Abstract. — Size-specific fecundi- 

 ties of spiny lobster Panulirus mar- 

 ginatus were compared for two time- 

 periods: pre- and early exploitation 

 or "before" (1978-81), and post- 

 exploitation or "after" ( 1991 ). Fecun- 

 dity was further evaluated within 

 each time-period at two collection 

 sites that represented the major lob- 

 ster fishing grounds (Maro Reef and 

 Necker Island) in the Northwestern 

 Hawaiian Islands. Complementary 

 data on egg size and spawning- 

 frequency index were compared be- 

 tween study sites and time-periods. 

 Study sites and time-periods had 

 no observable effects on egg size or 

 spawning frequency, and there was 

 no temporal effect on fecundity at 

 Maro Reef. Fecundities at the two 

 sites differed, however; "after" size- 

 specific fecundity was an estimated 

 1619^ greater than "before" fecun- 

 dity at Necker Island. Observations 

 suggest that the recent increase in 

 fecundity at Necker Island may 

 reflect a compensatory (density- 

 dependent) response to greater ex- 

 ploitation at this site. Results are 

 discussed in terms of evidence for 

 density-dependent responses in 

 other, exploited spiny lobster stocks. 



Comparisons of spiny lobster 

 Panulirus marginatus fecundity, 

 egg size, and spawning frequency 

 before and after exploitation 



Edward E. DeMartini 

 Denise M. Ellis 



Honolulu Laboratory, Southwest Fisheries Science Center 



National Marine Fisheries Service. NOAA 



2570 Dole Street 



Honolulu, Hawaii 96822-2396 



Victor A. Honda 



Southwest Enforcement, Pacific Area Office 

 National Marine Fisheries Service, NOAA 

 300 Ala Moana Boulevard 

 Honolulu, Hawaii 96850-0001 



Manuscript accepted 19 August 1992. 

 Fishery Bulletin, U.S. 91:1-7 (1993). 



The spiny lobster Panulirus mar- 

 ginatus (Quoy & Gaimard) is endemic 

 to the Hawaiian Archipelago and 

 Johnston Island (Brock 1973, Uchida 

 et al. 1980). This species supported a 

 major commercial fishery in the main 

 Hawaiian Islands (MHI) prior to the 

 rapid increases in demand after 

 World War II (Uchida et al. 1980). 

 Not until the expansion of the fishery 

 into the Northwestern Hawaiian Is- 

 lands (NWHI) began in 1977 did the 

 species again support a valuable com- 

 mercial enterprise, complemented 

 with bycatches of slipper lobster 

 Scyllarides squamosus (H. Milne- 

 Edwards) and S. haanii (De Haan). 

 A fishery management plan was cre- 

 ated in 1983 to regulate the fishery 

 based on minimum size limits and 

 limited entry. 



Prior to 1990, annual landings av- 

 eraged 1-2 million spiny lobster 

 worth US$4- 6 million ex-vessel. Be- 

 ginning in 1990 and continuing until 

 the fishery closure in early 1991, 

 however, landings fell heavily, equal- 

 ing one-fifth of the long-term aver- 

 age (Landgraf 1991). These decreases 

 reflected real declines in abundance, 

 as both research and commercial 



catch per trap-haul (CPUE) similarly 

 declined (Landgraf 1991). The 

 present belief is that recent declines 

 in the spiny lobster CPUE reflect a 

 combination of continued, heavy ex- 

 ploitation and the occurrence of a se- 

 ries of poor year-classes, particularly 

 at Maro Reef, one of the two major 

 NWHI fishing grounds (Polovina 

 1991). 



Recent research by Polovina (1989) 

 has indicated that a density-depen- 

 dent decrease in the size-at-onset of 

 egg production occurred in NWHI 

 spiny lobster from 1977 to 1986-87. 

 Additional types of compensatory re- 

 sponses to lower population densities 

 may be operative and may have a 

 major influence on the dynamics of 

 these lobster populations, but data 

 are lacking (Polovina 1989). Included 

 among these compensatory mecha- 

 nisms is an increase in size-specific 

 fecundity, a phenomenon suggested 

 for other species of spiny lobsters 

 (Chittleborough 1976 and 1979, 

 Beyers & Goosen 1987, MacDiarmid 

 1989). 



With the a priori prediction that 

 size-specific fecundities might have 

 increased for NWHI spiny lobster 



