Aspects of the feeding ecology of the blue shark, {\it Prionace glauca\/} in the Western North Atlantic

Nancy E Kohler, University of Rhode Island

Abstract

Various aspects of the food and feeding ecology of the blue shark, Prionace glauca, in the Western North Atlantic are discussed. Stomach contents data were collected, condition indices were described, and estimates of the gastric evacuation rate, daily ration, and conversion efficiency were determined.^ A total of 1,199 blue sharks ranging in size from 53-285 cm fork length were examined for stomach contents. These data were analyzed for areal, sexual, seasonal, and size differences in types and amounts of prey items consumed. Overall, food was present in 52.4% of the stomach samples which contained a mean volume of 172.2 ml (0.39% body weight). Cephalopods represented the primary food group consumed by the blue shark with a variety of teleost prey of secondary importance. Areal and seasonal differences in food habits were described. Data on the average food volume, stomach capacity, degree of stomach fullness, and mean number of food items per sample were reported for the blue shark and the results compared to other apex predators in the Western North Atlantic.^ Condition and condition indices utilizing length and weight, percentage of liver weight to body weight, and caloric values, moisture content, and color of the liver were examined. These data were compared seasonally to determine a monthly progression of condition in the blue shark. Preliminary results showed that liver color may be used as an indicator of condition for the blue shark. Various aspects of the blue shark's life history were discussed in relation to these results.^ Estimates of the gastric evacuation rate, daily ration, and conversion efficiency were determined. Gastric evacuation rate was estimated by feeding free-swimming blue sharks a known quantity of food and retrieving them after various intervals of time. Field measurements of stomach content weights taken during eight 3-h intervals were used to calculate total ingestion over a 24-h period using a model from Elliott and Persson (1978). A mean daily ration for the blue shark was estimated at nearly 0.6% of its body weight. (Abstract shortened with permission of author.) ^

Subject Area

Biology, Oceanography

Recommended Citation

Nancy E Kohler, "Aspects of the feeding ecology of the blue shark, {\it Prionace glauca\/} in the Western North Atlantic" (1988). Dissertations and Master's Theses (Campus Access). Paper AAI8811561.
http://digitalcommons.uri.edu/dissertations/AAI8811561

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