482 



Fishery Bulletin 101(3) 



few days after tagging or by chronic tag loss spread over 

 an extended period of time, the latter being more difficult 

 to model. Furthermore, Seber (1970) mentioned that the 

 usefulness of the multiyear models depends not only on 

 the validity of the underlying assumptions but also on the 

 number of recaptures (i.e. parameter estimates based on a 

 small number of tag recaptures would be biased). From our 

 aquarium observations and field studies that show a small 

 number of lobsters caught during the second and third re- 

 capture periods, we conclude that a significant chronic tag 

 loss does occur for the American lobster due to molting (i.e. 

 the molt stage of the lobster at tagging and molting itself). 

 Chronic tag loss impedes the effectiveness of multiyear re- 

 capture models currently used (Heam et al, 1998; Hoenig 

 et al., 1998a; Frusher and Hoenig, 2001) because it is not 

 taken into account. We believe that assuming only a con- 

 stant short-term tag loss for lobsters tagged with streamer 

 tags is inadequate and can only bias estimates of survival 

 and exploitation rate. Correcting for chronic tag loss after 

 the first year at large for the American lobster, however, 

 requires further knowledge, and more studies would be 

 required to fully understand long-term tag loss. 



In conclusion, a high level of streamer tag loss is a major 

 obstacle for using tagging studies to estimate natural mor- 

 tality or to apply multiyear models for the American lobster. 

 Because streamer tag loss is related to molting, adjustment 

 is difficult because the molting frequency is size, sex, and 

 environment dependent (Comeau and Savoie, 2001). In our 

 attempt to estimate mortality at molt, it was found that 

 differences in recapture rates of lobsters tagged in premolt 

 and postmolt stages for a given molting period were not sta- 

 tistically significEmt, thus suggesting a low level of natural 

 mortality during the molt. The recapture rate for the 1996 

 tagging, for instance, was even higher for lobsters tagged in 

 the premolt stage. Hence, tagging with streamer tags to es- 

 tablish the level of natural mortality during the molt, or any 

 other mortality that could be low, for the American lobster 

 is not recommended. The alternative would be to develop 

 another insertion tag with better retention through the 

 molting process. Nevertheless, the streamer tag remains an 

 adequate choice for studying lobster ecology and population 

 biology. Streamer tags could be used to tag intermolt and 

 postmolt lobsters during single recapture tagging studies 

 to estimate the exploitation rate (Xiao et al., 1999). Based 

 on our observations, a minimum adjustment of 24.9% (SD 

 2.9%) and 4.4% (SD 1.6%) is suggested for lobsters tagged 

 in premolt and inter- or postmolt stages, respectively, and 

 recaptured during the first recovery period. 



Acknowledgments 



The authors wish to thank all fishermen from Caraquet 

 and the adjacent wharves that returned lobster tags and T 

 Brideau, B. Comeau, J. Roussel, and F. Savoie for their tech- 

 nical assistance in the field and during the tag collection. 

 We especially thank A. Godin and his staff at the Aquarium 

 et centre marin in Shippagan, New Brunswick, for their 

 professional help during the aquarium experiment. We also 

 want to thank J. M. Hanson and M. Moriyasu for critically 



reviewing the manuscript, and three anonymous reviews 

 for thoughtful suggestions that improved the quality of 

 this manuscript. 



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