The Differential Response to Decompression in Three Species of Nearshore Pacific Rockfish

Abstract

AbstractThe genus Sebastes (rockfishes) is an ecologically diverse group of fish, more than 60 species occurring off the Oregon, Washington, and California coasts. As of 2004, seven species of rockfish were classified as overfished by the Pacific Fishery Management Council. Because rockfishes often experience barotrauma to varying degrees when forced up from depth, the management of discard mortality has been difficult. In this study, the macroscopic, morphological, and physiological responses to decompression of black rockfish S. melanops, blue rockfish S. mystinus, and yellowtail rockfish S. flavidus, all nearshore species, were investigated. The rockfish were adjusted to 4.5 atmospheres absolute (ATA; 35 m) over a period of 7–10 d in hyperbaric pressure chambers and when neutrally buoyant were rapidly brought to surface pressure in a simulated ascent. They were then examined for barotrauma injury, and the heart ventricle, head kidney, liver, gill, and pseudobranch were collected for histological analysis. We observed more macroscopic barotrauma indicators in black rockfish and blue rockfish than in yellowtail rockfish. Histological analysis showed emphysema was present in the heart ventricle of more than one‐half of the black rockfish, 11% of the blue rockfish, and none of the yellowtail rockfish. No other tissue had observable injury at the histological level that was attributable to barotrauma. The lack of injury at the tissue level for black, blue, and yellowtail rockfishes decompressed from 4.5 ATA is remarkable.