The effects of sunfish on spotted salamander oviposition, hatching time, and larval survival

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Introduced species have negative effects on amphibian populations by reducing local recruitment and consuming larvae before metamorphosis. Fish can naturally colonize ponds periodically because of flooding and connectivity with river floodplains. However, many fish introductions have been intentional for commercial, recreational, and biocontrol purposes. In southeast Missouri (USA),Ambystoma maculatumwill attempt to breed in ponds even if introduced fish (Lepomisspp.) are present. We predicted that fish would have negative effects on salamander oviposition, hatching success and timing, and larval survival. In order to evaluate the effects of introduced fish onA. maculatumacross life stages, we conducted pond surveys and a series of mesocosm experiments. Using field surveys,A.maculatumdeposited significantly fewer eggs in ponds with fish. In short-term mesocosm experiments, we found that hatching time was not significantly affected by deposition site or fish cues, however, hatching success was lower for eggs deposited in fish ponds. NoA. maculatumlarvae survived when fish were present, regardless of egg deposition site. Our study is important because we found that, unless a female avoids depositing eggs with fish, one fish species can have profound effects on larval amphibian persistence. Therefore, small-scale fish introductions for recreation can act as a potential source for reduced recruitment and an increased risk of local extinction.