Large-scale experiment shows that nylon leaders reduce shark bycatch and benefit pelagic longline fishers

Ward, Peter; Lawrence, Emma; Darbyshire, Rebecca; Hindmarsh, Sheree

doi:10.1016/j.fishres.2007.09.034

Cited by 91 publications

(122 citation statements)

References 14 publications

Supporting

Mentioning

116

Contrasting

Order By: Relevance

“…turtle excluding devices, weak links for nets and acoustic alarms) are already available for some of them (e.g. Barlow and Cameron 2003;Gilman et al 2006;Ward et al 2008). However, many of these methods are costly, and so there is a clear need and an opportunity to develop minimum-cost methods that are feasible for implementation in small-scale fisheries in the SWIO and globally.…”

Section: Discussionmentioning

confidence: 99%

Marine megafauna interactions with small-scale fisheries in the southwestern Indian Ocean: a review of status and challenges for research and management

Temple

Kiszka

Stead

et al. 2017

Rev Fish Biol Fisheries

View full text Add to dashboard Cite

In developing regions, coastal communities are particularly dependent on small-scale fisheries for food security and income. However, information on the scale and impacts of small-scale fisheries on coastal marine ecosystems are frequently lacking. Large marine vertebrates (marine mammals, sea turtles and chondrichthyans) are often among the first species to experience declines due to fisheries. This paper reviews the interactions between small-scale fisheries and vulnerable marine megafauna in the southwestern Indian Ocean. We highlight an urgent need for proper documentation, monitoring and assessment at the regional level of small-scale fisheries and the megafauna affected by them to inform evidence-based fisheries management. Catch and landings data are generally of poor quality and resolution with compositional data, where available, mostly anecdotal or heavily biased towards easily identifiable species. There is also limited understanding of fisheries effort, most of which relies on metrics unsuitable for proper assessment. Management strategies (where they exist) are often created without strong evidence bases or understanding of the reliance of fishers on resources. Consequently, it is not possible to effectively assess the current status and ensure the sustainability of these species groups; with indications 123Rev Fish Biol Fisheries (2018Fisheries ( ) 28:89-115 https://doi.org/10.1007 of overexploitation in several areas. To address these issues, a regionally collaborative approach between government and non-governmental organisations, independent researchers and institutions, and smallscale fisheries stakeholders is required. In combination with good governance practices, appropriate and effective, evidence-based management can be formulated to sustain these resources, the marine ecosystems they are intrinsically linked to and the livelihoods of coastal communities that are tied to them.

show abstract

Section: Discussionmentioning

confidence: 99%

Marine megafauna interactions with small-scale fisheries in the southwestern Indian Ocean: a review of status and challenges for research and management

Temple

Kiszka

Stead

et al. 2017

Rev Fish Biol Fisheries

View full text Add to dashboard Cite

show abstract

“…A reduced longline soak time may also reduce the catch rate of sharks (Ward et al 2004, Erickson & Berkeley 2008, although if it also reduced the catch rate of billfish, there may be no net gain. The use of nylon leaders (as opposed to wire leaders) has been reported to reduce shark bycatch mortality (Ward et al 2008), but only under the assumption that sharks that bite off the hooks subsequently survive. In the case of swallowed hooks, that assumption is questionable.…”

Section: Discussionmentioning

confidence: 99%

Bycatch and discard mortality in commercially caught blue sharks Prionace glauca assessed using archival satellite pop-up tags

Campana¹,

Joyce²,

Manning³

2009

Mar. Ecol. Prog. Ser.

