Using logbook data to determine the immediate mortality of blue sharks (Prionace glauca) and tiger sharks (Galeocerdo cuvier) caught in the commercial U.S. pelagic longline fishery

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

“…Precision, however, in F r studies needs to be appraised in the context in which it is used or required. If matched to the precision of F c rates, however, then from a cost‐benefit perspective, this is not feasible using PSATs as precision in F c point estimates for blue shark is reported ±~0.001 points (Dapp et al., ) whereas precision in F r is ±~0.08 points (nearly a 100 fold difference). Clearly, in this situation, alternative methods like condition code offers a cost‐effective remedy to predict F r with some level of accuracy (Benoît et al., ; Braccini et al., ; Merremans et al., ; Musyl & Gilman, ).…”

“…In the meta‐analysis for blue shark, the summary effect size for F r was 0.17, and Dapp et al. (), also from meta‐analysis, synthesized a summary effect size of F c = 0.17. Next, estimates for M in the species ranged from 0.17 to 0.23/year (Table ).…”

“…But to assess the performance and efficacy of these measures and others (e.g. fin‐to‐carcass ratios, bans on wire leaders, shark lines and hook shape), the fate of discards must be ascertained (Awruch, Simpfendorfer & Pankhurst, ; Dapp, Huveneers, Walker, Mandelman & Kerstetter, ; Gilman, Chaloupka, Swimmer & Piovano, ; Graves, Luckhurst & Prince, ; Gray & Kennelly, ; Moyes, Fragoso, Brill & Musyl, ; Uhlmann, Ulrich & Kennelly, ). Davis () suggested mortality of discards was a major component in fisheries management.…”

“…Accurate estimates of the two sources comprising fishing mortality are also essential in producing accurate stock and other forms of ecological risk assessments (Gallagher, Kyne & Hammerschlag, ; Hobday, Smith, Stobutzki, Bulman & Daley, ; Kelleher, ; Kitchell, Kaplan, Cox, Martell & Essington, ; Pine et al., ; Punt, Smith, Tuck & Methot, ; Viana, Graham, Wilson & Jackson, ; Viana, McNally, Graham, Reid & Jackson, ). The vast majority of discards are unaccounted for in most stock assessments (Dapp et al., ) and the uncertainty as to the true values of F c and F r are major impediments to effective management and resource conservation in many fisheries (Campana, Joyce & Manning, ; Carruthers et al., ; Dapp et al., , ; Dapp, Walker, Huveneers & Reina, ; Molina & Cooke, ; Musyl et al, ). Fishing also has the capacity to exert sublethal effects at the population level (e.g.…”

“…Whilst measuring accurate F c rates is largely dependent on the quality of fisheries observer programmes and fleet coverage (Dapp et al., ; Walsh, Bigelow & Sender, ; Walsh, Ito, Kawamoto & McCracken, ), F r can be challenging to estimate due to cost‐benefit and logistics (Goodyear, ; Horodysky & Graves, ; Kerstetter & Graves, ; Musyl & Gilman, ; Musyl, Brill et al., ; Musyl, Domeier et al, ). It has been hypothesized that F c and F r rates might be expected to show congruence because prognostic factors responsible for F c in fisheries are likely to be many of the same ones acting on F r (Benoît, Hurlbut, Chasse & Jonsen, ; Braccini, Rijn & Frick, ; Campana, Joyce & Manning, ; Dapp et al., , ; Musyl & Gilman, ; Musyl, Brill et al., ; Musyl et al., ). Though there are several indirect and direct methods to estimate F r rates in pelagic sharks, each method has different strengths and weaknesses which impact cost‐benefit and ultimately experimental design and statistical power (Campana, Joyce, Fowler & Showell, ; Goodyear, ; Graves et al., ; Horodysky & Graves, ; Kerstetter & Graves, ; Musyl & Gilman, ; Musyl, Brill et al., ; Musyl et al., ).…”