This project proposes to hire a post-doctoral fellow to work with Alaska Fisheries Science Center (AFSC) survey and stock assessment scientists to devise and examine strategies for reducing the cost of conducting fishery-independent surveys given that agency funding may remain level or decline. The strategies must be robust to the different types of survey designs used by the Center in the different Large Marine Ecosystems (LMEs) and take into consideration the impacts to design-based and model-based survey abundance and variance estimates that are used as indices in stock assessment models for North Pacific Fishery Management Plan (FMP) species.

Issue Statement

Fisheries-independent surveys in Alaska are an annual event for the AFSC requiring many staff, multiple vessels, and ample financial resources. The data derived from these multi-species surveys are critical for the  annual assessment of fish and crab in Alaska’s LMEs. Data on fish abundance, biomass, size, sex and age are a priority during these surveys. In addition to these core variables, data necessary to take an ecosystem approach to fisheries management are also collected, making these cruises valuable platforms for collecting environmental intelligence. Yet when asked how could we make the multi-species surveys more cost effective, we do not have a simple answer. In fact, the question is very complicated, and the answer depends on many different variables, some of which may vary with time or environmental conditions. At risk is the disruption of a long time-series critical to the annual assessment of groundfishes and crab in Alaska. Before attempting to implement more cost effective surveys, we need to fully understand the consequences to all target species. This includes understanding the impacts of a more cost effective approach to design-based and model-based survey abundance and variance estimates that are used as indices in stock assessment models. Candidate alterations include changing the frequency, areal coverage, number of stations, or types/numbers of vessels conducting the surveys.

 

This project  is conceived as a collaboration of stock assessment and survey scientists to answer the question: what methods and criteria are appropriate to examine survey cost effectiveness and the economic and scientific impacts of altering our present strategies. Specific goal of the study is to  develop statistical tools to inform AFSC management on how to optimally reduce multispecies survey effort to minimize loss of information from survey data (e.g. fish abundance, biomass, size, sex and age) in the event of unavoidable reduction in survey effort with respect to groundfish surveys in Alaska. The work toward the goal will involve two stages:  1.finding the most efficient sample allocation/stratification strategy for single species survey and 2. allocating sampling effort in a multi-species survey with the respect to the importance of the species to management.

 

References

McGarvey, R. and P. Burch. 2016. Precision of systematic and random sampling in clustered populations: habitat patches and aggregating organisms. Ecological Applications, 26(1):233–248.

Thorson, J.T., 2017. Three problems with the conventional delta-model for biomass sampling data, and a computationally efficient alternative. Can. J. Fish. Aquat. Sci. 75, 1369–1382.

Kotwicki, S, Ressler, P.H., Ianelli J. N., Punt, A. E., and Horne, J. K. 2018. Combining data from bottom trawl and acoustic surveys to estimate an index of abundance for semipelagic species. Can J. Fish. Aquat. Sci. 75: 60–71.

 

key words

Survey design; abundance estimation; model-based estimation; species distribution; fisheries survey; stock assessment; variance; fish population

Citizenship:  Open to U.S. citizens, permanent residents and non-U.S. citizens

Level:  Open to Postdoctoral and Senior applicants