Fishery Bulletin 91(1). 1993 



during the recent period of low population densities, 

 we initiated a study of its fecundity and related repro- 

 ductive life history. Prior to our study, little quantita- 

 tive information existed on the fecundity of this spe- 

 cies, and data were limited to the waters off Oahu in 

 the MHI (Morris 1968, McGinnis 1972). Our objective 

 is to compare the size-specific fecundities of NWHI 

 spiny lobster between two time-periods: an early or 

 pre-exploitation (hereafter referred to as "before") pe- 

 riod in 1978-81, and a postexploitation ("after") period 

 in 1991, when population densities had declined to a 

 fraction of their pre-exploitation level. 



Methods and materials 



Specimen collection 



Spiny lobster were collected using baited commercial 

 traps at Maro Reef and on the offshore bank of Necker 

 Island, the second of the two major NWHI fishing 

 grounds (fig. 1, Polovina 1989). Lobsters were trapped 

 during multiple cruises aboard chartered commercial 

 vessels and the NOAA ship Townsend Cromwell dur- 

 ing the summertime (May- August) breeding seasons 

 of 1978-81 (the "before" period) and on a single cruise 

 by the Townsend Cromwell during June-July 1991 ("af- 

 ter"). Commercial traps fished for a standard (over- 

 night) soak period were used at each site during both 

 time-periods. Specimens were similarly handled aboard 

 the chartered vessels and the Townsend Cromwell. 



Sample processing 



Lobsters were sexed, carapace length (CD measured, 

 and the egg developmental stage of egg-bearing ("ber- 

 ried") females scored as either Stage 1 (orange = freshly 

 extruded), Stage 2 (brown = late development), or Stage 

 3 (white = hatching imminent). The CL, defined as the 

 distance along the middorsal line from the transverse 

 ridge between the supraorbital spines to the posterior 

 margin of the carapace, was measured to the nearest 

 0.1mm. Berried female specimens were either pro- 

 cessed fresh in the ship's wet lab or flash-frozen (damp) 

 aboard ship for processing ashore. 



In the laboratory, brood sizes were estimated using 

 Stage- 1 females whenever possible so as to minimize 

 the effect of potential egg loss (Morgan 1972, Annala & 

 Bycroft 1987). The eight pleopods including egg clusters 

 (setae bearing the egg masses) were separated by dis- 

 section and placed on absorbent paper towels. Egg clus- 

 ters were then stripped off the pleopods onto preweighed 

 weigh boats. Each individual female's total egg comple- 

 ment was weighed (damp weight to 0.1 mg) and then 

 reweighed following determination of egg subsample 



weights; these two weighings were then averaged to 

 provide a measure of the total egg mass. Random 

 subsamples comprising a minimum (by weight) of 1% 

 (£=1.5%) of the female's total egg mass were weighed 

 (0.1 mg) and later enumerated to estimate fecundity 

 (F t =total number of eggs) by proportion: 



