Showing papers by "National Marine Fisheries Service published in 2011"

Lessons in modelling and management of marine ecosystems: the Atlantis experience

Abstract: Models are key tools for integrating a wide range of system information in a common framework. Attempts to model exploited marine ecosystems can increase understanding of system dynamics; identify major processes, drivers and responses; highlight major gaps in knowledge; and provide a mechanism to ‘road test’ management strategies before implementing them in reality. The Atlantis modelling framework has been used in these roles for a decade and is regularly being modified and applied to new questions (e.g. it is being coupled to climate, biophysical and economic models to help consider climate change impacts, monitoring schemes and multiple use management). This study describes some common lessons learned from its implementation, particularly in regard to when these tools are most effective and the likely form of best practices for ecosystem-based management (EBM). Most importantly, it highlighted that no single management lever is sufficient to address the many trade-offs associated with EBM and that the mix of measures needed to successfully implement EBM will differ between systems and will change through time. Although it is doubtful that any single management action will be based solely on Atlantis, this modelling approach continues to provide important insights for managers when making natural resource management decisions.

Global Conservation Priorities for Marine Turtles

Abstract: Where conservation resources are limited and conservation targets are diverse, robust yet flexible priority-setting frameworks are vital. Priority-setting is especially important for geographically widespread species with distinct populations subject to multiple threats that operate on different spatial and temporal scales. Marine turtles are widely distributed and exhibit intra-specific variations in population sizes and trends, as well as reproduction and morphology. However, current global extinction risk assessment frameworks do not assess conservation status of spatially and biologically distinct marine turtle Regional Management Units (RMUs), and thus do not capture variations in population trends, impacts of threats, or necessary conservation actions across individual populations. To address this issue, we developed a new assessment framework that allowed us to evaluate, compare and organize marine turtle RMUs according to status and threats criteria. Because conservation priorities can vary widely (i.e. from avoiding imminent extinction to maintaining long-term monitoring efforts) we developed a ‘‘conservation priorities portfolio’’ system using categories of paired risk and threats scores for all RMUs (n = 58). We performed these assessments and rankings globally, by species, by ocean basin, and by recognized geopolitical bodies to identify patterns in risk, threats, and data gaps at different scales. This process resulted in characterization of risk and threats to all marine turtle RMUs, including identification of the world’s 11 most endangered marine turtle RMUs based on highest risk and threats scores. This system also highlighted important gaps in available information that is crucial for accurate conservation assessments. Overall, this priority-setting framework can provide guidance for research and conservation priorities at multiple relevant scales, and should serve as a model for conservation status assessments and prioritysetting for widespread, long-lived taxa.

Climate impacts on eastern Bering Sea foodwebs: a synthesis of new data and an assessment of the Oscillating Control Hypothesis

