Food Habits of the Federally Threatened Leopard Darter (Percina Pantherina)
Williams, Lance R., Williams, Marsha G., Grubh, Archis R., Swinehart, Elizabeth E., Standage, Richard W., The American Midland Naturalist
We examined food habits of the federally threatened leopard darter in six rivers in southeastern Oklahoma and southwestern Arkansas using guts collected from 1994 to 1997. The families Baetidae and Chironomidae were the most common food items selected by leopard darters. In general, leopard darters are selecting food items that are relatively common in the environment; thus, food availability may not be a factor limiting abundance.
The leopard darter, Percina pantherina, is a U.S. federally threatened species endemic to the Little River system in southeastern Oklahoma and southwestern Arkansas (Zale et al., 1994; Williams et al., 1999). Factors limiting the recovery of the leopard darter include, but are not limited to, water quality degradation caused by timber and agricultural industries (Eley et al., 1975; Rutherford et al., 1992), drought (Williams et al., 1999), poorly constructed road crossings (Toepfer et al., 1999; Schaefer et al, 2003) and impoundments (Zale et al., 1994). Ultimately, availability of suitable habitat for growth and spawning is likely the greatest limiting factor for a species like the leopard darter that lives approximately 18 mo and spawns once during its lifetime (James et ai, 1991; Zale et al., 1994).
Since its description (Moore and Reeves, 1955) and subsequent listing as threatened (U.S. Fish and Wildlife Service, 1978), the leopard darter has received considerable attention from researchers. Despite extensive surveys to document its distribution (Zale el al., 1994), population size and viability (Williams et al., 1999; Toepfer et al., 2000), life-history (James et al., 1991) and genetic structure (Echelle et al., 1999), no comprehensive diet study has been conducted because of the lack of available specimens. From 1994 to 1997, 131 leopard darters were collected from seven sites (five rivers) to provide tissue samples for a survey of genetic variation (Echelle et al., 1999). Because we had to sacrifice specimens to obtain the tissues necessary for genetic analysis, we also dissected and preserved the guts of each fish for a diet survey. Prior to our study, only two previous reports of diet had been published and from only very limited sample sizes, seven (Robison, 1978) and 19 (James et al., 1991) specimens. In this study, we examined the guts collected during the genetic survey (Echelle et al., 1999) to describe diet of the leopard darter. Our study represents the most comprehensive analysis of diet for this species to date, a potentially critical component to any successful recovery plan.
METHODS AND MATERIALS
From October 1994 to October 1997, a total of 131 leopard darters were collected from seven sites in the Little River basin (Fig. 1 ). Of those original collections, we examined 122 guts. Specimens from Big Eagle Creek were not examined for diet because they had been used in a captive swimming speed experiment (Toepfer et al., 1999) and were, thus, being fed a commercial diet prior to dissection. All other specimens were preserved in liquid nitrogen in the field. In the laboratory, fish were thawed and guts (esophagus, stomach, and small intestine) removed and stored in 70% ethanol solution for permanent storage. Gut contents were examined for each fish specimen and contents identified (usually to family) and counted (Williams et al., 2003).
We found a total of nine families of macroinvertebrates representing six orders in the 122 leopard darter guts that were examined, 23 of which were empty (Table 1). The most common families in guts were Baetidae (at all sites), Chironomidae (at all sites except Robinson Fork) and Heptageniidae (all sites). A number of taxa were found in guts at only one site (Table 1), with the majority from Mountain Fork River which had the greatest number of guts examined.
Several recent studies indicate that leopard darter populations may be relatively secure at present (Williams et al. …