Pelagic Longline Fishing Gear: A Brief History and Review of Research Efforts to Improve Selectivity

Abstract

A B S T R A C TPelagic longline gear had several independent evolutions, but the most widespread form appears to have been originally developed by the Japanese as early as the mid-19 th century. Technological developments such as polyamide monofilament line and modern fishing vessel construction have resulted in the evolution and expansion of this gear type as the primary worldwide method of commercially harvesting large pelagic fishes such as broadbill swordfish and tunas.Although the adaptability of the gear through changes in materials, lengths, and deployment strategies has resulted in generally high selectivity for many target species, the bycatch of protected species by pelagic longlines is considered a global problem in the conservation effort to sustain populations of sea turtles, sea birds, and some istiophorid billfishes (sailfishes; spearfishes; marlins). Recent research on the modification of pelagic longline fishing strategies uses this inherent adaptability of the gear to avoid or reduce the mortality of bycatch species. This is an alternative to the traditional management strategy of closed areas, which fishermen view as less effective and generally more restrictive (limiting) with respect to target catches. This work with academic partners and commercial fishermen has resulted in the development of bycatch reduction strategies which include safe handling and release gear and protocols, use of circle hooks in place of traditional J-style hooks, restrictions on gangion and mainline lengths, and corrodible hooks.

Effects of Hook and Bait on Targeted and Bycatch Fishes in an Equatorial Atlantic Pelagic Longline Fishery

“…The fishing method has remained nearly unchanged since then, with just a few minor changes incorporated in the last decade. specifically, fishermen shifted from "traditional gear" to "modern gear" (for gear description, see Watson and kerstetter 2006) making use of mainlines and gangions of monofilament and using lightsticks or flashlights. in certain areas and seasons, pelagic sharks may be a major component and multifilament wire gangions and mackerel bait are used.…”

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

“…In the Hawaiian swordfish (Xiphias gladius) fishery, following a closure of four years, the fishery was reopened with a number of conditions such as a maximum annual quota for the entire fleet of 17 loggerhead and 16 leatherback (Dermochelys coriacea) sea turtles, restricted annual fishing effort, prescribed use of fish bait and large 18/0 circle hooks instead of squid bait and 9/0 J-hooks, and 100% observer coverage (Gilman et al, 2006(Gilman et al, , 2007Pradhan and Leung, 2006). In the US Atlantic fishery, circle hooks are also mandatory, while the International Commission for the Conservation of Atlantic Tunas (ICCAT), encourage their use throughout the Atlantic Ocean (Watson and Kerstetter, 2006). Other strategies for mitigation have shown limited ability to avoid or reduce incidental capture (e.g.…”

“…long-lived, low fertility, delayed maturity, and high adult survival, are threatened with extinction owing to unsustainable levels of incidental mortality (Lewison et al, 2004). The pelagic longline fishery is commonly used throughout the world to catch large predatory fishes such as tuna, billfish, and shark (Brothers et al, 1999;Watson and Kerstetter, 2006). The fishery is considered relatively selective with respect to capturing targeted fish by species and size compared with gillnetting and trawling (Alverson et al, 1996;Bjordal and Løkkeborg, 1996; but see Ovetz, 2007).…”

Spatio-temporal distribution and target species of longline fisheries off Southeastern/Southern Brazil between 2000 and 2011

“…This fishery is primarily directed to the capture of albacores (Thunnus alalunga, T. obesus, T. albacares), swordfish (Xiphias gladius) and sharks (specially Prionace glauca) (BROTHERS et al, 1999;WATSON;KERSTETTER, 2006), species which are of great economic importance worldwide because of their high market value (EVANGELISTA et al, 1998;HAZIN, 2006), for both the flesh and, as in the case of sharks, the fins (MAZZOLENI; SCHWINGEL, 1999;QUAGGIO et al, 2008).…”