Suspected Natural Hybridization of Striped Bass and White Bass in Two Arkansas Reservoirs

In 1981, hybrid striped bass (Morone saxatilis x Morone chrysops) appeared in Lake Maumelle and Beaver Lake, Arkansas, both which had only been stocked with striped bass (Morone saxatilis). Therefore, it was suspected that natural hybridization might have occurred between striped bass and native populations of white bass (Morone chrysops). Scale sample analysis revealed that the hybrid striped bass collected from Lake Maumelle were from 1978 and 1979 year classes. Hybrids from the 1979 year class were collected from Beaver Lake. Review of historical stocking data did not reveal any potential errors in which hybrid striped bass might have been stocked in place of striped bass. Meristic counts and measurements of collected fish indicated that significant (P < 0.05) morphological differences existed between striped bass and hybrid striped bass (4 measurements) and also between white bass and hybrid striped bass (1 measurement). The observed meristic characteristics of the hybrid striped bass conformed to those of reciprocal hybrid striped bass (M. chrysops o x M. saxatilis o), which would theoretically be the fish most likely produced in the wild in Lake Maumelle and Beaver Lake. Electrophoretic analysis revealed that all striped bass and white bass in the sample were pure species representatives. Further examination revealed that all hybrid striped bass collected had genotypes consistent with F1 hybrids. This determination eliminated certain possible hatchery errors which could have occurred. No determination could be made electrophoretically as to whether the hybrid striped bass were original or reciprocal hybrids. Historical rainfall data indicated that the 1978 year class of hybrid striped bass occurred during a year of “normal” spring precipitation. However, both 1979 year classes occurred during a year of extremely high rainfall in the Lake Maumelle and Beaver Lake watersheds.

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