Smirnov, a. I. 



1969. Hybrids of Pacific salmon of the genus Oncorhynchus, 

 characteristics of development and prospects of utiliza- 

 tion. In B. I. Cherfas (editor), Genetika, selektsiya i 

 gibridizatsiya ryb, p. 139-159. Izdatel'stvo "Nauka," 

 Moscow. (Translated by Isr. Prog. Sci. Transl. 1972, p. 

 131-147 in B. I. Cherfas [editor], Genetics, selection, and 

 hybridization of fish, avail. U.S. Dep. Commer., Natl. 

 Tech. Inf. Serv., Springfield, Va. 22151 as TT 71-50112.) 

 Suzuki, R., and Y. Fukuda. 



1971a. Survival potential of Fj hybrids among salmonid 

 fishes. Bull. Freshwater Fish. Res. Lab. (Tokyo) 21:69-83. 



1971b. Growth and survival of Fi hybrids among salmonid 

 fishes. Bull. Freshwater Fish. Res. Lab. (Tokyo) 

 21:117-138. 

 Terao, T., and H. Hayashinaka. 



1961. On the artificial hybridization among the salmonid 

 fishes. L Sci. Rep. Hokkaido Fish Hatchery 16:51-62. 

 (Translated from Jap., 1968, Fish. Res. Board Can., 

 Transl. Ser. 1047.) 



James L. Mighell 



Northwest Fisheries Center 



National Marine Fisheries Service, NOAA 



2725 Monflake Boulevard East 



Seattle, WA 98112 



Alaska Regional Office 



National Marine Fisheries Service, NOAA 



P.O. Box 1668, Juneau, AK 99801 



James R. Dangel 



TRAP CONTRIBUTIONS TO LOSSES IN 

 THE AMERICAN LOBSTER FISHERY 



Studies to evaluate the impact of unbuoyed traps 

 on American lobster, Homarus aviericanus, sur- 

 vival were conducted in Maine waters from July 

 1971 to June 1973. 



Materials 



On 22 July 1971, 98 tagged lobsters of various 

 legal and illegal sizes and both sexes were placed 

 in 35 unbaited conventional square traps, with 30- 

 mm lath spacing, without buoy lines, on the sea 

 bottom near Jonesport, Maine, in depths ranging 

 from about 10 to 20 m (Table 1). On 29 July 1971, 

 four tagged lobsters were added to one trap from 

 which the previous occupants had escaped by 24 

 July. 



The 84-m- study site, considered by fishermen 

 not to be a good lobster habitat, having a muddy 

 bottom and no rocks which could be utilized as 

 cover, was purposely selected because its use would 



not interfere with commercial fishing and traps 

 would be protected from storm damage. 



Methods 



Traps were checked on nine occasions before 15 

 October 1971, by scuba diving. When traps were 

 checked by diving, it was possible to count the 

 lobsters and observe evidence of cannibalism, but 

 tagged lobsters could not readily be distinguished 

 from others that entered the traps. In order to 

 differentiate tagged from untagged lobsters, all 

 traps were brought to the surface for more 

 thorough examination. This practice was com- 

 menced on 15 October 1971 and continued 

 throughout the remaining period of the study. 



Traps were retrieved 16 times between 15 Oc- 

 tober 1971 and 26 June 1973, making a total of 25 

 checks during the investigation. The length of 

 time between observations of the 2-yr period 

 ranged from 1 to 161 days, with a median interval 

 of 13 days and a mean of 28 days. Observations 

 were curtailed during the low temperature months 

 because of the inactivity of lobsters in relatively 

 shallow water. 



Results 



During the first summer-fall season, 43% of the 

 tagged lobsters cannot be accounted for; 25% 

 remained captive; 20% escaped and were recap- 

 tured; and 12% were cannibalized. During the 

 second summer-fall season, 126% recruitment oc- 

 curred; 22% cannot be accounted for; 18% of both 

 tagged and recruited lobsters were cannibalized; 

 55% remained in the traps; and 5% of tagged lob- 

 sters escaped and were recaptured. 



A minimum 67 "wild" lobsters were recruited by 

 the traps, of which 24 still remained captive when 

 the study was terminated. Two tagged lobsters 

 that departed their original traps entered other 

 experimental traps which they in turn left before 

 entering two of the commercial traps surrounding 

 the study site. A tagged male lobster missing from 

 trap no. 6 was caught in a conmiercial trap 0.4 km 

 from the study area on 28 April 1973, after having 

 remained in trap no. 6 for 22 mo and having 

 moulted once in October 1971 from sublegal to 

 legal size. Four traps failed to recruit any lobsters; 

 9 recruited one each; 13, two each; 6, three each; 2, 

 four each; and 1, six. Only five traps recruited more 

 lobsters than were initially placed in them, six 

 recruited a like number. 



449 



