THE EARLY LIFE HISTORY AND FOOD HABITS OF HATCHERY-REARED GUADALUPE BASS Micropterus treculii  

The Guadalupe Bass Micropterus treculii is endemic to streams draining the Edwards Plateau in central Texas. Fingerling Guadalupe Bass are produced at the A. E. Wood Fish Hatchery, San Marcos, Texas and stocked into these streams to restore threatened populations and combat hybridization with Smallmouth Bass Micropterus dolomieui. Survival in fingerling rearing ponds has fallen in recent years for unknown reasons and meeting the fingerling stocking request is challenging. In addition to lower fingerling production, this low survival in ponds may lead to lost genetic diversity of stocked fingerlings.

While the life history and feed preferences of other Micropterus spp. are well described, much of the early life history of Guadalupe Bass is unreported. A better understanding of this critical period may improve hatchery culture practices, fingerling production and management efforts. Early developmental characteristics and milestones at 20 and 24^oC, deformity prevalence, and prey preferences of Guadalupe Bass were therefore documented in a hatchery setting. Eggs and fry were repeatedly photographed under a microscope and observed in culture tanks and ponds from fertilization to harvest of 38-mm fingerlings.

The egg incubation period was 61.1±4.4 h at 21.2^oC and 47.9±2.9 h at 24.0^oC (28-29 growing degree days). Similarly, larval development, yolk depletion, and swim-up proceeded faster at the higher temperature. A high prevalence of developmental abnormalities, particularly of the gape and heart chamber, were observed early in the production season. Preliminary genetic analysis suggests this was not related to parentage. Normally-developed fry commenced exogenous feeding on a variety of zooplankton soon after swim-up with no first-feed preference detected. Swim-up fry readily consumed Artemia nauplii in hatchery tanks, and Brachionus sp., Daphnia sp., copepods and chironomid larvae within 72 h of stocking in ponds. Maximum prey size increased as fry grew. These observations will be used to refine culture and management practices for Guadalupe Bass.