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Fishery Bulletin 101(3) 



lobsters were recaptured for up to three years following 

 their tagging, the recapture rate was drastically reduced 

 between the first and second recapture period (Table 3). No 

 lobsters were recaptured after four years. 



Based on the information from our aquarium observa- 

 tions, the adjusted recapture rates of the field tagging stud- 

 ies showed no difference between lobsters tagged in the 

 premolt and postmolt stages (Table 3). Because the 1995 

 July tagging was carried out one week later and the molt- 

 ing season was early that year (Comeau and Savoie, 2001), 

 the adjusted recapture rate, based only on late premolt 

 lobsters, was 35.2% (CI 30.8, 42.1). The confidence inter- 

 vals calculated from Monte-Carlo simulations were always 

 wider for lobsters tagged in the premolt stage (Table 3). 



Discussion 



Our results suggest that streamer tag loss for the American 

 lobster depended upon the molt stage of the lobster at the 

 time of tagging. Tag-induced mortality without molting was 

 observed mainly within four days of tagging for lobsters 

 tagged in late premolt and postmolt stages; whereas lob- 

 sters tagged in early premolt and intermolt stages seemed 

 to be less afTected by tagging trauma because none died 

 following the tagging process. Autopsies revealed that the 

 length of time between tagging and death was related to a 

 specific tagging trauma and depended upon the molt stage. 

 Perforation of the pericardial sac caused massive bleed- 

 ing and resulted in death within 30 min of tagging. The 

 rupture of the dorsal thoraco-abdominal membrane, which 

 also caused bleeding, killed the lobsters within days. Per- 

 foration of the hepato-pancreas killed the lobsters within 

 weeks. These types of tagging trauma that caused death 

 were reported by Krouse and Nutting (1990) for American 

 lobsters tagged with Australian western rock lobster {Pan- 

 ulirus longipes cygnus) insertion tags. With more careful 

 tagging manipulations, these types of trauma could pos- 

 sibly be reduced. However, even with extreme care during 



tagging manipulations, the rupture of the dorsal thoraco- 

 abdominal membrane for lobsters tagged in the postmolt 

 stage might be difficult to avoid. Tagging postmolt lobsters 

 was sometimes difficult because the abdominal muscles of 

 some lobsters were thin, and insuring the insertion of the 

 tag through these muscles was a delicate operation. Thus, 

 streamer tags not completely embedded into well-devel- 

 oped abdominal muscles could be a serious problem for tag 

 retention. Tag shedding without molting was observed only 

 for one lobster tagged in the postmolt stage. In general, 

 lobsters tagged with streamer tags during intermolt and 

 postmolt stages had a lower level of tag loss than lobsters 

 tagged in the premolt stage. The level of streamer tag loss 

 was the highest for lobsters tagged in the late premolt 

 stage. 



Tag-induced mortality observed during or shortly after 

 molting was almost exclusively observed for lobsters 

 tagged in the late premolt stage. Although lobsters tagged 

 in the early premolt stage did not die from tagging trauma, 

 they shed proportionately more tags during molting than 

 lobsters tagged in the late premolt stage. Unlike tag loss for 

 lobsters that did not molt, tag loss at molting was not the 

 result of the perforation of internal organs or a question- 

 able tag insertion during tagging but was caused by the 

 tag being firmly attached to the old thoraco-abdomincal 

 membrane and being shed, still attached to the exuvia. For 

 tagged lobsters that died during molting, which were al- 

 most exclusively lobsters tagged in the late premolt stage, 

 tag loss was caused by massive bleeding resulting from the 

 rupture of the entire new thoraco-abdominal membrance 

 by the tag that was still firmly attached to the old thoraco- 

 abdominal membrane. In addition, we observed a high level 

 (21%) of tag misalignment due to the partial attachment 

 of the tag to the old carapace for lobsters that did not have 

 tag loss during molting. For these lobsters, incorrect in- 

 sertion of the strcanuT tag was not an issue. Hence, firm 

 tag attachment of the tag to the dorsal thoraco-abdominal 

 membrane of the old carapace (which causes tag-induced 

 mortality or tag shedding) is a serious problem. 



