SPAWN 
LARGE MATURE OVA 
1.1-L5mm 
INTERMEDIATE YELLOW OVA 
.6—-1.Omm 
SMALL WHITE OVA 
1-—.5mm 
PERCENT DIFFERENTIATED OVA 
a 
{e) 
4 
WwW 
oO 
So 
— 
oO 
°o 
NOVEMBER 
DECEMBER 
JANUARY 
FEBRUARY 
MARCH 
APRIL 
AY 
JUNE 
JULY 
AUGUST 
Fig. 5—Differentiation of ova during the year, as inferred 
from data in Table 1. 
cent were in the small-ova category, 25 percent inter- 
mediate, and 11 percent in the large-ova group. 
The general pattern of differentiation during the 
spring months was a decrease in the percentage of small 
ova and an increase in the percentage of large ova 
(Table 1). The number of intermediate ova after 
April remained approximately the same (Fig. 5). 
Essentially the same pattern was found in Etheostoma 
gracile by Braasch & Smith (1967:6), but they also 
found a general increase in the relative proportion of 
intermediate ova present. 
The ovaries of the dusky darter gradually increased 
in size during the prespawning period (17 percent of 
the standard length of a September specimen, 21 per- 
cent in a March specimen, 27 percent in an April 
specimen, 35 percent in a May specimen, and 34 per- 
cent in a June specimen) as the eggs developed. The 
gradual enlargement of the ovaries coincided with en- 
largement of the testes in the male; both showed most 
pronounced increases in April and reached their greatest 
sizes in May and June. The ovaries of postspawning 
females were greatly reduced in size. 
Between 500 and 2,000 ova were produced by one 
female in one season, but only about 10 percent reached 
mature size. The number of mature eggs in specimens 
examined ranged from 80 to 196. Although an actuai 
count of eggs laid by a dusky darter could not be made, 
other studies on darters indicate that they normaily lay 
the total complement of mature eggs (Fahy 1954:166; 
Winn 1958a:181). A relationship exists between the 
size of the female and the number of eggs produced, the 
larger females producing more eggs. 
Mature ova tended to be concentrated near the 
center of the ovary and, in preserved specimens, were 
easily detached from the surrounding tissue. 
Following the act of spawning, unlaid eggs atrophied 
and were ultimately absorbed. The ovaries gradually 
shrank and lost the yellow-orange color, A quiescent or 
recovery stage followed the absorption of the egg ma- 
terials, during which time no egg development was 
detectable. 
As spawning time approached, the genital papilla 
enlarged, becoming tubular, and the breeding colors 
intensified. The breeding female became more intensely 
colored; the yellow color of the dorsum became brighter, 
the undersides remained white, and the lateral blotches 
appeared more intense. While the melanophores of 
the breeding male were jet black and interspersed with 
numerous blue-green iridocytes, melanophores of the 
breeding female were brown in color and iridocytes 
were sparse. The striking yellow of the dorsum resulted 
from concentrations of yellow pigment along the pos- 
terior edge of each scale. 
Spawning 
The dates of spawning and duration of the spawning 
period appeared to vary from year to year, probably 
as a result of climatic and river conditions. In 1967, 
juveniles collected on August 4 averaged 30 mm in 
standard length, and to have attained such a size the 
eggs were probably laid sometime in July. 
In 1968, darters could not be obtained in June 
because of high water, but on July 7 six adult females 
were captured. One appeared to be in an immediate 
postspawning condition and five contained large num- 
bers of mature ova, indicating that they had not yet 
spawned. It is probable that the peak of the 1968 
spawning was in early July. However, a 26-mm young 
collected on July 7 was the result of a spawning perhaps 
as much as a month earlier. 
In 1969, peak spawning occurred between May 27 
and June 8. Females collected on the first date were 
filled with mature ova; most of those collected on June 
8 had spawned and were without mature ova. On both 
dates both males and females were very abundant in 
the shallower portions (1-3 feet deep) of the gravel 
raceway, the apparent spawning habitat. 
The Embarras River was subject to several floods 
during the study period, and the unusually deep 
channels, inundated floodplains, and turbid water could 
have hindered spawning. The comparatively late 
spawning in 1968 (and perhaps also in 1967) is 
assumed to have been late because of the June floods. 
It appears that spawning in June is the preferred time 
for the species at this latitude. 
Reproductive behavior is varied in darters, and the 
relative complexity is believed to be correlated with the 
extent of specialization. Little information is available 
on the mating behavior of Percina, the principal pub- 
lished studies being those for P. peltata (New 1966; 
Loos & Woolcott 1969), P. notogramma (Loos & 
Woolcott 1969), P. caprodes (Winn 1958a, 1958: 
192-194), P. maculata (Petravicz 1938; Winn 19584, 
1958b:194), and P. copelandi (Winn 1953, 19584, 
1958b:202). 
Although actual spawning was not observed, some 
