FISHERY BULLETIN: VOL. 78, NO. 2 



..\\ .\\\V ' 





Figure 8. — Juvenile Isopsetta isolepis, 44 mm SL, showing details of skeletal structure. 



Myers 1974), and in the Columbia River (Misitano 

 1977). A similar coastal distribution is indicated 

 off Washington with reduced numbers occurring 

 in Puget Sound (Waldron 1972; Blackburn 1973). 

 Thus spawning takes place primarily in coastal 

 areas rather than bays and estuaries. 



Larvae occur in the plankton off Oregon mainly 

 in winter and spring (Waldron 1972; Misitano 

 1977; Richardson see footnote 4) although in 1971 

 larvae were taken in every month of the year ex- 

 cept September, November, and December (Rich- 

 ardson see footnote 4). In 1972 they were taken in 

 every month sampled, March through August 

 (Richardson see footnote 4). In 1971, abundance 

 peaked in May, and in 1972, smaller abundance 

 peaks were observed in March and May ( Richard- 

 son see footnote 4). Spring occurrences of larvae 

 have been reported off Washington and in Puget 

 Sound (Waldron 1972; Blackburn 1973). 



Monthly length-frequency distributions and 

 median lengths of larvae collected off Oregon indi- 

 cate winter-spring spawning (Figure 9). Small 

 larvae <5 mm were taken January through May 

 1971, October 1971, and March and April 1972. 

 Median lengths increased progressively from 2 to 

 16 mm in January through June 1971 and from 4 

 to 16 mm in March through June 1972. 



Based on available data, /. isolepis apparently 

 settles to the bottom in coastal areas and rernains 

 near the coast during the early juvenile period. 

 Newly transformed juveniles (18-38 mm) have 

 been collected off the mouth of the Columbia River 

 in depths of 34-56 m (Table 5). Juveniles in this 



Table 5. — Data from beam trawl collections of juvenile Isop- 

 setta isolepis taken off the mouth of the Columbia River, 1975. 



size range have not been reported from bays, es- 

 tuaries, and nearshore coastal areas where 

 juvenile Parophrys uetulus have been found (Wes- 

 trheim 1955; Kendall 1966; Beardsley 1969; Wil- 

 liam Johnson's data listed in Pearcy and Myers 

 1974; Peden and Wilson 1976; Laroche and Holton 

 1979; Cummings and Schwartz^^ Higley and Hol- 

 toni2; Krygieri3). Although Misitano (1977) re- 

 ported that both /. isolepis and P. uetulus use the 

 Columbia River as a nursery area, he was refer- 

 ring to fish >85 mm long (>95 mm for 7. isolepis). 

 Thus, smaller I. isolepis juveniles apparently use 

 offshore coastal areas during their first year of life 

 as opposed to the bay, estuarine, and near coastal 

 nursery habitats of P. uetulus. 



"Cummings, E., and E. Schwartz. 1971. Fish in Coos Bay, 

 Oregon, with comments on distribution, temperature, and sa- 

 linity of the estuary. Oreg. Fish Comm., Res. Div., Coastal 

 Rivers Invest. Inf. Rep. 70-11, 22 p. 



i^Higley, D. L., and R. L. Holton. 1975. Biological baseline 

 data, Youngs Bay, Oregon, 1974. Final Rep. Alumex Pacific 

 Aluminum Corp., 1 November 1973 through 30 April 

 1975. Oreg. State Univ., Sch. Oceanogr. Ref 75-6, 91 p. 



'^E. Krygier, Research Assistant, School of Oceanography, 

 Oregon State University, Corvallis, OR 97331, pers. commun. 

 June 1978. 



414 



