Several REEM staff and contractors attended and presented results at the North Pacific Research Board Alaska Marine Science Symposium held in Anchorage, Alaska on 21-25 January 2013.
Drs. Stephani Zador and Kirstin Holsman presented a poster titled “Identifying and comparing ecosystem stressors in the eastern Bering Sea and Gulf of Alaska.” The poster describes a pilot study to develop metrics to represent the condition of marine ecosystems that can be used 1) to establish reference points useful for Alaska’s Integrated Ecosystem Assessment (IEA) and 2) to enable comparisons across ecosystems. The authors modified recent ecosystem index approaches (e.g., the Ocean Health Index by Halpern et al. 2012) to reflect conditions and stressors that are particular to Alaska, applied the index assessment to data collected from surveys of Alaska marine ecosystem experts, and conducted comparative analyses between the eastern Bering Sea (EBS) and Gulf of Alaska (GOA) ecosystems.
Drs. Stephani Zador, Olav Ormseth, and Heather Renner (U.S. Fish and Wildlife Service Alaska Maritime National Wildlife Refuge) presented a poster titled “Red flags or red herrings? Using ecosystem indicators to detect anomalous conditions in the Gulf of Alaska in 2011.” In this poster the authors presented the status of ecosystem indicators that cumulatively suggest that anomalous conditions occurred in the Gulf of Alaska during 2011. The first indications were noted in upper trophic organisms (seabirds and Pacific halibut) that experienced reproductive failures and potential nutrient deficiencies, respectively. Abundance indices of plankton and forage fish, halibut stomach contents, and ocean surface currents also indicated that anomalous conditions occurred during 2011. The authors compared multiple lines of evidence that suggested that changes in bottom-up forcing factors negatively influenced productivity at the lower trophic level, which in turn negatively influenced upper trophic organisms. They concluded that 1) synthesis of indicators’ status across multiple trophic levels can reveal broad-scale changes in the environment that may have important biological and management implications, and 2) upper trophic organisms in particular serve as integrative indicators that provide near real-time cues of environmental state.
Drs. Ivonne Ortiz, Kerim Aydin and Al Hermann (NOAA’s Pacific Marine Environmental Laboratory) presented the poster “FEAST Forage and Euphausiid Abundance in Space and Time: assumptions, knowledge, and gaps.” The poster summarizes insights and capabilities of the fish component of an end-to-end vertically integrated model based on dynamic prey fields, bioenergetics, and a suite of fish species (e.g., walleye pollock, Pacific cod, and arrowtooth flounder, among others). Model parameters and assumptions are based on retrospective data analysis and also close collaboration between modelers and observational field researchers on zooplankton, bioenergetics and early fish development. Capabilities and gaps: i) the model fits observed temperatures and cold pool extension, but data is still required to evaluate non-shelf areas; ii) relative survival of age zero fish under different climate conditions can be evaluated but not predicted accurately; survival can be tuned for single years; iii) core output includes predicted fish distribution by length, iv) sudden bouts of growth are caused by zooplankton blooms in the model but variation in timing is critical to calibration and prediction, and v) euphausiids production and predation is still controversial, with acoustic abundance estimates an order of magnitude higher than simulated values and other field measurements.
Dr. Kirstin Holsman (JISAO/REEM) presented a talk titled “The influence of climate change and predation on biological reference points estimated from multispecies and single species stock assessment models” which focused on recent results of the multispecies stock assessment model (MSM) for three species of groundfish from the Bering Sea. In particular, she presented 1) methods to estimate annual mortality from temperature and size-specific bioenergetics-based consumption rates, 2) approaches to using model projections to derive multispecies biological reference points (BRPs), and 3) results of application of the model to pollock, Pacific cod, and arrowtooth flounder from the Bering Sea. Initial results indicate that climate-driven changes in water temperature may affect unfished biomass estimates (and concomitant target harvest rates) but various control rules for harvest have larger impacts on BRPs through changes in predator abundances. In general, both temperature and predator harvest rates have the largest effects on prey species with high rates of predation (i.e., pollock) whereas BRPs from MSM are approximately equal to those from single-species stock assessment models for species with low predation rates.
By Stephani Zador, Ivonne Ortiz, and Kirstin Holsman
