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Climate change is altering the distribution and abundance of fish species in ways not anticipated by current management policy. We created spatially explicit, dynamic models of marine habitats that can inform stock assessments for 25 commercial species on the US Northeast Shelf. The habitat models integrated substrate and seabed features along with the dynamic properties of the ocean. Changes in climate-mediated habitat can affect the survey results by altering the availability component of catchability. Changes in availability were examined (1980–2014) by combining species distribution models with hindcast ocean models. Three patterns in availability were evident: (1) the availability for most species varied over time with no trend; (2) for a number of estuary-dependent species, availability varied with no trend and then dropped dramatically in 2009 when the federal trawl survey changed vessels; and (3) for a set of mid-depth, non-estuary dependent species, availability showed a continuous decline over time. There were few changes in dynamic habitat as the bottom water temperature did not exhibit a strong trend over the time-period studied, resulting in little climate-attributed changes in catchability. Changes in survey design can also have dramatic impacts on catchability, highlighting the method's ability to detect both climate driven and survey driven changes in catchability. [ABSTRACT FROM AUTHOR]

A pressing challenge for climate-vulnerable fisheries is how to manage now for present and future climate change. In contrast to climate forecasting approaches, we track integrated signals of change for example populations in a climatically forced region and use stochastic dynamic programming to compare the performance of a range of management-ready policies over all possible future states. Our main results highlight: (i) that biomass-linked harvest control rules (HCRs) can partially compensate for changing production, even if the HCR is time invariant; and (ii) that the form of utility (e.g. risk neutral or risk averse) can result in remarkably different optimal decision paths. Performance over future horizons degrades marginally from dynamic HCRs to static HCRs (except at low productivity where differences are more pronounced) but markedly when the biomass level is ignored altogether, as is the case in many managed fish populations globally. Understanding the processes whereby climate affects productivity is important for interpreting past data, but forecasts are not needed for tactical decision making now. Instead, we argue that the priorities for managing fish stocks influenced by climate change are to: measure the current productivity, assess the current abundance of the stock, and respond with a dynamic HCR. [ABSTRACT FROM AUTHOR]

Marine ecosystems have been heavily impacted by fishing pressure, which can cause major changes in the structure of communities. Fishing directly removes biomass and causes secondary effects such as changing predatory and competitive interactions and altering energy pathways, all of which affect the functional groups and size distributions of marine ecosystems. We conducted a meta-analysis of eighteen trawl surveys from around the world to identify if there have been consistent changes in size-structure and life history groups across ecosystems. Declining biomass trends for larger fish and invertebrates were present in nine systems, all in the North Atlantic, while seven ecosystems did not exhibit consistent declining trends in larger organisms. Two systems had alternative patterns. Smaller taxa, across all ecosystems, had biomass trends with time that were typically flat or slightly increasing. Changes in the ratio of pelagic taxa to demersal taxa were variable across the surveys. Pelagic species were not uniformly increasing, but did show periods of increase in certain regions. In the western Atlantic, the pelagic-todemersal ratio increased across a number of surveys in the 1990s and declined in the mid 2000s. The trawl survey data suggest there have been considerable structural changes over time and region, but the patterns are not consistent across all ecosystems. [ABSTRACT FROM AUTHOR]

Climate change and fishing can have major impacts on the distribution of natural marine resources. Climate change alters the distribution of suitable habitat, forcing organisms to shift their range or attempt to survive under suboptimal conditions. Fishing reduces the abundance of marine populations and truncates their age structure leading to range contractions or shifts. Along the east coast of the United States, there have been major changes in fish populations due to the impacts of fishing and subsequent regulations, as well as changes in the climate. Black sea bass, scup, summer flounder, and winter flounder are important commercial and recreational species, which utilize inshore and offshore waters on the northeast shelf. We examined the distributions of the four species with the Northeast Fisheries Science Center trawl surveys to determine if the along-shelf centres of biomass had changed over time and if the changes were attributed to changes in temperature or fishing pressure through changes in abundance and length structure. Black sea bass, scup, and summer flounder exhibited significant poleward shifts in distributions in at least one season while the Southern New England/Mid-Atlantic Bight stock of winter flounder did not shift. Generalized additive modelling indicated that the changes in the centres of biomass for black sea bass and scup in spring were related to climate, while the change in the distribution of summer flounder was largely attributed to a decrease in fishing pressure and an expansion of the length-age structure. While the changes in ocean temperatures will have major impacts on the distribution of marine taxa, the effects of fishing can be of equivalent magnitude and on a more immediate time scale. It is important for management to take all factors into consideration when developing regulations for natural marine resources. [ABSTRACT FROM AUTHOR]

Marine organisms that utilize nearshore environments for major components of their life histories are subject to both local-scale forcing such as water quality and estuarine degradation as well as large-scale forcing such as fishing and decadal-scale climate variability. Large-scale forcing has the potential to synchronize the dynamics of subpopulations, while local-level forcing can produce asynchronous subpopulation trends. Summer flounder (Paralichthys dentatus) and winter flounder (Pseudopleuronectes americanus) are important commercial and recreational flatfish along the east coast of North America which spend their first year of life in coastal habitats. We found that the two exhibited significant within-species coherence in commercial landings and fisheries-independent surveys across the northeast shelf of the United States, suggesting large-scale external drivers. In laboratory studies, temperature has been found to be an important factor regulating survival during the egg, larva and settlement phases of both species. We reconstructed a 40-year time-series of coastal water temperature for the major spawning and nursery areas to examine changes in the thermally available habitat. Estimates of winter flounder abundance were negatively correlated with the winter water temperature, but not with fishing mortality. Summer flounder abundance, by contrast, was negatively correlated with fishing mortality, but exhibited no link with temperature. In addition, time-varying stock–recruitment relationships indicated that stock productivity declined for winter flounder over time, while summer flounder productivity has varied without a trend. While both species declined in the 1980s and early 1990s due to heavy fishing pressure, the reduction in fishing over the last two decades has led to rebuilding of the summer flounder stock and an expansion of its age structure. Declining productivity due to warming estuarine conditions has kept the winter flounder stock at low levels despite low fishing pressure. The two stocks illustrate the importance of controlling fishing mortality in the management of natural marine resources while also accounting for changes in productivity due to climate variability and change. [ABSTRACT FROM AUTHOR]