Abstract: ICES Journal of Marine Science; doi:10.1093/icesjms/fsr036 Climate impacts on eastern Bering Sea foodwebs: a synthesis of new data and an assessment of the Oscillating Control Hypothesis George L. Hunt Jr 1 *, Kenneth O. Coyle 3 , Lisa B. Eisner 4 , Edward V. Farley 4 , Ron A. Heintz 4 , Franz Mueter 5 , Jeffrey M. Napp 2 , James E. Overland 6 , Patrick H. Ressler 2 , Sigrid Salo 6 , and Phyllis J. Stabeno 6 School of Aquatic and Fishery Sciences, University of Washington, PO Box 355020, Seattle, WA 98195, USA NOAA-National Marine Fisheries Service, Alaska Fisheries Science Center, 7600 Sand Point Way NE, Seattle, WA 98115, USA Institute of Marine Science, University of Alaska, Fairbanks, AK 99775-7220, USA NOAA-National Marine Fisheries Service, Alaska Fisheries Science Center, Auke Bay Laboratories, 17109 Pt. Lena Loop Rd., Juneau, AK 99801, USA Juneau Center, School of Fisheries and Ocean Sciences, University of Alaska Fairbanks, 11120 Glacier Highway, Juneau, AK 99801, USA NOAA/OAR Pacific Marine Environmental Laboratory, 7600 Sand Point Way, NE, Seattle, WA 98115 –6249, USA *Corresponding Author: tel: +1 206 441 6109; fax: +1 260 685 7471; e-mail: geohunt2@uw.edu Hunt, G. L., Coyle, K. O., Eisner, L. B., Farley, E. V., Heintz, R. A., Mueter, F., Napp, J. M., Overland, J. E., Ressler, P. H., Salo, S., and Stabeno, P. J. Climate impacts on eastern Bering Sea foodwebs: a synthesis of new data and an assessment of the Oscillating Control Hypothesis. – ICES Journal of Marine Science, doi:10.1093/icesjms/fsr036 Received 29 June 2010; accepted 17 February 2011. Walleye pollock (Theragra chalcogramma) is an important component of the eastern Bering Sea ecosystem and subject to major fisheries. The Oscillating Control Hypothesis (OCH) predicted that recruitment of pollock year classes should be greatest in years with early ice retreat and late blooms in warm water, because more energy would flow into the pelagic (vs. benthic) community. The OCH further predicted that, with pollock population growth, there should be a shift from bottom-up to top-down regu- lation. New data support the predictions that in those years with early ice retreat, more primary production accrues to the pelagic compartment and that large numbers of age-0 pollock survive to summer. However, in these years, production of large crustacean zooplankton is reduced, depriving age-0 pollock of lipid-rich prey in summer and autumn. Consequently, age-0 pollock energy reserves (depot lipids) are low and predation on them is increased as fish switch to age-0 pollock from zooplankton. The result is weak recruitment of age-1 recruits the following year. A revised OCH indicates bottom-up constraints on pollock recruitment in very warm periods. Prolonged warm periods with decreased ice cover will likely cause diminished pollock recruitment and catches relative to recent values. Keywords: Bering Sea, climate change, crustacean zooplankton, Oscillating Control Hypothesis, sea ice cover, Theragra chalcogramma, walleye pollock, year-class strength. Introduction The Oscillating Control Hypothesis (OCH) was developed as a conceptual model of how walleye pollock (Theragra chalco- gramma) recruitment in the southeastern Bering Sea might be affected by climate variability (Hunt et al., 2002a, 2008). The OCH was based on several assumptions about the relation- ships between temperature, zooplankton, and the growth and survival of young pollock. It was an extension of the ideas of Walsh and McRoy (1986) working in the Bering Sea and of Bailey (2000), who had determined that the control of walleye pollock recruitment in the Gulf of Alaska had shifted from bottom-up control of early larval survival to top-down control of juvenile stages. The OCH extended Bailey’s work by attempting to develop explicit mechanistic hypotheses that would link pollock recruitment to the effects of climate in the southeastern Bering Sea. This paper reviews the assumptions and predictions of the OCH (Hunt et al., 2002a) and updates the OCH to account for new information available since 2002. The result is a new version of the OCH, which still predicts variation in the dominant mechanism for control of pollock recruitment and now hypothesizes that the dominant mechanism affecting pollock recruitment in stanzas of very warm years will be bottom-up impacts on the survival of age-0 pollock in their first autumn and winter. The eastern Bering Sea supports major fisheries, the largest of which is for walleye pollock, a gadid that is or has been the subject of fisheries throughout the northern Pacific Ocean from Puget Sound, WA, to the east coast of Japan and the Sea of Okhotsk (Hunt and Drinkwater, 2005). In the eastern Bering Sea, pollock biomass expanded rapidly in the 10 years after the 1976/ 1977 “regime shift” (Hare and Mantua, 2000), buoyed by the extra- ordinarily strong 1978 year class (Ianelli et al., 2010). Because International Council for the Exploration of the Sea. Published by Oxford Journals. All rights reserved. For Permissions, please email: journals.permissions@oup.com

Impacts of changing sea-ice conditions on Arctic marine mammals

Abstract: Arctic sea ice has changed dramatically, especially during the last decade and continued declines in extent and thickness are expected for the decades to come. Some ice-associated marine mammals are already showing distribution shifts, compromised body condition and declines in production/abundance in response to sea-ice declines. In contrast, temperate marine mammal species are showing northward expansions of their ranges, which are likely to cause competitive pressure on some endemic Arctic species, as well as putting them at greater risk of predation, disease and parasite infections. The negative impacts observed to date within Arctic marine mammal populations are expected to continue and perhaps escalate over the coming decade, with continued declines in seasonal coverage of sea ice. This situation presents a significant risk to marine biodiversity among endemic Arctic marine mammals.

Understanding and Estimating Effective Population Size for Practical Application in Marine Species Management

Abstract: Effective population size (N(e)) determines the strength of genetic drift in a population and has long been recognized as an important parameter for evaluating conservation status and threats to genetic health of populations. Specifically, an estimate of N(e) is crucial to management because it integrates genetic effects with the life history of the species, allowing for predictions of a population's current and future viability. Nevertheless, compared with ecological and demographic parameters, N(e) has had limited influence on species management, beyond its application in very small populations. Recent developments have substantially improved N(e) estimation; however, some obstacles remain for the practical application of N(e) estimates. For example, the need to define the spatial and temporal scale of measurement makes the concept complex and sometimes difficult to interpret. We reviewed approaches to estimation of N(e) over both long-term and contemporary time frames, clarifying their interpretations with respect to local populations and the global metapopulation. We describe multiple experimental factors affecting robustness of contemporary N(e) estimates and suggest that different sampling designs can be combined to compare largely independent measures of N(e) for improved confidence in the result. Large populations with moderate gene flow pose the greatest challenges to robust estimation of contemporary N(e) and require careful consideration of sampling and analysis to minimize estimator bias. We emphasize the practical utility of estimating N(e) by highlighting its relevance to the adaptive potential of a population and describing applications in management of marine populations, where the focus is not always on critically endangered populations. Two cases discussed include the mechanisms generating N(e) estimates many orders of magnitude lower than census N in harvested marine fishes and the predicted reduction in N(e) from hatchery-based population supplementation.

