compare means among three or more groups (Rem- 

 mington and Schork 1970). Wilcoxon sum of ranks or 

 Kruskal-Wallis tests were used to compare indices 

 (Sokal and Rohlf 1981). Regression lines were com- 

 pared using techniques in Neter and Wasserman 

 (1974). 



Results and Comparisons 



Age, Growth, and Condition 



Young-of-the-year splittail appeared in samples in 

 late May 1980 and early June 1981 with a mean of 32 

 mm SL in both years (Fig. 2). Lengths ranged from 23 

 to 54 mm. The back-calculated length for scale for- 

 mation was 22 mm. Splittail grew at about 20 mm/mo 

 through September, then that rate decreased to <5 

 mm/mo through February. In March fish began to 



grow again and added about 10 mm/mo during the 

 next growing season. During the remaining 3 yr, fish 

 added 5-7 mm/mo in length. These results were cor- 

 roborated by back-calculating fish length from scales 

 (Table 1). Annuli were formed in March 1979 and in 

 late February 1980 in most specimens. Back- 

 calculated growth rates were similar within the first 

 and second age groups in 1979 and 1980 [age group 

 0:F= 2.78 < F (095;212) ; age group 1:F= 0.8 < F (095 . 2 

 18) ] but differed in the third age group \F = 20.7 > 

 F (095;2 lfi) j. Growth increments determined from back- 

 calculation also were not significantly different 

 between drought years (1976-77) and wet years 

 (1978-80) in the first two age groups (age group 0: t = 

 0.2 < t 095 ; age group 1: t = 1.0 < t 095 ). These growth 

 rates are similar to those found by Caywood (1974) in 

 the upper Delta. The largest fish encountered in this 

 study was 387 mm SL, which is approximately the 



February 1979 

 n=337 



,_ 10 "1 November 197 



CD n=147 



I ° K — r- 



_5 10 1 February 1980 

 z I n=166 





Standard length (mm) 

 FIGURE 2.— Length (SL) frequency histograms of splittail samples, Suisun Marsh, Calif., 1979-81. 



649 



