Another site, 72 mile north of Greenup, was similar 
but had more extensive stretches of gravel Griese 
METHODS 
Minnow-seine collections were made at 2-week in- 
tervals from August to November 1967 and at irregular 
intervals throughout 1968, 1969, and 1970 as material 
was needed to obtain information for all seasons. A 
total of 45 collecting and observation trips was made 
to the study area between August 4, 1967 and September 
‘0, 1970. 
In the field notes were made on the river and weather 
conditions, pigmentation of the darters, and the habitats 
in which specimens were captured. During the spring 
and early summer months, water and air temperatures 
were routinely recorded. 
Occasionally various habitats were sampled to deter- 
mine habitat preferences, but most efforts were concen- 
trated in the channels, where the species was most easily 
obtained. During the winter months numerous habitats 
were sampled in an effort to find the overwintering habi- 
tat of the species. Obtaining specimens during the win- 
er and during periods of high water proved difficult, 
and no specimens were secured during January or De- 
cember. Specimens collected during the 3-year study 
period were distributed as follows: February, 1; March, 
[5 April, 1; May, 35; June, 50; July, 19; August, 16; 
september, 75; October, 25; November, 15. 
Supplemental specimens in the Illinois Natural His- 
ory Survey ichthyological collection provided informa- 
ion to help fill the gaps resulting from the difficulty of 
ollecting specimens during the cold months. A total 
f 440 preserved specimens was examined in the study. 
Inly the 238 specimens collected and examined from 
he study area were used for the growth measurements, 
ind only collections from the study area made during the 
tudy period were used in discussions of population char- 
cteristics. 
Specimens were dropped into 10-percent formalin as 
oon as they were captured. Later they were measured, 
heir age and sex were determined, and details of color 
attern and the presence of external parasites were noted. 
Jnless stated otherwise, all measurements given in the 
ext are standard lengths. Age determinations were 
nade by counting annuli on scales removed from just 
bove the lateral line below the junction of the spinous 
nd soft dorsal fins. 
Some specimens from each collection were dissected 
nd examined for stomach contents, the presence of 
lacroscopic parasites in the alimentary canal, and gonad 
ondition. Gonads were measured, and a few were 
lotted dry and weighed on a chain balance. Ovaries 
lowed significant increases in weight as the spawning 
rason approached, but testes were too small to be 
reighed accurately. Ova were counted in several fe- 
tales. The stomachs of some potential predators of 
» phoxocephala were examined for darter remains. 
' 
5 
Living P. phoxocephala specimens were brought to 
the laboratory several times during the study to observe 
their behavior in aquaria. When it became evident that 
aquarium-held captives were not going to spawn, eggs 
and sperm were stripped from ripe adults in several 
unsuccessful attempts to obtain embryos. 
On October 17, 1967 a quantitative sample was tak- 
en / mile north of Greenup with an electric seine 
(Page & Smith 1970:5) to estimate the composition 
of the fish fauna at the site and the number of individuals 
per areal unit of habitat. 
HABITAT AND ASSOCIATED SPECIES 
In the Kaskaskia River of Illinois, Thomas (1970:7) 
found P. phoxocephala to be most abundant in the 
middle river, rare in the headwaters, and occasional in 
the lower river. The moderate-to-fast current over grav- 
el and the high riffle-to-pool ratio in the middle river 
were considered responsible for the increased abundance 
in the middle river (ibid.:7, Loe 
In Ohio, Trautman (1957:545) found P. phoxoce- 
phala to be most common over “extensive bars and 
rifles which contained clean sand and small gravel that 
was almost free of silt.” In Kansas, the species occurs 
“in swiftly-flowing, shallow water, over a bottom of loose 
gravel or of bedrock littered by stones” (Cross 1967: 
292). In the portion of the Embarras River used for 
both the P. sciera and the P. phoxocephala life-history 
studies, the two species were generally found occupying 
the same habitat, the relatively shallow, gravel-bottomed 
portion of the river channel. P. phoxocephala was 
somewhat less restricted to gravel than was P. sciera and 
occasionally was taken in the channel over sand. 
Collections from elsewhere in Illinois have revealed 
more plasticity by P. phoxocephala in habitat choice 
than was exhibited by the population in the Embarras 
River. Specimens have been taken from small-stream 
rifles, large rocky riffles, and even sandy pools of large 
rivers. However, the abundance of P. phoxocephala in 
the middle Embarras River indicates the optimal habitat 
for the species to be the gravel-bottomed raceways of 
medium-sized rivers with moderate current. 
Juvenile P. phoxocephala remained in the spawning 
habitat (shallow riffles along gravel bars) several weeks 
after hatching. At approximately 1 month of age the 
young darters moved out into the deeper water of the 
channel. 
Page & Smith (1970:6) summarized the species di- 
versity in a section of the Embarras River blocked off 
with minnow seines and sampled with an electroseine. 
They found P. phoxocephala to be the second most com- 
mon darter and the 13th most common species of fish; 
it constituted 0.5 percent of the total fish population. 
Collections taken in the other study areas over a 3-year 
period tend to substantiate this numerical relationship 
between P. phoxocephala and associated species. 
The species most commonly associated with P. phoxo- 