Interacting effects of phenotypic plasticity and evolution on population persistence in a changing climate.

Abstract: Climate change affects individual organisms by altering development, physiology, behavior, and fitness, and populations by altering genetic and phenotypic composition, vital rates, and dynamics. We sought to clarify how selection, phenotypic plasticity, and demography are linked in the context of climate change. On the basis of theory and results of recent empirical studies of plants and animals, we believe the ecological and evolutionary issues relevant to population persistence as climate changes are the rate, type, magnitude, and spatial pattern of climate-induced abiotic and biotic change; generation time and life history of the organism; extent and type of phenotypic plasticity; amount and distribution of adaptive genetic variation across space and time; dispersal potential; and size and connectivity of subpopulations. An understanding of limits to plasticity and evolutionary potential across traits, populations, and species and feedbacks between adaptive and demographic responses is lacking. Integrated knowledge of coupled ecological and evolutionary mechanisms will increase understanding of the resilience and probabilities of persistence of populations and species.

Climate change in the southeastern Bering Sea: impacts on pollock stocks and implications for the oscillating control hypothesis

Abstract: Concern about impacts of climate change in the Bering Sea prompted several research programs to elucidate mechanistic links between climate and ecosystem responses. Following a detailed literature review, Hunt et al. (2011) (Deep-Sea Res. II, 49, 2002, 5821) developed a conceptual framework, the Oscillating Control Hypothesis (OCH), linking climaterelated changes in physical oceanographic conditions to stock recruitment using walleye pollock (Theragra chalcogramma) as a model. The OCH conceptual model treats zooplankton as a single box, with reduced zooplankton production during cold conditions, producing bottom-up control of apex predators and elevated zooplankton production during warm periods leading to top-down control by apex predators. A recent warming trend followed by rapid cooling on the Bering Sea shelf permitted testing of the OCH. During warm years (2003–06), euphausiid and Calanus marshallae populations declined, post-larval pollock diets shifted from a mixture of large zooplankton and small copepods to almost exclusively small copepods, and juvenile pollock dominated the diets of large predators. With cooling from 2006–09, populations of large zooplankton increased, post-larval pollock consumed greater proportions of C. marshallae and other large zooplankton, and juvenile pollock virtually disappeared from the diets of large pollock and salmon. These shifts in energy flow were accompanied by large declines in pollock stocks attributed to poor recruitment between 2001 and 2005. Observations presented here indicate the need for revision of the OCH to account for shifts in energy flow through differing food-web pathways due to warming and cooling on the southeastern Bering Sea shelf.

Current and Future Patterns of Global Marine Mammal Biodiversity

Abstract: Quantifying the spatial distribution of taxa is an important prerequisite for the preservation of biodiversity, and can provide a baseline against which to measure the impacts of climate change. Here we analyse patterns of marine mammal species richness based on predictions of global distributional ranges for 115 species, including all extant pinnipeds and cetaceans. We used an environmental suitability model specifically designed to address the paucity of distributional data for many marine mammal species. We generated richness patterns by overlaying predicted distributions for all species; these were then validated against sightings data from dedicated long-term surveys in the Eastern Tropical Pacific, the Northeast Atlantic and the Southern Ocean. Model outputs correlated well with empirically observed patterns of biodiversity in all three survey regions. Marine mammal richness was predicted to be highest in temperate waters of both hemispheres with distinct hotspots around New Zealand, Japan, Baja California, the Galapagos Islands, the Southeast Pacific, and the Southern Ocean. We then applied our model to explore potential changes in biodiversity under future perturbations of environmental conditions. Forward projections of biodiversity using an intermediate Intergovernmental Panel for Climate Change (IPCC) temperature scenario predicted that projected ocean warming and changes in sea ice cover until 2050 may have moderate effects on the spatial patterns of marine mammal richness. Increases in cetacean richness were predicted above 40u latitude in both hemispheres, while decreases in both pinniped and cetacean richness were expected at lower latitudes. Our results show how species distribution models can be applied to explore broad patterns of marine biodiversity worldwide for taxa for which limited distributional data are available.

