Effects of Intensive Stocking of Hybrid Striped Bass on the Population Structure of Gizzard Shad in a West Texas Impoundment, a Case Study

Lake Tanglewood, Texas, is a eutrophic reservoir with an excessively abundant gizzard shad Dorosoma cepedianum population comprised of primarily large individuals (>180 mm total length [TL]). Fingerling (40 mm TL) hybrid striped bass (Morone saxatilis x M. chrysops) were stocked at high rates in 1992 (490/ha) and 1993 (245/ha) to restructure the gizzard shad population. Small gizzard shad (<180 mm TL) declined in abundance 1 year after hybrid striped bass were introduced, presumably as a result of hybrid striped bass predation. With reduced recruitment, large gizzard shad abundance steadily declined. Gizzard shad year class production increased after the abundance of large gizzard shad declined, suggesting that a high density of large gizzard shad may suppress gizzard shad year class production. Largemouth bass Micropterus salmoides, and black crappie Pomoxis nigromaculatus abundance and size appeared to be positively related to the presence of abundant smaller size classes (<180 mm TL) of gizzard shad.

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