OVIPOSITION SITE SELECTION AND AVOIDANCE OF FISH BY STREAMSIDE SALAMANDERS (AMBYSTOMA-BARBOURI)

The effect of fish (Lepomis cyanellus) on distribution of egg masses of the streamside salamander (Ambystoma barbouri) was studied in a Kentucky stream. Although adult salamanders are not vulnerable to fish, larvae are extremely vulnerable; natural selection should favor adult oviposition behavior that minimizes contact between hatchling larvae and predators. In 1987, stream pools without fish had significantly higher densities of salamander eggs than did pools with fish. Between 1987 and 1988, fish in our study pools were killed by stream drying; this created a natural experiment addressing the effects of fish presence on adult oviposition behavior. In 1988, the new fishless pools had significantly more eggs in them than they had in 1987 when they contained fish. In contrast, a comparison of 1987 fishless pools with these same pools in 1988 did not show a similar increase in egg densities. Complete stream surveys in 1987 and 1988 indicated that fishless pools contained significantly greater densities of eggs and egg masses than did riffles or runs. Thus, pools without fish appear to be the preferred stream habitat for adult salamander oviposition. Competition for oviposition sites (rocks) did not appear to influence any of the comparisons. Because eggs are deposited such that fish cannot feed on them, our field surveys of egg masses suggest that selective oviposition by female streamside salamanders facilitates streamwide fish-salamander coexistence.