Metabolic rate and natural history of Ozark cavefish, Amblyopsis rosae, in Logan Cave, Arkansas

Synopsis

We investigated the effects of mass, season, and activity on oxygen consumption of the federally threatened Ozark c/avefish, Amblyopsis rosae, at Logan Cave National Wildlife Refuge, Benton County, Arkansas. We used an acclimatization protocol to measure in-situ metabolic rates. There was a significant effect of mass on the metabolic rate of Ozark cavefish and this relationship differed significantly among seasons. We observed a positive relationship between mass and oxygen consumption during summer and autumn but a negative relationship for winter and spring. There was a 1°C water temperature change between summer/autumn sampling and winter/spring sampling, but it is not likely temperature alone accounted for seasonal variation in mass-oxygen consumption relationships. Activity in the respirometer did not vary significantly among seasons and was not correlated with fish mass or time of day. Seasonal relationships between mass and oxygen consumption may therefore reflect alterations in environmental conditions (i.e. food availability, ambient dissolved oxygen), condition, changes in susceptibility to handling stress, or may reflect low numbers of fish tested. Natural history observations were made throughout the study. Four females were seen in late August with ova visible in the body cavity. On 20 June 1996 we first observed five small cavefish (approximately 10 mm TL) in a pool just upstream of the sinkhole entrance that were likely less than a month old. One large adult (55 mm TL) was seen in the same pool with the young fish for six weeks, until two small fish were displaced by a storm event. Although this does not provide a clear sign of parental care, it does suggest that cannibalism is not always the rule for this species as previously suggested.