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Home , Heterocarpus ensifer, Lobster, Scyllarides squammosus, Shrimp, Slipper lobster, Spiny lobster

The and in Hawaii

JEFFREY J. POLOVINA

The Lobster m long), each averaging 3 trips per facilitate the escapement of sublegal year. A typical vessels sets about 800 (lobsters under minimum le­ Introduction traps per day and remains at almost gal harvest size). The traps are typi­ 2 months per trip. The NWHI lobster cally baited with chopped The commercial lobster fishery in fishery is Hawaii's most valuable de­ (Scomber sp.) and fished in strings of Hawaii is a trap fishery which harvests mersal fishery; in recent years, annual several hundred traps per string most fre­ several lobster in the North­ landings have averaged about 600 met­ quently set in depths from 20 to 70 m. western Hawaiian Islands (NWHI)­ ric tons (t) (1 million lobsters), valued an isolated range of islands, islets, Synopsis of the Fishery at about $6 million U.S. ex-vessel banks, and reefs extending 1,500 n.mi. (Fig. 4). Since 1988, about 80% of the The historical landings from the lob­ northwest, from Nihoa Island to Kure landings have been ster fishery exhibit a classical trend of Atoll (Fig. 1). The fishery targets two (Polovina I). a developing fishery with a period of species: the endemic spiny lobster A commercial trap made low catches at the beginning of the marginatus (Quoy and by Fathoms Plus2 is used by all the fishery (1977-83) followed by a rapid Gaimard, 1825) and the common slip­ fishermen. This is a dome-shaped, increase in landings as more vessels per lobster squammosus (Milne-Edwards, 1837) (Fig. 2,3). Two single-chambered trap made of molded entered the fishery and markets were black polyethylene which measures developed (1984--86) and most recently other species-the ridgeback slipper 980 x 770 x 295 mm, with a mesh size a decline in landings as the population lobster S. haanii (de Haan, 1841) of 45 x 45 mm (inside dimensions). (Morin and MacDonald, 1984) and the is reduced by (1987-91) Each trap has two entrance cones lo­ (Fig. 4). In the early years of the ­ Chinese antarcticus (Lund, 1793)-are caught cated on opposite sides. Each trap also ery (1977-84) and since 1988, land­ incidentally in low abundance. has two escape vent panels each con­ ings have been about 80% spiny and sisting of four 67 mm diameter circu­ 20% slipper lobsters. However, for a Lobster concentrations in the NWHI were documented by research cruises lar vents located on opposite sides to three-year period from 1985 to 1987 in 1976, and commercial trapping be­ the fishery targeted and largely de­ pleted a previously lightly exploited gan in 1977 (Uchida and Tagami, IJ. J. Polvina. 1991. Status of lobster stocks in 1984). Since 1983, the lobster fleet has the Northwestern Hawaiian Islands, 1990. U.S. population of slipper lobsters. Dep. Commer., Natl. Mar. Fish. Serv., South­ ranged from 9 to 16 vessels (15 to 35 Stock assessment has used the an­ west Fish. Sci. Cent. Admin. Rep. H-91-04, 16 p. nual catch of spiny and slipper lobsters 2Mention of trade names or commercial firms does not imply endorsement by the National and trapping effort data from the com­ Jeffrey J. Polvina is with the Honolulu Labora­ Marine Fisheries Service, NOAA. merciallogbooks since 1983 (Table 1). tory, Southwest Fisheries Science Center Na­ tional Marine Fisheries Service, NOAA, 2570 Dole Street, Honolulu, Hawaii 96822-2396. Table 1.-Annuallandings of spiny and slipper lobsters

