MOFFITT ET AL.: DISTRIBUTION AND YIELD OF DEEPWATER SHRIMP 



Table 7.— Equilibrium yield for Heterocar- 

 pus shrimps In the 500-825 t depth range 

 for a fishing mortality of 0.5. 



Table 8.— Catch rates of pandalid shrimp in the tropical Pacific. 



longirostris proved to be the major components of 

 the catch within their respective depth zones. 

 Heterocarpus ensifer was the shallowest dwelling 

 and the least abundant of the three major species 

 in the Marianas. Its range of abundance was 366 to 

 503 m (200 to 275 fathoms) and the peak catch rate 

 was 0.17 kg/trap-night at 366 m. In Hawaii, H. en- 

 sifer appears to be the most abundant species. 

 Average catch rates are between 1.5 and 6.6 

 kg/trap-night in a somewhat wider reported depth 



of abundance of 274 to 600 m (Clarke 1972; 

 Struhsaker and Aasted 1974; Gooding 1984). In the 

 Southern Hemisphere; H. ensifer is not found in 

 great abundance and is replaced in the 300 to 500 

 m depth range by a very closely related species, H. 

 sibogae (King 1983). 



Heterocarpus laevigatus is an important part of 

 the catch throughout the central and western 

 Pacific. In the Marianas, this was the most common 

 species. Its abundance peaked between 549 and 777 

 m (300 and 425 fathoms) and the maximum catch 

 rate of 2.33 kg/trap-night was obtained at 777 m. 

 In the Northwestern Hawaiian Islands (NWHI), the 

 same standard half-round traps caught just under 

 1.0 kg/trap-night in an optimum depth range of 500 

 to 800 m (Gooding 1984). Commercial vessels using 

 larger traps obtained catches of 2.5 to 5.0 kg/trap- 

 night in the Hawaii area and found that the opti- 

 mum depth range is shallower in the main Hawaii- 

 an Islands (530 to 622 m) than in the NWHI (640 

 to 732 m) (Hawaiian Divers 1983*; Oishi 1983; Good- 

 ing 1984). In the South Pacific, H. laevigatus is 

 reported to be abundant at depths of 549 to 640 m 

 and catch rates range from 0.4 to 1.1 kg/trap-night 

 depending on the area studied (King 1983). 



Before this study, H. longirostris had been known 

 to science from only four specimens taken in the 

 Indian Ocean (Moffitt 1983). In the Marianas, it 

 occurs in sufficient quantity to suggest a commer- 

 cial potential. Heterocarpus longirostris is probably 

 present in many other areas in the Pacific but has 

 not been found because its optimum depth range is 

 below those sampled. 



In the Marianas, sex ratio varied with depth for 

 all three of the major species of Heterocarpus. For 

 each species, a larger percentage of the catch is com- 

 posed of females at the shallower end of the species' 

 depth range. A similar distribution in Hawaii has 

 been reported for H. ensifer (Clarke 1972) and H. 

 laevigatus (Dailey and Ralston 1986). 



Changes in the mean size with depth have been 

 reported for H. ensifer and H. laevigatus. Wilder 

 (1977) and Gooding (1984) reported increases in size 

 with increasing depth for H. ensifer from Guam and 

 the NWHI, respectively. Clarke (1972), on the other 

 hand, found that a higher proportion of larger in- 

 dividuals in Hawaii occupied the depth of greatest 

 abundance, while smaller individuals were found in 

 shallower or deeper water. Gooding (1984) noted a 



^Hawaiian Divers, Inc. 1983. Deepwater shrimp utilization 

 study for Hawaii. Report prepared under NOAA Cooperative 

 Agreement No. 80-ABH-00065 for the Southwest Region, West- 

 ern Pacific Program Office, National Marine Fisheries Service, 

 NOAA, 47 p. 



347 



