Matthew Baker, NPRB
Bottom Trawl Surveys of the Aleutian Islands Characterize Demersal Fish and Invertebrate Populations
Every two years, NOAA scientists conduct a comprehensive bottom trawl survey of marine waters surrounding the Aleutian Islands. The purpose of the survey is to provide a fishery-independent time series of fish abundance that began in 1980 and to characterize the distributions and biological conditions of important benthic fishes and invertebrates. The survey area extends from Unimak Pass to west of Attu Island, and 420 stations are sampled based upon a stratified-random design of previously sampled stations. Two commercial fishing vessels are chartered and fitted with research bottom trawls, and the survey is stratified based upon region, sub-region, and depth to 500 m. The bottom trawl is for 15 minutes, and precise data are taken on distance traveled, net width, depth, and temperature. The catch is brought on board, identified, measured, and biological samples are removed for laboratory analysis. The densities of fishes and invertebrates are calculated, averaged among stations, and are used to estimate the relative abundance for the stratum. Estimates are incorporated in groundfish stock assessments that are used to define species statuses and trends, demography, and fishery potential. In addition, the survey results are used to describe the Aleutian ecosystem including temperature patterns and population trends for forage fish, benthic invertebrates, and miscellaneous fish species. The trawl survey also serves as a platform for special studies and collections for the scientific community, and these collaborations have resulted in descriptions of new fishes and invertebrate species, habitat characterizations, and understanding food webs.
Practical approaches are needed to preserve the health, biodiversity, and resilience of marine ecosystems. Identification of Important Ecological Areas (IEAs) provides a systematic way to prioritize spatial conservation, response, and restoration efforts. We present an analytical method for identifying IEAs in Aleutian Islands large marine ecosystem. Once identified, IEAs should be incorporated into management efforts to avoid unnecessary impacts associated with the exploitation of marine resources. We define Important Ecological Areas as geographically delineated areas which by themselves or in a network have distinguishing ecological characteristics, are important for maintaining habitat heterogeneity or the viability of a species, or contribute disproportionately to an ecosystem's health, including its productivity, biodiversity, functioning, structure, or resilience. As an exercise in valuation, determining “relative importance” requires a process for establishing and comparing values of individual or multiple ecological features on a similar scale, which is accomplished using standard deviates. Ecological features used in this case study included primary productivity, relative abundance of groundfish, marine mammals, seabirds, and habitat-forming invertebrates for which datasets were available. Given the escalating stresses placed on marine habitats generally, a compelling case may be made for assigning the priority to preserving the ecological services provided by IEAs.
A Fisheries Ecosystem Plan (FEP) is a strategic policy and planning document to guide regional fisheries management councils (Council) in their management actions relating to the Large Marine Ecosystems under their jurisdiction. They are a tool that can serve as a framework for continued incorporation of ecosystem goals and actions into fisheries management. The Aleutian Islands FEP was among the first developed; since then other regions have developed FEPs with formats that have evolved to better serve within Council processes and timelines. FEPs have matured from compilations of ecosystem information and risks, to tools that deliver targeted evolving ecosystem evaluations that inform and guide improvements to fishery management. The Aleutian Islands FEP is reviewed every 5 years. In advance of the review next year, we present here a summary of key sections of the current Aleutian Islands FEP. We also present key features of more recent FEPs, including that being developed for the eastern Bering Sea, which is based on Conceptual Models and Themed Action Modules. Our aim is to raise awareness of FEPs as a policy tool and invite researchers, communities, industry, NGOs, agencies and other interested parties, to bring forth issues of concern, as well as new research and future plans that may be relevant to the upcoming review.