UNIT 16 

 WESTERN PACIFIC INVERTEBRATE FISHERIES 



the mid 1940's. Much of this decline has been at- 

 tributed to the combined effect of a shift in oceano- 

 graphic conditions affecting recruitment and fish- 

 ing mortahty in the mid 1980's. The spawning 

 potential ratio (SPR), which is used to measure 

 the status of the stocks, has ranged between 74 

 and 88'!b over the past three seasons (1993-97). 

 Overfishing is defined in the fishery manage- 

 ment plan in terms of recruitment' overfishing. 

 The criterion used to assess overfishing is the SPR: 

 the ratio of the spawning potential of a cohort" in 

 a fished condition relative to that in an unfished 

 condition. The fishery management plan defines 

 the 20% level as a minimum SPR threshold, be- 

 low which the stock is considered overfished, and 

 establishes a warning SPR threshold at 50%, in- 

 dicating the need for additional conservation 

 measures. The NWHI lobster fishery is managed 

 with a constant harvest rate such that there is only 

 a 10% chance in any given year that the fishing 

 mortality will exceed the mortality associated with 

 the minimum SPR threshold. Since 1994, SPR 

 values have been substantiallv above the minimum 

 threshold level, indicating that the levels of fish- 

 ing effort exerted during the 1994-97 commer- 

 cial fishing seasons, and resulting fishing mortal- 

 ity and exploitation rate, would not cause long- 

 term recruitment overfishing under equilibrium 

 conditions (Table 16-2). 



Coral 



Because there has been no fishery on precious 

 corals over the past 20 years, little solid evidence 

 is available on recovery of the population from the 

 low levels which existed when the Magnuson- 

 Stevens Act was first passed in 1976. However, 

 recent video analysis suggests that the unfished 

 beds have recovered much of their potential and 

 that new beds have been identified. Nonetheless, 

 it also appears that illegal foreign fishing in some 

 remote areas during the 1980's had a very signifi- 

 cant impact on some beds. In 1997, one company 

 obtained a permit to fish precious coral at 



Landings (t) 

 30 - 



25 



Landings 



'Recruitment is the process ot new generations oi young fish 

 or .ininuis entering the stocl<. 

 "Recruits from the s,^me ve,ir are called cohorts. 



80 

 Year 



Makapu u, Oahu, under a 2-year quota for 2,000 

 kilograms (kg) of pink coral and 600 kg each tor 

 bamboo and gold coral. Harvesting began in early 

 1998. Historical landings of precious corals are 

 shown in Figure 16-2. 



ISSUES 



Bank-specific Status of Lobster Stocks 



The proportion of fishing effort and reported 

 catch at each bank within the NWHI region has 

 varied both spatially and temporally throughout 

 the 20-year history of this fishery. While as many 

 as 16 banks have been fished on an annual basis, 

 the majority of fishing effort has been directed at 

 four banks: Maro Reef, Gardner Pinnacles, St. 

 Rogatien, and Necker Island (Figure 16-3). The 

 observed spatial-temporal shifts in fishing effort 

 between banks is attributed to declines in the spiny 

 lobster catch per unit of effort; as spiny lobsters 

 were fished down and catch rates at one bank tell 

 below a minimum economic threshold, fishing ef- 

 fort shitted to a more productive bank. In recent 

 years, fishing has generally been limited to Necker 

 Island, where there has been a relatively higher con- 

 centration ot spmv lobsters. 



Figure 16-2 



Landings of precious coral 

 in metric tons (t). 1966-97. 



Year 



SPR (%) 



Table 16-2 



Annual estimates of spawn- 

 ing potential ratio (SPR) for 

 NWHI lobsters. 



1 85 



