96 



BULLETIN OF THE UNITED STATES FISH COMMISSION. 



THE RATE OF GROWTH. 



The question often asked is, How long does it take an adult marketable lobster to 

 grow? It is impossible to answer this with certainty, since complete data for solving 

 the problem have not been gathered. We can, however, give a tentative answer which 

 is probably not far from the truth. 



In order to ascertain the average age of a lobster 10£ inches long (weight, 1| 

 pounds), it would be necessary to know, first, the number of molts which the animal had 

 passed through, and, secondly, the time interval between each molt. The number 

 of molts can be approximately determined by means which I shall presently discuss. 

 The time interval can only be ascertained by keeping the animals alive for a period of 

 years and carefully recording their growth. Both factors are very variable quantities, 

 as I have already shown. The length of one yearling lobster which was raised from 

 the egg was only 36 mm., while three other lobsters measured from 35 mm. to 51.8 mm., 

 when not over five months old. Lobsters which live in harbors where they find abun- 

 dant food undoubtedly grow much faster than those farther from shore. It would 

 hardly be expected, moreover, that lobsters kept under artificial conditions would 

 grow as rapidly as when free in the ocean. 1 



In table 24 I have recorded the molts of eight lobsters varying from 5£ to 11J 

 inches in length. The actual increase in length varied from 1 inch to 1£ inches, and 

 the increase percentage (that is, the ratio whicli the increase bears to the total length 

 before molting) from 6.66 to 18.18. The average percentage of increase in all these 

 cases is 12.01. 



Table 24. — Increase in the length of lobsters at the time of molting. 



No. 



Date. 



Sex. 



Length 



before the 



molt. 



Length 



after the 



molt. 



Increase 

 in length. 



Increase 

 percent. 



Remarks. 







Inches. 



Inches. 



Inches. 







1 



Oct, 22,1890 



Female . 



5i 



H 



1 



18.18 



Carapace of molted shell unbroken ; 

 preserved a few days after molt- 

 ing; gastroliths gone; stomach 

 filled with pieces of fish, which 

 had been ted to it; carapace 

 leathery. Plates 45a and 456. 



2 



Oct. 29,1890 



Male 



11 



12 



1 



9.09 



Carapace unbroken ; preserved im- 

 mediately after molting; gastro- 

 liths in their sacs in the walls 

 of masticatory stomach. See cut 8, 

 plate C. For chemical analysis of 

 gastroliths, see Appendix II, 

 No. 4a of table. 



3 



Nor. 6, 1890 



. ..do 



n 



H 



1 



9.68 



Carapace unbroken. 



4 



Nov. 10, 1890 





9 



104 



H 



16.66 



Do. 



5 

 6 



Nov. 11, 1890 

 Juue 8,1891 





74 



8 

 10^ 



h 



1& 



6.66 

 13.13 



Do. 



Carapace unbroken; measured July 



...do .... 

















2. See table 28. 



7 



July 13,1891 



...do.... 



Hi 



12J 



li 



11.11 



Carapace unbroken ; measured July 

 17. See account of molting of this 

 lobster, pp. 83-85; also plate B. 



8 







64. 



n 



2 



Ik 54 



Recorded by Packard (W). 











12.01 









'The best way to ascertain the growth of the lobster would be to fence in securely with wire 

 netting a convenient area in a lobster pound, place a few lobsters in the inclosure, and feed them reg- 

 ularly. They should be examined every week and carefully measured. They could be distinguished 

 by branding the tail-fan. By selecting lobsters of different sizes (3, 5, 8, 10 inches long), the rate of 

 growth at different periods of life could be gradually determined. 



