Interactions between Striped Bass and Other Game Fish in Reservoirs
Leandro E. Miranda and Scott W. Raborn
Abstract.—Competitive interactions among reservoir fishes may be pronounced because fish assemblages in these artificial environments have had little time to develop niche-partitioning strategies that alleviate negative interspecific interactions. Such interactions may at times have been intensified by introductions of predators such as striped bass Morone saxatilis, introduced to create additional fisheries and control pelagic clupeids. Possible interactions between existing fish assemblages and striped bass include predation and competition. While there is a perception among angler groups that predation by striped bass on coexisting game fish is significant, most studies have reported little or no predation on game fish by striped bass and have considered predation rare and inconsequential. Moreover, predation that occurs will likely be compensatory and fail to reduce overall game fish survival. Any indirect effect of striped bass predation by restricting prey-sized game fish to limited refuge sites remains unknown. Exploitative competition may be more common. Although infrequently, introduced striped bass have depleted prey resources shared with other piscivores, particularly when stocking rates have been high, when there is a high rate of natural reproduction, or when prey supply has plunged in response to environmental fluxes. Fluctuation in prey supply, associated with ordinary environmental variability, and associated time lags in prey supply and predator demand, preclude adjusting predator densities to exactly balance demand with supply. The frequency of low supply–demand ratios varies across systems and exhibits seasonal trends. Nevertheless, chronic supply–demand imbalances are manageable where the predator assemblage is at least partially controlled through stocking, harvest regulations, or both. Because of the poor state of knowledge concerning the parameters defining balance and because uncontrollable annual fluctuations preclude exact management of alternating prey levels, we suggest adjusting stocking to manage demand so that it equals the median historical prey supply. Simulating the removal of striped bass and predicting the aftermath may be the most cost-effective way to provide decision support for stakeholders involved in determining if a striped bass stocking program is beneficial to most users.