The Early Life History of the Guadalupe Bass: Lessons for Culturing a Threatened Species

Abstract

AbstractGuadalupe Bass Micropterus treculii fingerlings are produced at the A. E. Wood State Fish Hatchery in San Marcos, Texas, and stocked into streams draining the Edwards Plateau in central Texas as part of a conservation program to restore threatened populations and combat hybridization with Smallmouth Bass M. dolomieu. Despite an intensive conservation effort, much of the early life history (including morphological development and first feeding characteristics) required for the intensive production of Guadalupe Bass is unreported in the mainstream literature. A better understanding of this critical period may improve culture practices, fingerling production, and management efforts. We documented spawning and early developmental characteristics and milestones over a temperature range of 20–24°C and the prey composition of Guadalupe Bass in a hatchery setting. Eggs and fry were photographed under a microscope and observed in culture tanks and ponds from initial stocking to fingerling harvest. A dominant‐male, polygynous spawning structure was confirmed. Egg incubation (28–29 growing degree‐days), larval development, yolk depletion, swim‐up, and life stage transition proceeded faster at higher temperature. Eggs (mean diameter, 2.1 mm), fry (mean hatchling TL, 4.7 mm), and yolk reserves (mean hatchling yolk volume, 2.02 μL) were larger than reported for Largemouth Bass M. salmoides. Normally developed fry commenced exogenous feeding on a variety of zooplankton soon after swim‐up (120–144 h posthatch and 6.95–8.05 mm TL at 23.4°C), while yolk was still present, and consumed progressively larger aquatic invertebrates over time. Swim‐up fry with a range in gape width of 0.75–0.89 mm readily consumed brine shrimp Artemia spp. nauplii as first feed. Guadalupe Bass appear to be a relatively pliable species, and current culture practices are generally sound. The observations presented can be used to refine culture and management practices.