Lobster Fishery
Introduction
The commercial lobster fishery in Hawaii is a limited-entry trap fishery that harvests several lobster species in the Northwestern Hawaiian Islands (NWHI).
The Northwestern Hawaiian Islands are an isolated range of islands, islets, banks, and reefs which extend 1,500 nmi northwest of the main Hawaiian islands from Nihoa Island to Kure Atoll. The commercial lobster fishery has operated in the NWHI since 1977, targeting primarily two species: spiny lobster, Panulirus marginatus, and slipper lobster, Scyllarides squammosus. Two other species--green spiny lobster, P. penicillatus, and ridgeback slipper lobster, S. haanii, -- are caught incidentally in low abundance.
The NWHI lobster fishery is Hawaii's most valuable demersal fishery. From 1984 to 1990 annual landings averaged about 150 metric tons or 1 million lobsters total valued at about $6 million ex-vessel. Since 1988, about 80% of the landings have been spiny lobster.
Vessels and Gear
Lobster concentrations in the NWHI were documented by research cruises in 1976, and commercial trapping began in 1977. Since 1983, the lobster fleet has ranged from 9 to 16 vessels that are 15 to 35 meters long. They average three trips per year. A typical vessel remains at sea almost 2 months per trip and sets about 800 traps per day.
A commercial shellfish trap made by Fathoms Plus? is used by all the lobster fisherman. This is a dome-shaped, single-chambered trap made of molded black polyethylene, which measures 980 by 770 by 295 mm, with a mesh size of 45 by 45 mm (inside dimensions). Each trap has two entrance cones located on opposite sides and two escape vent panels each consisting of four 67-mm-diameter circular vents located on opposite sides to facilitate the escape of lobsters under the minimum legal harvest size. The traps are typically baited with chopped mackerel and fished in strings of several hundred traps per string most frequently set in depths from 20 to 70 meters.
Landings
The historical landings from the lobster fishery exhibit a classical trend of a developing fishery with a period of low catches at the beginning of the fishery from 1977 to 1983. This is followed by a rapid increase in landings as more vessels entered the fishery and markets were developed from 1984 to 1986 and most recently by a decline in landings as the population was reduced by overfishing from 1987 to 1991. In the early years of the fishery from 1977 to 1984 and since 1988 landings have been about 80% spiny and 20% slipper lobsters. However, from 1985 to 1987 the fishery targeted and largely depleted a previously lightly exploited population of slipper lobsters.
Stock assessment has used the annual catch of spiny and slipper lobsters and trapping effort data from the commercial lobster logbooks since 1983. Both spiny and slipper lobsters may be caught in the same trap, but fishermen can alter the proportion of each species by selecting the trapping area and depth. Logbooks record only the number of traps hauled and do not specify when efforts target spiny or slipper lobsters. Since 1983 when logbook reporting was in effect, the combined CPUE for legal slipper and spiny lobsters has declined from 2.75 to 0.56 lobsters per trap-haul.
Stock assessment of the lobster resource is hindered by the relatively short catch and effort time series and our inability to age lobsters. Both the level of fishing mortality relative to natural mortality and the relative spawning biomass suggest that fishing effort alone was not sufficient to cause the decline in CPUE observed in 1990 and 1991. Current research suggests this decline is the result of poor recruitment due to oceanographic conditions at some banks which resulted in a concentration of fishing effort at the remaining banks where recruitment was strong.
From 1992 to 1997, the NWHI lobster fishery faced several major developments. There was a complete closure in 1993, an emergency closure after the season opened in 1994, an experimental permit fishery of only one vessel in 1995 with a very restricted quota, and then a return to relatively normal operations in 1996 with a small quota and a larger quota forthcoming in 1997.
The 1993 closure was created by the preseason estimate of catch rates that resulted in zero quota. The 1994 closure occurred when in-season reports of catch rates were less than those anticipated by the stock assessment. This lead to an emergency closure 8 weeks into the season. The fishery remained closed for the remainder of 1994.
The fishery and environmental causes of the 1993 closure are discussed in Haight and Polovina (1992). In brief, stock assessment biologists believe that the spawning stock biomass at Maro Reef, which is a major bank in the NWHI lobster fishery, declined dramatically due to poor post-larval recruitment and subsequent fishing down of the remaining population in the years following 1986. The recruitment problem appears associated with higher sea level heights, which changed patterns of larvae lobster transport.