Potential impacts of climate change on Northeast Pacific marine foodwebs and fisheries

Abstract: Although there has been considerable research on the impacts of individual changes in water temperature, carbonate chemistry, and other variables on species, cumulative impacts of these effects have rarely been studied. Here, we simulate changes in (i) primary productivity, (ii) species range shifts, (iii) zooplankton community size structure, (iv) ocean acidification, and (v) ocean deoxygenation both individually and together using five Ecopath with Ecosim models of the northeast Pacific Ocean. We used a standardized method to represent climate effects that relied on time-series forcing functions: annual multipliers of species productivity. We focused on changes in fisheries landings, biomass, and ecosystem characteristics (diversity and trophic indices). Fisheries landings generally declined in response to cumulative effects and often to a greater degree than would have been predicted based on individual climate effects, indicating possible synergies. Total biomass of fished and unfished functional groups displayed a decline, though unfished groups were affected less negatively. Some functional groups (e.g. pelagic and demersal invertebrates) were predicted to respond favourably under cumulative effects in some regions. The challenge of predicting climate change impacts must be met if we are to adapt and manage rapidly changing marine ecosystems in the 21st century.

Zooplankton species composition is linked to ocean transport in the Northern California Current

Abstract: In the Northern California Current (NCC), zooplankton communities show interannual and multiyear shifts in species dominance that are tracked by survival of salmon populations. These zooplankton community changes correlate with the Pacific Decadal Oscillation (PDO) index: a 'warm-water' copepod species group is more abundant during warm (positive) phases of the PDO and less abundant during cold (negative) phases; the reverse occurs for a 'cold-water' species group. The observed relationship led to the hypothesis that the relative dominance of warm/cold-water copepods in the NCC is driven by changes in the horizontal advection of surface water over different phases of the PDO. To test this hypothesis, variation in surface water advection to coastal regions of the NCC over the period of 1950-2008 was investigated using a Regional Ocean Modeling System (ROMS) and passive tracer experiments, then was compared with zooplankton collected off Oregon since 1996. Results showed that surface water advection varied with the phase of the PDO; the low-frequency component of advection anomalies strongly correlated with copepod species composition (R > 0.9). During positive phases of the PDO, current anomalies were northward and onshore, resulting in transport of warmer waters and the associated copepods into the region. During negatives phases, increased equatorward current anomalies led to a copepod community that was dominated by cold-water taxa. Our results support the hypothesis that climate-driven changes in basin-scale circulation controls copepod community composition in the NCC, and demonstrate that large-scale climate forcings downscale to influence local and regional ecosystem structure.

Functional responses and scaling in predator-prey interactions of marine fishes: contemporary issues and emerging concepts.

Abstract: Predator–prey interactions are a primary structuring force vital to the resilience of marine communities and sustainability of the worlds oceans. Human influences on marine ecosystems mediate changes in species interactions. This generality is evinced by the cascading effects of overharvesting top predators on the structure and function of marine ecosystems. It follows that ecological forecasting, ecosystem management, and marine spatial planning require a better understanding of food web relationships. Characterising and scaling predator– prey interactions for use in tactical and strategic tools (i.e. multi-species management and ecosystem models) are paramount in this effort. Here, we explore what issues are involved and must be considered to advance the use of predator–prey theory in the context of marine fisheries science. We address pertinent contemporary ecological issues including (1) the approaches and complexities of evaluating predator responses in marine systems; (2) the scaling up of predator–prey interactions to the population, community, and ecosystem level; (3) the role of predator–prey theory in contemporary fisheries and ecosystem modelling approaches; and (4) directions for the future. Our intent is to point out needed research directions that will improve our understanding of predator–prey interactions in the context of the sustainable marine fisheries and ecosystem management.

Integrating Stomach Content and Stable Isotope Analyses to Quantify the Diets of Pygoscelid Penguins

Abstract: Stomach content analysis (SCA) and more recently stable isotope analysis (SIA) integrated with isotopic mixing models have become common methods for dietary studies and provide insight into the foraging ecology of seabirds. However, both methods have drawbacks and biases that may result in difficulties in quantifying inter-annual and species-specific differences in diets. We used these two methods to simultaneously quantify the chick-rearing diet of Chinstrap (Pygoscelis antarctica) and Gentoo (P. papua) penguins and highlight methods of integrating SCA data to increase accuracy of diet composition estimates using SIA. SCA biomass estimates were highly variable and underestimated the importance of softbodied prey such as fish. Two-source, isotopic mixing model predictions were less variable and identified inter-annual and species-specific differences in the relative amounts of fish and krill in penguin diets not readily apparent using SCA. In contrast, multi-source isotopic mixing models had difficulty estimating the dietary contribution of fish species occupying similar trophic levels without refinement using SCA-derived otolith data. Overall, our ability to track inter-annual and species-specific differences in penguin diets using SIA was enhanced by integrating SCA data to isotopic mixing modes in three ways: 1) selecting appropriate prey sources, 2) weighting combinations of isotopically similar prey in two-source mixing models and 3) refining predicted contributions of isotopically similar prey in multi-source models.

