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

We investigated the effects of mass, season, and activity on oxygen consump tion of the federally threatened Ozark cavefish, Amblyopsis rosae, at Logan Cave National Wildlife Refuge, Benton County, Arkansas. We used an acclima tization protocol to measure in-situ metabolic rates. There was a significa nt effect of mass on the metabolic rate of Ozark cavefish and this relation ship differed significantly among seasons. We observed a positive relations hip between mass and oxygen consumption during summer and autumn but a nega tive relationship for winter and spring. There was a 1 degreesC water tempe rature change between summer/autumn sampling and winter/spring sampling, bu t it is not likely temperature alone accounted for seasonal variation in ma ss-oxygen consumption relationships. Activity in the respirometer did not v ary significantly among seasons and was not correlated with fish mass or ti me of day. Seasonal relationships between mass and oxygen consumption may t herefore reflect alterations in environmental conditions (i.e. food availab ility, ambient dissolved oxygen), condition, changes in susceptibility to h andling 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 obser ved 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 ad ult (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 n ot provide a clear sign of parental care, it does suggest that cannibalism is not always the rule for this species as previously suggested.