Abstract
After 20+ years as a research scientist, I recently made a career change to a scientific administrator in NOAA Fisheries. Part of the NOAA Fisheries mission is to provide scientific advice ...for fisheries using ecosystem based approaches to management. Where I used to see fisheries science as a relatively straightforward discipline, I now recognize fisheries as a complex socio-ecological system that spans natural and social sciences. With this recognition has come an appreciation for the concept of wicked problems and for the incremental approach to policy-making. Here I describe my perspectives before and after this recognition and present 10 lessons for myself as a guide to providing science in support of fisheries management.
Fisheries oceanography is largely an applied discipline with a major goal of improving fisheries management and marine conservation. Johan Hjort's critical period hypothesis, and its decedents, ...remain a dominant theme and focuses on year-class success as mediated by prey availability and feeding. Bottom-up forcing, a related hypothesis, focuses on the sequential transfer of energy through the pelagic foodweb from primary productivity to fishery productivity. Another approach assumes that trophic interactions of adults determine abundance. Fisheries assessment and management, however, is based on the hypothesis that fishery abundance is determined by time-varying fishing and year-class success related to spawning-stock biomass. These approaches, their basic hypotheses, and underlying processes and mechanisms suggest very different dynamics for fishery populations. Other hypotheses challenge these traditional views: predation of early life stages, parental condition, shifting migration pathways, and physiological limits. Support for these other hypotheses is reviewed and the research needs are described to apply these hypotheses to fisheries assessment and management. Some of these hypotheses were identified by Hjort (e.g. parental condition hypothesis) and others are relative new (e.g. early life stage predation hypothesis). Moving into the future, we should focus on Hjort's approach: multi-hypothesis, integrative, and interdisciplinary. A range of hypotheses should be pursued with an emphasis on comparing and linking multiple hypotheses. The results then must be incorporated into fishery assessments and management decisions to support the long-term sustainability of exploited species and the conservation of threatened and endangered species.
Many studies illustrate variable patterns in individual species distribution shifts in response to changing temperature. However, an assemblage, a group of species that shares a common environmental ...niche, will likely exhibit similar responses to climate changes, and these community-level responses may have significant implications for ecosystem function. Therefore, we examine the relationship between observed shifts of species in assemblages and regional climate velocity (i.e., the rate and direction of change of temperature isotherms). The assemblages are defined in two sub-regions of the U.S. Northeast Shelf that have heterogeneous oceanography and bathymetry using four decades of bottom trawl survey data and we explore temporal changes in distribution, spatial range extent, thermal habitat area, and biomass, within assemblages. These sub-regional analyses allow the dissection of the relative roles of regional climate velocity and local physiography in shaping observed distribution shifts. We find that assemblages of species associated with shallower, warmer waters tend to shift west-southwest and to shallower waters over time, possibly towards cooler temperatures in the semi-enclosed Gulf of Maine, while species assemblages associated with relatively cooler and deeper waters shift deeper, but with little latitudinal change. Conversely, species assemblages associated with warmer and shallower water on the broad, shallow continental shelf from the Mid-Atlantic Bight to Georges Bank shift strongly northeast along latitudinal gradients with little change in depth. Shifts in depth among the southern species associated with deeper and cooler waters are more variable, although predominantly shifts are toward deeper waters. In addition, spatial expansion and contraction of species assemblages in each region corresponds to the area of suitable thermal habitat, but is inversely related to assemblage biomass. This suggests that assemblage distribution shifts in conjunction with expansion or contraction of thermal habitat acts to compress or stretch marine species assemblages, which may respectively amplify or dilute species interactions to an extent that is rarely considered. Overall, regional differences in climate change effects on the movement and extent of species assemblages hold important implications for management, mitigation, and adaptation on the U.S. Northeast Shelf.