Humpback whale abundance in the North Pacific estimated by photographic capture-recapture with bias correction from simulation studies

Abstract: We estimated the abundance of humpback whales in the North Pacific by capture-recapture methods using over 18,000 fluke identification photographs collected in 2004–2006. Our best estimate of abundance was 21,808 (CV = 0.04). We estimated the biases in this value using a simulation model. Births and deaths, which violate the assumption of a closed population, resulted in a bias of +5.2%, exclusion of calves in samples resulted in a bias of −10.5%, failure to achieve random geographic sampling resulted in a bias of −0.4%, and missed matches resulted in a bias of +9.3%. Known sex-biased sampling favoring males in breeding areas did not add significant bias if both sexes are proportionately sampled in the feeding areas. Our best estimate of abundance was 21,063 after accounting for a net bias of +3.5%. This estimate is likely to be lower than the true abundance due to two additional sources of bias: individual heterogeneity in the probability of being sampled (unquantified) and the likely existence of an unknown and unsampled breeding area (−8.7%). Results confirm that the overall humpback whale population in the North Pacific has continued to increase and is now greater than some prior estimates of prewhaling abundance.

Crucial role of mechanisms and modes of toxic action for understanding tissue residue toxicity and internal effect concentrations of organic chemicals.

Abstract: This article reviews the mechanistic basis of the tissue residue approach for toxicity assessment (TRA). The tissue residue approach implies that whole-body or organ concentrations (residues) are a better dose metric for describing toxicity to aquatic organisms than is the aqueous concentration typically used in the external medium. Although the benefit of internal concentrations as dose metrics in ecotoxicology has long been recognized, the application of the tissue residue approach remains limited. The main factor responsible for this is the difficulty of measuring internal concentrations. We propose that environmental toxicology can advance if mechanistic considerations are implemented and toxicokinetics and toxicodynamics are explicitly addressed. The variability in ecotoxicological outcomes and species sensitivity is due in part to differences in toxicokinetics, which consist of several processes, including absorption, distribution, metabolism, and excretion (ADME), that influence internal concentrations. Using internal concentrations or tissue residues as the dose metric substantially reduces the variability in toxicity metrics among species and individuals exposed under varying conditions. Total internal concentrations are useful as dose metrics only if they represent a surrogate of the biologically effective dose, the concentration or dose at the target site. If there is no direct proportionality, we advise the implementation of comprehensive toxicokinetic models that include deriving the target dose. Depending on the mechanism of toxicity, the concentration at the target site may or may not be a sufficient descriptor of toxicity. The steady-state concentration of a baseline toxicant associated with the biological membrane is a good descriptor of the toxicodynamics of baseline toxicity. When assessing specific-acting and reactive mechanisms, additional parameters (e.g., reaction rate with the target site and regeneration of the target site) are needed for characterization. For specifically acting compounds, intrinsic potency depends on 1) affinity for, and 2) type of interaction with, a receptor or a target enzyme. These 2 parameters determine the selectivity for the toxic mechanism and the sensitivity, respectively. Implementation of mechanistic information in toxicokinetic–toxicodynamic (TK–TD) models may help explain timedelayed effects, toxicity after pulsed or fluctuating exposure, carryover toxicity after sequential pulses, and mixture toxicity.We believe that this mechanistic understanding of tissue residue toxicity will lead to improved environmental risk assessment.

Where the wild things are: predicting hotspots of seabird aggregations in the California Current System

Abstract: Marine protected areas (MPAs) provide an important tool for conservation of marine ecosystems. To be most effective, these areas should be strategically located in a manner that supports ecosystem function. To inform marine spatial planning and support strategic establishment of MPAs within the California Current System, we identified areas predicted to support multispecies aggregations of seabirds ("hotspots"). We developed habitat-association models for 16 species using information from at-sea observations collected over an 11-year period (1997-2008), bathymetric data, and remotely sensed oceanographic data for an area from north of Vancouver Island, Canada, to the USA/Mexico border and seaward 600 km from the coast. This approach enabled us to predict distribution and abundance of seabirds even in areas of few or no surveys. We developed single-species predictive models using a machine-learning algorithm: bagged decision trees. Single-species predictions were then combined to identify potential hotspots of seabird aggregation, using three criteria: (1) overall abundance among species, (2) importance of specific areas ("core areas") to individual species, and (3) predicted persistence of hotspots across years. Model predictions were applied to the entire California Current for four seasons (represented by February, May, July, and October) in each of 11 years. Overall, bathymetric variables were often important predictive variables, whereas oceanographic variables derived from remotely sensed data were generally less important. Predicted hotspots often aligned with currently protected areas (e.g., National Marine Sanctuaries), but we also identified potential hotspots in Northern California/Southern Oregon (from Cape Mendocino to Heceta Bank), Southern California (adjacent to the Channel Islands), and adjacent to Vancouver Island, British Columbia, that are not currently included in protected areas. Prioritization and identification of multispecies hotspots will depend on which group of species is of highest management priority. Modeling hotspots at a broad spatial scale can contribute to MPA site selection, particularly if complemented by fine-scale information for focal areas.

