Masters Theses

Date of Award

6-1984

Degree Type

Thesis

Degree Name

Master of Science

Major

Zoology

Major Professor

David A. Etnier

Committee Members

Mary Ann Handel, Richard Strange

Abstract

The ecology and life history of one of three extant populations of the yellowfin madtom, Noturus flavipinnis Taylor were studied, primarily by direct observations. Snorkeling at night with under­water flashlights was the most successful technique, as the species is nocturnal.

The yellowfin madtom was commonly found in shallow pools in Citico Creek. It inhabits a 3.6 km stretch of the creek from a small dam at creek km 13.8 to creek km 17.4. The size of this localized population was estimated by tag-recapture methods to be 549 individuals (312-1453, modified Schnabel). Recapture of six individually paint-tagged fish indicated that the population exists as separately isolated subpopulations, with little or no movement between pools.

Length-frequency histograms indicated that the yellowfin madtoms in Citico Creek may reach an age of three years, and that males attain a slightly larger average size than females. The largest specimen captured was 115 mm SL.

Initiation of nesting behavior is probably triggered by water temperatures of 20-23° C, and nests were found as early as 29 May and as late as 8 July. Newly fertilized eggs averaged 3.4 mm in diameter and were deposited beneath large, flat rocks. Males were observed guarding developing embryos and larvae. Clutch sizes averaged 89 embryos for two reproductive seasons, and the ovaries of four female N. flavipinnis contained a mean of 177 ripe ova. Therefore, it is assumed that the species is polyandrous.

Ovarian eggs are separable into three distinct size classes. The mature ova from five females examined were 2.5-3.3 mm in diameter. Individual N. flavipinnis are not reproductively mature until their third summer of life (age two), and probably only spawn twice during their lifetime.

Freeswinming juveniles were observed in the Citico Creek population as early as August, and appeared to prefer smaller size substrate particles than adults. One recently hatched individual was 8.1 mm SL, and five young-of-the-year had reached an average standard length of 37.8 mm by November.

A total of 40 taxa representing sixteen families of organisms were identified from the guts of twelve N. flavipinnis. The diet is almost exclusively insect larvae, with dipterans, ephemeropterans, plecopterans, and trichopterans being the most important prey types consumed. The yellowfin madtom is probably mostly nocturnal and opportunistic in its feeding behavior.

Although the Citico Creek population of N. flavipinnis appears to be relatively healthy, it is dangerously small and extremely localized. This fact, coupled with the possible decline of the other two known populations, warrants continued protection (and possibly even upgrated from Threatened to Endangered) of the species.

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