Many studies have documented long-term changes in adult marine fish distributions and linked these changes to climate change and multi-decadal climate variability. Most marine fish, however, have ...complex life histories with morphologically distinct stages, which use different habitats. Shifts in distribution of one stage may affect the connectivity between life stages and thereby impact population processes including spawning and recruitment. Specifically, many marine fish species have a planktonic larval stage, which lasts from weeks to months. We compared the spatial distribution and seasonal occurrence of larval fish in the Northeast U.S. Shelf Ecosystem to test whether spatial and temporal distributions changed between two decades. Two large-scale ichthyoplankton programs sampled using similar methods and spatial domain each decade. Adult distributions from a long-term bottom trawl survey over the same time period and spatial area were also analyzed using the same analytical framework to compare changes in larval and adult distributions between the two decades. Changes in spatial distribution of larvae occurred for 43% of taxa, with shifts predominately northward (i.e., along-shelf). Timing of larval occurrence shifted for 49% of the larval taxa, with shifts evenly split between occurring earlier and later in the season. Where both larvae and adults of the same species were analyzed, 48% exhibited different shifts between larval and adult stages. Overall, these results demonstrate that larval fish distributions are changing in the ecosystem. The spatial changes are largely consistent with expectations from a changing climate. The temporal changes are more complex, indicating we need a better understanding of reproductive timing of fishes in the ecosystem. These changes may impact population productivity through changes in life history connectivity and recruitment, and add to the accumulating evidence for changes in the Northeast U.S. Shelf Ecosystem with potential to impact fisheries and other ecosystem services.
Changing climatic conditions are affecting the relationship between fishing communities and the marine resources they depend on. This shift will require an adaptive response on the part of policy ...makers and fishery managers. In the U.S., the National Oceanic and Atmospheric Administration (NOAA) established, in its fisheries agency (NOAA Fisheries), a set of social indicators of fishing community vulnerability and resilience to evaluate the impacts of changes in fishery management regimes. These indicators enhance the analytical capabilities within NOAA Fisheries for conducting fisheries social impact assessments and informing ecosystem-based fishery management. Building on the existing Community Social Vulnerability Indicators (CSVIs), new measures of climate change vulnerability are defined for the U.S. Eastern and Gulf coasts. These new indicators are used to assess the impact of sea level rise on critical commercial fishing infrastructure and the dependence of communities on species identified as vulnerable to the effects of climate change. Examples are provided in this article to demonstrate the utility of these new indicators to policy makers and the NOAA strategic goal for building resilient coastal communities that are environmentally and economically sustainable. Integration of CSVIs and the new climate change vulnerability indices highlight community needs for unique solutions in order to adapt to environmental and social changes and maintain their well-being.
•A sea level rise risk indicator is developed at the community level.•Sea level rise risk alone may not capture all effects upon shoreline businesses.•A fish species vulnerability to climate change indicator is developed at the community level.•Indirect effects of climate change will have impacts for fishing dependent communities.
•Future changes in suitable thermal habitat for marine species on the U.S. NE Shelf.•Increasing ocean temperatures results in northward shifts for many species.•Potentially major changes in species ...complex in different regions of the Shelf.•Species may shift from one management jurisdiction to another.•Shifts of marine taxa may substantially effect local fishing communities.•Changes will depend on the pace of climate change and species’ adaptability.
The U.S. Northeast Continental Shelf marine ecosystem has warmed much faster than the global ocean and it is expected that this enhanced warming will continue through this century. Complex bathymetry and ocean circulation in this region have contributed to biases in global climate model simulations of the Shelf waters. Increasing the resolution of these models results in reductions in the bias of future climate change projections and indicates greater warming than suggested by coarse resolution climate projections. Here, we used a high-resolution global climate model and historical observations of species distributions from a trawl survey to examine changes in the future distribution of suitable thermal habitat for various demersal and pelagic species on the Shelf. Along the southern portion of the shelf (Mid-Atlantic Bight and Georges Bank), a projected 4.1°C (surface) to 5.0°C (bottom) warming of ocean temperature from current conditions results in a northward shift of the thermal habitat for the majority of species. While some southern species like butterfish and black sea bass are projected to have moderate losses in suitable thermal habitat, there are potentially significant increases for many species including summer flounder, striped bass, and Atlantic croaker. In the north, in the Gulf of Maine, a projected 3.7°C (surface) to 3.9°C (bottom) warming from current conditions results in substantial reductions in suitable thermal habitat such that species currently inhabiting this region may not remain in these waters under continued warming. We project a loss in suitable thermal habitat for key northern species including Acadian redfish, American plaice, Atlantic cod, haddock, and thorney skate, but potential gains for some species including spiny dogfish and American lobster. We illustrate how changes in suitable thermal habitat of important commercially fished species may impact local fishing communities and potentially impact major fishing ports along the U.S. Northeast Shelf. Given the complications of multiple drivers including species interactions and fishing pressure, it is difficult to predict exactly how species will shift. However, observations of species distribution shifts in the historical record under ocean warming suggest that temperature will play a primary role in influencing how species fare. Our results provide critical information on the potential for suitable thermal habitat on the U.S. Northeast Shelf for demersal species in the region, and may contribute to the development of ecosystem-based fisheries management strategies in response to climate change.
