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Fishery Bulletin 101(2) 



Vancouver Island (Ketchen, 1986). For these four areas of 

 tag recapture, annual catch (excluding discards) was used 

 to estimate relative effort. Because catches are reported for 

 the whole year, tag recaptures in the year of release were 

 not standardized. We standardized tag recaptures in each 

 area as the number of recaptured fish per 1000 t. 



Figure 2 



(A) Titanium pins and modified olonfjated disc 

 tags developed for spiny dogfish. (Bl Modified 

 tag attached to spiny dogfish showing position 

 of attachment, label of tag, and wire pins hold- 

 ing label in position. (C) Diagram of plexiglass 

 tag applicator 



In order to elucidate differences in movement due to size 

 at release or sex, the following categories were used: males 

 <70 cm (Ml); males >70 cm (M2); females <70 cm (Fl); fe- 

 males 71-85 cm (F2); females >86 cm (F3). Size categories 

 were based on approximate size at maturity and habitat 

 use. Males mature at about 70 cm, which coincides with 

 their movement from a mainly pelagic habitat to a deeper 

 mid-water and demersal habitat. Females undergo a simi- 

 lar habitat change at 70 cm; however, their size at maturity 

 is approximately 85 cm. Recoveries by the categories were 

 then examined by area of recapture. 



Results 



Suitability of tag 



McFarlane and Beamish ( 1986) reported preliminary results 

 for the modified tag used in the present study compared to 

 Petersen disc tags and Floy anchor tags. In contrast to the 

 Petersen disc tag, the Floy anchor tag was quickly abraded 

 and lost. Of 1688 fish receiving both tags, 49 were recov- 

 ered from 1978 to 1982. All recovered fish had a Petersen 

 disc tag; however only 1 1 fish had both tags, and 9 of these 

 were recaptured during the first 18 months. McFarlane 

 and Beamish also compared the modified Petersen disc 

 tag to Petersen disc tags (McFarlane and Beamish, 1986). 

 Petersen discs attached to spiny dogfish in 1978 and 1979 

 and recaptured from 1978 to 1980 were compared to modi- 

 fied Petersen disc tags applied from 1979 to 1982 and stan- 

 dardized for catch. The standardized recovery percentage 

 (3.9%) for the modified Petersen disc tag compared to the 

 Petersen disc tag (2.4%) was significantly higher (P=0.01). 

 Because the materials used in the tags were similar and 

 none of the modified tags were returned with one pin miss- 

 ing, the decrease in percentage of recoveries of Petersen tags 

 probably was due to mortality caused by tag wounds and 

 not to disc or pin loss. For a description of the tag wounds 

 see McFarlane and Beamish (1986). Both titanium pins 

 remained in the tag in all recovered fish. A metallurgical 

 stress test indicated that the pins were durable in salt water 

 and might be expected to last more than 20 years (McFar- 

 lane and Beamish, 1986). In the present study we report 

 that fish with the modified Petersen disc tag were recap- 

 tured with tags intact 20 years after release. After correct- 

 ing for differences between years in catch (t) for tagged fish 

 recaptured in the Strait of Georgia in 1988-90, a chi-square 

 test on the ratios of the numbers released to the numbers 

 returned indicated no significant level of difference in return 

 percentages between the standard hard plastic tag and the 

 more flexible plastic tag used in 1988 (P=0.304). 



Tag return rates 



Within the Strait of Georgia, tagging took place every year 

 from 1978 to 1988 with the exception of 1986 (Table 2). Off 

 the west coast of Vancouver Island, tagging was conducted 

 in 1984, 1985, and 1987 (Table 2). Tagging was conducted in 

 northern British Columbia waters in 1980, 1982, and 1987 

 (Table 2). In total, 70,770 fish were tagged throughout all 



