Life History of Pinewoods Darter 
9 
Age and Growth. — Apparently one mark (annulus) was formed on 
scales per year. Minimum marginal increments (Bagenal and Tesch 
1978) in 1-year-old fish occurred during March and April (Table 2). 
Although sample sizes were small, 2- and 3-year-old fish also had small 
scale marginal increments during spring (Table 2). Consistency of time 
of mark formation between age classes, strong relationship between fish 
length and scale size (r = 0.97), and increasing fish size with increasing 
number of scale marks (Table 3) indicated that marks on scales were 
valid annuli. Annuli exhibited many of the characteristics described by 
Lachner et al. (1950) for other darters, and annuli were apparent in both 
the anterior and lateral fields (Fig. 3). Although some annuli were faint, 
only one of the 313 fish had unreadable scales. 
Because of the extended spawning season and the rapid growth of 
young, growth by month of the various year classes was difficult to 
distinguish in a length-frequency graph (Fig. 4). Earliest young-of-the- 
year (age class 0) recruits were first collected in June and July and 
“recruitment” continued into September (Fig. 4). Fish <15 mm SL were 
not efficiently collected by our gear. Late-spawned young-of-the-year 
appeared as a minor component from October through December. In 
any given month each age class exhibited a wide range of sizes, presum- 
ably reflecting the long spawning season (Fig. 5). Our data also indi- 
cated a broad overlap in sizes of age classes, particularly age classes 1 
and 2 in October and all three age classes in January (Fig. 5). The two 
largest males (60 mm SL) were collected in September but differed 
greatly in age (17 and 29 months). The largest female was 51 mm SL 
and 36 months old. 
Growth was most rapid during the first year. Males and females 
attained 58% and 66%, respectively, of their observed average maximum 
lengths (Table 3). During this year there were no significant sexual dif- 
ferences in growth rate (t = 1.32, df = 173, P > 0.05). However, in age 
classes 1 and 2 males grew significantly longer (t = 3.66, df = 91, P < 
0.005 for age class 1; t = 3.22, df = 33, P < 0.005 for age class 2) (Fig. 6). 
In most collections males were larger than females of the same age (Fig. 
5). Significant differences also existed between males and females in 
weight-length relationships as indicated by analysis of covariance (F = 
12.38, df = 1,318, P < 0.05). Females were slightly heavier than males of 
the same length, with a weight-length relationship of WT = 8.1 x 10~ 6 
SL 3 23 , r = 0.98. Male weight-length relationship was WT = 12.6 x 10' 6 
SL 3 09 , r = 0.98. Because all fish were used to develop the weight-length 
relationships, some of the intersexual differences could be attributed to 
the females’ having a greater increase in body weight than do males 
during spawning (Fig. 2). 