Atlantic bluefin tuna are a symbol of both the conflict between preservationist and utilitarian views of top ocean predators, and the struggle to reach international consensus on the management of ...migratory species. Currently, Atlantic bluefin tuna are managed as an early-maturing eastern stock, which spawns in the Mediterranean Sea, and a late-maturing western stock, which spawns in the Gulf of Mexico. However, electronic tagging studies show that many bluefin tuna, assumed to be of a mature size, do not visit either spawning ground during the spawning season. Whether these fish are spawning in an alternate location, skip-spawning, or not spawning until an older age affects how vulnerable this species is to anthropogenic stressors including exploitation. We use larval collections to demonstrate a bluefin tuna spawning ground in the Slope Sea, between the Gulf Stream and northeast United States continental shelf. We contend that western Atlantic bluefin tuna have a differential spawning migration, with larger individuals spawning in the Gulf of Mexico, and smaller individuals spawning in the Slope Sea. The current life history model, which assumes only Gulf of Mexico spawning, overestimates age at maturity for the western stock. Furthermore, individual tuna occupy both the Slope Sea and Mediterranean Sea in separate years, contrary to the prevailing view that individuals exhibit complete spawning-site fidelity. Overall, this complexity of spawning migrations questions whether there is complete independence in the dynamics of eastern and western Atlantic bluefin tuna and leads to lower estimates of the vulnerability of this species to exploitation and other anthropogenic stressors.
We tested the hypothesis that recent oceanographic changes associated with climate change in the Northeast United States continental shelf ecosystem have caused a change in spatial distribution of ...marine fish. To do this, we analyzed temporal trends from 1968 to 2007 in the mean center of biomass, mean depth, mean temperature of occurrence, and area occupied in each of 36 fish stocks. Temporal trends in distribution were compared to time series of both local- and large-scale environmental variables, as well as estimates of survey abundance. Many stocks spanning several taxonomic groups, life-history strategies, and rates of fishing exhibited a poleward shift in their center of biomass, most with a simultaneous increase in depth, and a few with a concomitant expansion of their northern range. However, distributional changes were highly dependent on the biogeography of each species. Stocks located in the southern extent of the survey area exhibited much greater poleward shifts in center of biomass and some occupied habitats at increasingly greater depths. In contrast, minimal changes in the center of biomass were observed in stocks with distributions limited to the Gulf of Maine, but mean depth of these stocks increased while stock size decreased. Large-scale temperature increase and changes in circulation, represented by the Atlantic Multidecadal Oscillation, was the most important factor associated with shifts in the mean center of biomass. Stock size was more often correlated with the total area occupied by each species. These changes in spatial distribution of fish stocks are likely to persist such that stock structure should be re-evaluated for some species.
Offshore renewable energy development is being sought by US coastal states to meet their renewable energy goals. Numerous offshore wind development projects are being proposed along the Atlantic ...coast, and additional areas are being explored in the Pacific. Commercial-scale offshore wind will share the seas with marine fisheries that provide immense economic, recreational, and cultural value as well as local food security. An acceleration in the number of proposed wind projects combined with a lack of clarity on how fishing activities are to be incorporated into the planning process has created numerous challenges for the fishing community and for fisheries managers. This paper explores ecological, human, and fishery management interactions with wind development, focusing on the Northeast US Shelf Large Marine Ecosystem. With an emphasis on a regional perspective, we identify key challenges to and opportunities for the goal of coexistence of offshore wind energy development and fishing activities, and we make several recommendations toward achieving this goal. Although the challenges to achieving coexistence of these two industries are significant, we argue that they are surmountable and can be overcome through a combination of collaboration, regional approaches, and innovation.
The state-space model framework provides a natural, probabilistic approach to stock assessment by modeling the stochastic nature of population survival and recruitment separately from sampling ...uncertainty inherent in observations on the population. We propose a state-space assessment model that is expanded to simultaneously treat environmental covariates as stochastic processes and estimate their effects on recruitment. We apply the model to southern New England yellowtail flounder (Limanda ferruginea) using data from the most recent benchmark assessment to evaluate evidence for effects of the mid-Atlantic cold pool and spawning stock biomass on recruitment. Based on Akaike’s information criterion, both the cold pool and spawning stock biomass were important predictors of recruitment and led to annual variation in estimated biomass reference points and associated yield. We also demonstrate the effect of the stochasticity of the mid-Atlantic cold pool on short-term forecasts of the stock size, biomass reference point, and stock status.
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