Sphyrion Tag Shedding and Tag Induced Mortality of the American Lobster, Homarus Americanus H. Milne Edwards, 1837 (Decapoda, Nephropidae)
Sphyrion tags are commonly used for studying movement and growth of the American lobster, Homarus americanus. Observations in the laboratory suggested that shedding of sphyrion tags and tag induced mortality occurred mainly within the first 5 days after tagging or during molting, depending upon the molt stage of the lobster at tagging. Shedding rate varied from 3.1 % (within 5 days after tagging) for individuals tagged at the early premolt stage to 21.7% (during molting) for those tagged at the late premolt stage. Tag induced mortality varied from 3.1 % (within 5 days after tagging) for individuals tagged at the early premolt stage to 23.3% (within 5 days after tagging) for those tagged at the postmolt stage. Shedding of tags and tag induced mortality were significantly high for lobsters tagged at the late premolt and postmolt stages, respectively. Therefore, it is preferable that lobsters be tagged during the intermolt period to minimize shedding of sphyrion tags and tag induced mortality. A tag-recapture study in the field showed that the recapture rate of lobsters tagged with streamer tags was significantly higher (43.8%) than that for those tagged with sphyrion tags (19.2%). This suggests that tag loss among lobsters tagged with streamer tags may be less than that among lobsters tagged with sphyrion tags.