FISHERY BULLETIN: VOL. 80. NO. 1 



Visual Tags 



Sixteen single bolt tags were attached between 

 January and December 1975. One was lost 

 within seconds, and three others were lost within 

 24 h. Two tags had twisted after 2 mo, damaging 

 the fin and requiring removal of the tag. Another 

 tag was believed to have ripped through the fin of 

 a third animal. Two recaptured dolphins had 

 bolt migration scars, and the tags were lost. Of 32 

 single bolt tags identified in the field, only 3 were 

 sighted more than 2 wk after tagging. 



From December 1975 through May 1976, 19 

 dolphins were tagged with double bolt tags. Tags 

 were identified on free-ranging dolphins 187 

 times through July of 1976, and one tag was 

 sighted 2 mo after attachment. Broken tags were 

 observed eight times, and nine sightings were 

 unidentified due to algae and barnacle fouling 

 (Fig. 2D). Several tags were observed to have 

 only the upper anterior edges broken, implying 

 that breakage was from physical contact. 

 During recaptures, four intact tags were re- 

 moved because barnacles on the inner surface of 

 the tag caused skin abrasions. Six broken tags 

 were removed. Bolt migration was not as 

 common as with single bolt tags, probably 

 because of the stability offered by the rear bolt. 

 Although none of the bolt wounds appeared fully 

 healed, none appeared infected when the 

 animals were recaptured and examined. 



Visual tags were often discernible up to 200 m 

 away. The numerals were rarely readable at 

 distances >50 m, but even broken tags, tag bolts, 

 and tag scars were useful for identification of 

 some dolphins. 



Freeze Brands 



Freeze brands were recognizable on marked 

 animals at distances of <30 m, although 

 photographic analysis was often necessary to 

 confirm identification. Some brands were 

 difficult to identify because they were incom- 

 plete or because of the relatively poor color con- 

 trast of the brand against the skin (Figs. ID, 2C). 



One of the dolphins captured by Irvine and 

 Wells (1972) in March 1971 and freeze branded 

 (on both sides of the dorsal fin) was captured 

 again in December 1975. The animal had a 

 readable freeze brand on only one side of the fin. 

 On another dolphin branded in the same manner 

 in March 1971 and additionally recognizable 

 because of a deformed lower jaw, the brand was 



readable in May 1971 (Evans et al. 1972), butthe 

 brand was no longer visible upon recapture in 

 February 1976. 



Roto Tags 



From February 1976 through July 1976, 53 

 Roto tags were placed on 38 dolphins, including 3 

 animals released with 2 tags. Roto tags were 

 known to be lost from 17 animals and were 

 replaced on 10 of them. A healed indented notch 

 on the trailing edge of the fin was the only 

 evidence of tag loss. Two Roto tags were replaced 

 due to barnacle fouling on the inner surfaces. 

 Brown algae and/or barnacles obscured the tag 

 numbers on most recaptured dolphins, but the 

 tags were still readable on close examination. 



Roto tag color could be observed from up to 70 

 m in calm seas. When examined photographi- 

 cally, position of the tag on the fin or placement 

 in relation to other tags or marks helped verify 

 identity. No dolphins were identified exclusively 

 with Roto tags. 



Spaghetti Tags 



Seventeen spaghetti tags were attached to 

 13 dolphins, including 4 dolphins initially 

 released with two tags. None of the animals 

 reacted noticeably to the attachment process. 

 Six tags were missing from four animals re- 

 captured 10 wk after tagging. Three tags were 

 removed from three other dolphins because 

 the entry wounds appeared to be festering. 



Animals that had lost their tags bore healed 

 but discolored scars that were similar in size to 

 the festering entry wounds described above. No 

 scratches or other evidence that the dolphins 

 may have attempted to remove the tags by 

 rubbing were noted. The wounds, up to 1.9 cm in 

 diameter, apparently were created by movement 

 of the base of the tag streamer on the skin. 



One spaghetti tag was observed in May 1977, 

 345 d after attachment. Several orange colored 

 spaghetti tags became faded within 4 wk, an 

 observation not reported by other investiga- 

 tors. 



Natural Marks 



Twelve untagged dolphins with recognizable 

 natural marks were identified a total of 87 times. 

 Photographs of an individual taken first in 1970- 

 71, then during this study in 1976, and by Wells 



140 



