Biology and Management of Deepwater Snappers of the Hawaiian Archipelago Item Type article Authors Haight, Wayne R.; Kobayashi, Donald R.; Kawamoto, Kurt E. Download date 05/10/2021 21:16:26 Link to Item http://hdl.handle.net/1834/26494 Biology and Management of Deepwater Snappers of the Hawaiian Archipelago WAYNE R. HAIGHT, DONALD R. KOBAYASHI, and KURT E. KAWAMOTO Introduction groupers (Serranidae), and jacks Species and Distribution s~appers Commercial exploitation of deep­ (Carangidae). However, .are The commercially important deep­ the most important group 10 the fIsh­ water snappers in Hawaii began before water snapper complex in Hawaii is ery, both by numbers and revenue. J the turn of the century (Cobb, 1903), composed of seven species of the Most of the commercially important and except for a hiatus during World lutjanid subfamily Etelinae: Pristipo­ species have a relatively high age at War II, has continued to the present. moides filamentosus (opakapaka), P. maturity, long life span, and slow The fishery operates throughout the seiboldii (kalekale), P. zona/us fa~to~s, Hawaiian archipelago, but the inhab­ growth rate. These c?mbined (gindai), Etelis carbunculus (ehu), E. with considerable varIatIOn 10 larval ited Main Hawaiian Islands (MHI) ex­ coruscans (onaga), Aprion virescens recruitment, make these fishes highly perience the highest explo~tation. by (uku), and Aphareus rutilans (le~i). susceptible to overfishing. Recent evi­ both commercial and recreatIOnal fIsh­ Some commercial landings of an In­ dence suggests that some of the spe­ ermen. The uninhabited islands and troduced snapper, Lutjanus kasmira cies may be overfished, and several atolls northwest of Niihau, called the (taape), are also made, but this species others are approaching a level of con­ Northwestern Hawaiian Islands usually occurs in shallower water ~han cern l ,2 (Ralston and Polovina, 1982; (NWHI) (Fig. 1), are fished mainly by the other species. The commerCIally Ralston, 1984). commercial fishermen. important deepwater lutjanids inhabit Historically, minimum size limits The deepwater handline fishery tar­ the deep slopes of island coasts and have been the only measure used to gets a multispecies group of f~sh~s con­ banks at depths of 100 to 400 m. These manage both the MHI and NWHI sisting of snappers (LutJamdae), banks and deep slopes comprise an area stocks. Since 1989, the NWHI have over 6 times that of shallow water reefs been managed on a limited entry sys­ in the state. Biological production in tem. Minimum size limits remain the The authors are with the Honolulu Laboratory, these deepwater areas is thought to be Southwest Fisheries Science Center NatIOnal only management tool currently in ef­ quite different from shallow-water Marine Fisheries Service, NOAA, 2570 Dole fect in the MHI. Several management Street, Honolulu, Hawaii 96822 coral reef areas (Agegian et aI., 1988). measures are being evaluated to main­ Throughout their spatial and depth tain adequate spawning stock biomass range, deepwater snappers in Hawaii in the future. These include changing are typically distributed in a clumped minimum size limits, creating closed pattern, and are often associated ~ith ABSTRACT - Commercial and recre­ refuge areas, and imposing bag limits ational deepwater (100-400 m) bottom­ underwater headlands and areas of hIgh fishing in Hawaii targets a multlspeCies and closed fishing seasons. relief. Four of the deepwater snapper group oflutjanid snapp,ers. RelatIvely ltttle This report presents a summary of species found in Hawaii were observed is known about the life hIstory of these available information regarding the bi­ in situ from manned submerSIbles and species. Research in Hawaii and elsewhere ology, fishery, and management of in the tropical Pacific suggests that most an unmanned remotely operated ve­ ofthe species are slow growing, long lived, these valuable species. hicle (ROY) and were found to form and have a relatively high age at sexual large aggregations of up to 100 in?i­ maturity. Stock assessment is difficult be­ viduals near submerged promontones cause of the multispecies nature of the I(WPRFMC) Western Pacific Regional Fishery fishery. However, re~en~ analysis of com­ Management Council. 1991. Annual bottomflsh and areas of high relief (Brock and mercial fishery data mdlcates that som,e of and seamount groundfish report, 85 p. Chamberlain, 1968; Ralston et aI., 2S Ralston and K. E. Kawamoto. 1985. A pre­ the species may currently be ov~rexplOlted. li~inary 1986; Haight, 1989). This clumped dis­ Research is underway to determme the effi­ analysis of the 1984 size structure of Hawaii's commercial opakapaka landings and tribution pattern is also apparent when cacy ofmanagement measures such as mini­ a consideration of age at entry and yield per fishing from the surface. mum-size limit changes or seasonal and recruit. U. S. Dep. Commer., NOAA, Natl. Mar. spatial fishery closures to maintain optimal Fish. Serv., Southwest Fish. Cent., Admin. Rep. A contributing factor in the distribu­ spawning biomass. H-85-1, 9 p. tion pattern of these fish may be that 20 Marine Fisheries Review .3~:;;.tlANK-------+--------+--------+--------+-------+----- HANCOCK 30.