586 



Fishery Bulletin 91(3), 1993 



sient lingcod may have become resident just outside 

 the boundaries of the study area or returned at a later 

 date. Fish Y2, for example, was apparently absent from 

 the study area for 10 days before returning (Fig. 1). 

 Conventional tagging studies are required to address 

 these long-term issues. However, conventional tagging 

 studies suffer from other problems. For example, the 

 lack of fishing effort in the area due to seasonal clo- 

 sures would reduce the probability of tag recapture, 

 and a minimum size limit (65cm) would impose a size- 

 selectivity on the recaptured fish. 



Our measurements of lingcod movement rate were 

 comparable to those reported by Matthews ( 1992). She 

 observed movement rates of 1.17 km/d for displaced 

 male lingcod, intermediate to the rates of 1.42 km/d 

 and 0.80 km/d that we computed for lingcod in tran- 

 sient and resident groups, respectively. Furthermore, 

 our estimate of nocturnal ( 1600-0800 h) movement rate 

 was 2.1m/min, identical to the rate that Matthews 

 (1992) measured between 2400-0600 hours. The con- 

 trol lingcod in our study remained within the maxi- 

 mum home range size of 0.4 km 2 recorded by Matthews 

 (1992). 



It was not possible for us to determine whether ling- 

 cod moved toward their capture site after leaving the 

 study area. Homing has been documented for adult 

 lingcod (Hart, 1943; Cass et al., 1983; Matthews, 1992), 

 but other factors undoubtedly affect fish movement. 

 For example, the prevailing current in the Strait of 

 Georgia flows to the northwest owing to land masses 

 and prevailing winds from the southeast (Thomson, 

 1981). Hart (1943) observed from tag returns that most 

 lingcod released in the Strait of Georgia moved in a 

 northwesterly direction. 



The purpose of this study was to determine whether 

 stocking with juvenile lingcod could promote natural 

 stock rebuilding. Because 6 of the 13 displaced fish 

 did remain within the 12 X 4 km study area while 

 their tags were active (28 days), restocking with ju- 

 venile lingcod is a potential enhancement tool. For 

 transplanted fish to contribute to the spawning stock, 

 they must remain in the new area and survive there 

 until reproduction (spawning/nest guarding) is com- 

 plete. Annual natural mortality rates for lingcod are 

 24<7r (Schnute et al., 1989). Mortality rates due to 

 sport fishing and marine mammal predation may be 

 higher (Collicutt and Shardlow, 1989; Olesiuk et al., 

 1990; Smith et al., 1990). To compensate for these 

 mortalities, the number of age 2-3 year lingcod trans- 

 planted must be at least two to three times the num- 

 ber required to achieve a target spawning biomass 

 one year later. A harvest of this magnitude could be 

 detrimental to the donor stock. Until the depleated 

 stock is re-established, the enhanced area should be 



closed to lingcod retention, and if possible, to all 

 fishing activities. Hook and release mortality is not 

 known but could decrease survivorship if fishing pres- 

 sure is intense. 



Acknowledgments 



The long hours of tracking endured by Claudia Hand, 

 Greg Workman, and Anita Gurak are gratefully ac- 

 knowledged. We also thank Antan Phillips and Doug 

 Miller for sharing their boat-handling expertise. K. 

 Groot, J. Rice, and K. R. Matthews provided helpful 

 comments on the manuscript. 



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