Evaluating the Efficiency of Flushed Stomach-tube Lavage for Collecting Stomach Contents from Dogfish Sharks

Abstract

Concern over the use of lethal techniques to collect basic biological data from sharks has necessitated the development of nonlethal methods of data collection. We evaluated the nonlethal method of removing stomach contents using acrylic tubes. Stomach contents of Spiny Dogfish (Squalus acanthias) captured with bottom trawls and longlines were collected using acrylic tubes flushed with seawater. The largest tube used during the trawl survey was 30 mm in diameter, while a larger tube (37 mm in diameter) was used during longline sampling due to catches of larger dogfish. The average ef- ficiency of stomach content removal was 79.5% overall, and improved to 93% with the addition of the larger tube. Selection of a tube with a diameter 10-20 mm less than mouth width can be reasonably expected to recover over 90% of stomach contents. Stomach- tube lavage is a useful and efficient method for nonlethal sampling of stomach contents from Spiny Dogfish, and perhaps other small sharks.