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2012 International Council for the Exploration of the Sea (ICES) Annual Science Conference (continued, pg 2.)

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Potential movement of fish and shellfish stocks from the Subarctic to the Arctic Ocean: Part B evaluation of the vulnerability of fish and shellfish stocks to changing environmental conditions. (Anne B. Hollowed, Harald Loeng, and Benjamin Planque)

An assessment of the likelihood that 17 fish or shellfish stocks or stock groups will move from the Subarctic areas into the Arctic Ocean is conducted. In this paper we assess the vulnerability of fish and shellfish stocks to exposure to climate induced environmental changes in Arctic and Subarctic ecosystems resulting from climate change. We assess the sensitivity and adaptability of 17 stocks from five ecosystems: the Barents Sea, the Eurasian shelves of the Arctic, the Bering Sea, and the Chukchi and Beaufort Seas. These comparisons reveal that several species are considered as candidate species to migrate into the high Arctic in the future, but it is anticipated that only six stocks have a high probability of establishing viable resident populations in the region. The ability of species to survive in the Arctic depends on how they respond to the physical and biological conditions of the region. Marine fauna that currently reside in the area exhibit adaptations that make them well suited for the challenging conditions of the Arctic. Examples of these adaptations include the following: i) capability of rapid growth to maximize the benefit of a short production season; ii) specific physiological characteristics to survive in cold conditions; iii) capability of inhabiting deep-ocean conditions to avoid ice in winter; iv) diversity of diets; v) broad spawning range, with low site fidelity, vi) high migration/dispersal rates; and vii) phenotypic plasticity.
 

Habitat & Climate: Species distribution and interaction in Arctic and Subarctic systems.  Delineating ecological regions and identifying biophysical drivers of community composition. (Matthew Baker and Anne Hollowed)

Species dynamics and interactions across systems are uniquely influenced by the constraints of physical habitat and differential response of species to common physical variables. Understanding spatial structure in marine systems and delineating meaningful spatial boundaries is integral to ecosystem approaches to fisheries management.  We develop and apply multivariate statistical methods to define spatially coherent ecological units or ecoregions, as one approach to defining management units in large marine ecosystems. We examine the role of habitat in moderating species distributions and interactions. We use random forest and other multivariate statistical methods to assess the importance of habitat in defining species distributions and quantify the importance of dominant physical variables for individual species. We also quantify multi-species or community composition turnover along environmental gradients and use these outputs to identify discrete ecoregions within large marine ecosystems. We evaluate the relative importance of predictor variables and apply clustering methods to define important regional boundaries. Spatial management and multispecies management of marine fisheries resources require robust methods to synthesize physical and biological data to identify regional structure within ecosystems and determine the relative impacts of various environmental and biological drivers. By integrating physical and biological data, we propose a quantitative method to partition ecosystems along ecologically significant gradients, which can serve as the basis for defining spatial management units applicable to ecosystem based management. We demonstrate this approach by identifying species distributions and delineating distinct ecoregions in the eastern Bering Sea. We also illustrate how dynamic physical drivers, such as climate, shift habitat gradients and alter ecoregion boundaries under different temperature regimes.
 

Age validation of Pacific cod using stable oxygen isotopes (δ18O). (Craig R. Kastelle, Thomas E. Helser, Dan G. Nichol, Delsa M. Anderl, Jennifer McKay, John W. Valley, and Ian J. Orland)

Measurements of stable oxygen and carbon isotopes (δ18O and δ13C) were obtained from Pacific cod (Gadus macrocephalus) ear bones (otoliths) using micro-sampling coupled with mass spectrometry. Up to 9-10 discrete measurements were obtained by micro milling from any one annual growth zone. Otoliths from nine Pacific cod that were tagged with temperature recording tags and at liberty between 1-2 years in the eastern Bering Sea and Gulf of Alaska were analyzed. The δ18O in the otoliths is partly a function of water temperature. Therefore,  sequential δ18O measurements representing the full lifespan of the fish were examined for seasonal variations. We further investigated the relationship between temperature and δ18O in the otoliths with the use of an ion microprobe and mass spectrometry. The goals of this study were to 1) validate Pacific cod ageing criteria of typical growth-zone counts with seasonal signatures of otolith δ18O, and 2) verify the relationship between otolith δ18O and temperature using archival tag temperatures. In more than half of the samples, Pacific cod otolith δ18O showed the expected cyclical pattern consistent with seasonal variation in temperatures. In some of these, the number of δ18O maxima showed a close correspondence to the estimated age from growth-zone counts, validating standard age interpretation methods, but overall the results were not completely definitive. However, there was a statistically significant relationship between δ18O and archival tag temperatures (r=0.74, p<0.01). The finer resolution measurements from the ion microprobe were compared to those based on micromilling to evaluate otolith δ18O and temperature.
 

