Escaping the surface: The effect of capture depth on submergence success of surface-released Pacific rockfish

We evaluated the effect of capture depth and fish size on the ability of several Pacific rockfishes Sebastes spp. to resubmerge after hook-and-line capture and surface release. We observed fish as they were released into a bottomless floating enclosure, and we recorded submergence success within a 5-min time limit. Submergence success was greater than 80% for all rockfish captured in depths less than 30 in. Yellowtail rockfish S. flavidus (N = 51) were 100% successful at submerging in less than 49 s at all depths sampled (10-51 m). At capture depths of 40-51 m, submergence success was 89% for quillback rockfish S. maliger (N = 9), 65% for black rockfish S. melanops (N = 46), and 30% for canary rockfish S. pinniger (N = 40). At depths of 30-51 m, submergence success was 32% for blue rockfish S. mystinus (N = 31). The external signs of barotrauma (e.g., exopthalmia, eversion of the esophagus) increased with depth of capture and were least prevalent in yellowtail rockfish and quillback rockfish. The presence of severe esophageal eversion (beyond the buccal cavity) was strongly negatively associated with submergence success for several species (P < 0.01). At 40-51-m capture depths, the frequency of severe esophageal eversion by species was correlated with the frequency of submergence failure (P < 0.05). Logistic regression showed a negative relationship between depth of capture and submergence success for black rockfish (P < 0.001), blue rockfish (P < 0.001), and canary rockfish (P < 0.05). Larger body length negatively influenced submergence success only in blue rockfish (P < 0.05).