Spiny Dogfish Mortality Induced by Gill-Net and Trawl Capture and Tag and Release

Abstract

Abstract The spiny dogfish Squalus acanthias was once classified as an underutilized species along the U.S. East Coast, but it constituted a lucrative fishery in the 1990s until recruitment overfishing caused stock collapse. Coastwide restrictions currently apply; federal stock assessment models use bycatch mortality estimates of 50% for trawling, 75% for gill netting, and 100% for hook-and-line fishing. This study examined mortality at the southern end of commercial fishing operations caused by trawling for 30- and 90-min periods and by gill nets of various mesh sizes set for 19- to 24-h periods. Both experiments used tagged and untagged fish placed in rectangular cages anchored to the seafloor for 48 h. Tags were the Floy SS-94 single-barb nylon dart with a stainless steel wire insert. A total of 635 spiny dogfish were captured by trawl and all were alive, for a 0% initial mortality rate. A total of 2,284 spiny dogfish were collected by gill net for an initial mortality rate of 17.5%. There was no addit...