476 



Abstract — Streamer tags are com- 

 monly used to study the ecology and 

 population biology of the American lob- 

 ster (Homarus americanus). Aquarium 

 observations suggest that streamer 

 tag loss, either through tag-induced 

 mortality or tag shedding, is related to 

 the molt stage of the lobster at the time 

 of tagging, and the molting event itself. 

 Tag-induced mortality, where lobsters 

 did not molt, occurred within eleven 

 and sixteen days following tagging for 

 lobsters tagged in postmolt (4%) and 

 late premolt (10%) stages, respectively; 

 whereas no lobsters tagged in early 

 premolt or intermolt stages died. Tag- 

 induced mortality at time of molting 

 was observed for lobsters tagged in 

 late premolt stage (11%), and tag shed- 

 ding was observed for lobsters tagged 

 both in early (25%) and late premolt 

 (11%) stages, but was significantly 

 higher (P=0.014) for lobsters tagged 

 in early premolt stages. Autopsies 

 revealed that lobsters died mainly of 

 organ perforations (hepato-pancreas 

 and pericardial sac) following the tag- 

 ging process, and rupture of the dorsal 

 thoraco-abdominal membrane during 

 the molting process. The total tag loss 

 was estimated at 4% for lobsters tagged 

 after molting, and 27%^ and 31% for lob- 

 sters tagged in early and late premolt 

 stages, respectively. There was no tag 

 loss for lobsters tagged in the intermolt 

 stage during four months of labora- 

 tory observations (July-October). To 

 minimize streamer tag loss, lobsters 

 should be tagged during the intermolt 

 or postmolt stage. Based on field stud- 

 ies, recapture rates for lobsters tagged 

 in premolt stage are always lower than 

 those of lobsters tagged in postmolt 

 stage. Furthermore, recapture rates 

 during the second year, for lobsters 

 that molt in the year following tagging, 

 were drastically reduced, and no lobster 

 was recaptured after four years at large. 

 Finally, to account for tag loss during 

 the first year at large, a minimal adjust- 

 ment of 24.9% (SD 2.9%) and 4.47, (SD 

 1.6%) for the recapture rate of lobsters 

 tagged immediately before and after the 

 molting season, respectively, is recom- 

 mended. Adjustments beyond one year 

 at large are not recommended for the 

 American lobster at this time. 



Manuscript approved for publication 

 19 February 2003 by Scientific Editor 



Manuscript received 4 April 2003 at 

 NMFS Scientific Publications Office. 



Fish. Bull. 101:476-483 (2003). 



The effect of timing of tagging on streamer-tag 

 recapture rates for American lobster 

 (Homarus americanus) 



Michel Comeau 



Manon Mallet 



Department of Fisheries and Oceans 



343 University Ave 



Monaon, New Brunswick, Canada E1C 9B6 



E-mail-address (for M Comeau) comeaumra'dfo-mpo gc ca 



Tagging methods to study the move- 

 ment, growth, and exploitation rate 

 for the American lobster {Homarus 

 americanus) have improved over the 

 last 70 years. One major improvement 

 in the mid 1960s was the introduction 

 of an insertion tag called the "sphyrion 

 tag" that is anchored to muscle tissue 

 (Scarratt and Elson, 1965), instead of 

 body tags (Templeman, 1935) or cara- 

 pace-piercing tags (Wilder, 1953) used 

 earlier. By the late 1980s, the sphyrion 

 tag was replaced by another insertion 

 tag called the polyethylene "streamer 

 tag" (Landsburg, 1991; Moriyasu et al., 

 1995) initially developed for shrimps 

 (Penaeus spp.; Marullo et al., 1976). 

 Insertion tags have the advantage 

 of being retained through a series of 

 molts, thus providing information on 

 long-term movement and more accurate 

 data on growth. 



Tag loss could greatly bias the esti- 

 mate of population characteristics and 

 fishery parameters (Ricker, 1975). For 

 obtaining population estimates from 

 mark-recapture data, tag loss gener- 

 ally refers to the reduction of the initial 

 number of tagged animals by means 

 other than fishing. In a series of tagging 

 studies, Comeau et al. (1999) noticed a 

 constant pattern of lower tag recovery 

 rates for lobsters tagged in the premolt 

 stage than for lobsters tagged in the 

 postmolt stage. They indicated that the 

 level of fishermen participation (recov- 

 ery rate) could be a possible cause of 

 tag loss because they noticed a steady 

 decline of recapture rates where mul- 

 tiyear tagging studies were conducted. 

 However, because the same type of 

 streamer tag was used and each lobster 

 was handled individually, the fishermen 



participation could not explain the dif- 

 ference between recapture rates for 

 lobsters tagged in premolt and postmolt 

 stages for a given year; hence possible 

 tag loss at molting was suspected as 

 the cause of the lower recapture rates 

 (Comeau et al., 1999). Furthermore, in 

 an attempt to estimate mortality rates, 

 Comeau and Mallet (2001) used a 

 mark-recapture model and simulations 

 to evaluate the best estimator. They 

 concluded that the level of tag loss is 

 high and could be a serious problem for 

 estimating fishery parameters for the 

 American lobster if information on tag 

 loss is not available. 



Moriyasu et al. (1995) showed that 

 sphyrion tag loss for lobsters held in 

 aquaria varies between 3% and 23% 

 depending on the molt stage at tag- 

 ging. They also mentioned that lobsters 

 tagged with sphyrion tags showed a 

 significantly lower return rate (19%) 

 than lobsters tagged with streamer tags 

 (44%) in a recapture study in the field 

 and suggested a possible lower level of 

 tag loss among lobsters tagged with 

 streamer tags. However, they did not es- 

 timate the tag loss for streamer-tagged 

 lobsters. Recently, Rowe and Haedrich 

 (2001) showed that the shedding rate 

 for streamer tags in the field could 

 reach 18% (40% for molted animals and 

 11% for nonmolting animals) after 8-12 

 months based on double tagging with 

 a secondary carapace marking. They 

 also found that streamer tag shedding 

 was not related to sex or size, but they 

 did not study the level of tag-induced 

 mortality. 



Various causes can reduce the initial 

 number of tagged animals, mainly tag 

 shedding, tag-induced mortality, and 



