Table 6. — Modes from probability analysis of length 

 frequencies, compiled by year, 1967 through 1970. 



Number 

 of modes 



1967 



1968 



1969 



1970 



1. 



85 



85 



85 



8H 



2. 



91 



91 



91 



91 



3. 



97 



97 



91 



95 



1. 



105 



105 



102 



106 



5. 



111 



116 



113 



110 



bination of probability modes per 14% grouping 

 supports the premise that these percent group- 

 ings represent assumed age or molt groups in 

 a year. However, this situation could lead to 

 some anomalies in the total mortality estimate 

 within years for the grouping from 81 to 92 mm. 

 This could come about from the protected 

 size range of the 85-mm probability mode in 

 one year producing a probability mode at 91 

 mm in the next year. 



This combination of possibilities would also 

 account for the absence of visually discernable 

 modes after 85 mm of the monthly and yearly 

 percent frequencies because the size ranges 

 about the succeeding modes would overlap 

 each other to a considerable extent. 



Other determinations from cluster 

 samples. — In conjunction with the analysis 

 on length frequencies from the cluster samples, 

 we also made estimates of the mean length 

 and weight and the percent of females, culls, 

 and shedders. We compiled this information 

 by sample-day, with monthly and yearly means 

 and percentages with standard errors from 

 August 1966 through 1970 (Table 7). Usually 

 the mean lengths by day, month, and year are 

 quite similar; this situation could indicate the 

 possibilities of heavy exploitation and a similar 

 selectivity range of the described trap dimen- 

 sions. 



To be expected, the mean weight and associ- 

 ated percentages of culls are closely related 

 and help to explain some of the variability in 

 mean weight related to the same mean carapace 

 length. The percentage of culls between and 

 within areas and years could be a valuable 

 asset in determining ways of improving the 

 catch in pounds (the important item to fisher- 

 men). Some fishermen and biologists have 



postulated that the rough handling of prerecruit 

 sizes of lobsters (sublegals) in traps leads to 

 either a heavy mortality of these lobsters before 

 they enter the fishery or an increase in the 

 percentage of culls when lobsters reach legal 

 size. Perhaps it would be well for administrators 

 and industry people to consider lath spacing 

 as another means of increasing the catch in 

 pounds. 



The actual time available for sampling each 

 boat and its catch dictates that the estimate of 

 shedder percentages must be a subjective 

 measure. We determined if a lobster was hard- 

 or soft-shell by a slight amount of hand pressure 

 on the lateral surfaces of the carapace and 

 chelipeds. This was accomplished in the 

 process of measuring and weighing the lobster. 

 Then by this method we have a subjective 

 estimate for what we term "recent shedders." 



This subjective determination is made even 

 more difficult by the dealers usually buying 

 at two prices (hard- versus soft-shell) during 

 the months of peak molting. Their determina- 

 tion of a shedder does not always agree with 

 ours, but we are stymied by the dealers separat- 

 ing the hard- and soft-shell lobsters. Therefore, 

 the estimation of the percent of shedders in 

 the commercial fishery can only be considered 

 a rough approximation. This estimate in some 

 months was so inexact that we eliminated it 

 from the tabulations. As a consequence, we 

 concluded tentatively that: (1) lobsters in the 

 southwestern section of the State begin ecdysis 

 earlier in the year than those from the north- 

 eastern part; this situation could be influenced 

 by the general seasonal warming of the ocean 

 from southwest to northeast, and (2) the per- 

 centage of shedders by month gives us addi- 

 tional evidence of the effect of ecdysis on 

 recruitment during August through November 

 of each year; the importance of this determina- 

 tion will be discussed in the catch and effort 

 section. 



Catch and Effort Analysis 



Ricker (1958), Beverton and Holt (1957), and 

 many others have discussed the importance 

 of the relationship of catch to effort. In the 

 lobster fishery this has become increasingly 

 important because Dow (1961) and Dow and 



29 



