Comeau and Mallet: Effect of timing of tagging on tag recapture rates for Homarus americanus 



479 



A total of TCX ( 134) of the lobsters tagged in the premolt 

 stage molted between 30 June and 8 September (between 

 7 and 77 days after tagging) without any tag loss (Table 1). 

 Tag-induced mortality represented 8'7f (15) of the tag loss 

 (Table 1). Autopsies revealed that the majority (11) of the 

 lobsters tagged in late premolt stage died from the rupture 

 of the dorsal thoraco-abdominal membrane (Table 2); the 

 tag was still attached to the old membrane and had caused 

 the rupture of the new one. The four remaining lobsters 

 died from poor healing of the tissue at the point of entry 

 and exit of the tag, revealing a punctured dorsal thoraco- 

 abdominal membrane (Table 2 ). For all lobsters that healed 

 poorly and later died, one side of the tag had been pulled 

 inside the body cavity during molting. One death was not 

 related to tagging but was caused by the crusher claw 

 becoming wedged within the old carapace, thus prevent- 

 ing the animal from successfully completing the molting 

 process. Furthermore, the autopsy for this lobster did not 

 reveal any sign of tagging trauma. 



Tag shedding was observed during molting for 21% (29) 

 of the lobsters tagged in the premolt stage (Table 1). Tag 

 shedding was observed for lobsters tagged in both early and 

 late premolt stages (Table 1) but was significantly higher 

 (X^=5.9; P=0.014) for lobsters tagged in the early premolt 

 stage. Twenty-one percent (28) of lobsters tagged in the 

 premolt stage that molted had a misaligned tag (pulled to 

 one side). 



Only 4% (8) of the lobsters tagged in the postmolt stage 

 died during the second experiment, and only one individual 

 (<1%) shed a tag (Table 1 ). The autopsies revealed that tags 

 were not well embedded in the muscle tissue and large 

 scars were observed on the dorsal thoraco-abdominal mem- 

 brane of seven individuals (Table 2). These lobsters died 



within 1 1 days of tagging. The death of the other individual 

 was not related to tagging for there was no sign of tagging 

 trauma. Three percent (5) of the lobsters had a misaligned 

 tag at the end of the experiment. 



From a total of 229 lobsters initially tagged for the 

 first experiment, 17% (38) were in the intermolt stage. 

 Although the sample number was small, none of these 

 lobsters shed their tag, died from the tagging procedure, 

 or molted. This finding indicates that these small male 

 lobsters (67-78 mm CD skipped an entire molting season 

 (July-August) in 1998 and retained their tags without risk. 

 Only one (3%) lobster had a misaligned tag at the end of 

 the experiment. No lobster that was returned to the sea 

 after the experiments had infected wounds from the tag 

 insertion procedure. 



Field studies 



Tag-induced mortality was observed within 30 min in 

 every tagging study conducted between 1994 and 1996, 

 varying in rate between 0.4% to 3.5%. The majority of the 

 lobsters tagged in early July 1994, 1995, and 1996 were in 

 the premolt stage because 94% to 99% had molted before 

 being recaptured the following fishing season. Except for 

 two lobsters (1.1%) tagged in 1994 that were recaptured 

 the following fishing season with a size increase, all of lob- 

 sters tagged in September-October were in the postmolt 

 stage. Recapture rates based on the first recapture period 

 for lobsters tagged in early July (premolt) were signifi- 

 cantly lower than the recapture rates for lobsters tagged 

 in September-October (postmolt) for the 1994 (/2=io.6; 

 P=0.001) and 1995 (x''^=11.4.; P=0.0007) tagging, but not 

 for the 1996 (^^=2.0; /'=0.156) tagging (Table 3). Although 



