ASPECTS OF THE LIFE HISTORY OF THE FLUFFY SCULPIN, 



OLIGOCOTTUS SNYDERI 



Mary C. Freeman,^ Nate Neally,^ and Gary D. Grossman^ 



ABSTRACT 



We examined age structure, growth rates, and diets of male and female Oligocottus snyderi Greeley at 

 Dillon Beach, CA, where this sculpin numerically dominates the mid- and lower intertidal fish assemblage 

 Two age classes, 0+ and 1 + , were present; maximum lifespan was about 1.5 years. Instantaneous popula- 

 tion growth rates were highest for the O-t- age class, and most individuals attained spawning size during 

 the first year of life Growth rates for both age classes were highest during the high productivity Upwell- 

 ing period and minimal during the low productivity, Oceanic-Davidson Current period. 



Males and females primarily consumed gammarid amphipods and polychaetes. Larger individuals (>50 

 mm SL) of both sexes consumed a wider variety of prey, including shrimps, crabs, and isopods. Among 

 year and seasonal dietary changes were minimal. Females consumed two times more gammarids by weight 

 than males during the low productivity Oceanic-Davidson Current period, when ovarian recrudescence 

 occurs. Females may increase food consumption to meet the increased energetic demands of egg production. 



Rapid sexual maturation and growth and the occurrence of recruitment during upwelling probably are 

 adaptations to the pronounced annual cycle of productivity. These adaptations, together with intense utiliza- 

 tion of an abundant prey (gammarids) not widely consumed by other assemblage members, probably con- 

 tribute to 0. snyderi's numerical dominance in the rocky intertidal of central California. 



The fluffy sculpin, Oligocottus snyderi Greeley, is a 

 common species which inhabits the rocky intertidal 

 from Baja California to Sitka, AK (Miller and Lea 

 1972). Between central California and British Col- 

 umbia, 0. snyderi frequently is very abundant (Green 

 1971; Cross 1981; Yoshiyama 1981; Grossman 1982). 

 This species occurs primarily in mid- and lower in- 

 tertidal areas (Green 1971; Yoshiyama 1981), and 

 often is associated with surfgrass (Green 1971; 

 Nakamura 1976a). The general absence of this 

 species from the high intertidal is probably due to 

 its inability to tolerate higher temperatures which 

 frequently occur in high intertidal pools (Nakamura 

 1976b). 



Life histories of intertidal fishes, particularly cot- 

 tids, are poorly known (Gibson 1969, 1982). Publish- 

 ed information on the demography of 0. snyderi is 

 restricted to the work of Moring (1981), who ex- 

 amined age structure of a northern California 0. 

 snyderi population, and Grossman and deVlaming 

 (1984), who described the species' reproductive 

 ecology. This paper presents data on age structure, 

 growth rates, and dietary habits of an 0. snyderi 

 population at Dillon Beach, CA, a site that is sub- 



ject to pronounced annual cycles of oceanic produc- 

 tivity (Parrish et al. 1981). Oligocottus snyderi 

 numerically dominates the intertidal fish assemblage 

 at Dillon Beach (Grossman 1982); the present study 

 explores demographic and ecological characteristics 

 which may account for this species' ecological suc- 

 cess in the rocky intertidal. 



MATERIALS AND METHODS 



Collections 



Oligocottus snyderi were collected from a series 

 of mid- and lower intertidal pools at Dillon Beach, 

 CA, on 15 dates from January 1979 to July 1981 (see 

 Grossman in press a for sampling dates). Repeated 

 collecting did not affect assemblage structure (Gross- 

 man 1982, in press a). Fish were obtained by 

 spreading a 10% solution of quinaldine in 

 isopropanol through the pools and then collecting 

 individuals after anesthetization. Over 1,400 0. 

 snyderi were collected. Specimens were preserved 

 in buffered Formalin^ and were later washed and 

 transferred to 45% isopropanol. Individuals were 

 measured to the nearest millimeter standard length 

 (SL) and weighed to the nearest 0.1 g. Sexes of all 



1 School of Forest Resources, University of Georgia, Athens, GA 

 30602. 



^Department of Wildlife and Fisheries Biology, University of 

 California, Davis, CA 95616. 



^Reference to trade names does not imply endorsement by the 

 National Marine Fisheries Service, NOAA. 



Manuscript accepted January 1985. 

 FISHERY BULLETIN: VOL. 83, NO. 4, 1985. 



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