Stewart. Defining migration rates of Porophrys vetulus 



473 



counted for to perform a simultaneous analysis. Where 

 possible, recoveries in the same month as the tagging 

 program were excluded (and subtracted from tag re- 

 leases, n=287) to avoid potentially skewed estimates 

 of movement and fishing mortality rates before any 

 movement could reasonably have occurred. Exclusion of 

 immediate recoveries is common practice when analyz- 

 ing tag-recovery data (McGarvey and Feenstra, 2002; 

 Robichaud and Rose, 2004). This decision also obvi- 

 ated having to scale the fishing mortality rate during 

 the first month by the number of days after tagging, 

 which is problematic when tagging has occurred over 

 a number of days or is reported only by the month in 

 which it took place. Many different methods of tagging 

 were used in these studies, but all tags were assumed 

 to have the same rate of tag loss. Comparison of tag 

 loss rates for disk and spaghetti tags, although limited, 

 has not identified substantial differences (Meehan and 



MilburnM, although variation certainly exists given 

 the advances in tagging methods over the four decades 

 spanned by these studies. The reporting rates for tags 

 captured by different fisherman were another source of 

 variability; all recoveries were assumed to have been 

 reported at the same rate in all time periods because 

 there was no information with which to address this 

 issue. Researchers conducting all studies primarily 

 tagged adult fish of both sexes, and recoveries were ob- 

 tained with commercial or similar fishing gear; however 

 little detail regarding the age or length structure of the 

 fish tagged was available. No accounting was made for 



1 Meehan, J. M., and G. S. Milburn. 1965. Comparison of 

 returns from dart and Peterson disc tags on Dover sole. Fish 

 Commission of Oregon Research Briefs. 13:127. Oregon 

 Department of Fish and Wildlife, 3406 Cherry Avenue NE, 

 Salem. OR 97303. 



