ASPECTS OF THE REPRODUCTIVE BIOLOGY, 



SPATIAL DISTRIBUTION, GROWTH, AND MORTALITY OF 



THE DEEPWATER CARIDEAN SHRIMP, HETEROCARPUS LAEVIGATUS, 



IN HAWAII 



Murray D. Dailey 1 and Stephen Ralston 2 



ABSTRACT 



The recent rapid development of fisheries for the Heterocarpus laevigatas in Hawaii and elsewhere in 

 the tropical Pacific has created the need for biological information to manage the resource. This study 

 reports on a 16-month sampling program of commercial shrimp catches in Hawaii, during which the depth 

 of capture, carapace length (CL), sex, and reproductive condition of 7,368 H. laevigatas were determined. 



The overall sex ratio of H. laevigatus was 1:1.16 in favor of females and depended on the depth 

 sampled; there were relatively fewer females as depth increased. Seasonal variation in sex ratio was 

 evident which may have been due to changing catchability and availability or a sex related dispersion 

 pattern. Sex ratio also depended on size category, displaying a standard pattern with no evidence of 

 protandry. 



Females mature at 40 mm CL (64% of asymptotic length) and ovigerous individuals are found year 

 round. However, the main reproductive season is from August-February, with over 50% of females 

 carrying eggs from October-January. Mature shrimp may undergo a depth related seasonal migration 

 in synchrony with breeding. Mature males and females were found deeper (700 m) during the reproduc- 

 tive season than not (550 m). Females apparently settle in deep water and migrate gradually to shallower 

 water as they grow. 



Seasonal length-frequency data suggest H. laevigatus is not semelparous. Separate analyses of CL- 

 frequency distributions of male and female shrimp indicate their von Bertalanffy asymptotic sizes are 

 57.9 and 62.5 mm CL, respectively. Growth coefficients (K) estimated by modal progression were 0.35 

 and 0.25 per year for males and females, and total instantaneous mortality rates were 1.51 and 0.73 

 per year, respectively. 



The deepwater caridean shrimp, also known as 

 "ono" or smooth nylon shrimp, Heterocarpus laevi- 

 gatus, (Family Pandalidae) occurs throughout the 

 tropical Pacific Ocean, where it is found in benthic 

 deepwater habitats (450-900 m) (Wilder 1977; King 

 1983). While early trapping surveys in the Hawaiian 

 Islands revealed its local abundance (Clarke 1972; 

 Struhsaker and Aasted 1974), little information was 

 available concerning its biology. These early studies 

 did show, however, that H. laevigatus was poten- 

 tially of commercial importance, with a preliminary 

 maximum sustained yield estimate of 454-907 metric 

 tons (t) derived for the Hawaiian Archipelago 

 (Department of Land and Natural Resources 1979). 

 More recently the Western Pacific Regional Fishery 

 Management Council 3 (WPRFMC) has revised this 

 estimate to 400-4,000 t. 



■Hawaiian Fishing Research Company, 737 Bishop Street, Suite 

 2910, Honolulu, HI 96813; present address: Department of 

 Biology, California State University at Long Beach, Long Beach, 

 CA 90840. 



2 Southwest Fisheries Center Honolulu Laboratory, National 

 Marine Fisheries Service, NOAA, 2570 Dole Street, Honolulu, HI 

 96822-2396. 



Manuscript accepted July 1986. 



FISHERY BULLETIN: VOL. 84, NO. 4, 1986. 



A commercial trap fishery for this species sub- 

 sequently developed in the Hawaiian Islands, and 

 in 1984 the WPRFMC began the process of develop- 

 ing a fishery management plan for the Heterocar- 

 pus shrimp resources of the region. Landings from 

 the Hawaiian fishery exceeded 135 t in 1983 but 

 have declined sharply since, although commercial 

 interest in the resource remains great (WPRFMC 

 fn. 3). Recent research surveys in Hawaii have now 

 more clearly defined this species' depth, temporal, 

 and geographic distributions (Oishi 1983; Hawaiian 

 Divers 1983 4 ; Gooding 1984), although the life 

 history of H. laevigatus remains largely unknown. 

 The only substantive biological studies to date were 



3 Western Pacific Regional Fishery Management Council. 1984. 

 Status of fisheries assessment of development and management 

 needs for selected crustacean species in the western Pacific region. 

 Unpubl. manuscr., 60 p. Southwest Fisheries Center Honolulu 

 Laboratory, National Marine Fisheries Service, NOAA, 2570 Dole 

 Street, Honolulu, HI 96822-2396. 



4 Hawaiian Divers. 1983. Deepwater shrimp utilization study 

 for Hawaii. Report prepared under NOAA Cooperative Agree- 

 ment No. 80-ABH-00065 for the Southwest Region, Western 

 Pacific Program Office, National Marine Fisheries Service, NOAA, 

 Honolulu, HI, 47 p. 



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