628 



Fishery Bulletin 104(4) 



rence for Dover sole in our collections (ODFW'^), and 

 the greatest range in their age (Table 1), occurred 

 during summer — a period when Dover sole move into 

 shallow nearshore waters (Hagerman, 1952; Markle et 

 al., 1992). This migration into nearshore waters brings 

 fish into contact with an increasing population of pin- 

 niped predators. 



The majority of Dover sole otoliths recovered from 

 scats were those of fish younger than four years. In 

 contrast, Dover sole landed in Oregon's commercial 

 fishery between 1984 and 2004 were aged to be be- 

 tween three and 60 years old and the average age 

 was 13 years (ODFW^). Of the 45,026 fish aged from 

 the commercial fishery, over 50% were ages similar 

 to those recovered from seal scat samples (four to 12 

 years) and had an average length of 33.4 cm. Of the 

 fish checked, 79% were identified as mature. However, 

 the majority (70.5%) of otoliths analyzed in our study 

 were from one, two-, and three-year-old fish, whereas 

 only one of the commercially caught fish was in this 

 age range. Four- to six-year-old fish made up 0.3% of 

 the commercially sampled fish and seven- to 12-year- 

 olds made up the largest portion at 53.5%. This lack 

 of younger age fish in the commercial fishery is partly 

 due to the discarding of smaller unmarketable fish at 

 sea. Sampson and Wood (2001) reported that from 1956 

 through 2000, between 5% and 14.6% of the commer- 



cial Dover sole catch at sea was discarded because of 

 the small unmarketable size of the catch. What effect a 

 consistent removal of older age fish and the discarding 

 of younger fish by the commercial fishery, coupled with 

 the take of younger age fish by an increasing number 

 of predators could have on the population as a whole, 

 is unknown. 



Many species of marine fishes other than Dover sole 

 contribute to important commercial fisheries in Oregon 

 (ODFW"). Estimating prey age from fish otoliths recov- 

 ered from seal and sea lion scats will be useful for re- 

 searchers when describing impacts on long-lived marine 

 species such as rockfish, which may be at greater risk to 

 this long-term and increasing predation by coastal pin- 

 nipeds. Love et al. (2002) reported that rougheye rock- 

 fish (Sebastes aleutianus) live to at least 205 years and 

 yelloweye rockfish (S. ruberrimus) to 118 years, whereas 

 other species such as calico (S. dalli) and squarespot 

 (S. hopkinsi) may only live for a decade or two. These 

 older fish in some cases also have a late maturity; for 

 example, only half of all yelloweye rockfish are mature 

 at an age of 22 years. 



As the sustainability of these species and the fisheries 

 that target them become difficult to manage, there will 

 be more interest in the impact of predators on these fish 

 populations. Determining fish age has enabled biologists 



' ODFW (Oregon Department of Fish and Wildlife). 1984-2004. 

 Unpubl. data. [Data are on file at Oregon Department of 

 Fish and Wildlife Newport-Marine Program office, 2040 

 S.E. Marine Science Drive, Newport, Oregon 97365.] 



s ODFW (Oregon Department of Fish and Wildlife). 2000. Or- 

 egon Marine Fisheries 2000 status report, 109 p. [Available 

 from Oregon Department of Fish and Wildlife Newport- 

 Marine Program office, 2040 S.E. Marine Science Drive, 

 Newport, Oregon 97365.1 