1983' 158 18 176 64 2.75 90 1984 677 207 884 371 2.38 78 1985 1022 900 1922 1041 1.83 53 ABSTRACT - A description ofthe lob­ 1986 843 851 1694 1293 1.31 50 ster and deepwater shrimp fisheries in 1987 393 352 745 806 0.92 53 Hawaii, addressing harvest levels, biol­ 1988 888 174 1062 840 1.26 84 ogy, and research, is presented. Bothfish­ 1989 944 222 1166 1069 1.09 81 1990 591 187 778 1182 0.66 76 eries ar~ trapfisheries. The lobsterfishery 1991 3 131 35 166 292 0.56 79 IS a limited entry fishery with 1991 land­ !ngs of200 metric tons. The shrimpfishery I D.ata were provided to the Honolulu Laboratory, National Marine Fisheries Service, as required by the Fishery Management Plan of the Western Pacific Regional Fishery Management Council. IS unregulated, with very sporadic effort, , April-December 1983. and annual landings below 200 metric tons. 3 January-May, November-December 1991

28 Marine Fisheries Review .3;",­__~~~O;.._CK + + + +­ -I­ 30° I~'i~~i KURE ATflLL MIDWAY I. 0,;: (I) 0 ,.w:,.". 'dT'i:::'"",:::., '"" LI SI AN SK I I. ~,~,::';' '~" ,:.BANK GANRADCNLEERS I----"""'=------t-----=--MAR'O.. ··'.P~~"""'"''__1f__-----__+------_t-----250 \i .. (~ '::~', •.~.•~CKER I. FRENCH ,..... FRIGATE SHOALS

MAIN HAWAIIAN ISLANDS PACIFIC o C E A N 180' 175 0 170 0 165 0 160 0

Figure I.-The Hawaiian Archipelago, including the Northwestern Hawaiian Islands.

Both spiny and slipper lobsters may be fort of 1.2 million trap-hauls corre­ year with an asymptotic caught in the same trap but fishermen sponds to a mortality (F) of length of 13.2 cm, a mean natural mor­ can alter the proportion of each spe­ 1.2/year or 1.7 times M. Based on the tality estimate of 0.37/year, and esti­ cies by selecting the trapping area and minimum harvest sizes and this level mates for the ages at the onset of sexual depth. Logbooks record only the num­ of fishing mortality, the spawning stock maturity of 2.7 and 1.7 years for males ber of traps hauled and do not specify biomass per recruit is estimated at 40% and females, respectively (MacDonald, when effort targets spiny or slipper lob­ of the level in the absence of fishing. 1984). Trapping surveys mapped the ster. Since 1983 when logbook report­ Both the level of fishing mortality rela­ spatial distribution of P. marginatus in ing was in effect, the combined catch tive to natural mortality and the relative the NWHI and indicated that the high­ per unit effort (CPUE) for legal slipper spawning biomass suggest that fishing est catch rates ranged from depths of and spiny lobsters has declined from effort alone was not sufficient to cause 55-73 m in the southeastern portion of 2.75 to 0.56 lobster per trap-haul (Fig. 4). the decline in CPUE observed in 1990 the NWHI to 19-54 m in the north­ Stock assessment of the lobster re­ and 1991. Current research suggests this western portion of the Hawaiian Ar­ source is hindered by the relatively decline is the result of poor recruitment chipelago (Uchida and Tagami, 1984). short catch and effort time series and (due to oceanographic conditions) at some The settlement of post-larval lobster, our inability to age lobsters. A dynamic banks which resulted in a concentration , were monitored at Kure Atoll, production model, fit to the combined of fishing effort at the remaining banks French Frigate Shoals, and Oahu with spiny and slipper lobster catch and ef­ where recruitment was strong. surface collectors (MacDonald, 1984). fort data for the entire NWHI, esti­ Puerulus settlement appeared seasonal Research mates an equilibrium production curve at the ends of the Hawaiian Archi­ with a maximum sustainable yield of After the initial research cruises pelago; the greatest settlement occurred 900,000 lobsters/year from a fishing documented lobster concentrations in in the summer at Kure Atoll and in the effort of 740,000 trap-hauls, resulting the WHI in 1976, research focused winter at Oahu while at French Frigate in a CPUE of 1.22 lobsters/trap-haul on the of the spiny lobster Shoals, more centrally located, settle­ (Polovina1). A CPUE time-series model . Tagging stud­ ment appeared more uniformly through­ estimates the annual instantaneous ies at Kure Atoll and French Frigate out the year (MacDonald, 1986). natural mortality (M) at 0.7/year and Shoals estimated a von Bertalanffy Research conducted during 1984­ catchability (q) at 1.0 x 10-6 growth curve for growth (in carapace 87 developed escape vents to reduce (Polovina1). Thus the 1990 fishing ef­ length) to have a parameter K of 0.31/ the catch and hence mortality of sub­

