FREEMAN ET AL.: LIFE HISTORY OF FLUFFY SCULPIN 



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Collection Dote, 1979 



Figure 2.— Growth curves for age 0+ and 1+ Oligocottvs snyderi. 

 The standard lengths Q ± SE) of each sex in the two age classes 

 are shown for the 1979 collections. June, July, and August age + 

 SLs do not include late recruited individuals (see text and Figure 1). 



about equal for age 0+ males and females. The low 

 mean lengths calculated for age 0+ females in Octo- 

 ber and November resulted from the inclusion of 

 small individuals probably recruited late in Upwell- 

 ing, but which were not easily separable from the 

 remainder of the cohort. Hence, calculated growth 

 rates probably underestimate age + female growth 

 from August to October and overestimate growth 

 from October to December. 



Dietary Habits 



Oligocottus synderi's diet at Dillon Beach consisted 

 primarily of gammarid amphipods and polychaetes. 

 Summed across all collections, gammarids composed 

 78% and 66% of the gut contents of females and 

 males, respectively. Polychaetes totaled 10% of the 

 female diet and 14% of the male diet. Shrimp re- 

 mains, mainly Heptacarpus taylori, contributed 5% 

 and 4% to female and male diets, respectively. A 

 total of 20 prey taxa were consumed by 0. snyderi; 

 however, no other prey category composed more than 

 3% of the diet, with the exception of unidentifiable 

 hard-bodied prey remains, which totaled 5% of the 

 gut contents of males. Dietary breadth based on all 

 collections was higher for males than females (2.17 

 vs. 1.61), because males consumed greater amounts 

 of minor prey types. 



The major seasonal dietary changes for both males 

 and females were decreased gammarid consumption 

 and increased polychaete consumption during Up- 

 welling as compared with the ODC period (Tkbles 

 3, 4). Dietary breadth also was greater for both sexes 

 during Upwelling than in the ODC period (2.02 vs. 



1.44 for females, and 2.19 vs. 2.09 for males). Dif- 

 ferences were observed between male and female 

 diets. Specifically, in the ODC period, gammarids 

 composed a greater proportion of female than male 

 diets (83% vs. 68%), whereas males consumed pro- 

 portionately more eggs, Idotea spp. (Isopoda), and 

 crabs (Ikble 4). Although standard lengths and 

 weights of ODC males (138) and females (132) used 

 for gut analyses were not significantly different (SL: 

 t = 1.058, P > 0.1; weight: t = 1.036, P > 0.1), females 

 had significantly greater amounts of food in their 

 stomachs (t = 4.857, P = 0.0001, Ikble 4). This dif- 

 ference is attributable to the weight of ingested gam- 

 marids because 131 (FO) females contained a total 

 of 8.4 g of gammarids, whereas 132 males contain- 

 ed only 4.3 g (total weight). 



Examination of food habits across size classes 

 shows that larger individuals generally possessed a 

 more diverse diet than smaller individuals (Figs. 3, 

 4). Dietary breadth was significantly higher (Wilcox- 

 on signed-rank test, n = 12, T = 69, P < 0.01) for 

 50-69 mm SL fish than for 30-49 mm SL individuals 

 when compared across both sexes for all years. In- 

 dividuals <30 mm SL consumed mainly gammarids 

 and isopods; polychaetes and shrimp were major prey 

 only for larger fish. Pagurus spp. and crabs, in- 

 cluding Cancer spp. and Pachycheles spp., were found 

 only in individuals >40 mm SL. 



The general observation of decreased gammarid 

 consumption by larger 0. snyderi, concomitant with 

 increased polychaete and shrimp consumption, ap- 

 plies to collections made throughout the 3-yr study 

 period. The majority of among year variation in food 

 habits resulted from the presence of large, rare prey 

 items in single individuals (Figs. 3, 4). An exception 

 was the high consumption of polychaetes by males 

 collected in July 1981 (Fig. 3). In this case, poly- 

 chaetes occurred in all of the 50-69 mm fish and in 

 56% of the 30-49 mm fish, and composed a con- 

 siderably higher proportion of the diet than during 

 previous Upwelling collections. 



DISCUSSION 



Age-Structure and Growth 



At Dillon Beach, a habitat displaying marked 

 seasonal fluctuations in productivity (Grossman 

 1982, in press b; Grossman and deVlaming 1984), 0. 

 snyderi is short lived, with a maximum lifespan of 

 about 1.5 yr and a maximum length of about 70 mm 

 SL. Whereas two age classes were observed in this 

 study, Moring (1981) observed as many as three age 

 classes in Trinidad Bay. Standard lengths attained 



649 