Regulations
The Fishery Management Plan (FMP) for the western Pacific crustacean fisheries was prepared by the Western Pacific Regional Fishery Management Council (WPRFMC) and went into effect in 1983. Lobster permits were issued by the Regional Director (RD), Southwest Region, National Marine Fisheries Service (SWR, NMFS). These permits allowed lobster fishing operations in the U.S. Exclusive Economic Zone (EEZ) from 3 to 200 nmi offshore American Samoa, Guam, Hawaii, the Northern Mariana Islands, and U.S. possessions in the western Pacific, but no federally permitted lobster vessels fished outside of the NWHI EEZ.
The Fishery Monitoring and Economics Program (FMEP) of the Pacific Islands Fisheries Science Center (PIFSC), collected biological and economic information exclusively from permitted vessels on NMFS Daily Lobster Catch Report Forms.
Currently the plan prohibits the harvest of slipper lobster with a tail width of less than 56 mm and spiny lobster with a tail width of less than 50 mm. It prohibits the retention of egg-bearing females, requires that all traps have escape vents to reduce handling and release-induced mortality on sublegal lobsters, and mandates that vessels submit logbooks recording daily catch and trapping effort.
A decline in CPUE from 1.25 lobster per trap-haul in 1988 to 0.6 in 1990, as well as concerns that vessels from other fisheries in worse condition were considering entering the lobster fishery, motivated the fishermen to work with the WPRFMC to develop a limited-entry and harvest-quota plan. Further, to protect the spawning biomass of the stock while the plan was being developed, the WPRFMC passed emergency regulations to close the fishery for 6 months in 1991.
In March 1992, the lobster FMP was amended to include provisions for a limited-entry system for a maximum of 15 vessels, an annual fleet harvest quota, and a closed season from January through June to protect the spawning biomass before the summer spawning. The quota is set to achieve an average CPUE over the fishing season of 1.0 lobster per trap-haul. A preseason quota is set using an estimate of the population size at the end of the previous fishing season and estimates of natural mortality and recruitment. A final quota is set after the first month of fishing based on the CPUE during that month. Information from research surveys can also be used in the quota calculations. Currently, fishermen and managers are considering whether an individual quota would be an improvement over the current fleet quota.
Following the abbreviated 1994 season, the WPRFMC proposed Amendment 8 to the Crustacean Fisheries FMP. The amendment proposed three changes in the FMP. These are a framework approach to the annual quota system, revocation of the use-it-or-lose-it requirement for permit holders and changes to various arrival notification procedures. Subsequent refinements to the FMP were made in 1995 and 1996 (Amendment 9) based on simulation research conducted by Dinardo (1995).
Research
After initial research cruises documented lobster concentrations in the NWHI in 1976, research focused on the biology of the spiny lobster. Trapping surveys mapped the spatial distribution of the spiny lobster in the NWHI and indicated that the highest catch rates ranged from depths of 55 to 73 m in the southeast portion of the NWHI to 19 to 54 m in the northwest portion of the Hawaiian Archipelago.
The settlement of post-larval lobster, puerulus, were monitored at Kure Atoll, French Frigate Shoals, and Oahu with surface collectors. Puerulus settlement appeared seasonal at the ends of the Hawaiian Archipelago; the greatest settlement occurred during the summer at Kure Atoll and during the winter at Oahu while at French Frigate Shoals, more centrally located, settlement appeared more uniformly throughout the year.
Research conducted during 1984 to 87 developed escape vents to reduce the catch and hence mortality of sublegal spiny lobster, less than 50-mm tail width, and sublegal slipper lobster, less than 56-mm tail width without reducing legal catches.
An estimated 2,000 plastic traps are lost annually in the NWHI. Concern has been raised that lobsters entering those lost traps may be unable to exit and therefore die. Recent field and tank studies have investigated whether lobsters can escape unbaited lobster traps. The results indicate that lobsters using the traps for shelter are able to exit, and no mortality from the retention of slipper or spiny lobster in traps was observed.
Ongoing research is directed toward understanding the factors responsible for observed spatial and temporal variation in adult lobster abundance within the Hawaiian Archipelago. Results from larval tows and local oceanography studies suggest that long-term differences in lobster densities between banks in the NWHI are caused by differences in the amount of relief provided by the benthic habitat on the banks.
Temporal variation in spiny lobster stocks at the two most productive banks in the fishery, Maro Reef and Necker Island, has been studied with both commercial and research data. The mechanisms responsible for the apparent link between sea level and lobster recruitment are not known and are the subject of current research. The El Ni?o Southern Oscillation (ENSO) is thought to play a factor in the variation in relative sea level throughout the archipelago.
The return on investment as a function of vessel size has been studied. The most profitable vessels in the fleet are midsize vessels. The vessels are 20-30 m long, have five to nine crew members, and are able to set 600-820 traps per day.