55(2). /993 29 the traps for shelter are able to exit, and no mortality due to the retention of slipper or spiny lobster in traps was observed (Parrish and Kazama, 1992). Ongoing research is directed toward understanding the factors responsible for observed spatial and temporal varia­ tion in adult lobster abundance within the Hawaiian Archipelago. Results from larval tows and studies on local oceanography suggest that long-term differences in lobster densities between banks in the NWHI are not due to local larval densities but to 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 com­ mercial and research data. Research and commercial trapping data both show a wide variation in recruitment to the fishery for spiny lobster at Maro Reef relative to Necker Island, 360 n.mi. to the southeast. A high correla­ tion is observed between recruitment to the fishery at Maro Reef and the relative sea level between French Frig­ ate Shoals and Midway Island four years earlier. Geosat altimeter data in­ dicate that the variation in relative sea level between French Frigate Shoals and Midway is linked to the El Nino Southern Oscillation (ENSO). The mechanisms responsible for the appar­ ent link between sea level and lobster recruitment are not known and are the subject of current research. However, the sea level index may prove to be a useful forecast of recruitment to the fishery at Maro Reef four years later Figure 2.-The spiny lobster, Panulirus marginatus. (Polovina and Mitchum, 1992). One economic study (Clarke and Pooley, 1988) has examined the return legal spiny lobster «50 nun tail width) sublegal spiny and slipper lobsters than on investment as a function of vessel and sublegal slipper lobster «56 nun did nonvented control traps, without size. The most profitable vessels in the tail width) without reducing legal significantly reducing legal catches of fleet are the midsize vessels. These catches. A circular vent design takes either species (Everson et aI., In press). vessels are 20-30 m long, have 5-9 advantage of the different morphology An estimated 2,000 plastic traps are crew members, and are able to set 600­ of the spiny and slipper lobsters to al­ lost annually in the NWHI. Concern 820 traps per day. Larger vessels face low escapement at different tail sizes has been raised that lobsters entering cost constraints while smaller vessels for each species. Specifically, research those lost traps may be unable to exit face operational problems. found that traps equipped with two vent and therefore die. Recent field and tank Management panels consisting of four 67 nun diam­ studies have investigated whether lob­ eter circles placed at the bottom of the sters can escape unbaited lobster traps. The fishery has been managed un­ trap caught 83% and 93% fewer The results indicate that lobsters using der Federal jurisdiction with a fishery

