Abstract.- Spiny lobsters PawM- 

 liruf: marginatum from the Hawaiian 

 Archipelago have undergone heavy 

 fishing pressure since 1980 and have 

 experienced increases in asymptotic 

 length and decreases in mean length 

 at onset of egg production. Prior to 

 the expansion of the fishery, allo- 

 zyme variation was surveyed, and 

 populations were found to be poly- 

 morphic at seven loci. In 1987 we col- 

 lected spiny lobsters from two of the 

 preNHOusly sampled locations (Necker 

 Island and Maro Reef) to test for sig- 

 nificant changes in population struc- 

 ture or level of genetic variability. 

 No significant changes through time 

 were found at five of the seven loci. 

 Significant differences were detected 

 at EstS and EstD; however, frequen- 

 cies at esterase loci have been pre- 

 viously shown to fluctuate through 

 time. Observed number of allelic 

 classes and observed heterozygosi- 

 ties have remained unchanged. The 

 data suggest that no change in the 

 amount of variability has occurred in 

 spiny lobster since the expansion of 

 the fishery. 



Genetic Variation in Higlily 

 Exploited Spiny Lobster 

 Panulirus marginatus Populations 

 from the Hawaiian Archipelago 



Lisa W. Seeb 

 James E. Seeb 



Fisheries Research Laboratory. Department of Zoology 

 Southern Illinois University, Carbondale, Illinois 62901-651 I 

 Present address Alaska Department of Fish and Game 

 333 Raspberry Road. Anchorage, Alaska 99518-1599 



Jeffrey J. Polovina 



Honolulu Laboratory, Southwest Fisheries Science Center 



National Marine Fisheries Service, NOAA 



2570 Dole Street, Honolulu, Hawaii 96822-2396 



Manuscript accepted 2;> June 1990. 

 Fishery Bulletin. U.S. 88:713-718. 



Commercial trapping for the spiny 

 lobster Panulirus marginatus in the 

 northwestern Hawaiian Islands be- 

 gan in 1976 shortly after research 

 cruises documented the resource in 

 abundance. Two banks, Necker Is- 

 land and Maro Reef, have been most 

 heavily fished since the beginning 

 of the fishery. In 1986 and 1987 re- 

 search cruises repeated the earlier 

 sampling at Necker Island and Maro 

 Reef by trapping at the same sites on 

 each bank with the same gear to 

 document any changes that had oc- 

 curred in density, population, and 

 genetic parameters (Polovina 1989). 

 The repeat sampling documented 

 substantially reduced lobster densi- 

 ties as indicated by catch rates, which 

 in 1986-87 were 37% and 68% of 

 their 1977 levels at Necker Island 

 and Maro Reef, respectively (Polo- 

 vina 1989). A statistically significant 

 (P<0.05) increase in the asymptotic 

 lengths and decreases in the mean 

 lengths at onset of egg production oc- 

 curred between the 1977 and 1986- 

 87 sampling at both locations (Polo- 

 vina 1989). 



While changes in these population 

 parameters could be due to density- 

 dependence relationships, some type 

 of genetic change also may have oc- 



curred from selection induced by the 

 fishing pressure (Nelson and Soule 

 1987). For example, the fishery har- 

 vests lobsters at about the size the 

 females first begin producing eggs. 

 It is estimated that spiny lobster 

 enter the fishery at 3.1 years of age 

 and that the mean age females begin 

 producing eggs is 2.5 years (Polovina 

 1989). Thus, heavy fishing pressure 

 may select for female lobsters that 

 sexually mature at a smaller size. Re- 

 duction in the total amount of genetic 

 diversity or changes in the stock 

 structure of the exploited populations 

 are also potential results of intense 

 fishing pressure (Allendorf et al. 

 1987). These latter types of genetic 

 changes can often be monitored 

 through allozyme analyses (Nelson 

 and Soule 1987), and are the subject 

 of this paper. 



Spiny lobsters from seven localities 

 in the Hawaiian Archipelago were 

 collected between 1978 and 1980, 

 prior to the expansion of the commer- 

 cial fishery, and analyzed for allo- 

 zyme variation by Shaklee and Sa- 

 mollow (1984). Although overall 

 levels of variation were quite low, 

 they observed polymorphism at 7 of 

 the 46 loci examined. However, no 

 clear pattern of genetic differentia- 



713 



