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Abstract— Fecundity (F, number of 

 bixHwied eggs ) and egg size were estimated 

 for Hawaiian spiny lobster iPanulirus 

 margirmtus) at Necker Bank, North- 

 western Hawaiian Islands (NWHI), in 

 June 1999, and compared with previous 

 (1978-81, 1991) estimates. Fecundity in 

 1999 was best described by the power 

 equations F = 7.995 CL ^■""", where CL 

 is carapace length in mm (f-^'=0.900), 

 and F = 5.174 TW ^ ^ss^ ^here TW is tail 

 width in mm (r2=0.889) (both n=40; P< 

 0.001). Based on a log-linear model 

 ANCOVA, size-specific fecundity in 1999 

 was 18% greater than in 1991, which 

 in turn was 16% greater than during 

 1978-81. The additional increase in size- 

 specific fecundity observed in 1999 is 

 interpreted as evidence for flirther com- 

 pensatory response to decreased lobster 

 densities and increased per capita food 

 resources that have resulted either from 

 natural cyclic declines in productivity, 

 high levels of harvest by the commercial 

 lobster trap fishery, or both. The density 

 decline is well-documented by a fivefold 

 decrease in commercial catch-per-trap- 

 haul (CPUE) during the late 1980s to 

 early 1990s and by a similar decrease 

 m research CPUE for all-sized (includ- 

 ing juvenile) P. marginatus through the 

 1990s. Fecundity increases are consis- 

 tent with decreases in median body size 

 at sexual maturity, first described from 

 comparisons of 1977-81 and 1986-87 

 specimens and consistently observed 

 thereafter during the 1990s. Egg size 

 covaried with fecundity; in 1999, indi- 

 vidual eggs within broods had a 11% 

 greater mass (15% greater volume) than 

 eggs brooded in 1991. Implications of 

 these obsei-vations are discussed in rela- 

 tion to possible future management mea- 

 sures for a commercial lobster fishery in 

 the NWHI. More generally, our findings 

 argue for the need to routinely reevalu- 

 ate compensatory responses in e.xploited 

 stocks of lobsters and other resources. 



Temporal changes in population density, 

 fecundity, and egg size of the Hawaiian spiny 

 lobster iPanulirus marginatus) at Necker Bank, 

 Northwestern Hawaiian Islands 



Edward E. DeMartini 



Gerard T. DiNardo 



Happy A. Williams 



Honolulu Laboratoi7 



Southwest Fisheries Science Center 



National Manne Fishenes Service 



2570 Dole Street 



Honolulu, Hawaii 96822-2396 



E-mail address (for E. E DeMartini): Edward DeMartini@nooa gov 



Manuscript accepted 20 September 2002. 

 Fish. Bull. 101:22-31 (2003). 



The endemic Hawaiian spiny lobster 

 (Panulirus marginatus) has been the 

 principal target of the Northwestern 

 Hawaiian Island (NWHI) commercial 

 trap fishery since the mid- to late 1970s 

 (Uchida and Tagami, 1984; Polovina, 

 2000). Landings and exvessel (whole- 

 sale) value have fluctuated greatly over 

 the years, in part because of annual 

 variations in trapping effort and a 

 1-yr fishery closure in 1993, but have 

 been generally lower during the 1990s 

 because of declines in oceanic produc- 

 tivity and recruitment and increased 

 exploitation (Polovina and Moffitt, 1995; 

 Polovina et al., 1995). The fishery was 

 closed in 2000 because of increasing 

 uncertainty in the population models 

 used to assess stock status. In Decem- 

 ber 2000 President Clinton, through 

 Executive Order (EO) 13178 and later 

 through EO 13196, established the 

 Northwestern Hawaiian Islands Coral 

 Reef Ecosystem Reserve which may 

 prohibit commercial lobster fishing in 

 the NWHI for at least 10 years. Ajinual 

 research surveys of the National Marine 

 Fisheries Service (NMFS), Honolulu 

 Laboratory, have demonstrated a 

 decline (Fig. 1) in spiny lobster density 

 (CPUE, catch-per-trap-haul) at Necker 

 Bank, NWHI, one of the sites at which 

 spiny lobsters have been consistently 

 targeted since about the mid-1970s. 



Polovina (1989) first described a den- 

 sity-dependent decrease in median body 

 size at sexual maturity and an increase 

 in asymptotic body size for spiny lobster 

 at Necker Bank, based on a contrast 



between specimens collected during 

 1977-81 and 1986-87. DeMartini et al. 

 (1993) observed an increase in size-spe- 

 cific fecundity for specimens collected in 

 1991, used to further characterize the 

 Necker Bank population's status after- 

 exploitation. Compensatory increases 

 in juvenile growth and survival and in- 

 creases in size at maturity as responses 

 to decreased density following increased 

 fishery exploitation have been observed 

 for other spiny lobster stocks (e.g. see 

 Pollock, 1995a, 1995b). 



In this article, our objectives were to 

 estimate recent (1999) berried female 

 fecundity and egg size for the Hawai- 

 ian spiny lobster at Necker Bank and 

 to relate these to prior, analogous esti- 

 mates for lobsters collected in 1991 and 

 1978-81, analyzed by DeMartini et al. 

 (1993). We then use the 1999 fecundity 

 estimates and 1999 commercial catch 

 data to characterize recent egg produc- 

 tion by the Necker Bank population. 

 We conclude with a brief discussion of 

 the management implications of com- 

 pensatory reproductive responses by 

 the population. 



Methods and materials 



All specimens used in this study were 

 trapped from Necker Bank surround- 

 ing Necker Island (23°34'N, 164°42'W), 

 NWHI, during the species' mid-spring 

 to mid-summer peak period of egg 

 brooding at mid-archipelago latitudes 

 (Uchida and Tagami, 1984). Specimens 



