Invasive bivalve establishment as a secondary effect of eradication-focused nuisance aquatic plant management

Abstract

Holbrook DL, Schad AN, Dick GO, Dodd LL, Kennedy JH. 2020. Invasive bivalve establishment as a secondary effect of eradication-focused nuisance aquatic plant management. Lake Reserv Manage. 36:423–431. We evaluated changes in aquatic vegetation cover and community structure in hydrilla (Hydrilla verticillata)-infested constructed experimental ponds after applying the management tools of triploid grass carp (Ctenopharyngodon idella) stockings, herbicide applications, and native macrophyte planting (emergent, floating-leaved, and submersed species). In ponds where aquatic vegetation was most reduced due to management (herbicide and >72 grass carp per vegetated hectare stockings), a secondary infestation of the invasive bivalve (Asian clam or Corbicula fluminea) was observed. Asian clam abundances were analyzed in relation to grass carp stocking densities (0, 40–42, 72–81, and 110–129 per vegetated hectare), depth, and changes in native and invasive vegetation community structure and cover. Data analyses showed inverse relationships of Asian clam abundances to vegetation cover and to depth, as well as a synergetic relationship with grass carp stocking density. Implications of this research indicate that when a nuisance aquatic plant management strategy is focused on full or near eradication of a target species, inevitable damage to native species that might otherwise preserve beneficial ecological components may result in secondary issues, such as the expansion of additional invasive species due to opening of habitats. Excessive control efforts of a targeted nuisance plant species, and the results here highlight potential unintended consequences of over management of natural resources.