Short-term response of giant trevally (Caranx ignobilis) to capture and handling in a catch-and-release fly fishing recreational fishery, Republic of the Seychelles, Western Indian Ocean.

Abstract

Giant trevally (Caranx ignobilis, GT) are growing in popularity as a target for tourism-based recreational fisheries throughout their range in the Indo-Pacific. Although predominately catch-and-release (C&R), to date there is no species-specific scientific evidence to support capture and handling guidelines. As such, we examined how GT caught via fly fishing gear while in shallow water responded to capture and handling in the Alphonse Island Group, Republic of the Seychelles. Specifically, we evaluated the physical injury for GTs captured via fly fishing gear, as well as their reflex impairment and post-release activity (using tri-axial accelerometer biologgers) following three air exposure treatments (0 s, 15 s, 30 s). We also had a reference treatment where GTs were caught and landed quickly via a handline, and not exposed to air (0 s) prior to release. Hooking location for both gear types was predominately the jaw or corner of the mouth (fly fishing, n = 30; 83.3%; handline; n = 12, 85.7%), but one fish hooked in a critical location for each capture gear. Across all treatments, only one fish (2%) in the handline treatment was considered a potential short-term post-release mortality following being deeply hooked in the gills and subsequently losing equilibrium upon release. GT reflex impairment and overall post-release activity measured via overall dynamic body acceleration were not influenced by fight time and air exposure treatments used in our study. For GTs across all treatments, locomotor activity was lower in the initial minutes following release than during the second half of the ten minute monitoring period. Overall, our study suggests that GTs in the Alphonse Island Group are resilient to being caught via fly fishing, handled, and air exposed for up to 30 s. However, given the diversity of angling locations for GTs (e.g., shallow flats, deeper reefs) and gear types (e.g., conventional tackle, lures with several treble hooks), additional assessments are needed to help act as the foundation for more universal best practices that can inform management plans for GT recreational fisheries.