Anne B. Hollowed

Why fishing magnifies fluctuations in fish abundance

It is now clear that fished populations can fluctuate more than unharvested stocks. However, it is not clear why. Here we distinguish among three major competing mechanisms for this phenomenon, by using the 50-year California Cooperative Oceanic Fisheries Investigations (CalCOFI) larval fish record. First, variable fishing pressure directly increases variability in exploited populations. Second, commercial fishing can decrease the average body size and age of a stock, causing the truncated population to track environmental fluctuations directly. Third, age-truncated or juvenescent populations have increasingly unstable population dynamics because of changing demographic parameters such as intrinsic growth rates. We find no evidence for the first hypothesis, limited evidence for the second and strong evidence for the third. Therefore, in California Current fisheries, increased temporal variability in the population does not arise from variable exploitation, nor does it reflect direct environmental tracking. More fundamentally, it arises from increased instability in dynamics. This finding has implications for resource management as an empirical example of how selective harvesting can alter the basic dynamics of exploited populations, and lead to unstable booms and busts that can precede systematic declines in stock levels.

Pacific Basin climate variability and patterns of Northeast Pacific marine fish production

Abstract A review of oceanographic and climate data from the North Pacific and Bering Sea has revealed climate events that occur on two principal time scales: a) 2–7 years (i.e. El Nino Southern Oscillation, ENSO), and b) inter-decadal (i.e. Pacific Decadal Oscillation, PDO). The timing of ENSO events and of related oceanic changes at higher latitudes were examined. The frequency of ENSO was high in the 1980s. Evidence of ENSO forcing on ocean conditions in the North Pacific (Nino North conditions) showed ENSO events were more frequently observed along the West Coast than in the western Gulf of Alaska (GOA) and Eastern Bering Sea (EBS). Time series of catches for 30 region/species groups of salmon, and recruitment data for 29 groundfish and 5 non-salmonid pelagic species, were examined for evidence of a statistical relationship with any of the time scales associated with Nino North conditions or the PDO. Some flatfish stocks exhibited high autocorrelation in recruitment coupled with a significant step in recruitment in 1977 suggesting a relationship between PDO forcing and recruitment success. Five of the dominant gadid stocks (EBS and GOA Pacific cod, Pacific hake and EBS and GOA walleye pollock) exhibited low autocorrelation in recruitment. Of these, Pacific hake, GOA walleye pollock and GOA Pacific cod exhibited significantly higher incidence of strong year classes in years associated with Nino North conditions. These findings suggest that the PDO and ENSO may play an important role in governing year-class strength of several Northeast Pacific marine fish stocks.

Flatfish recruitment response to decadal climatic variability and ocean conditions in the eastern Bering Sea

Abstract This paper provides a retrospective analysis of the relationship of physical oceanography and biology and recruitment of three Eastern Bering Sea flatfish stocks: flathead sole (Hippoglossoides elassodon), northern rock sole (Lepidopsetta polyxystra), and arrowtooth flounder (Atheresthes stomias) for the period 1978–1996. Temporal trends in flatfish production in the Eastern Bering Sea are consistent with the hypothesis that decadal scale climate variability influences marine survival during the early life history period. Density-dependence (spawning stock size) is statistically significant in a Ricker model of flatfish recruitment, which includes environmental terms. Wind-driven advection of flatfish larvae to favorable nursery grounds was also found to coincide with years of above-average recruitment through the use of an ocean surface current simulation model (OSCURS). Ocean forcing of Bristol Bay surface waters during springtime was mostly shoreward (eastward) during the 1980s and seaward (westerly) during the 1990s, corresponding with periods of good and poor recruitment. Distance from shore and water depth at the endpoint of 90-day drift periods (estimated time of settlement) were also found to correspond with flatfish productivity.

Change is coming to the northern oceans

Cod and pollock abundances and distributions shift as climate and ocean conditions change The cold-temperate regions of the North Pacific and North Atlantic oceans, from about 40°N latitude to the Arctic fronts, support large and productive fisheries (1), particularly in the northernmost regions: the Bering Sea in the Pacific and the Barents Sea in the Atlantic. The two main near-bottom fish species in the Bering and Barents seas are walleye pollock (Gadus chalcogrammus) and Atlantic cod (G. morhua), respectively. In the past decade, the two species have responded differently to ocean warming. These response patterns appear to be linked to a complex suite of climatic and oceanic processes that may portend future responses to warming ocean conditions.

Are exploited fish populations stable

Shelton and Mangel (1) examined patterns of variability in fish populations and concluded that the higher stock variability observed in exploited species results from heightened effects of stochastic forcing in the supposed absence of nonlinear dynamics. In contrast, Anderson et al. (2) found that higher variability in these stocks is attributable to amplified nonlinear behavior in noisy ecological systems under exploitation. Here, we reconcile these apparently conflicting views and demonstrate that stochasticity of demographic parameters directly enhances nonlinearity (2–4), thus challenging assessments of stability based on statistical fits to noise-free models.

Trade-offs associated with different modeling approaches for assessment of fish and shellfish responses to climate change

Considerable progress has been made in integrating carbon, nutrient, phytoplankton and zooplankton dynamics into global-scale physical climate models. Scientists are exploring ways to extend the resolution of the biosphere within these Earth system models (ESMs) to include impacts on global distribution and abundance of commercially exploited fish and shellfish. This paper compares different methods for modeling fish and shellfish responses to climate change on global and regional scales. Several different modeling approaches are considered including: direct applications of ESM’s, use of ESM output for estimation of shifts in bioclimatic windows, using ESM outputs to force single- and multi-species stock projection models, and using ESM and physical climate model outputs to force regional bio-physical models of varying complexity and mechanistic resolution. We evaluate the utility of each of these modeling approaches in addressing nine key questions relevant to climate change impacts on living marine resources. No single modeling approach was capable of fully addressing each question. A blend of highly mechanistic and less computationally intensive methods is recommended to gain mechanistic insights and to identify model uncertainties.

