Graduation Year

2004

Document Type

Thesis

Degree

M.S.

Degree Granting Department

Biology

Major Professor

Philip J. Motta.

Keywords

fisheries, prey capture, plasticity, functional morphology

Abstract

(1) Hatchery-reared Florida largemouth bass, Micropterus salmoides floridanus, feed on inert pellet food while their wild counterparts capture elusive prey. Differences in levels of prey elusivity often mandate the use of alternate methods of prey capture and are accompanied by a related phenotypic change. (2) This study investigates (a) differences between the prey capture kinematics and strike modes of hatchery and wild juvenile Florida largemouth bass raised on pellets and live prey, and (b) whether elusivity-based variation in prey capture translates to a phenotypic and functional change during skull development. (3) Analysis of high-speed videography demonstrates that wild bass capture live prey with very rapid movements and large excursions. Hatchery bass of the same age, raised and feeding on pellets, however, used slower kinematics with smaller excursions, yielding strikes with a higher degree of suction.

(4) Capture events of hatchery bass fed live prey for the first time were characterized by movements that were faster than their wild counterparts, but had smaller excursion measurements and resulted in a decreased level of capture success. After five exposures to elusive mosquito fish, hatchery bass adapted their behaviors to capture prey at the kinematic level of wild bass. (5) The developmental pattern of the skull was conserved between hatchery and wild bass until 80-99mm TL. At this point, wild bass quickly developed morphological changes of the jaw apparatus including a more fusiform head and elongated jaw structures. Natural development in hatchery bass, however, was retarded at this size. Post-release, the skulls of hatchery fish converged towards those of wild bass by 135mm TL. Despite this variation in skull development, no theoretical advantage in food capture was found between these two groups.

(6) It is likely that a lack of experience in live prey capture might constrain hatchery bass from utilizing the total functional potential of their specialized morphology, and therefore, exposure to elusive prey should be enforced in rearing-techniques of hatchery fishes in order to improve the low post-stock survival rates of this species.

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