The effects of capture depth and handling time on barotrauma response and postrelease behavior of ice-angled Black Crappie

ABSTRACT Objective Black Crappie Pomoxis nigromaculatus are often targeted in deep basins by ice anglers practicing catch and release (C&R). Past research shows that Black Crappie caught under these conditions are vulnerable to barotrauma caused by rapid decompression, but the impact of barotrauma on release success (e.g., returning to depth and exhibiting recovery behavior) is not well established. This study aims to characterize the effects of barotrauma on fish releasability under various angling and handling scenarios. Methods Black Crappie were angled between depths of 3.5 and 9.5 m, assessed for barotrauma, and subjected to high-handling (60–90-s) or low-handling (≤30-s) treatments. Fish were released on a tethering system, along with untethered controls and weighted descender controls, to monitor postrelease performance and recovery outcomes with forward-facing sonar and an underwater camera. Results Barotrauma symptoms and release success had a strong negative correlation, and capture depth was the best predictor for both variables. Fish in the low-handling treatment were more likely to return to their capture depth than fish in the high-handling treatment, but release success remained poor at capture depths of about 8 m or greater. Moreover, many fish were observed lying motionless on bottom or floating back to the surface shortly after returning to depth. The tethering system used in this study was effective in retaining fish for observation but partially restricted their movements and acted as an additional interactive stressor. Consequently, we address the potential of forward-facing sonar as a research tool to noninvasively monitor fish in future C&R studies. Conclusions Ice-angled Black Crappie began experiencing severe barotrauma injuries and reduced postrelease performance at capture depths of around 8 m. Symptoms such as exophthalmia and stomach eversion are good visual indicators that fish are poor candidates for release. Reducing handling time can improve the likelihood of a successful release but cannot fully mitigate the effects of barotrauma. Managers should consider mortality risk when developing Black Crappie management strategies for systems exceeding 8 m in depth and should advise anglers against intensive C&R angling efforts beyond such depths.