DISTRIBUTION AND YIELD OF 

 THE DEEPWATER SHRIMP HETEROCARPUS RESOURCE 



IN THE MARIANAS 



Robert B. Moffitt and Jeffrey J. Polovina^ 



ABSTRACT 



A shrimp trapping survey was conducted at 22 islands and banks in the Mariana Archipelago during 

 a 2-year field period. Three species of deepwater shrimp were found in abundance at various depths: 

 Heterocarpiis ensifer at 366-550 m, H. laevigatus at 550-915 m, H. longirostris >915 m. Heterocarpus 

 laevigatus was the largest and most abundant of the three and has the greatest economic potential. 

 Estimates of the unexploited biomass of this species by bank were calculated from estimates of catchabOity, 

 relative abundance, and habitat area. An archipelago average of the unexploited trappable biomass was 

 estimated to be 0.8 t/nmi". Evaluation of length-frequency distributions produced estimates of asymp- 

 totic length (Loo) of 55 mm carapace length, instantaneous growth constant (K) of 0.3 yr" ', and instan- 

 taneous total mortality (Z) of 0.75 yr"^ A recommended yield of 162.0 t/year (0.2 t/nmi" per year) for 

 the entire archipelago was calculated using the Beverton and Holt yield-per-recruit equation based on 

 minimum spawning stock considerations. Of this yield, 85% would come from the southern islands (e.g., 

 Guam and Saipan), 13% from the northern islands (e.g.. Pagan and Anatahan), and 2% from the western 

 seamounts (e.g., Arakane Reef and Pathfinder Reef). 



The Mariana Archipelago in the western Pacific 

 Ocean stretches from Guam in the south at lat. 13°N 

 to Farallon de Pajaros (also called Uracas) in the 

 north at lat. 20°N (Fig. 1). Within the approximately 

 270,000 nmi- area of the 200 mi zone around the 

 archipelago are two political entities— the Territory 

 of Guam and the Commonwealth of the Northern 

 Mariana Islands (CNMI)— and three geological 

 formations— the southern island chain, the northern 

 island chain, and the western seamount chain (Karig 

 1971). The purpose of this study was to assess the 

 standing stock and sustainable yield of the deep- 

 water pandalid shrimp resources in the Marianas. 

 Pandalid shrimp catches account for about 9% of 

 the world shrimp landings or about 155,000 1 in 1982 

 (FAO 1984). About 98% of this catch is of a few 

 species of the genus Pandalus trawled at depths of 

 70-240 m in the cold-water areas of the North Atlan- 

 tic, North Pacific, and Bering Sea. The next largest 

 pandalid fishery is the trawl fishery for Hetero- 

 carpus reedi conducted at depths of 155-424 m in 

 the waters off Chili and Peru (Holthuis 1980). The 

 landings from this fishery were 3,450 1 in 1982 (FAO 

 1984). In recent years, pandalid shrimp resources 

 with commercial potential have been identified from 

 deepwater trapping surveys conducted at depths of 



200-1,200 m in the central and western Pacific 

 (Clarke 1972; Wilder 1977; King 1980, 1981a, 1981b; 

 Moffitt 1983). The primary component of these 

 catches has been species of the genus Heterocarptcs, 

 including H. laevigatus, H. ensifer, H. sibogae, H. 

 longirostris, and H. gibbosus. Trawling for these 

 species has produced poor results (Struhsaker and 

 Yoshida 1975) which may be due to the depths in- 

 volved, the rough bottom surrounding the Pacific 

 islands, or behavioral characteristics of the shrimp. 

 In Hawaii a rapidly expanding commercial trap 

 fishery has been established with 1983 annual land- 

 ings of about 135 t. Catches of 1,350 t have been 

 projected for the near future by the Western Pacific 

 Regional Fishery Management Council (WPRFMC 

 1984). This projected yield has not materialized and 

 does not appear to be forthcoming since the larger 

 shrimp trapping vessels have left the fishery for 

 economic reasons. Commercial ventures in Guam 

 and the CNMI have been sporadic and short lived; 

 landings of 0.3 1 were reported in 1982, the last year 

 that the resource was fished. ^ 



SAMPLING GEAR AND METHODS 



Shrimp trapping operations in the Mariana Archi- 



'Southwest Fisheries Center Honolulu Laboratory, National 

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

 96822-2396. 



^Western Pacific Fishery Information Network data on file at 

 the Southwest Fisheries Center Honolulu Laboratory, National 

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

 96822-2396. 



Manuscript accepted January 1987. 

 FISHERY BULLETIN: VOL. 85, NO. 2, 1987. 



339 



