Application of three-dimensional acoustic telemetry to assess the effects of rapid recompression on reef fish discard mortality

Abstract

Geopositioning underwater acoustic telemetry was used to test whether rapid recompression with weighted return-to-depth (descender) devices reduced discard mortality of red snapper (n = 141) and gray triggerfish (n = 26) captured and released at 30–60 m depths at two 15 km2 study sites in the northern Gulf of Mexico. Cox proportional hazards modelling indicated red snapper released with descender devices had significantly lower discard mortality within the first 2 d (95% CI = 18.8–41.8% for descender-released vs. 44.0–72.4% for surface-released, unvented fish), while there was no significant effect of descender devices on discard mortality of gray triggerfish. Predation by large pelagic predators was estimated to account 83% of red snapper and 100% of gray triggerfish discard mortality. Discard mortality due to predation has likely been overlooked in previous mark-recapture, laboratory, and enclosure studies, suggesting cryptic population losses due to predation on discards may be underestimated for red snapper and gray triggerfish. Large-area three-dimensional positioning acoustic telemetry arrays combined with collaboration and data sharing among acoustic telemetry researchers have the potential to advance our knowledge of the processes affecting discard mortality in reef fishes and other taxa.

Under pressure: Comparing in situ and boat tagging methods using time-to-event analyses

“…The models, however, suggested an increase in 1 min of handling time slightly decreased the risk of disappearance for boat-tagged sh, though the con dence intervals neared or crossed 1 in all cases, indicating little to no effect. Handling time may not have been very in uential in risk of disappearance, but it is still surprising that increased time may have reduced risk, especially as handling times for sh tagged on the boat were high compared to other tagging studies (Starr et al 2007, Bohaboy et al 2019 and minimizing handling of sh has been reported as one of the most important considerations in implantation surgeries (Rub et al 2014). For in situ tagging, handling time was not included in best-tting models, but that may be because there was little variance in the handling times of sh tagged in situ.…”

“…We used time-to-event analysis (also called survival analysis) to compare the risk of tagged sh disappearing from the receiver array between the two tagging methods. The Cox proportional hazards model is a common analytical method for assessing what variables cause the most risk to survival in discard mortality and delayed mortality studies (Curtis et al 2015, Runde et al 2019, Bohaboy et al 2019). We used the Cox proportional hazards model to examine which tagging variables most in uenced the risk of sh disappearing from the receiver array.…”

“…Additionally, newly tagged sh may be more susceptible to predation, especially if the sh must travel through the water column before reaching a protective habitat (Piraino and Szedlmayer 2014). Acoustic tagging release method experiments have demonstrated that sh descender devices, which return sh to depth, can increase sh survivorship (Bohaboy et al 2019), but devices that both return a sh to depth and protect against predators (e.g., cages) are best for increased sh survivorship (Piraino and Szedlmayer 2014;Williams et al 2015). However, a review of barotrauma treatment (venting and descending devices) in catch-and-release studies revealed inconsistency about which method is most bene cial in reducing or treating barotrauma, likely because of differences in environmental or speciesspeci c physiological variables and differences in assessment methods (Eberts and Somers 2017).…”

Assigning Fates in Telemetry Studies Using Hidden Markov Models: an Application to Deepwater Groupers Released with Descender Devices

“…The incorporation of miniaturized sensors into tags enables scientists to collect a greater variety of information about tagged animals and offers flexibility in study design and objectives (Wilson et al 2015). For example, sensors for metrics such as temperature (Gorsky et al 2012), pH (Halfyard et al 2017), light (Seitz et al 2019), depth (Bohaboy et al 2020), and acceleration (Curtis et al 2015) can provide much insight into biology, movement, and survival (Runde et al 2018). However, the pace of these technological advances has often outstripped the development of methods for the analysis of the data they produce.…”

“…The use of descender devices to recompress barotraumatized fishes has been explored for several species and taxa, including Walleye Sander vitreus (Eberts et al 2018), Red Snapper Lutjanus campechanus (Drumhiller et al 2014; Bohaboy et al 2020), Pacific rockfishes Sebastes spp. (Theberge and Parker 2005), Black Sea Bass Centropristis striata (Rudershausen et al 2020), and deepwater groupers (Runde and Buckel 2018).…”