Another consideration in terms of fishing 

 effectiveness might be vessel speed. Boat 

 dimensions are approximately the same as 

 Dow and Trott (1956) described; however, 

 usually more powerful engines are used today 

 than at the time of the original study, thereby 

 possibly reducing the time to and from the 

 fishing grounds and between trap-hauls by trip. 



Dow (1955) mentioned the use of electronic 

 gear, depth recorders primarily, that could be 

 another factor in fishing effectiveness. 



POPULATION PARAMETERS 



With the data from some previous sections, 

 we estimated certain population parameters. 

 These parameters are used directly in the 

 simple yield equation described by Beverton 

 and Holt (1957). Therefore, these estimates 

 are vitally important to the objective of deter- 

 mining the biological minimum size for maxi- 

 mum sustainable yield. 



Von Bertalanffy Growth Equation 



The determinations from the length frequency 

 analysis make it necessary to consider this 

 relationship in a different way than usual. First, 

 we do not know the actual age of any sized 

 lobster. It follows then that we do not know 

 the age composition of any size mode. Second, 

 there is a possibility that these size modes 

 represent molt classes, and further that one 

 or more of these molt classes might be in the 

 same age group. Following this reasoning, I 

 attempted to calculate the parameters of the 

 von Bertalanffy Growth Equation by combining 

 probability modes to correspond to 14% incre- 

 ments as hypothesized in the probability analy- 

 sis. The estimated parameters, determined by 

 the method of Tomlinson and Abramson (1961), 

 are obviously incorrect; for example, the maxi- 

 mum expected carapace length is 13.0 mm. 



As an alternative, I used the consecutive 

 modes from the probability analysis of the 

 length frequencies. This might constitute a 

 molt group-length relationship rather than the 

 usual age-length correlation. 



This information was used in the method of 

 Tomlinson and Abramson (1961). The perti- 

 nent estimates and standard errors are: 



A 



/oo 

 A 



k 



A 



where: 



A 

 too 



A 



k 

 A 



266.77 ± 59.04 

 0.04785 ± 0.01566 

 -0.77250 ± 0.43685 



maximum expected length 



constant proportional to catabolic rate 



hypothetical age at zero length. 



These growth parameters are much more 

 logical; leading to the dilemma of deciding 

 whether we are dealing with molt or age groups. 

 To resolve this, I reasoned that the intent of 

 the use of the von Bertalanffy Growth Equation 

 is to demonstrate the growth pattern for lobsters 

 which intuitively (comparison of calculated 

 parameters) is better reflected by using con- 

 secutive size modes from the probability 

 analysis. 



Weight-Length Relationship 



We fitted a logarithmic transformation of the 

 basic equation W = aL b by the method of 

 least squares. There were 336 males and 391 

 females used in these calculations. The follow- 

 ing real values by category are: 



W = 0.001669 L 2 * 2781 (males) 



W = 0.001657 L 2B3377 (females) 



W = 0.001682 L 2 * 2826 (sexes combined). 



A t test on the b values revealed no signifi- 

 cant difference between the sexes; therefore, 

 the sexes were combined (Fig. 16). The 95% 

 confidence limits on the slope or b value for 

 the sexes combined placed the upper limit 

 at 2.86099 and the lower limit at 2.79554. The 

 95% confidence limits on this intercept or a 

 value placed the upper limit at 0.001889 and 

 the lower at 0.001509. 



We also calculated the weight-length rela- 

 tionships by the same method for the com- 

 mercial sizes only. While there still is no 

 significant difference between males and fe- 

 males, the confidence intervals about the slopes 

 bracketed "3" in each case. We surmise that 

 there is a change in the weight-length relation- 

 ship after lobsters reach legal size. This situa- 

 tion might have importance in the section on 

 yield. 



42 



