Secondary Production of Tiger Salamanders (Ambystoma tigrinum) in Three North Dakota Prairie Lakes

In three prairie lakes studied in 1981–82, larval tiger salamander (Ambystoma tigrinum) densities reached highs of 5000∙ha−1, maximum biomass (wet weight) was 180 kg∙ha−1, and maximum annual production was 565 kg∙ha−1. Within a given lake, overwinter survival of larvae varied markedly from year to year. Overwinter survival of larvae was excellent in Lake II; in spring 1981, densities were 800–1000∙ha−1. In 1982, no larvae overwintered in Lake II, and none overwintered in Lake I in either 1981 or 1982. In May 1981, larvae were large (mean weight of 150 g) and their biomass of 150 kg∙ha−1 was nearly as large as the maximum biomass of 160 kg∙ha−1 in late July of larvae from the year's cohort. This was in contrast with 1982 in Lake II and with both 1981 and 1982 in Lake I when there was an extremely low biomass in the spring, composed of many small larvae. The large larvae that overwintered in Lake II in 1981 did not prey on young-of-the-year larvae; their high densities may have actually reduced invertebrate predation on salamander larvae; in July, larval salamander densities of 5000∙ha−1 were the highest measured.