30 Marine Fisheries Review being developed the WPRFMC passed emergency regulations to close the fish­ ery for 6 months (May through Octo­ ber, 1991). In March 1992, the lobster FMP was amended to include provi­ sions 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 sea­ son of 1.0 lobster per trap-haul. A pre­ season 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 improve­ ment over the current fleet quota. The lobster fishery has sufficient management regulations, which if ap­ plied correctly, should make the fish­ ery sustainable and economically profitable. However, environmental factors may result in both considerable annual as well as decadal-scale varia­ tion in the exploitable lobster popula­ tion and hence landings. The Deepwater pandalid shrimp are found in some abundance throughout the tropical and subtropical Pacific (King, 1984; Moffitt and Polovina, 1987). In Hawaii, research trapping showed that laevigatus Figure 3.-The slipper lobster, . (Fig. 5) and the smaller and more shal­ low dwelling species, H. ensifer, could be readily caught in the depth range management plan (FMP) administered mandates that vessels submit logbooks 350-825 m in baited traps (Struhsaker by the Western Pacific Regional Fish­ recording daily catch and trapping ef­ and Aasted, 1974). During the past de­ ery Management Council (WPRFMC) fort. A decline in CPUE from 1.25 cade there have been two periods when since 1983. Currently the plan prohib­ lobster per trap-haul in 1988 to 0.6 in the resource, particularly the more valu­ its the harvest of slipper lobster (S. 1990 as well as concerns that vessels able species H. laevigatus, has been squammosus) with a tail width of <56 from other fisheries in worse condi­ the target offishing. In the early 1980's mm and spiny lobster (P. marginatus) tion were considering entering the lob­ a small trap fishery was initiated around with a tail width of <50 mm, prohibits ster fishery, motivated the fishermen the main Hawaiian Islands. The ves­ the retention of -bearing females, to work with the WPRFMC to develop sels typically used large, pyramid­ requires that all traps have escape vents a limited entry and harvest quota plan. shaped traps with a volume of almost 2 to reduce handling and release-induced Further, to protect the spawning biom­ m3, and a large vessel might set up to mortality on sublegal lobsters, and ass of the stock while the plan was 50 traps a day (Tagami and Barrows,

55(2), /993 31 1200 3.0

0 Total Landing ~ I' .. 1000 CPUE 2.5 ~ -; ..Cl 0 .c ..::I '"Q. .. 800 2.0 ..c. E-<'".. .9­ ", 0:: Vi ~ 'tl ..Cl 600 1.5 0 '"= 8 '" ~ 'is.= ~ Q" ....'" 400 1.0 U 0 -; ~ .() :a= .. IS = 0.5 IS ..::I'" 0 -; u '0 ~Lc_ E-< , 0.0 1977 1979 1981 1983 1985 1987 1989 1991 Year

Figure 4.-Total lobster landings and commercial catch per unit effort (CPUE) from the lobster fishery in the Northwestern Hawaiian Islands. Data since 1983 are based on vessel logbooks required under the fishery management plan.

\ '\

Figure 5.-The deepwater shrimp, Heterocarpus laevigatus.