Reduced recruitment performance in natural populations of anadromous salmonids associated with hatchery-reared fish

Abstract: We found a negative relationship between the reproductive performance in natural, anadromous populations of steelhead trout (Oncorhynchus mykiss), coho salmon (O. kisutch), and Chinook salmon (O. tshawytscha), and the propor- tion of hatchery fish in the spawning population. We used intrinsic productivity as estimated from fitting a variety of re- cruitment models to abundance data for each population as our indicator of reproductive performance. The magnitude of this negative relationship is such that we predict the recruitment performance for a population composed entirely of hatch- ery fish would be 0.128 of that for a population composed entirely of wild fish. The effect of hatchery fish on reproductive performance was the same among all three species. Further, the impact of hatchery fish from ''wild type'' hatchery brood- stocks was no less adverse than hatchery fish from traditional, domesticated broodstocks. We also found no support for the hypothesis that a population's reproductive performance was affected by the length of exposure to hatchery fish. In most cases, measures that minimize the interactions between wild and hatchery fish will be the best long-term conservation strategy for wild populations. Resume´ : Nous observons une relation negative entre la performance reproductive de populations naturelles de truites arc- en-ciel anadromes (Oncorhynchus mykiss), de saumons coho (O. kisutch) et de saumons chinook (O. tshawytscha )e t la proportion de poissons de pisciculture dans les populations de reproducteurs. Nous utilisons la productiviteintrinseque esti- mee en ajustant une varietede modeles de recrutement aux donnees d'abondance de chaque population comme indice de performance reproductive. L'importance de cette relation negative est telle que nous predisons que la performance du re- crutement dans une population composee entierement de poissons de pisciculture serait de 0,128 celle d'une population composee totalement de poissons sauvages. L'effet des poissons de pisciculture est le meme chez les trois especes. De plus, l'impact des poissons de pisciculture provenant de stocks reproducteurs de pisciculture de « type sauvage » n'est pas moins negatif que celui des poissons de pisciculture de stocks reproducteurs traditionnels et domestiques. Nous ne trouvons aucun appui a l'hypothese qui veut que la performance reproductive d'une population soit affectee par la duree de son ex- position aux poissons de pisciculture. Dans la plupart des cas, les mesures qui minimisent les interactions entre les pois- sons sauvages et les poissons de pisciculture constituent la meilleure strategie de conservation a long terme pour les populations sauvages. (Traduit par la Redaction)

Satellite remote sensing for an ecosystem approach to fisheries management

Abstract: Satellite remote sensing (SRS) of the marine environment has become instrumental in ecology for environmental monitoring and impact assessment, and it is a promising tool for conservation issues. In the context of an ecosystem approach to fisheries management (EAFM), global, daily, systematic, high-resolution images obtained from satellites provide a good data source for incorporating habitat considerations into marine fish population dynamics. An overview of the most common SRS datasets available to fishery scientists and state-of-the-art data-processing methods is presented, focusing on recently developed techniques for detecting mesoscale features such as eddies, fronts, filaments, and river plumes of major importance in productivity enhancement and associated fish aggregation. A comprehensive review of remotely sensed data applications in fisheries over the past three decades for investigating the relationships between oceanographic conditions and marine resources is provided, emphasizing how synoptic and informationrich SRS data have become instrumental in ecological analyses at community and ecosystem scales. Finally, SRS data, in conjunction with automated in situ data-acquisition systems, can provide the scientific community with a major source of information for ecosystem modelling, a key tool for implementing an EAFM.

Movements and behaviors of swordfish in the Atlantic and Pacific Oceans examined using pop‐up satellite archival tags

