Effectiveness of descending devices to mitigate the effects of barotrauma among rockfishes (Sebastes spp.) in California recreational fisheries

Fishes caught from depth often suffer from barotrauma, which can result in high mortality rates (close to 100% for some species) when released at the surface. To mitigate for this, the recreational fishing community proactively developed several different types of descending devices designed to assist unwanted or prohibited fish back toward the bottom for release. Post-release survival using recompression techniques has been documented for some species, which has allowed fisheries managers to begin revising estimates of total fishing mortality in some cases, but the effectiveness of the different commercially-available descending device types has not been quantified. We conducted 24 Commercial Passenger Fishing Vessel charters at 11 sites along the coast of California, and invited volunteer recreational anglers aboard the charters to test the effectiveness of five different commercially available device types, and respond to a survey of their device preferences. During release, all fish were descended either to 46 m (150 ft) depth or directly to the bottom, whichever depth was shallower. While there were some significant differences between device types, all devices were effective for releasing rockfishes back to depth. Initial post-release mortality (defined as all mortality events observable from the vessel while fishing) across all devices was relatively low (7.5%) in capture depths less than 100 m, but increased significantly to 16.4% at capture depths from 100 to 135 m. Our results suggest that rockfishes should be released at least half-way to the bottom (preferably directly to the bottom) for the device to be effective in minimizing post release mortality. The time required to use the devices averaged under three minutes regardless of device type, meaning that all device types could be used efficiently on deck, but anglers showed a clear preference for the SeaQualizer. This device produced some of the lowest release error rates and lowest initial post-release mortality of rockfishes aboard the charters, so angler preference coincided with device effectiveness. Collaborating with the recreational fishing community was an extremely important aspect to this study, provided more robust results, and fostered working relationships that can be built upon in future research projects.