FREEMAN ET AL.: LIFE HISTORY OF FLUFFY SCULPIN 



recruitment observed in March 1980 coincided with 

 the onset of upwelling, whereas both recruitment and 

 upwelHng were delayed until May 1979. 



If some individuals do survive to reproduce dur- 

 ing their second year, the larger sizes attained by 

 males during their second growing season may be 

 advantageous during spawning. This is because male 

 0. snyderi have a lengthened and prehensile first 

 anal ray with which they clasp females during 

 copulation, and the larger a male is in relation to a 

 female, the more efficiently he will be able to clasp 

 her (Morris 1956). 



Dietary Habits 



Oligocotttcs snyderi at Dillon Beach consumed 

 primarily gammarid amphipods and polychaetcs. 

 These data are consistent with previous observations 

 (Johnston 1954; Nakamura 1971; Yoshiyama 1980), 

 although they differ somewhat from results obtain- 

 ed by Cross (1981) from two sites in northern Wash- 

 ington. Cross (1981) reported that harpacticoid 

 copepods were a major prey for 0. snyderi at one 

 site; similarly, polychaetes also were consumed only 

 at one site However, Cross (1981) also observed high 

 gammarid consumption by 0. snyderi, as well as by 

 most other intertidal species he studied. In addition, 

 gammarids have been cited as a major prey in other 

 intertidal fish assemblages (Mitchell 1953; Johnston 

 1954; Zander 1979, 1982; Grossman in press b). At 

 Dillon Beach, gammarids frequently were consum- 

 ed by resident and seasonal intertidal fishes, 

 although only one other resident (Apodichthys 

 flavidus Girard) possessed a diet dominated by gam- 

 marids (Grossman in press b). Among year, seasonal 

 comparisons, however, show that a variety of minor 

 prey types also are consumed by 0. snyderi. 



Combinations of shrimps, crabs, hermit crabs, 

 Idotea, and other irregularly consumed prey con- 

 stituted a considerable proportion of 0. snyderi's diet 

 throughout the year. This was particularly evident 

 in larger fish, which suggests that capture of these 

 prey is either more difficult for small fish due to mor- 

 phological, physiological, or behavioral constraints, 

 or involves increased predation risk. Similarly, a shift 

 from gammarids to larger prey concomitant with in- 

 creasing length was observed for the majority of 

 intertidal fishes at Dillon Beach (Grossman in press 

 b), and for some species studied by Cross (1981). In 

 contrast, Yoshiyama (1980) was unable to detect 

 dietary differences between small and large 0. 

 snyderi, or two other intertidal cottids. Yoshiyama 

 pooled small samples collected throughout a year, 

 however, which may have obscured seasonal changes 



in prey consumption. Because his samples were 

 small, Yoshiyama also may have underestimated con- 

 sumption of rare prey. 



Although seasonal dietary changes were minor, 

 there is evidence that females possessed higher in- 

 gestion rates than males during the ODC period. 

 During this season of lowered productivity, females 

 consumed two times more gammarids (by weight) 

 than males, although mean fish length and gam- 

 marid frequency of occurrence were nearly identical 

 between sexes. This difference between consumption 

 rates may not be artifactual. Females develop and 

 carry vitellogenic eggs during this period (Grossman 

 and deVlaming 1984), and consequently have high 

 energy demands. There was no evidence that inter- 

 sexual or ontogenetic dietary differences resulted 

 from differential distribution or collection 

 disturbance 



The high prey weight observed in males and 

 females collected during the ODC period is of in- 

 terest in light of the low growth rates observed dur- 

 ing winter months. Moring (1979, 1981) also ob- 

 served cessation of growth during winter for both 

 0. snyderi and 0. maculosus in northern California. 

 He suggested that reduced foraging activity caused 

 by increased wave action during winter might par- 

 tially explain this growth reduction. Dietary data 

 from Dillon Beach do not support this conclusion 

 because ODC specimens contained a greater total 

 weight of prey than individuals collected during 

 Upwelling, even though a greater number of in- 

 dividuals were examined during the latter period. 

 The Dillon Beach study site probably is more 

 sheltered from winter storm activity, however, than 

 the Trinidad Bay sites observed by Moring (Gross- 

 man pers. obs.). In the absence of ingestion rate data 

 for both seaons, results based on gut content weight 

 alone are equivocal. Moring (1981) also suggested 

 that gonadal development during the winter months 

 might be responsible for reduced growth; this could 

 also apply to 0. snyderi at Dillon Beach. 



In conclusion, 0. snyderi the most abundant inter- 

 tidal cottid at Dillon Beach, possesses a suite of 

 characteristics which suggest that productivity has 

 influenced the biology and behavior of this species. 

 For example, 0. snyderi reaches sexual maturity dur- 

 ing its first year of life, and spawns at a time which 

 enables recruitment to take place during the season 

 of highest productivity (i.e, Upwelling (Grossman and 

 deVlaming 1984)). Grossman (1982, in press b) 

 presented strong evidence that productivity cycles 

 also affect many other species at Dillon Beach, 

 because this assemblage appears to be organized 

 through interspecific exploitative competition for 



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