Abstract: Swordfish are highly specialized top-level predators that have been challenging to study. In this paper, data from 31 pop-up satellite archival tags attached to swordfish from (i) the eastern Pacific, (ii) central Pacific, and (iii) western North Atlantic-Caribbean were analyzed. Common across locations was a pronounced diel vertical pattern with daytime hours spent primarily below the thermocline and nighttime hours spent in warmer waters, close to the surface. One exception to this pattern was periodic daytime basking events which were most common in cooler waters off California. Maximum daytime depths were significantly correlated with light penetration as measured by the diffuse attenuation coefficient at 490 nm. Temperature did not appear to influence daytime depths, and swordfish tolerated both extremely low temperatures (4� C) and rapid and dramatic temperature changes (>20� C). Temperature did appear to influence the nighttime depths in the Pacific where fish typically remained in the surface mixed layer. In contrast, in the warm tropical Atlantic this was not the case, and nighttime depths were much deeper. In all areas, nighttime depth increased around the full moon. Given the parallels between the vertical movement patterns of swordfish and those of the deep sound scattering layer we suggest that swordfish vertical distribution patterns, especially during daytime, are influenced largely by resource availability. At night, when swordfish are typically targeted by fisheries, both ambient light and temperature influence movements. Understanding vertical movement patterns of swordfish can help evaluate gear vulnerability, improve population assessments, and potentially reduce fisheries bycatch.

Bayesian state-space model of fin whale abundance trends from a 1991–2008 time series of line-transect surveys in the California Current

Abstract: Summary 1. Estimating temporal trends in animal abundance is central to ecology and conservation, but obtaining useful trend estimates is challenging when animal detection rates vary across surveys (e.g. because of differences in observers or conditions). Methods exist for obtaining abundance estimates using capture–recapture and distance sampling protocols, but only recently have some of these been extended to allow direct estimation of abundance trends when detection rates vary. Extensions to distance sampling for >2 surveys have not yet been demonstrated. 2. We demonstrate a Bayesian approach for estimating abundance and population trends, using a time series of line-transect data for endangered fin whales Balaenoptera physalus off the west coast of the United States. We use a hierarchical model to partition state and observation processes. Population density is modelled as a function of covariates and random process terms, while observed counts are modelled as an overdispersed Poisson process with rates estimated as a function of population density and detection probability, which is modelled using distance sampling theory. We used Deviance Information Criteria to make multi-model inference about abundance and trend estimates. 3. Bayesian posterior distributions for trend parameters provide strong evidence of increasing fin whale abundance in the California Current study area from 1991 to 2008, while individual abundance estimates during survey years were considerably more precise than previously reported estimates using the same data. Assuming no change in underlying population dynamics, we predict continued increases in fin whale numbers over the next decade. Our abundance projections account for both sampling error in parameter estimates and process variance in annual abundance about the mean trend. 4. Synthesis and applications. Bayesian hierarchical modelling offers numerous benefits for analysing animal abundance trends. In our case, these included its implicit handling of sampling covariance, flexibility to accommodate random effects and covariates, ability to compare trend models of different functional forms and ability to partition sampling and process error to make predictions. Ultimately, by placing distance sampling within a more general hierarchical framework, we obtained more precise abundance estimates and an inference about fin whale trends that would have otherwise been difficult.

Guidelines for incorporating fish distribution shifts into a fisheries management context

Abstract: The impacts of climate change have been demonstrated to influence fisheries resources One way climate has affected fish stocks is via persistent shifts in spatio-temporal distribution Although examples of climate-forced distribution shifts abound, it is unclear how these shifts are practically accounted for in the management of fish stocks In particular, how can we take into account shifting stock distribution in the context of stock assessments and their management outputs? Here, we discuss examples of the types of fish stock distribution shifts that can occur We then propose a decision tree framework of how shifting stock distributions can be addressed Generally, the approaches for addressing such shifts fall into one of three main alternatives: re-evaluate stock identification, re-evaluate a stock unit area, or implement spatially explicit modelling We conclude by asserting that the approach recommended here is feasible with existing information and as such fisheries managers should be able to begin addressing the role of changes in stock distribution in these fish stocks The implications of not doing so could be notably undesirable

Small-scale fisheries of Peru: a major sink for marine turtles in the Pacific

Abstract: Summary 1. Over the last few decades, evidence of marine vertebrate bycatch has been collected for a range of industrial fisheries. It has recently been acknowledged that large impacts may also result from similar interactions with small-scale fisheries (SSF) due largely to their diffuse effort and large number of vessels in operation. Marine mammals, seabirds, turtles as well as some shark species have been reported as being impacted by SSF worldwide. 2. From 2000 to 2007, we used both shore-based and onboard observer programmes from three SSF ports in Peru to assess the impact on marine turtles of small-scale longline, bottom set nets and driftnet fisheries. 3. We reported a total of 807 sea turtles captured, 91AE8% of which were released alive. For these three sites alone, we estimated c. 5900 turtles captured annually (3200 loggerhead turtles Caretta caretta, 2400 green turtles Chelonia mydas, 240 olive ridleys Lepidochelys olivacea and 70 leatherback turtles Dermochelys coriacea). 4. SSF in Peru are widespread and numerous (>100 ports, >9500 vessels, >37 000 fishers), and our observed effort constituted c. 1% of longline and net deployments. We suggest that the number of turtles captured per year is likely to be in the tens of thousands. Thus, the impacts of Peruvian SSF have the potential to severely impact sea turtles in the Pacific especially green, loggerhead and leatherback turtles. 5. Implications of the human use of turtle products as ‘marine bushmeat’ are also raised as an important issue. Although such utilization is illegal, it is difficult to foresee how it can be managed without addressing the constraints to the livelihoods of those depending almost entirely on coastal resources. 6. Syntheses and applications. Our analysis demonstrates that, despite logistical challenges, it is feasible to estimate the bycatch per unit of effort in SSF by combining methods that account for fishing effort and bycatch, such as using onboard and shore-based observers. We highlight sea turtle bycatch in SSF in the southeast Pacific as a major conservation concern but also suggest possible paths for mitigation.

