FISHERY BULLETIN: VOL. 71, NO. 1 



lobsters from the commercial catch in the fol- 

 lowing size classes: 



Carapace length 



81-90 mm 

 91-100 mm 

 >100 mm 



Percentage of total catch 

 Commercial Berried females 



80 



17 



3 



11 

 29 

 60 



Because lobsters ranging in carapace length 

 from 81 to 90 mm constituted approximately 

 80 Sr of the commercial catch and only 11 "^r of 

 the berried fem.ale sample, it is apparent that 

 only a very small percentage of females mature 

 below 90-mm carapace length. Certainly the 

 most marked disparity in size composition was 

 for carapace lengths greater than 100 mm (3Sr 

 commercial and 60 /r berried females). This 

 would seem to validate the previous conclusion 

 that most females above 100-mm carapace length 

 are mature. 



SUMMARY 



This study which is concerned with the anal- 

 yses of data collected from 1968 through 1970 

 on the natural population of American lobsters 

 along the Maine coast has yielded the following 

 information: 



1. Sex ratio was 1:1, thus suggesting that 

 differences in growth rate and molting frequency 

 do not exist between mature males and immature 

 females. 



2. Molting was concurrent for males and fe- 

 males, with shedding reaching a peak in late 

 summer. 



3. The length-weight relationship for sexes 

 combined was log W = —2.9052 + 2.9013 logL. 



4. Length-frequency histograms revealed the 

 high rate of exploitation by the commercial fish- 

 ery and an increase in unavailability of lobsters 

 progressively smaller than 70-mm carapace 

 length. 



5. Male lobsters begin maturing at relatively 

 small sizes (509^ mature at about 44-mm cara- 

 pace length); however, because native Maine 

 females rarely mature below the minimum legal 



size of 81-mm carapace length and males must 

 approximate females' size to successfully mate, 

 it is doubtful that prerecruit males contribute 

 reproductively to the natural population. 



6. Female maturity was assessed by the fol- 

 lowing methods: 1) classification of ovaries 

 by color and ovum diameter to three stages of 

 development; 2) examination of seminal recep- 

 tacles for spermatophores ; 3) morphometric re- 

 lationship of abdominal width: carapace length 

 ratio to carapace length; and 4) length-fre- 

 quency distribution of native Maine berried fe- 

 males. From estimates by these four independ- 

 ent methods, I concluded that females seldom 

 become sexually mature at a size less than 81-mm 

 carapace length, and then only a small fraction 

 of those females between 81 and 90 mm attain 

 maturity, whereas, at carapace lengths greater 

 than 100 mm, nearly all females are assumed 

 to be mature. Bearing in mind the minimum 

 legal size regulation of 81-mm carapace length, 

 I demonstrated in this study that the majority 

 of females are harvested commercially prior to 

 their first opportunity to spawn. An obvious 

 change in management suggested by the results 

 of this study would be to increase the minimum 

 size limit to insure successful spawning by a 

 sizeable portion of the population. Based on 

 results of this study and those from the com- 

 mercial sampling phase of the Maine lobsters 

 project, Thomas (1971, see footnote 3) deals 

 specifically with minimum size limit increases 

 as a means to achieve a maximum sustainable 

 yield. 



ACKNOWLEDGMENTS 



I am indebted to James C. Thomas for his 

 guidance and support throughout the course of 

 this study and his review of the manuscript. 

 Richard Hanley, Gerald Brackett, Robert Nunan, 

 Stephen Ham, and Andrew Dolloff" assisted with 

 field collections and data compilations. Gareth 

 Coffin of the Northeast Fisheries Center, Nation- 

 al Marine Fisheries Service, West Boothbay 

 Harbor, Maine, performed the photographic 

 work. 



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