DeMartini et al.: Population density, fecundity, and egg size of Panulirus marginatus 



23 



for 1999 were collected on a cruise of the 

 NOAA ship Townsend Cromwell. Details of 

 specimen collection and processing of the 

 1978-81 and 1991 samples are described by 

 DeMartini et al. (1993). The 1999 samples 

 were collected during 9-22 June 1999 from 

 the bank terrace at a median 27-m depth 

 by using molded plastic ("Fathom Plus") 

 traps baited with 1 kg of mackerel (Scomber 

 Japonicus) and fished with a standard (over- 

 night) soak. 



Shipboard processing 



Specimens were processed identically to 

 those collected in June 1991. All specimens 

 were processed alive within minutes of trap 

 retrieval. Both carapace length (CL: defined 

 as the straight line distance between the 

 anterior edge of the supraorbital ridge and 

 the posterior edge of the carapace along the 

 dorsal midline) and tail width (TW: defined 

 as the straight line distance across the abdo- 

 men at the widest spot between the first and 

 second abdominal segments ) of each specimen 

 were measured to 0.1 mm with dial calipers. 

 TW is the present metric of choice for lobster 

 management in the NWHI trap fishery. CL 

 was the metric used to characterize body size 

 in many prior research and management 

 studies of the species, and its measurement 

 was needed for comparison with results of 

 studies made prior to the mid-1980s. Ber- 

 ried (ovigerous) females were scored for egg 

 developmental stage by using a gross visual 

 proxy (brooded eggs noted as either orange or 

 brown in color to the unaided eye). Berried 

 specimens were individually flash-frozen for 

 laboratory evaluation ashore. 



Laboratory analyses 



700 



^ 600 



o 



o 



500 



300 - 



100 - 



- 



1982 



1986 1988 



1998 2000 



1982 1984 1986 



1988 



1990 1992 



Year 



1994 1996 1998 



2000 



Fecundity, here defined in the limited sense of 

 a single brooded egg mass (see Chubb, 2000), 

 was estimated for 5-10 females per 5-mm 

 TW class in order to provide at least 40 total 

 specimens spanning the entire size range for 

 analyses. Except for sample sizes, procedures 

 were identical to those used for the 1991 collection. Only 

 females bearing orange egg clusters with embryos lacking 

 visible melanin pigment (early embryonic development) 

 were considered in order to minimize the probability of 

 physical damage, egg loss, and fecundity underestima- 

 tion during capture and handling, which is an apparent 

 problem only for broods of heavily pigmented (brown), late- 

 development eggs with soft capsules (DeMartini, unpubl. 

 data). Frozen specimens were thawed overnight at 3°C. 

 All four pairs of egg-bearing pleopods were then removed 

 from the abdomen, gently blotted (damp-dry) on a paper 

 towel, and weighed individually to 0.1 mg on an electric 



Figure 1 



Time series plots of (A) the Northwestern Hawaiian Islands (NWHI) 

 commercial trap catch and landings of Panulirus marginatus (no. of 

 lobsters x 1000) and effort (no. of trap-hauls x 1000); and (B) total P. 

 marginatus catch-per-trap-haul (CPUE) at Necker Bank, NWHI, during 

 the 1983-99 commercial fishing seasons and as assessed on 1988-1999 

 lobster research cruises. (Research CPUE data are lacking for years prior 

 to 1988.) Dashed lines framing the research CPUE curve in B represent 

 bootstrapped 95'7f confidence intervals (DiNardo et al.-). 



microbalance. Eggs were then carefully teased off pleopod 

 setae with jeweler's forceps and stored after being wrapped 

 in cool, damp paper towels to minimize evaporative weight 

 loss. Individual pleopods were then rew-eighed and the 

 weight of each pleopod's egg complement was calculated 

 by difference. Three subsamples of 0.1-0.2 g, each compris- 

 ing about 700-1000 eggs total (about 100 eggs per pleopod, 

 pooled over all 8 pleopods), were next weighed to 0.1 mg, 

 their component eggs counted, and relative fecundity (RF, 

 number of eggs per gram of brooded eggs) was calculated 

 as a simple ratio, with the three subsamples used to calcu- 

 late a mean and standard error of RF. Fecundity (F, defined 



