AimTo address the uncertainty associated with climate‐driven biogeographical changes in commercial fisheries species through an ensemble species distribution modelling (SDM) approach.LocationNortheast US Continental Shelf Large Marine Ecosystem (NEUS‐LME).MethodsWe combined an ensemble SDM platform (BIOMOD 2) and a high‐resolution global climate model (NOAA GFDL CM2.6) to quantify spatiotemporal changes in habitat of two commercially important species in the Northeast US Continental Shelf Large Marine Ecosystem (NEUS‐LME); American lobster (Homarus americanus); and sea scallop (Placopecten magellanicus). An ensemble SDM was calibrated using multi‐decadal fisheries‐independent surveys (1984–2016). Statistically weighted species‐specific ensemble SDM outputs were combined with 80 years of projected bottom temperature and salinity changes in response to a high greenhouse gas emissions scenario (an annual 1% increase in atmospheric CO2).ResultsStatistically significant changes (p < .05) in habitat suitability for both species were found over a large portion of the study area. Sea scallop undergoes a northward shift over the study period, while American lobster moves further offshore. The ensemble projections showed that several management zones were identified with increases and decreases in species‐specific habitat. Uncertainty due to variations in ensemble member models was also found in the direction of change within each management zone.Main conclusionsThis study provides ensemble estimates of climate‐driven changes and associated uncertainties in the biogeography of two economically important species in the United States. Projected climate change in the NEUS‐LME will pose management challenges, and our ensemble projections provide useful information for climate‐ready management of commercial fisheries.

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A bioclimate envelope model was developed to evaluate the impacts of climate variability on spatiotemporal availability of suitable habitat for the Atlantic sea scallop Placopecten magellanicus in the Gulf of Maine (GOM). Bioclimate envelopes were established through habitat suitability indices (HSIs) based on bottom temperature, bottom salinity, current velocity, depth, and bottom composition. The relationship between Atlantic sea scallop abundance and each environmental variable was quantified using suitability indices, which were generated based on standardized scallop abundance sampled over 10 years of dredge survey data. Boosted regression tree models were used to determine the relative importance of each environmental variable to scallop abundance, thereby establishing a weighting scheme within the HSI. A regional circulation model was coupled with the weighted HSI to hindcast spatiotemporal dynamics of suitable habitat for Atlantic sea scallop in coastal and offshore waters of the GOM from 1978 to 2013. Higher habitat suitability was found along inshore areas compared with offshore areas. Model predictions indicated an increasing trend in habitat suitability in inshore waters since 1978 and decreasing habitat suitability in offshore waters. This research provides a novel modeling framework with which to enhance research and management of commercially valuable Atlantic sea scallop stocks over broad spatiotemporal scales in the climatically altered GOM.

Abstract-Diel sampling was conducted during June-September 2013, in the shore zone and adjacent nearshore zone of Delaware Bay, Delaware, to identify day and night changes in nekton density, species richness, and the species assemblage. Mean species richness and total nekton density in the shore zone were higher at night. A detailed examination of abundant species revealed that bay anchovy (Anchoa mitchilli), weakfish (Cynoscion regalis), spot (Leiostomus xanthurus), and blue crab (Callinectes sapidus) occurred in higher densities in the shore zone at night than during the day. Bluefish (Pomatomus saltatrix) occurred in higher densities during the day. Additionally, small (<20 mm in fork length) Atlantic silverside (Menidia menidia) and bay anchovy, were observed in abundance in the shore zone only during daytime. Day and night differences in predatorprey dynamics were likely a primary driver of diel differences in nekton abundances observed in the shore zone. No diel differences in species richness, nekton density, or species assemblage were found in the adjacent nearshore area. Daytime sampling predominates in studies of shore-zone nekton and our results show the value of also sampling at night. Future research should include samples throughout the diel cycle and include tagging and movement data to allow a better understanding of diel dynamics of nekton along sandy beach shores.

Shoreline hardening alters the morphology of the intertidal zone 10 and has been shown to impact various measures of shore zone habitat quality. Diet composition and stomach fullness of two predatory fishes, the Bluefish Pomatomus saltatrix and Weakfish Cynoscion regalis, were compared between natural (beach) shorelines and adjacent hardened (riprap) shorelines at three sites in Delaware Bay 15 during July and August 2013 to assess differences in shore zone habitat function. Young Bluefish were available from one site, and their diet consisted primarily of Bay Anchovy Anchoa mitchilli, Atlantic Silversides Menidia menidia, and the mysid shrimp Neomysis americana. Bluefish diet composition differed significantly