32 Marine Fisheries Review 1988). Landings from this fishery 1992). The depletion study based on Hawaii, HI, UNIHI-SEAGRANT-MR-84­ 01, p. 199-220. peaked in 1984 at over 190 metric tons intensive trapping estimated a _-;:--,-_. 1986. Recruitment of the puerulus ofH. laevigatus with an ex-vessel value catchability coefficient which when of the spiny lobster Panulirus marginatus in Hawaii. Can. J. Fish. Aquat. Sci. of $1.5 million ($7.85/kg) from 7 ves­ applied to trapping data around the 43(11):2118-2125. sels, 23-40 m in length (Ralston and main Hawaiian Islands estimated an Moffitt, B. M., and F. A. Parrish. 1992. An Tagami, 1992). However by the late exploitable biomass of H. laevigatus assessment of the exploitable biomass of Heterocarpus laevigatus in the main Hawai­ 1980's most of the vessels had left the of 271 t (Ralston and Tagami, 1992). ian Islands Part 2: Observations from a sub­ fishery as declining catch rates and the While the deepwater shrimp resource mersible. Fish. Bull. 90(3):476-482 high cost of the deep trapping made may support a very limited local fish­ Moffitt, R. B., and J. J. Polovina. 1987. Distri­ bution and yield of the deepwater shrimp the fishery unprofitable. There was a ery or perhaps periodic heavy pulse Heterocarpus resource in the Marianas. Fish. resurgence in the fishery in 1990, when fishing, it is unlikely to be the object Bull. 85:339-349. Morin, T. D., and C. D. MacDonald. 1984. landings of over 100 t were reported, of heavy sustained exploitation. Initial Occurrence of the slipper lobster Scyllarides primarily the result of intensive fish­ high catch rates appear to drop rap­ haanii in the Hawaiian Archipelago. Pro­ ing by a single vessel but this level of idly, gear loss is appreciable and costly ceedings of the Biological Society of Wash­ ington 97(2):404-407. production was not sustainable at a due to the trapping depths, and mar­ Parrish, F. P., and T. K. Kazama. 1992. Evalua­ profitable CPUE3. Currently there are no kets are not well established. tion of ghost fishing in the Hawaiian lobster management regulations for this resource. fishery. Fish. Bull. 90:720-725. Polovina, J. J., and G. T. Mitchum. 1992. Vari­ Recent research has conducted sub­ ability in spiny lobster Panulirus marginatus mersible surveys of shrimp densities Literature Cited recruitment and sea level in the Northwestern Hawaiian Islands. Fish. Bull. 90:483-493. on different habitats and estimated Clarke, R. P., and S. G. Pooley. 1988. An eco­ Ralston, S., and D. T. Tagami. 1992. An as­ shrimp biomass from an intensive trap­ nomic analysis of lobster per­ sessment of the exploitable biomass of ping depletion study (Moffitt and formance in the Northwestern Hawaiian Is­ Heterocarpus laevigatus in the main Hawai­ lands. U.S. Dep. Commer., NOAA Tech. ian Islands. Part I: trapping surveys, deple­ Parrish, 1992; Ralston and Tagami, Memo. NMFS-SWFC-I06, 45 p. tion experiment, and length structure. Fish. 1992). The submersible surveys ob­ Everson, A. R., R. A. Skillman, and J. J. Bull. 90(3):494-504. served that H. ensifer tended to group Polovina. In press. Evaluation of rectangu­ Struhsaker, P., and D. C. Aasted. J974. lar and circular escape vents in the North­ Deepwater shrimp trapping in the Hawaiian around large anemones and other western Hawaiian Islands lobster fishery. N. Islands. Mar. Fish. Rev. 36(10): 13-21. benthic relief over an otherwise flat, Am. J. of Fish. Manag. Tagami, D. T., and S. Barrows. 1988. Deep-sea sandy bottom and were very active in Gooding, R. M., J. J. Polovina, and M. D. shrimp trapping of Heterocarpus laevigatus Dailey. 1988. Observations of deepwater in the Hawaiian Archipelago by a commer­ the presence of a baited trap (Gooding shrimp, , from a sub­ cial fishing vessel. U. S. Dept. Commerce, et. aI., 1988; Moffitt and Parrish, 1992). mersible off the island of Hawaii. Mar. Fish. NOAA Tech. Memo. NMFS, NOAA-TM­ Rev. 50(1):32-39. NMFS-SWFC-I03, 14 p. However, H. laevigatus were solitary King, M. G. 1984. The species and depth distri­ Uchida, R. N., and D. T. Tagami. 1984. Biol­ and showed little activity around baited bution of deepwater caridean ogy, distribution, population structure, and traps. Greater densities ofH. laevigatus (, ) near some Southwest pre-exploitation abundance of spiny lobster, Pacific islands. Crustaceana 47:174-191. Panulirus marginatus (Quoy and Gaimard were observed on volcanic than on cor­ MacDonald, C. D. 1984. Studies on recruit­ 1825), in the Northwestern Hawaiian Islands. alline substrata (Moffitt and Parrish, ment in the Hawaiian spiny lobster, In R. W. Grigg and K. Y. Tanoue (Editors), Panulirus marginatus. In R. W. Grigg and Proceedings of the second symposium on K. Y. Tanoue (Editors), Proceedings of the resource investigations in the Northwestern 3Commercial Landings, State of Hawaii, Divi­ second symposium on resource investiga­ Hawaiian Islands, Vol. 1, May 25-27,1983 sion of Land and Natural Resources, Division tions in the Northwestern Hawaiian Islands, Honolulu. Univ. of Hawaii, HI. UNIHI­ of Aquatic Resources, 1990. Vol. J, May 25-27 1983 Honolulu. Univ. of SEAGRANT-MR-84-01, p. 157-197.

55(2), 1993 33