Size-maturity relationships, based mainly on obser- 

 vations of ovary color and ova size in nonovigerous 

 females for five Newfoundland lobster populations, 

 indicate 100% maturity (physiological) for sizes at 

 which tagging results show that substantially < 100% 

 of the nonovigerous females lay eggs in a given 

 spawning season (Ennis 1980). Resorption of the 

 mature ovary near the expected time of oviposition is 

 a common phenomenon in//, americanus (Aiken and 

 Waddy 1980a) and presumably is the main reason for 

 failure on the part of physiologically mature females 

 to express their maturity by extruding eggs. Clearly, 

 it is an "expressed" or functional size-maturity 

 relationship that is required to assess the impact of 

 size limit and/or exploitation rate changes in a fishery 

 on annual egg production. Using the pleopod cement 

 gland staging technique described by Aiken and 

 Waddy (1982) as a basis for predicting egg extrusion, 

 such a relationship was derived for two Newfound- 

 land populations. These are compared with physio- 

 logical size-maturity relationships for the same 

 populations. 



Materials and Methods 



52° 



-I — 



52° 



50° 



48° 



$2° 



FIGURE 1. — Map of Newfoundland showing location of Arnold's 

 Cove and Comfort Cove. 



Pleopods were obtained from 172 nonovigerous 

 female lobsters caught between 24 June and 17 July 

 1981 and 77 caught between 14 and 18 June 1982 

 near Arnold's Cove, Placentia Bay, and 246 caught 

 between 1 and 7 July 1982 at Comfort Cove, Notre 

 Dame Bay, Newfoundland, (Fig. 1) using traps and by 

 scuba diving. Sizes ranged from 40 to 111 mm CL 

 (carapace length) at Arnold's Cove and from 58 to 

 113 mm at Comfort Cove. Pleopods were examined 

 for molt stage according to the method of Aiken 

 (1973) and for cement gland development according 

 to the method of Aiken and Waddy (1982) to deter- 

 mine whether molting or egg extrusion would occur 

 during the current molting/spawning period. In this 

 study it was predicted that females with cement 

 glands in stages and 1 would not extrude eggs dur- 

 ing the current spawning period whereas those with 

 stage 2 or higher cement glands would (see Aiken 

 and Waddy 1982 for descriptions of cement gland 

 stages). A validation study (Ennis 1983) has 

 demonstrated that egg extrusion prediction based on 

 cement gland staging is quite reliable. Of the predic- 

 tions that could be validated, 947c were correct. The 

 only incorrect predictions were for females with stage 

 2 cement glands of which 2 out of 9 (22%) failed to 

 extrude eggs. Accordingly, in the data analyzed here 

 the number of animals with stage 2 cement glands in 

 each size group was reduced by 22% to obtain a more 

 accurate estimate of the number that would actually 



extrude eggs. Where 22% of the number was < 0.5, 

 nothing was subtracted. 



The two Arnold's Cove samples were combined. 

 For each area the numbers examined and numbers 

 functionally mature (i.e., going to extrude eggs during 

 the current season) were grouped by 1 mm CL and 

 subjected to probit analysis. Although good statisti- 

 cal fits were obtained (P values >0.9), the fitted 

 curves did not approximate the data very well at the 

 upper and lower ends. Proportions from the same 

 data were analyzed using the logistic equation 



Y = 



1 +e b+cX 



(1) 



An SAS 1 program, which performs this analysis by 

 means of a nonlinear regression procedure using the 

 Marquardt method, was used. Curves were obtained 

 with substantially improved visual fits to the data. 



Previously published size-maturity relationships 

 for Arnold's Cove and Comfort Cove lobsters (Ennis 

 1980) were based mainly on detailed examination of 

 the gonads of nonovigerous females, but ovigerous 

 females in the samples were included as mature 

 animals. For this paper the ovigerous specimens 

 were excluded from these samples and the data 



*SAS User's Guide: Statistics, 1982 ed. SAS Institute Inc., Cary, 

 N.C., 584 p. 



245 



