Hooking injury, physiological status and short-term mortality of juvenile lemon sharks (Negaprion bevirostris) following catch-and-release recreational angling.

A J Danylchuk,A M L Brooks,K J Murchie,J W Mandelman,C D Suski,C R Haak,S J Cooke

doi:10.1093/conphys/cot036

Abstract

Sport fishing for sharks, including fishing with the intent to release, is becoming more prevalent within the recreational angling community. Common targets of recreational anglers are juvenile lemon sharks (Negaprion brevirostris) that frequent shallow tropical nearshore habitats. In this study, we captured 32 juvenile lemon sharks (530-875 mm total length) with conventional angling gear (i.e. spinning rods, dead fish bait and 5/0 barbed circle hooks) from the coastal waters of Eleuthera, The Bahamas, to determine the consequences of capture for individual sharks. Each shark was examined for hooking injuries, blood sampled to quantify physiological disturbance, assessed for reflex impairment and then monitored to assess post-release behaviour and mortality. Four sharks (12.5%) died following release during the 15 min tracking period. Principal components (PC) analysis revealed four axes describing 66.5% of the variance for blood physiology parameters, total length and water temperature. The PC1 and PC3 scores, characterized by positive factor loadings for indicators of exercise-induced stress and blood ion concentrations, respectively, were significantly related to fight time but were not associated with short-term mortality. Short-term mortality was significantly related to factor scores for PC4 that loaded heavily for water temperature and total length. Ten sharks (31%) exhibited impaired reflexes, with loss of bite reflex being most prevalent. Sharks that died had the following characteristics: (i) they had two or more impaired reflexes; (ii) they were hooked in the basihyal; (iii) they exhibited no movement after the initial bout of directional swimming; and (iv) they experienced high water temperatures (i.e. >31°C). Collectively, these results indicate that for juvenile lemon sharks inhabiting tropical flats, fight time can influence the degree of physiological disturbance, while water temperature contributes to the likelihood of survival following release.

Highlights

Many shark populations worldwide are threatened by anthropogenic activities, including direct commercial harvest (Myers et al, 2007) and incidental fishing capture (McKinnell and Seki, 1998; Lewison et al, 2004; Molina and Cooke, 2012)
We observed a 12.5% mortality rate for juvenile lemon sharks following catch-andrelease angling. This rate is lower than the 26% mortality of common thresher sharks (Alopias vulpinus) following catchand-release recreational angling off the California coast (Heberer et al, 2010) and the 24% (72 h) mortality reported in hook-and-line caught dogfish (Squalus acanthias) in the Gulf of Maine (Mandelman and Farrington, 2007a), pen effects could have artificially inflated mortality estimates in the latter study
Lemon shark mortality was much lower when compared with the at-vessel mortality observed in carcharhinid sharks in commercial hook fisheries such, as pelagic longline [e.g. dusky, Carcharhinus obscurus (49%); silky, Carcharhinus falciformis (66%); and night, Carcharhinus signatus (81%); Beerkircher et al, 2002] or demersal longline [sandbar, Carcharhinus plumbeus (36%); dusky (81%); and blacktip, Carcharhinus limbatus (88%); Morgan and Burgess, 2007]

Summary

Introduction

Many shark populations worldwide are threatened by anthropogenic activities, including direct commercial harvest (Myers et al, 2007) and incidental fishing capture (McKinnell and Seki, 1998; Lewison et al, 2004; Molina and Cooke, 2012). Manire et al, 2001; Morgan and Carlson, 2010; Brooks et al, 2012; Frick et al, 2012; Skomal and Mandelman, 2012 for a review), few studies to date have examined recreational hookand-line capture in elasmobranchs Among those that have, angling has been shown to inflict physical injury and pathology due to hook retention (Borucinska et al, 2002) and to elicit metabolic disturbances (Hoffmayer and Parsons, 2001; Hoffmayer et al, 2012), including those associated with the exercise/fight time (Skomal and Chase, 2002; Brill et al, 2008; Heberer et al, 2010). There is a need for better understanging of aspects of the angling and handling process, the resulting physical injury and physiological disturbance and the post-release survivorship in sharks to enable the development of best practices for catch-and-release recreational angling of sharks (Gallagher et al, 2012)

Objectives

Methods

Results

Conclusion