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PALATABILITY OF NORTHWESTERN AMPHIBIAN LARVAE TO NATIVE AND INTRODUCED FISHES: IMPLICATIONS FOR CONSERVATION
Citation:
Pearl, C. A., M. J. Adams, A V. Nebeker, AND R. B. Bury. PALATABILITY OF NORTHWESTERN AMPHIBIAN LARVAE TO NATIVE AND INTRODUCED FISHES: IMPLICATIONS FOR CONSERVATION. Presented at Joint Wildlife Society/American Fisheries Society Conference, Portland, OR, February 14-16, 2001.
Description:
Non-native gamefish have been introduced throughout the Pacific Northwest, representing one of the most marked alterations of wetlands used by native amphibians. In laboratory tests, we examined susceptibility of larvae of 3 salamander and 3 frog species to selected species of native and introduced fish found in the Willamette Valley. Larvae of the newt Taricha granulosa possess dermal tetrodotoxin and were consumed less often than similarly-sized larvae of the salamanders Ambystoma macrodactylum and A. gracile. These test results suggest that young newts possess skin toxin at even early developmental stages, and that the parotoid glands in larval A. gracile are either undeveloped or not sufficient to deter fish predators in laboratory environments. Introduced Rana catesbeiana larvae were consumed less often than either of two native frogs, Rana aurora or Hyla regilla. This evidence suggests that both native frogs are palatable to all fish tested. Contrary to results in California, non-native mosquitofish (Gambusia affinis) were not major consumers of native frog larvae, which may relate to their small gape size and the size of amphibian larvae used in trials. Of all fish species tested, bluegill (Lepomis macrochirus) appeared to demonstrate strongest preference for a palatable native anuran rather than the introduced bullfrog larvae. This selection of prey combined with potential for bluegill to indirectly facilitate increased larval survivorship in bullfrogs suggest that bluegill should be considered among the most harmful of the introduced fishes to native amphibians in the Willamette Valley. Fish introductions have dramatically altered lower elevation waters, and mitigative measures should be considered (e.g., occasional draining of ponds or creation of semi-permanent waters) where conservation of wetland-breeding amphibians is an objective.