Hawaii's pelagic fisheries

Marine Fisheries Review, Spring, 1993 by Christofer H. Boggs, Rusell Y. Ito

Up until 1980 distant-water longliners from Japan caught between 1,300 and 5,000 t of tuna and billfish annually within the Exclusive Economic Zone (EEZ) around Hawaii (Yong and Wetherall, 1980) but since 1980 there has been no legal foreign longline fishing conducted in the EEZ. The Fishery Management Plan (FMP) enacted by the Western Pacific Regional Fishery Management Council (WPRFMC) was designed to regulate billfish catches by these foreign distant-water longliners (WPRFMC(5)). The Japanese distant-water pole-and-line fishery for skipjack tuna that operated in the Northwestern Hawaiian Islands (NWHI) through 1992 was the only foreign fishery operating legally within the EEZ after 1980 (Boggs and Kikkawa, 1993).

Although the primary target species of the domestic longline fishery are different from those of the troll and handline fisheries, the longline fishery also catches about 1,300 t (2.8 million lb) of yellowfin tuna, blue marlin, and mahimahi (combined). This creates a potential for fishery interaction between the longline and small-vessel troll and handline fisheries. Potential interactions, impacts on endangered species, the possibility of localized overfishing, and gear conflicts (Pooley, 1990) prompted the WPRFMC to establish regulations for the domestic longline fishery in 1990 (Dollar and Yoshimoto(6)). A moratorium on entry of longline vessels into the Hawaii fishery and prohibited areas for longline fishing were established in 1991.

The Longline Fishery

Fishing Methods

Longline fishing gear consists of a main line strung horizontally across 1-100 km of ocean, supported at regular intervals by vertical float lines connected to surface floats. Descending from the main line are branch lines, each ending in a single, baited hook. The main line droops in a curve from one float line to the next and bears some number (2-25) of branch lines between floats. Fishing depth depends on 1) the lengths of the float lines and branch lines, 2) the sag in the main line, and 3) the position of the branch line, the deepest branch line positions being in the middle of the droop. Fishing depth affects the efficiency with which different species are captured (Hanamoto, 1976, 1987; Suzuki et al., 1977; Boggs, 1992).

One longline "set" is made per day of fishing, and for long main lines the deployment and retrieval may take almost 24 hours. Often the end of the line deployed first is retrieved last, so individual hooks may fish for a few hours, or all day (average ca. 12 hours). Traditionally the gear was set so that it fished primarily during daylight. For bait, Hawaii longliners used locally caught scad, Decapterus and Selar spp.; imported squid, Loligo sp.; sardines, Sardinops caerulea; herring, Clupea pallasi; and saury, Cololabis saira.

The Hawaii longline fishery began in 1917 off Waianae, Oahu, using techniques imported from Japan. Hawaii longline vessels evolved from the wooden sampan-style baitboats used in the pole-and-line fishery for skipjack tuna (June, 1950). The sampans used in the early years of the fishery (ca. 1950) were 12-19 m (40-63 ft) in length, high-bowed, and diesel-powered. They carried about 12 t of ice to chill an average catch of about 3 t (7,000 lb) of fish caught over an average trip of 10.5 days (June, 1950).