76 James C. Widlak and Richard J. Neves 



Reproduction 



Darters less than 35 mm long could not be sexed by external char- 

 acteristics or by gonadal examination and were considered juveniles. 

 Adult males and females were easily distinguished by their sexual di- 

 chromism. Males in breeding condition were readily distinguishable from 

 non-breeding males by body coloration. Non-breeding males lacked 

 coloration on fins and pelvic region and were similar in appearance to 

 non-breeding females. Their testes were small and translucent. In con- 

 trast, the vertical fins of breeding males were edged with a band of dark 

 green and inner bands of white and bright red. The basal portion of 

 these fins was dusky gray. Paired fins were yellow or greenish-yellow 

 basally and edged with bright red. The pelvic region was dark green and 

 the abdomen creamy white to yellow. Body coloration varied from light 

 tan to dark brown, with bright red lateral spots. Testes were enlarged, 

 creamy white, and opaque. Bright coloration was apparent on males 

 throughout the year, but enlargement of testes was not observed until 

 March. Males in spawning condition were collected throughout spring 

 and summer, but testes were reduced in size in all fish collected in Sep- 

 tember. About 72% of age I males, all those longer than 40 mm, were 

 sexually mature. 



Females were less colorful although breeding females were gener- 

 ally darker than others. They lacked the bright coloration on the fins 

 and body; vertical and paired fins were heavily spotted with black. The 

 body was darker than that of the male and lacked red spots, but the 

 caudal base of both sexes had prominent white spots. All females col- 

 lected between September and mid-February had resting ovaries, and 

 ova development first became apparent in March. By May the ovaries 

 contained both maturing and fully ripe ova. Females also reached sex- 

 ual maturity at age I; 56% of age I females were in spawning condition. 

 The smallest ripe female (42 mm long) was collected in July 1981. 



Sex ratios of redline darters at the study site were strongly skewed 

 in favor of males. The overall ratio of males to females was 2.7:1, a 

 significant deviation from a 1:1 sex ratio (x 2 = 146.4, p < 0.005). Sea- 

 sonal differences or sampling biases may have contributed to the appar- 

 ent temporal changes in distribution of the sexes. During summer, the 

 sex ratio averaged 2.5:1, since both sexes were present in riffles for 

 spawning. As females moved out of shallow riffle areas after spawning, 

 the sex ratio increased to 5:1 (September) and then returned to 2.5:1 as 

 age individuals were recruited into the population. It is likely that 

 electrofishing was selective for males. Darters shocked in swift riffles 

 were swept into the water column and easily netted, while those in other 

 areas often remained on the bottom and were more difficult to collect. 



Total egg complements of 85 female redline darters ranged from 50 



