Juvenile and small adult cowcod (Sebastes levis) show high post-release survival following angling-induced barotrauma

The cowcod, Sebastes levis, is a large slow-growing rockfish species found along the West Coast of the United States and Baja California, Mexico that has been historically heavily exploited off of southern California. As the cowcod population recovers from past overfishing, previously closed fishing areas and depths are reopening, leading to increased fisher interactions with the species, particularly juveniles and small adults, which are typically found at shallower depths closer to shore. In this study, we quantify post-release survival rates of juvenile and small adult cowcod (< 50 cm) following angling-induced barotrauma in comparison to previous work focused on larger adult cowcod. All cowcod were captured using recreational hook-and-line gear and descended back to depth using commercially available fish descending devices. Kaplan-Meier survivorship modeling showed an overall survival rate of 92.9 % (95 % CI: 80.3–100 %) for the 14 cowcod examined (22.9–49.5 cm fork length). This survival rate was nearly twice that determined previously for larger cowcod. The higher survival rate of smaller individuals may reflect their thinner tissues, allowing for expanding gas from the swim bladder to escape the body, thereby preventing some of the severe internal organ damage typically associated with barotrauma in larger cowcod. Combination of our results with previous research thus suggests that small cowcod caught by recreational anglers can be released with high survival rates, while larger cowcod are less likely to survive capture and barotrauma.