158

155

View full text Add to dashboard Cite

Blue sharks Prionace glauca are the most frequently discarded fish species during commercial pelagic longline fishing operations worldwide, yet their post-release mortality rate has never been measured. A generalized linear model of 12 404 blue sharks observed during the Canadian Atlantic pelagic longline swordfishery suggested a hooking mortality of 12 to 13%, yet scientific examination of 902 of these sharks indicated that hooking mortality was actually higher. A random sample of 40 of these blue sharks were tagged with satellite pop-up archival transmission (PAT) tags, then monitored for periods of up to 6 mo after release. All of the surviving sharks exhibited a depthholding recovery behaviour for a period of 2 to 7 d after release. All healthy sharks survived, while 33% of those that were badly injured or gut hooked subsequently died. Overall blue shark bycatch mortality in the pelagic longline fishery was estimated at 35%, while the estimated discard mortality for sharks that were released alive was 19%. Survival time models indicated that 95% of the mortality occurred within 11 d of release, indicative of death by trauma rather than starvation. The annual blue shark catch in the North Atlantic was estimated at about 84 000 t, of which 57 000 t is discarded. A preliminary estimate of 20 000 t of annual dead discards for North Atlantic blue sharks is similar to that of the reported nominal catch, and could substantially change the perception of population health if incorporated into a population-level stock assessment. KEY WORDS: Discard mortality · Hooking mortality · Tagging · Bycatch · Satellite tags Resale or republication not permitted without written consent of the publisherMar Ecol Prog Ser 387: [241][242][243][244][245][246][247][248][249][250][251][252][253] 2009 ronmental conditions at the time of release (Davis 2002). The difficulty in quantifying post-release mortality is due to the scarcity and/or expense of methods for tracking released fish in the wild over periods of time of up to several months. Most studies have attempted to avoid this issue by holding fish in cages or pens for several days after capture (e.g. Neilson et al. 1989). However, holding pens provide a clearly artificial and spatially constrained environment, and thus have the potential to introduce (or avoid) sources of mortality that would not be present under natural, free-swimming conditions. As a result, some sort of tag-recapture or telemetry program is required to properly estimate the post-release mortality rate of discarded fish (Davis 2002, Pollock & Pine 2007, Skomal 2007. Such a program would be well suited for monitoring released fish in the wild for extended periods of time, and has been successfully applied in estimating short-term discard mortality rates in large pelagic fish such as striped marlin (Tetrapturus audax) (Domeier et al. 2003). An additional advantage of such studies is that evidence of physical trauma or stress indicators from blood chemistry can ultimately be linked to the subsequent s...

show abstract

“…In the north-west Pacific and Australia there were negligible differences between blue shark captures with circle and tuna hooks (Yokota et al, 2006;Ward et al, 2009), and in Hawaii there was a significant 36% decrease in shark captures between pre-and postregulations (Gilman et al, 2006). While sharks are considered bycatch and their capture undesirable in several fisheries around the world (Gilman et al, 2008;Ward et al, 2008), they are target species and frequently comprise the bulk of captures in the Brazilian pelagic longline fishery (Hazin et al, 2008). Thus, increase in captures reported in this study is a welcome result for the fishing companies and is beneficial for sea turtles by increasing the probability of the acceptance of circle hooks by the fishing industry.…”

Section: Bony Fish and Shark Target Capture Ratesmentioning

confidence: 99%

Circle hook effectiveness for the mitigation of sea turtle bycatch and capture of target species in a Brazilian pelagic longline fishery

Sales¹,

Giffoni²,

Fiedler³

et al. 2010

Aquatic Conservation

View full text Add to dashboard Cite

ABSTRACT1. Incidental catches by the pelagic longline fishery is a major global threat for loggerhead (Caretta caretta) and leatherback (Dermochelys coriacea) sea turtles.2. The reduction of incidental capture and post-release mortality of sea turtles in the Brazilian pelagic longline fishery, operating in the south-western Atlantic Ocean, was investigated by comparing the performance of 18/0 circle hooks with 9/0 J-type (control) hooks. Hook selectivity experiments were performed between 2004 and 2008, in a total of 26 trips, 229 sets and 145 828 hooks. The experimental design included alternating control and experimental hooks along sections of the mainline.3. An overall decrease in capture rates for loggerhead turtles of 55% and for leatherbacks of 65% were observed when using circle hooks. In addition, deep-hooking in loggerheads decreased significantly from 25% using J-hooks to 5.8% with circle hooks, potentially increasing post-release survival.4. Circle hooks increased catch rates of most of the main target species, including tunas (bigeye Thunnus obesus and albacore T. alalunga), and sharks (blue Prionace glauca and requiem sharks of the genus Carcharinus), with no difference in the capture rates of yellowfin tuna (T. albacares), shortfin mako shark (Isurus oxyrinchus), hammerhead sharks (Sphyrna lewini and S. zygaena), and dolphinfish or mahi mahi (Coryphaena hippurus). On the other hand, a significant decrease in the capture rate of swordfish (Xiphias gladius) was detected when using circle hooks.5. Overall, results support the effectiveness of using circle hooks for the conservation of loggerhead and leatherback sea turtles, with positive effects on capture of most target species of the south-western Atlantic longline fishery.

show abstract

Large-scale experiment shows that nylon leaders reduce shark bycatch and benefit pelagic longline fishers

Cited by 91 publications

References 14 publications

Marine megafauna interactions with small-scale fisheries in the southwestern Indian Ocean: a review of status and challenges for research and management

Marine megafauna interactions with small-scale fisheries in the southwestern Indian Ocean: a review of status and challenges for research and management

Bycatch and discard mortality in commercially caught blue sharks Prionace glauca assessed using archival satellite pop-up tags

Circle hook effectiveness for the mitigation of sea turtle bycatch and capture of target species in a Brazilian pelagic longline fishery

Contact Info

Product

Resources

About