- ~~..~~J KURE ATa~L ('tID~AY I. ,:;?:·PEARL & HERMES REEF SALMON BA:Ko , I'J '<} .::. LAYSAN I. RAITA L1SIAN SKI I. ~:,~,(';' ':!;'i ,::,BANK GARDNER I-----~,__-----,,-----MARO· ....P....IU!N""'A"'C""LE...,S'--If-- ---l --t 25' REEF \j ':0:, '.:~:.; NECKER I. ·:f··. 1 FRENCH ,..... FRIGATE SHOALS ----/--20· MAIN HAWAIIAN ISLANDS PACIFIC o C E A N 180· 175· 170· 165· 16 D· 155· Figure I. - The Hawaiian Archipelago currents striking deepwater areas of rily piscivorous and showed little over­ hours. Catch rates decreased at this high relief form localized zones of tur­ lap in diet composition between trophic time, and egg masses were observed bulent vertical water movement, in­ guilds. adhering to the fishing gear. By mid­ creasing the availability of planktonic afternoon the school became less com­ Reproduction prey items (e.g. Brock and Chamber­ pacted and catch rates increased. lain, 1968). In an ecological study of Relatively little is known about the Opakapaka caught during this time the bottomfish resources of Johnston reproduction and early life history of were in spawning condition, some fe­ Atoll, Ralston et al. (1986) found P. deepwater snappers in Hawaii. Size at males released eggs and males released filamentosus in much higher densities maturity has been estimated for only milt. Free-floating eggs were noted on the upcurrent versus the down­ two species in the MHI and two spe­ covering a large surface area around current side of the atoll, and postulated cies in the NWHI. In the MHI, uku the vessel. The observations were made that this was related to increased avail­ reaches sexual maturity at 47 cm fork in mid-April. 3 ability of allochthonous planktonic prey length (FL), which is 46% of maxi­ Gonadal studies on four of the spe­ in the neritic upcurrent areas due to mum size (Loo). Onaga reaches sexual cies in Hawaii indicate that spawning oceanic currents impacting the atoll. maturity at 61 cm FL (62% Loo) may occur serially over a protracted Although snappers throughout the (Everson et aI., 1989). In the NWHI, period but is at a maximum during the world are generally thought of as top ehu reaches maturity at about 30 cm summer months, and peaks from July level carnivores, several snapper spe­ FL (46% Loo) and opakapaka reaches to September (Everson et aI., 1989; cies in the Pacific are known to incor­ maturity at around 43 cm FL (48% Uchida and Uchiyama, 1986). Esti­ porate significant amounts of zooplank­ Loo) (Everson, 1984; Kikkawa, 1984; mated annual fecundity is 0.5 to 1.5 ton, often gelatinous urochordates, in Grimes, 1987). million eggs. The eggs are relatively their diets (Parrish, 1987). Haight et There is a record of one anecdotal small (0.7 to 0.8 mm) and are released al. (1993) found zooplankton to be an observation on the spawning behavior into the water column. important prey item in four of the com­ of opakapaka in Hawaii. A NWHI com­ mercially important snappers in Ha­ mercial fisherman using a chromoscope 3(WPRFMC) Western Pacific Regional Fishery waii. The same study found that the depth sounder observed an opakapaka Management Council. 1988, 1986 annual re­ port of the fishery management plan for the six snapper species studied were either aggregation at about 150 m become bottomfish and seamount groundfish fisheries primarily zooplanktivorous or prima- very dense during the mid-morning of the western Pacific region, 150 p. 55(2), 1993 21 Larval and Juvenile Stages opakapaka first appear in the relatively Ralston (1987), in a comprehensive shallow (60-100 m) nearshore areas at review of published reports on snapper Newly hatched larvae of lutjanids in about 10 months of age (7-10 cm FL) growth and natural mortality, deter­ general are typical of those from fish during the fall and early winter months. mined that for the 10 species studied, with small pelagic eggs; the larvae have The young opakapaka remain in this mortality and growth rates were highly a large yolk sac, unpigmented eyes, habitat for the next 7 months until they correlated, with a mean M/K ratio of and no mouth. The yolk sac typically reach 18-24 cm FL,5 In situ scuba ob­ 2.0. Thus, if a value of K is available lasts 3-4 days, after which the mouth servations of the juvenile habitat found for a given species, its natural mortal­ is fully formed and the eyes become it to be a relatively flat, soft sediment ity rate can be estimated. Using an pigmented (Leis, 1987). The larval substrate devoid of relief (Parrish, age-length probability matrix for stages of snappers in Hawaii are poorly 1989). Recent trawl surveys suggest opakapaka applied to length frequency studied, perhaps because of their rarity juvenile opakapaka are fairly wide­ samples, Ralston (1981) estimated the in plankton samples.