Catch rate and at‐vessel mortality of circle hooks versus J‐hooks in pelagic longline fisheries: A global meta‐analysis

Abstract

We conducted a meta‐analysis of literature reporting on the use of circle hooks and J‐hooks in pelagic longline fisheries. Our study included more data than previous meta‐analyses of the effects of hook type, due to both a larger number of relevant studies available in recent years and a more general modelling approach. Data from 42 empirical studies were analysed using a random effects model to compare the effects of circle hooks and J‐hooks on catch rate (43 species) and at‐vessel mortality (31 species) of target and bycatch species. Catch rates with circle hooks were greater for 11 species, including four tuna species, six shark species and one Istiophorid billfish. Catch rates on circle hooks were lower for seven species, including two Istiophorid billfishes and two species of sea turtle. At‐vessel mortality was significantly lower with circle hooks in 12 species, including three tuna species, three Istiophorid billfishes, swordfish (Xiphias gladius) and three shark species. No species had significantly greater at‐vessel mortality when captured with a circle hook rather than a J‐hook. While our general approach increased model variability compared to more detailed studies, results were consistent with trends identified in previous studies that compared the catch rates and at‐vessel mortality (between hook types) for a number of species. Our results suggest that circle hooks can be a promising tool to reduce mortality of some bycatch species in pelagic longline fisheries, although the effects depend on the species and the metric (catch rate or at‐vessel mortality), emphasizing the need for fishery‐specific data in conservation and management decisions.

Meta‐analysis of post‐release fishing mortality in apex predatory pelagic sharks and white marlin

“…Sharks drown, gear becomes damaged (i.e. monofilament gets “smoked”) and line weights can shoot back into crew areas during line breaks and consequently this practice represents a large crew safety and liability risk (Fowler, ; Gilman, ; Poisson, Filmalter et al., ; Poisson, Séret et al., ; Poisson et al., ). When possible, adopt circle hooks over J hooks to reduce both F c and F r rates (Andraka, Mug, Hall, Pons & Pacheco, ; Caneco, Donovan & Harley, ; Serafy et al., ; Ward, Epe, Kreutz, Lawrence & Robins, ) with a trade‐off of increased shark catch rates (Gilman et al., ; Reinhardt et al., ). In the sensitivity analysis, elimination of J hooks (on baited hooks) in istiophorid billfish studies reduced mortality by ~3.3%.…”

“…To provide precision in true mortality rates, researchers are turning to evidence-based methods such as meta-analysis not only to increase overall power and cut costs, but also to test various hypotheses unavailable in single studies (Benoît et al, 2012;Dapp et al, 2015;Favaro & Côté, 2015;Gilman et al, 2016;Godin, Carlson & Burgener, 2012;Musyl et al, 2015;Reinhardt, Weaver, Latham, Dell'Apa & Serafy, 2017;Serafy, Orbesen, Snodgrass, Beerkircher & Walter, 2012). Synthesizing precise F r rates in pelagic fisheries by meta-analysis has been limited to Schlenker et al, 2016), (b) demonstrating the utility meta-analyses and (c) comparing the robustness of apex predatory pelagic species to the effects of fishing.…”

Ethical considerations in fish research

“…Foul-hooking or ingesting hooks can be quite serious; the risk of these injuries can be minimised by modifying fishing gear, such as switching from J-hooks to circle hooks (Reinhardt et al, 2018;Skomal et al, 2002). Depending on the nature of the injury, a fish should either be released immediately to minimise additional handling stress, or euthanised (Fobert et al, 2009).…”

“…Physical attributes of gear, including the timing and location of fishing, can affect the likelihood of encountering bycatch species. For instance, hook type and size can have effects on capture rates of certain species (Reinhardt et al, 2018). In addition, fishing depth, bait, time of day, season and environmental conditions (e.g., sea surface temperature) can all influence the likelihood of encountering bycatch (Watson & Kerstetter, 2006).…”

Robbing Peter to pay Paul: replacing unintended cross-taxa conflicts with intentional tradeoffs by moving from piecemeal to integrated fisheries bycatch management

“…While hook shape has the same effect on shark anatomical hooking position and survival rates as for other taxonomic groups, some pelagic sharks have a higher probability of capture on circle versus J-shaped hooks (Gilman et al 2016b;Reinhardt et al 2017). Based on results of a meta-analysis from 30 studies, pooled shark species had a 1.2 times significantly higher risk of capture on circle hooks than on J and tuna hooks.…”