FREEMAN ET AL.: LIFE HISTORY OF FLUFFY SCULPIN 



Table 1.— Length-weight relationships, described as W^ = a/.'', for 

 Oligocottus snyderi. Coefficients for the least-squares (In W = \r\ 

 a + bin L) and functional (In IV = In a' -h (bir) In L) regressions 

 are presented, as well as the correlation coefficients for the least- 

 squares regressions (r) and the number of individuals used in each 

 regression (A/). ODC = Oceanic-Davidson Current. 



Least-squares 

 regression 



Functional 

 regression 



F = 0.736, P > 0.25). Seasonal comparisons for each 

 sex showed that tlie male Upwelling and ODC slopes 

 were not significantly different (ANCOVA, F = 

 1.483, P > 0.10), whereas the females had a 

 significantly higher slope during the ODC period 

 (ANCOVA, F = 6.147, P < 0.025). 



Growth Rates 



Length-frequency histograms for 0. snyderi at 

 Dillon Beach indicated that two year classes were 

 present on most dates (Fig. 1). Recruitment began 

 in spring and peaked during summer. The onset of 

 recruitment differed between years. Age O-i- fish 

 were first taken in May of 1979; however, in 1980 

 recruitment began in March. Age O-i- individuals of 

 the 1979 cohort grew 20 mm in length (from 20-25 

 to 40-55 mm SL) by December of their first year. 

 Members of the 1978 cohort (= age l-i- fish) in- 

 creased in length from 40-55 to 60-70 mm SL dur- 

 ing spring, summer, and fall 1979. Individuals did 

 not appear to survive a second winter during 1980, 

 although a few males recruited in 1977 may have sur- 

 vived until spring of 1979 (Fig. 1). 



Sex ratios for the O-i- age class were significantly 

 different from unity in the August 1979 collection 

 in which there were significantly more males than 

 females (1.7:1; x^ = 7.32, P < 0.01). Age 1+ females 

 significantly outnumbered males in January 1979 

 (4:1; x^ = 6.05, P < 0.025), July 1979 (1.8:1; x^ = 

 4.38, P < 0.05), and December 1979 (3:1; x^ = 5.04, 

 P < 0.025). 



Instantaneous growth rates were calculated for 

 males and females from the two year classes pres- 

 ent in 1979 (Tkble 2). Prolonged recruitment (lasting 

 from May through August) resulted in apparent 

 depressed spring and summer growth rates for the 

 age O-I- class when all individuals were included in 

 the calculations of mean lengths (Tkble 2). Therefore, 



fish which appeared to have been recruited later than 

 the majority of the class were excluded from con- 

 sideration in the June, July, and August calculations, 

 as shown in Figure 1. Only the very large males col- 

 lected in January 1979 were excluded from the age 

 1 + mean length calculations, as these individuals ap- 

 parently were survivors from the 1977 year class and 

 probably died shortly thereafter. The highest 

 monthly instantaneous growth rates were obtained 

 during May and June, averaging 0.860 and 0.655 for 

 age O-I- males and females, and 0.209 and 0.188 for 

 age 1 -I- males and females (Tkble 2, Fig. 2). Growth 

 rates markedly decreased after August, averaging 

 0.065 and 0.169 for age O-i- males and females, and 

 and 0.061 for age l-i- males and females during 

 October and November (Ikble 2, Fig. 2). 



Males and females attained nearly equal lengths 

 in the first season of growth; however, age 1 -i- males 

 displayed significantly greater mean lengths (^tests, 

 P « 0.05) than age 1 + females from June through 

 November 1979 (Fig. 2). Growth rates were not 

 significantly higher for males than females in either 

 size class when compared from January to 

 December 1979 (age + :^ = 1.002, P> 0.1; age 1 + : 

 t = 1.232, P > 0.1); however, if only the data from 

 January to October are included for the age 1 + class, 

 males did have significantly higher growth rates (t 

 = 2.255, P < 0.05). This discrepancy is caused by the 

 low numbers of age 1 -i- fish collected in November 

 (14) and December (24). Length-frequency histo- 

 grams (Fig. 1) also show that age l-i- males are 

 larger than females, whereas length distributions are 



Table 2. — Instantaneous growth rates of Oligocottus snyderi males 

 and females in their first (age O-i-) and second (age 1-t-) years of 

 growth. Rates were calculated for the intervals between the 1979 

 collections. Values in parentheses were calculated with all in- 

 dividuals included in the age O-i- cohort (see text). 



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