and contribute to growth rate differences seen between locations and years. This may imply changes in ASC growth in the future with increasing warming in the Gulf of Maine. [ABSTRACT FROM AUTHOR]

Climate change is fueling unprecedented warming in marine environments. Crustaceans demonstrate strong physiological responses to rising temperatures including smaller molt increments, more frequent molting, and decreased size-at-maturity (SAM). Despite the potential for these changes to affect population and fisheries dynamics, there is limited research quantifying potential impacts. This is concerning, as crustacean fisheries are becoming increasingly important globally. Using an individual-based model for the valuable American lobster (Homarus americanus) fishery in the Gulf of Maine (GOM), we sought to address pressing questions about how climate-driven changes to growth and maturity could impact the population and fishery dynamics. To do so, we used counterfactual simulations informed by the literature and an expert survey to quantify the effects of smaller molt increments, increased molting, and decreased SAM on lobster spawning stock biomass (SSB) and landings. We found that all three changes to life history, combined, increased the SSB and landings relative to the base case. Notably, SSB in the terminal year of the time-series was 278.3%, 505.1%, and 748.5% greater than the base case under small, moderate, and extreme changes, respectively, to life history. However, when molt increment size and molting probability were changed but SAM was not, SSB and landings decreased relative to the base case, emphasizing the importance of SAM as a driver of productivity. Overall, these findings indicate that climate-driven changes to growth and maturity may favorably impact the population and fishery dynamics of lobster, contributing to sustained fishery yield in the GOM. This study emphasizes the utility of simulating the effects of climate-forced life history change for informing climate-ready fisheries management. Future work should explore the effects of other climate-driven life history changes alongside alternative management strategies for lobster and other crustaceans. [ABSTRACT FROM AUTHOR]

• Considerations of spatial-scale in HSI modeling may improve model estimates. • Coarse-scale model HSI estimates differ from models applied at smaller scales. • Models applied at smaller spatial scales more likely capture localized trends. Bioclimate envelope models were evaluated for possible spatial nonstationarity for American lobster (Homarus americanus) in the Gulf of Maine (GOM). Five environmental variables were considered, including bottom water temperature, bottom water salinity, distance offshore, sediment grain size, and latitude. Three models accounting for varying degrees of spatial nonstationarity were developed and evaluated. Spatial scales developed in these models were determined by the patterns of the GOM coastal currents and the associated affects these currents have on the GOM oceanography. This study suggests that incorporating spatial nonstationarity into habitat suitability modeling may lead to improved models. Forecast plots for the 2028−2055 period revealed that traditional modeling techniques applied at coarse spatial scales estimated higher suitability of habitat for juvenile lobsters than models at smaller spatial scales. For adult lobsters, coarse spatial model yielded higher suitability in both coastal waters in western GOM and farther offshore waters in eastern GOM, and generally estimated lower suitability in coastal eastern GOM waters and some offshore western GOM waters, compared to finer-scale spatial models. These results demonstrate how HSI estimates would vary based on the choice of spatial scales and its consequences. This information could benefit future stakeholders to prepare and adapt at more localized scales for changes that may occur in a region that is susceptible to climate change. [ABSTRACT FROM AUTHOR]