Climate and oceanic fisheries: recent observations and projections and future needs

Several lines of evidence show that climatic variation and global warming can have a major effect on fisheries production and replenishment. To prevent overfishing and rebuild overfished stocks under changing and uncertain environmental conditions, new research partnerships between fisheries scientists and climate change experts are required. The International Workshop on Climate and Oceanic Fisheries held in Rarotonga, Cook Islands, 3–5 October 2011, brought representatives from these disciplines together to consider the effects of climate variability and change on oceanic fisheries, the tools and strategies required for identifying potential impacts on oceanic fisheries, and the priority adaptations for sustaining future harvests, especially in the Pacific Ocean. Recommendations made by the workshop included (1) development and implementation of sustainable management measures for fisheries; (2) long-term commitment to monitoring necessary to assess stock status and to conduct integrated ecosystem assessments; (3) process oriented research to evaluate the potential of marine species for adaptation to a changing ocean environment; (4) provision of improved national meteorological and hydrological services to fisheries agencies, enterprises and communities; (5) continuing communication of potential impacts and adaptation strategies to stakeholders to reduce the threats to oceanic fisheries and capitalise on opportunities; and (6) continued collaborative efforts between meteorological, oceanographic, biological and fisheries researchers and management agencies to better monitor and understand the impacts of short-term variability and longer-term change on oceanic fisheries.

Climate and Fisheries: The Past, The Future, and The Need for Coalescence

In this chapter we review the history of fisheries science with respect to climate impacts on fisheries and prognosticate the future of this type of research. Our review of the development of climate and fisheries research reveals that advances in our discipline emerge from the coalescence of four factors: shifts in fisheries economics and policy; developments in theoretical ecology; innovations in small-scale field and laboratory studies; and progress in large-scale fisheries statistics and modeling. Major advances have occurred when scientists interacted in multidisciplinary forums. We find that efforts to understand the impact of climate on the annual production and distribution of fish have produced a primary level of understanding of the processes underlying stock structure, production, and distribution of fish species. We find that ecosystem-based approaches to management have been advocated to a greater or lesser degree throughout the last century. In the future, we expect that advances in scientific understanding and improved computing power will allow scientists to explore the complex nature of environmental interactions occurring at different spatial and tem- poral scales. New field programs will develop to support the development of spatially explicit models of fish that include complex interactions within and between species, and fish behavior. Field sampling programs will benefit from continuing innovations in technology that improve collection of information on the abundance, distribution of fish, and the environment. New technologies will also be utilized in laboratory studies to rapidly assess the reproductive potential, food habits, and genetic history of fish under different environmental conditions. We expect that interdisciplinary training will continue to serve as a catalyst for new ideas in climate and fisheries. However, as researchers shift their focus from retrospective studies and now-casts to long-term implications of fishing and climate on the ecosystem we expect that training in ocea- nography, ecological theory, and environmental policy will be needed to provide a foundation for the development of models that depict the trade-offs of nature and human use in a realistic manner. Finally, we challenge fisheries scientists to track the accuracy of long- to medium-term forecasts of future states of nature and the potential impact of climate and fisheries on them.

Spatio-temporal models reveal subtle changes to demersal communities following the Exxon Valdez oil spill

Andrew O. Shelton*, Mary E. Hunsicker, Eric J. Ward, Blake E. Feist, Rachael Blake, Colette L. Ward, Benjamin C. Williams, Janet T. Duffy-Anderson, Anne B. Hollowed, and Alan C. Haynie Conservation Biology Division, Northwest Fisheries Science Center, National Marine Fisheries Service, National Oceanic and Atmospheric Administration, 2725 Montlake Blvd. E, Seattle, WA 98112, USA Fish Ecology Division, Northwest Fisheries Science Center, National Marine Fisheries Service, National Oceanic and Atmospheric Administration, 2032 SE OSU Drive, Newport, OR 97365, USA National Center for Ecological Analysis and Synthesis, University of California Santa Barbara, 735 State St. Suite 300, Santa Barbara, CA 93101, USA College of Fisheries and Ocean Sciences, University of Alaska Fairbanks, 17101 Point Lena Loop Rd., Juneau, AK 99801, USA Alaska Department of Fish and Game, Division of Commercial Fisheries, 1255 W. 8th Street, Juneau, AK 99802, USA Resource Assessment and Conservation Engineering Division, Alaska Fisheries Science Center, National Marine Fisheries Service, National Oceanic and Atmospheric Administration, 7600 Sand Point Way NE, Seattle, WA 98115, USA Resource Ecology and Fisheries Management Division, Alaska Fisheries Science Center, National Marine Fisheries Service, National Oceanic and Atmospheric Administration, 7600 Sand Point Way NE, Seattle, WA 98115, USA

Impacts of Climate Change on Marine Organisms

Considerable progress has been made in understanding physiological responses of marine organisms to climate change (Portner and Farrell, 2008; Somero, 2011) and in projecting future responses of individual species (Chown and Gaston, 2008; Helmuth, 2009). Key to this understanding are findings that indicate that multiple climate-related and non-climate-related stressors interact in their impacts on marine organisms, and that physiological responses to these stressors can be highly variable across species and life-history stages.