Anatomical Hooking Location and Condition of Animals Captured with Pelagic Longlines: The Grand Banks Experiments 2002–2003

Abstract

experiments were conducted on the grand Banks of the north Atlantic ocean during 2002-2003 to evaluate the effect of circle hooks and mackerel bait on pelagic longline catches and bycatch, and compare the treatments to the industry standards at the time. circle hooks were 18/0, and both non-offset and 10° offset were used as separate treatments and compared to the 9/0 J-hook control hooks with 10°-30° offset. Bait treatment was mackerel (Scomber scombrus linnaeus, 1758), which was compared to the squid control (Illex spp.). we analyzed the effects of hook (one J-and two circle hooks), bait (mackerel and squid), temperature, soak time, and animal length on anatomical hooking location for seven fish species and two sea turtle species. we also analyzed the effects of the same variables, inclusive and exclusive of hooking location, on the odds of boating a dead fish. we found that hook was one of the most important variables in predicting anatomical hooking location, and that soak time and hook and/or anatomical hooking location were important in predicting the odds of observing a dead animal boatside. The importance of the other variables differed by species, and for several species no models were significant for predicting hooking location or for predicting observed mortality.

A review of capture and post‐release mortality of elasmobranchs

“…Reported AVM of the former may be as low as c . 5–30% (Megalofonou et al , ; Epperly et al , ; Gallagher et al , 2014 a ; Campana et al , ; Gilman et al , ), but studies with greater sample sizes have generally reported AVM to be in the region of 35–56% (Beerkircher et al , ; Coelho et al , , ; Bromhead et al , ). These estimates of AVM are of a similar magnitude to that reported for L .…”

“…These estimates of AVM are of a similar magnitude to that reported for L . nasus , 21–44% (Coelho et al , ; Epperly et al , ; Gallagher et al , 2014 a ; Campana et al , ). Campana et al () also used PSATs to understand PRM, which allowed overall mortality to be estimated at 49 and 59% for I .…”

Review of effects of pelagic longline hook and bait type on sea turtle catch rate, anatomical hooking position and at-vessel mortality rate

“…The less exposed points of circle hooks reduce the probability of foul-hooking organisms. When ingested, J-shaped hooks tend to result in deep hookings, while circle hooks with little or no offset tend to catch in the corner of the mouth (Cook and Suski 2004;Curran and Beverly 2012;Epperly et al 2012;Clarke et al 2014;Parga et al 2015). Due to the prevalent hooking location, circle hooks might result in higher pre-catch 1 and haulback survival rates, make it easier for crew to remove all terminal tackle, and thus increase the probability of post-release survival for turtles released alive (Chaloupka et al 2004;Cooke and Suski 2004;Godin et al 2012;Serafy et al 2012;Swimmer and Gilman 2012;Parga et al 2015).…”

“…Hook shape, however, likely has nominal effect on catch rates of hard-shelled turtles, which tend to get caught by ingesting the hook regardless of hook shape (e.g., Gilman 2011;Epperly et al 2012;Clarke et al 2014). For hard-shelled and leatherback turtles that ingest a hook, circle hooks result in a lower proportion of turtles swallowing the hook deeply, into the esophagus and deeper, and therefore likely result in a higher survival rate relative to J-shaped hooks.…”

“…Three were on catch rates (two on leatherbacks, one olive ridleys, Mejuto et al 2008;Coelho et al 2015), five on the proportion deeply hooked (three on loggerheads, two on leatherbacks, Watson et al 2005;Epperly et al 2012;Santos et al 2013;Coelho et al 2015), and four on at-vessel mortality rates (three on leatherbacks, one on loggerheads, Gilman et al 2007;Santos et al 2013;Coelho et al 2015). Most of these findings on bait type effect were from studies with simultaneous variability in hook shape and/or hook minimum width.…”