EXPLAINING SHIFTS IN BODY CONDITIONS IN ALEUTIAN ISLAND FISHES

The Aleutian Islands are host to a complex of important commercial fishes such as Pacific ocean perch (Sebastes alutus), Atka mackerel (Pleurogrammus monopterygius), and Pacific cod (Gadus macrocephalus). For nearly 15 years, the body conditions have been below average for individuals of these species collected in bottom trawls. In Pacific ocean perch and Pacific cod, body conditions have been on the decline for almost 30 years. These trends could be indicative of poor resource availability or other limitations of productivity. The present study examines a variety of environmental and dietary factors that may be leading to the observed trends in body condition. Data were collected during trawls conducted by the Alaska Fisheries Science Center (AFSC) throughout the Aleutian Islands between 1991 and 2018. The body condition indicator (BCI) for a given fish was calculated as log(observed weight) - log(modeled weight) where modeled weight (W) was determined from the formula W = aLb. a and b were estimated from a single log-log regression across all samples (all years and strata) of each species. Potential predictor variables including temperature, density, diet composition, and geography were plotted against BCI in general additive models (GAMs) to better understand factors that could be driving the decline in body condition.

For more information: hmfilas@eckerd.edu

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