Journal of Aquatic Plant Management 40: 79-87, 2002.

Rahman D. Valley and M.T. Bremigan

ABSTRACT

Controlling exotic aquatic weeds such as Eurasian watermilfoil (Myriophyllum spicatum L.) is a high priority for many aquatic plant management programs.  Yet, the effects of Eurasian watermilfoil invasion and subsequent removal on sportfish production and food webs are insufficiently understood.  Changes in aquatic plant abundance or architecture, caused by invasion and/or removal of exotic plants, may affect age-0 largemouth bass (Micropterus salmoides Lacepede) growth and recruitment.  We hypothesized that age-0 largemouth bass piscivory and growth : 1) decreases along a gradient of increasing Eurasian watermilfoil coverage and 2) benefits from low-dose applications of fluridone herbicide intended to shift Eurasian watermilfoil dominated plant communities to native dominated plant communities.  In a multiple lake evaluation of of the effects of selective removal of Eurasian watermilfoil on age-0 largemouth bass, percent coverage of Eurasian watermilfoil ranged 8% to 50% in lakes treated with 5 to 7 ppb fluridone and 43a% to 91% in reference lakes.  Coverage of native plants ranged from from 62% to 95%.  Selective removal of Eurasian watermilfoil did not have a significant positive effect on age-0 largemouth bass growth.  Rather, age-0 bluegill (Lepomis macrochirus Rafinesque) prey availabity, which varied considerably among lakes, had a strong positive effect on age-0 largemouth bass piscivory and growth.  Factors influencing age-0 bluegill availability and age-0 largemouth bass appear more related to size structure of largemouth bass populations than to plant cover.