UNIT 16 

 WESTERN PACIFIC INVERTEBRATE FISHERIES 



lobster. Future research is needed to .iddress knowl- 

 edge shortfalls of slipper lobster biology. Estimates 

 of the exploitable population of lobsters in the 

 NWHl have been based solely on commercial 

 catch and effort data from the NWHl lobster fish- 

 ery as a whole. This approach neglects the fact that 

 fishermen target areas with higher concentrations 

 of lobsters, and may lead to estimates of exploit- 

 able biomass that are biased. More accurate as- 

 sessments will require the integration of fishery- 

 independent data into assessments in an effort to 

 fine-tune the parameter estimates and assessment 

 of exploitable biomass on a bank-specific basis. 



Factors Affecting Abundance 



In predicting the response of the NWHl lob- 

 ster population to fishing harvest, it must be noted 

 that research to date has identified a dynamic 

 change in the spatial and temporal structure of 

 the NWHl lobster population. One major fish- 

 ing area, Maro Reef, continues to be character- 

 ized by low spiny lobster abundance. Based on 

 oceanographic research, size class and genetic struc- 

 ture analysis, and trends in catch per unit of ef- 

 fort, it appears that recruitment in the NWHl 

 spiny lobster population differs between the south- 

 eastern and northwestern segments of the archi- 

 pelago and remains depressed in the northwest- 

 ern segment relative to the 1975—85 level. Nu- 

 merous hypotheses have been advanced to explain 

 population fluctuations of lobsters in the NWHl, 

 including environmental, biotic (e.g. habitat and 

 competition), and anthropogenic (e.g. fishing). 

 Each hypothesis by itself offers a plausible, how- 

 ever simple, explanation to a rather complex phe- 

 nomenon operating in a system of very high di- 

 mensionality. It is likely that popidation fluctua- 

 tions of lobsters in the NWHl will be more accu- 

 rately described by a mix of the hypotheses pre- 

 sented, each describing a different set of mecha- 

 nisms. 



Multispecies Interactions 



The long-term effects of fishmg on ecosystems 

 are not well imderstood, and cautioirs management 

 controls are required. The removal of one species, 

 or complex of species, could result in species com- 



position shifts. Although both spiny and slipper 

 lobsters are harvested in the NWHl lobster fish- 

 erv, spiny lobster is the primary target at most 

 banks. As large numbers of spiny lobster were be- 

 ing removed from banks in the NWHl, the abun- 

 dance and spatial distribution of slipper lobster 

 on these banks apparently increased; areas tradi- 

 tionally defined as spiny lobster habitat appear now 

 to be occupied by slipper lobster. 



Progress 



Much progress in assessing the status of ex- 

 ploited lobster stocks of the Western Pacific Re- 

 gion has been made in the past several years. 

 Shoreside sampling of the commercial landings was 

 started in l')9(i and has provided valuable infor- 

 mation for characterizing the size-structure com- 

 position of the commercial landings. Likewise, 

 sampling of the commercial catch by at-sea ob- 

 servers was conducted in 1995 and 1997, provid- 

 ing information to characterize the commercial 

 catch, as well as spatial heterogeneity of lobster 

 abundance and size composition. These data were 

 used to enhance the annual NWHl lobster fish- 

 ery-independent survey anti provide a more rep- 

 resentative basis for future stock assessments. 



FOR FURTHER READING 



DiNardo, G. v.. W. R. Haij^ht, and J. A. Wctherall. 

 l')98. Status ot lobster stocks in the Northwestern 

 Hawaiian Islands, 1995-97, and otitlook for 1998. 

 National Marine Fisheries Service, Honolulu, Hawaii. 

 Southwest Fisheries Science Center Administrative Re- 

 port H-98-0S, }S p. 



Boehlert, G. W. 199.3. Fisheries of Hawaii and U.S.- 

 associated Pacific Islands. Marine Fisheries Review 



S5(2):l-1.38. 



Ostczeski, 1. 1997. The deepwater shrimp fishery of 

 the Northern Mariana Islands. National Marine Fish- 

 cries Service, Honolulu, Hawaii. Southwest Fisheries 

 Science Center Administrative Report H-97-10, 44 p. 



Pooley, S. G., and K. E. Kawamoto. 1998. Annual re- 

 port of the 199S-97 western Pacific lobster fishery. 

 National Marine Fisheries Service, Honolulu, Hawaii. 

 Southwest Fisheries Science Center Administrative Re- 

 port H-98-()9, 34 p. 



Hawaiian spiny lobster, 

 Oahu, Hawaii. 



1 87 



