6 
for rooted plants was noted by Trautman (1957:536); 
however, no rooted plants were present in our study 
area, and the species was abundant. Elsewhere in its 
range, this darter is reportedly common in habitats free 
of aquatic vascular plants (Blair 1959:10; Gerking 
1945:85; Suttkus & Ramsey 1967:140). 
Lotic habitats in moderate-sized creeks to large 
rivers are occupied by P. sciera. In the study area 
streams only 6-8 feet wide contained the species at 
least in the summer months. Records are also available 
for such large streams as the Wabash, Ohio, and 
Mississippi rivers. 
An opportunity to quantify the relative abundance 
of associated species was available with the use of the 
electric seine in the section of river blocked off with 
seines, and it provided a concept of the ecological com- 
munity of which the dusky darter was a component. 
Within the enclosed 507 square yards of water averaging 
1 foot in depth, 750 fishes of 18 species were collected. 
The minnows Pimephales vigilax, Notropis whipplei, 
and Notropis spilopterus were clearly the most abundant 
associated species (Fig. 3), their combined totals com- 
prising 78 percent of the total number of fish present. 
Other frequent associates were the minnows Phena- 
cobius mirabilis, Ericymba buccata, and Campostoma 
anomalum, and the hog sucker Hypentelium nigricans. 
Fig. 3.— Relative abundance of fish species associated 
with Percina sciera as determined by a quantitative sample 
from the Embarras River near the study area. 
Percina sciera ranked seventh in abundance (2.5 
percent of the total number of fish) and was more than 
five times as abundant as the second most abundant 
darter, Percina phoxocephala. Other darters found in 
the study area were Etheostoma blennioides, E. caeru- 
leum, E. nigrum, Ammocrypta pellucida, Etheostoma 
spectabile, Percina maculata, P. caprodes, Etheostoma 
asprigene, E. chlorosomum, E. gracile, E. flabellare, and 
E. histrio. 
REPRODUCTION 
Reproductive Cycle of the Male 
Most males were sexually mature and ready to 
spawn the first spring following their hatching. Of seven 
males approximately 1 year old collected May 27, 
1969, one 48 mm in standard length had undeveloped 
testes and no indication of breeding coloration, but six 
others more than 55 mm in standard length were more 
darkly pigmented and appeared ready to spawn at that 
time. However, yearling males were smaller and had 
less intense breeding colors than older males and were 
probably at a disadvantage in attracting females. 
As the breeding season approached, an over-all 
duskiness masked the normal olive-green ground color, 
and the row of lateral blotches became obliterated by 
blackish vertical bands which were narrowly but dis- 
tinctly separated from each other. The top of the head, 
belly, breast and fins also darkened, and a dark blotch 
developed on the posterior portion of the spinous dorsal 
fin. A faint, pale orange band appeared on the distal 
part of the spinous dorsal fin. 
Each scale on the dorsal half of the body could be 
seen, with magnification, to be sprinkled with several 
brilliant blue-green iridocytes that gave the fish an 
iridescence. Melanophores concentrated on the sub- 
distal portion of each pelvic fin and the soft dorsal fin 
to form a discrete, thin, pigmented band margined 
distally by a transparent band (Fig. 4). 
In our study period, the earliest specimen that 
showed pronounced breeding coloration was a 2-yeat- 
old male collected on April 28. He was darkly pig- 
mented over the entire body and had developed the 
dark vertical bands and dark blotch at the posterior 
base of the spinous dorsal fin. The height of breeding 
coloration was reached in late May, when large males 
lost the vertical bands and became almost uniformly 
black. 
Breeding males did not develop tubercles, and ac- 
cording to Collette (1965:577) none of the species of 
the subgenus Hadropterus has breeding tubercles. 
The development of the testes consisted of a gradual 
increase in size until spawning and then underwent 4 
sharp decrease. In a September-collected male, the 
length of one testis was 10 percent of the standard 
length; in a March specimen, 13 percent; in May and 
June specimens, 14 percent; but in a July specimen, 
only 8 percent. 
Reproductive Cycle of the Female 
Like males, females usually were sexually mature 
at 1 year of age but, unlike males, they were ready to 
spawn at a smaller size (approximately 40 mm il 
standard length). Yearling females collected in May 