Time to evolve? Potential evolutionary responses of fraser river sockeye salmon to climate change and effects on persistence.

Abstract: Evolutionary adaptation affects demographic resilience to climate change but few studies have attempted to project changes in selective pressures or quantify impacts of trait responses on population dynamics and extinction risk. We used a novel individual-based model to explore potential evolutionary changes in migration timing and the consequences for population persistence in sockeye salmon Oncorhynchus nerka in the Fraser River, Canada, under scenarios of future climate warming. Adult sockeye salmon are highly sensitive to increases in water temperature during their arduous upriver migration, raising concerns about the fate of these ecologically, culturally, and commercially important fish in a warmer future. Our results suggest that evolution of upriver migration timing could allow these salmon to avoid increasingly frequent stressful temperatures, with the odds of population persistence increasing in proportion to the trait heritability and phenotypic variance. With a simulated 2uC increase in average summer river temperatures by 2100, adult migration timing from the ocean to the river advanced by ,10 days when the heritability was 0.5, while the risk of quasi-extinction was only 17% of that faced by populations with zero evolutionary potential (i.e., heritability fixed at zero). The rates of evolution required to maintain persistence under simulated scenarios of moderate to rapid warming are plausible based on estimated heritabilities and rates of microevolution of timing traits in salmon and related species, although further empirical work is required to assess potential genetic and ecophysiological constraints on phenological adaptation. These results highlight the benefits to salmon management of maintaining evolutionary potential within populations, in addition to conserving key habitats and minimizing additional stressors where possible, as a means to build resilience to ongoing climate change. More generally, they demonstrate the importance and feasibility of considering evolutionary processes, in addition to ecology and demography, when projecting population responses to environmental change.

Evaluating post-release behaviour modification in large pelagic fish deployed with pop-up satellite archival tags

Abstract: Hoolihan, J. P., Luo, J., Abascal, F. J., Campana, S. E., De Metrio, G., Dewar, H., Domeier, M. L., Howey, L. A., Lutcavage, M. E., Musyl, M. K., Neilson, J. D., Orbesen, E. S., Prince, E. D., and Rooker, J. R. 2011. Evaluating post-release behaviour modification in large pelagic fish deployed with pop-up satellite archival tags. – ICES Journal of Marine Science, 68: 880–889.Post-release behaviour modification, possibly a result of capture and handling stress, was evaluated using empirical eigenfunction analysis to detect changes in vertical movement patterns recorded by 183 pop-up satellite archival tags (PSATs) deployed on large pelagic fish. Argos-transmitted summary, timed interval, and some archival data were included. Scoring of irregular post-release behaviour was based on a separation of plotted eigenfunction coefficient values by their mean, with the transection across the mean reference line denoting the duration of irregular behaviour. In all, 67 (36.6%) individual fish exhibited irregular behaviour, lasting from 3 to 60 d (mean = 15.8, s.d. = 10.4). An additional 27 (14.8%) displayed patterns suggestive of irregular behaviour. Data quality and quantity were important criteria for revealing behaviour patterns. Irregular behaviour was detected in 32.6% of Argos-transmitted dataseries, increasing to 60.6% in the higher-resolution archival series. Decreased vertical movement characterized the irregular behaviour of blue sharks (Prionace glauca) and porbeagles (Lamna nasus), whereas all other species showed increased vertical activity. The approach described provides a useful method of revealing behavioural modification during the post-release recovery period of PSAT-tagged large pelagic fish, although the extent of influence on normal behaviour is not fully understood.

Adding Value to Ecological Risk Assessment with Population Modeling

Abstract: Current measures used to estimate the risks of toxic chemicals are not relevant to the goals of the environmental protection process, and thus ecological risk assessment (ERA) is not used as extensively as it should be as a basis for cost-effective management of environmental resources. Appropriate population models can provide a powerful basis for expressing ecological risks that better inform the environmental management process and thus that are more likely to be used by managers. Here we provide at least five reasons why population modeling should play an important role in bridging the gap between what we measure and what we want to protect. We then describe six actions needed for its implementation into management-relevant ERA.