Effects of Shoreline Urbanization on Littoral Fish Assemblages

ABSTRACT

We evaluated modifications associated with shoreline urbanization with regard to effects on littoral habitat use by fishes in Lake Conroe, TX. Among four habitat types present, two had nonurbanized shorelines and were either vegetated or nonvegetated, and two had urbanized nonvegetated shorelines modified with either riprap or retaining walls. In each habitat type, four sites were randomly chosen for repeated sampling (once in each of fall, winter, spring, and summer) using depletion electrofishing inside a block-netted area. Nonvegetated and walled habitats had fewest species and weakest seasonal dynamics. Beginning in fall, vegetated habitat was characterized by various small-bodied taxa, primarily water-column and surface-feeding invertivores and piscivores, but as vegetation died back through the winter, it contained fewer characteristic species. Then in spring and summer, number of characteristic species in vegetation increased to include small-bodied benthic species, and large-bodied piscivores. The species association in walled habitat changed least across seasons, and was characterized by yellow bass (Morone mississippiensis). Associations in nonvegetated and walled habitats had fewer characteristic species than did other habitats, but these increased overall diversity of littoral assemblages in the reservoir. Cumulative effects of increasing urbanization accompanied by conversion of vegetated shoreline to walled habitat would lead to impoverished littoral assemblages. Riprap might be an acceptable alternative to retention walls for stabilizingshorelines. However, addition or protection of native aquatic vegetation also should be considered, especially with regard to mitigation of effects on fishes that are seasonally or uniquely associated with that habitat type, and whose populations had declined following past efforts to control vegetation.

Key Words:

• fish-habitat associations
• species richness
• littoral habitats
• shoreline modification
• vegetation
• canonical variates analysis
• Mantel tests