Can marine protected areas achieve their goals as management tools in northern regions?  Practical lessons from Alaska, New England, and Norway. (Susanne F. McDermott, Erik Olsen, Lene Buhl Mortensen, Esben Morland Olsen, Deborah Hart, Alan Haynie, William Stockhausen, Paul Spencer, John V. Olson, Tore Johannessen, Erlend Moksness, Geir Dahle)

Ecosystem based marine spatial planning is an environmental management approach that recognizes all interactions within a marine system, including humans.   Marine protected areas (MPAs) have become increasingly popular as management tools of ecosystem based marine spatial planning.  While many MPAs have been successfully established in tropical reef systems, fewer MPA examples exist in temperate or subartic systems (e.g. North Pacific, Bering Sea) where species diversity is lower, abundance of single species is higher, and many fish species exhibit large amounts of movement in one or more of their life history stages, thus covering large geographic areas.  We review MPAs in three different ecosystems: in the Northeast Atlantic (Norway), in the Northeastern U.S. Atlantic waters (George’s Bank) and in the Northeast Pacific (Alaska). We discuss the effectiveness of these closures with regards to their initial objectives and expected and unexpected effects. We evaluate the effectiveness of MPAs as management tools in the different ecosystems and management scenarios. This paper was developed as a collaborative project between the Alaska Fisheries Science Center (Seattle), Alaska Regional office (Anchorage), Northeast Fisheries Science Center (Woods Hole), and the Institute of Marine Research (Bergen).
 

Improving survey derived indices of abundance by combining bottom trawl and acoustic data. (Stan Kotwicki, Patrick Ressler, Jim Ianelli, and André E. Punt)

The abundance of semi-pelagic species is commonly estimated using acoustic-trawl and bottom trawl surveys, both of which sample a restricted vertical zone.  Acoustic instruments are effective in the water column, but have a near-bottom acoustic dead zone, in which fish near the seafloor cannot be detected.  Bottom trawl surveys cannot account for fish that are located above the so-called effective fishing height in the bottom trawl blind zone. These blind zones create negative biases in abundance estimates derived from either method. Here, we present a method for deriving less biased, improved indices of abundance by incorporating estimates of bottom trawl efficiency parameters derived from combining acoustic and bottom trawl data. Bottom trawl efficiency parameters used are: effective fishing height, density-dependent efficiency, and catchability ratio between acoustic and bottom trawl abundance data. This method was applied to the time series of abundance indices derived from bottom trawl and acoustic-trawl surveys of walleye pollock in the eastern Bering Sea. Two new time series of indices of abundance were estimated. First, the bottom trawl survey time series was corrected to account for the density dependence of the bottom trawl efficiency. Second, a new time series of combined acoustic-trawl and bottom trawl survey data was estimated. Both of the new time series were compared with old bottom trawl and acoustic-trawl survey specific indices with respect to relative trends, uncertainty, and expected biases.
 

Combining bottom trawl and acoustic data to quantify expected biases in abundance estimates from bottom trawl and acoustic surveys. (Stan Kotwicki, Alex De Robertis, Jim Ianelli, André E. Punt and John Horne)

Abundances of semi-pelagic fishes are often estimated using acoustic-trawl and bottom trawl surveys, both of which sample a limited fraction of the water column.  Acoustic instruments have a near-bottom acoustic dead zone (ADZ), in which fish near the seafloor cannot be detected.  Bottom trawl surveys cannot account for fish that are located above the effective fishing height (EFH) of the trawl. We present a modeling method that combines acoustic and bottom trawl abundance and habitat data to derive ADZ correction and bottom trawl efficiency parameters. Our results show that predictions of fish abundance in the ADZ can be improved by incorporating bottom habitat features such as depth and sediment particle size, as well as pelagic habitat features such as water temperature, light level, and current velocity. We also obtain predictions for trawl efficiency parameters such as EFH, density-dependent trawl efficiency, and proportionality coefficients for trawl and acoustic data by modeling bottom trawl catches as a function of acoustic measurements and the environmentally dependent ADZ correction.  This method is applied to walleye pollock in the Eastern Bering Sea to quantify expected biases associated with each survey method and the dependence of the biases on environmental variables. The catchabilities of acoustic and bottom trawl survey methods are dependent on environmental variables, and the sampling biases are not stationary in time and space as is commonly assumed for survey data. Applying models that combine both bottom trawl and acoustic data can mitigate these problems for stock assessment as well as spatial dynamics studies.
 

In addition to the Center’s participation in the 2012 ICES symposium,  Susanne McDermott attended a trilateral U.S./Norway/Canada workshop that took place 14 September in Bergen.  The purpose of the workshop was to evaluate the progress to date and suggest future pathways for collaborative research among the three countries.  The AFSC has been involved for many years in collaborative projects and AFSC interests currently focus on collaboration in these major areas:  polar research projects, ocean acidification, comparative ecosystem studies, and advanced sampling technology.  Mike Sigler is the point of contact for future collaborative projects.

By Susanne McDermott, Anne Hollowed, Matt Baker, Craig Kastelle, Stan Kotwicki, Mike Sigler and Sandra Lowe
 

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