DEVELOPMENT AND GROWTH 
Development 
The smallest specimen available (18.7 mm standard 
length, 22.4 mm total length) was collected in the study 
area on June 23, 1970. Presumably a product of the 
yeak spawning period of June 5—12, the fish was esti- 
nated to be 2 weeks old. Its body proportions (Fig. 6) 
vere essentially those of the adult, except that the head 
ind eyes were large in relation to the size of the body. The 
1ead length was 32 percent of the standard length versus 
in average of 27 percent of the standard length for 10 
dults. Squamation was nearly complete; the only areas 
acking scales were the cheeks, opercles, nape, and the 
terior two-thirds of the belly. 
Fig. 6—Two-week-old Percina phoxocephala 19 mm in 
andard length. 
The pigmentation of this small specimen was weak 
ut showed the pattern characteristic of adults. The 
orsal spots, lateral blotches, band around the snout, 
nd spots in the fins of adults were represented by con- 
entrations of melanophores. Yellow pigment in the 
yinous dorsal fin indicated the beginning of the orange- 
llow band characteristic of the adult P. phoxocephala. 
he lateral line was complete and fully pored. The head 
inals were nearly complete except for a wide medial 
‘terruption in the supratemporal canal. 
Slightly larger specimens (21—23 mm) were almost 
entical in morphology to the smallest specimen al- 
ough some had incomplete lateral lines. The special- 
ed midventer scales were discernible on males at about 
}mm, and the orange band was present in the spinous 
rsal fins of 25-mm specimens. At 27 and 28 mn, 
ales were lacking only on the nape, and most individ- 
ls had completed supratemporal canals. Scales were 
t present on the nape until specimens reached a stan- 
rd length of 33 mm. 
The pigmentation of P. phoxocephala continued to 
rken throughout life. Older individuals in any partic- 
ar collection always were slightly darker than the 
unger ones, 
‘owth 
Standard length frequencies of specimens of P. phoxo- 
phala taken from the study area indicated that rapid 
wth occurred during the first few months of life and 
> Srowth rate diminished with age. The growth curve 
Samples taken from the study area (Fig. 7) showed 
continuous average increase in size except during 
‘tober and November, when the mean standard lengths 
two samples averaged less than those of the Septem- 
9 
ber sample. This autumn reversal, which also occurred 
in the study of P. sciera, is assumed to be the result 
of an emigration of the larger fishes from the compara- 
tively shallow raceways (most efficiently sampled) to 
the deeper channel as winter approached. 
Inasmuch as the average size of 12-month-old P. 
phoxocephala specimens was 46 mm, the young fish at- 
tained half of their Ist year’s growth in about 2 weeks. 
Etheostoma gracile “attained almost half of their Ist 
year’s growth in about 1 week” (Braasch & Smith 1967: 
9). The growth rate of the Embarras River P. phoxo- 
cephala population was faster than that found for the 
Kaskaskia River population (Thomas 1970:14) and 
much more rapid than that of the population in Boone 
County, Iowa (Karr 1963:232). At the end of 1 year’s 
growth, the Embarras River population averaged 45.7 
mm in standard length; the Kaskaskia River population 
averaged 45.3 mm in total length; and the Iowa popu- 
lation averaged 34.1 mm in total length. 
There is little indication of sex influence on size. 
Ol 2+ (28) 
—_C__ 1+(57) 
YEARS 
—Cin_ 12 mos. (22) 
on 5 mos. (10) 
fin 4 mos. (18) 
—CH _ 3 mos. (18) 
ml 2 mos. (9) 
MONTHS 
tin_ | mo. (18) 
On 2 wks. (I1) 
O 10 20 30 40 50 60 70 80 
STANDARD LENGTH, mm 
Fig. 7.—Growth of Percina phoxocephala in millimeters of 
standard length. For each sample the horizontal line represents 
range; the vertical line, mean; the hollow rectangle, one stan- 
dard deviation to either side of the mean; and the black rec- 
tangle, two standard errors to either side of the mean. Numbers 
in parentheses are specimens measured. Samples of 1- and 2- 
year-old fish included Embarras River specimens from outside 
the study area. 
