Quantifying post‐release behaviour of a critically endangered elasmobranch over two capture events using high‐resolution archival tag data

Abstract

During catch‐and‐release angling, highly resident species are susceptible to multiple recapture events. Biologging offers the opportunity to study post‐release behaviour in detail; however, most studies have focused on a single capture‐release event. Using high‐resolution archival data and acoustic tracking, we present the post‐release behaviour of a single flapper skate ( Dipturus intermedius ) that was captured, tagged and recaptured 6 days later off the southwest coast of Ireland. As programmed, the archival satellite tag released 7 days after the initial capture event and 1 day after the second capture event, and the skate was monitored for an additional 212 days using an array of acoustic receivers. Analysis of the archival satellite tag dataset revealed atypical movements, characterised by increased mobility and vertical descents/ascents following release on both occasions. Generalised additive models corroborated that changes in depth and mobility were high after animal capture and release. Change point analysis identified that at 9 and 10 h after the first and second capture event, respectively, the skate's behaviour changed from increased mobility and rapid movements to more settled behaviour. The average integrated vertical movement (IVM) post‐capture, before the identified change points, was 441% higher than the mean hourly IVM outside this timeframe (5.15 versus 22.73 m/h). Acoustic tracking data corroborated that the skate remained near the capture area after both capture events. This study demonstrates the behavioural response of a flapper skate to two capture events and shows that, while capture led to 9–10 h of elevated activity, the skate remained in the capture area despite multiple capture events.