Response of a Reservoir Fish Community to Aquatic Vegetation Removal

Abstract

Over 3,600 hectares of submersed aquatic vegetation in Lake Conroe, Texas, were eliminated 1 year after 270,000 grass carp Ctenopharyngodon idella were stocked in 1981-1982. Seventeen fish species were commonly collected in cove rotenone samples and the biomasses of eight species declined (P < 0.10) after vegetation removal. The most notable declines were observed for several small, phytophilic Lepomis spp., for bluegill Lepomis macrochirus. and for crappie Pomoxis spp. Biomass of largemouth bass Micropterus salmoides did not decline (P = 0.12) but the density of age-1 and older fish did decline (P = 0.02). Biomass and density of two cyprinid species and channel catfish Ictalurus punctatus increased. Although biomass of longear sunfish Lepomis megalotis did not increase (P = 0.11), mean size declined and density increased an order of magnitude (P = 0.02). Density of threadfin shad Dorosoma petenense increased nearly fivefold after vegetation removal, coincident with a decline in mean size; however, variability was high and the difference could not be declared significant. Biomass of gizzard shad D. cepedianum fluctuated due to inconsistent year-class production that was not directly related to vegetation coverage. Seining revealed that populations of three cyprinodontid species, bantam sunfish Lepomis symmetricus. and brook silversides Labidesthes sicculus collapsed following vegetation removal, whereas catches of inland silversides Menidia beryllina and threadfin shad increased significantly. Gillnetting revealed that large year-classes were produced by yellow bass Mor one chrysops and white bass M. mississippiensis following vegetation removal. Although abundance of white crappie Pomoxis annularis declined in offshore regions sampled by gill nets, catches of black crappie P. nigromaculatus were similar before and after vegetation removal. No change in abundance or structure over this 7-year study could be detected for at least 10 populations. The original largemouth bass-crappie-hybrid striped bass (Mor one chrysops x M. saxatilis) fishery was replaced by a channel catfish-white bass-hybrid striped bass-largemouth bass-black crappie fishery after vegetation removal. The observed response of many species to vegetation removal could be predicted given published information, but mechanisms governing the dynamics of several important species were unclear.

Fish population dynamic in the newly impounded Nam Theun 2 Reservoir (Lao PDR)

“…Trees are a good support for food resource like biofilms and aquatic invertebrates. Furthermore, a structured shoreline is known to be an important factor for the nest-building fish (O'Brien, 1990;Bettoli et al, 1993) and enhancing the success of reproduction. Field observations underlined this higher fish colonisation of the flooded forest.…”

Identifying and quantifying environmental thresholds for ecological shifts in a large semi-regulated river

“…The increase in recreational fish indexed mass was overwhelmingly tied to increases in largemouth bass, northern pike (both visual predators) and bluegill (Lepomis macrochirus; a visual invertivore; Table 1). Many studies have documented the link between an increase in these three species and increased vegetation (Killgore et al 1989;Grimm & Backx 1990;Bettoli et al 1993;Grift 2001). The reduction in commercial fish indexed mass closely mirrored the reduction in non-native fish indexed mass, and was likely driven by the observed decline in common carp, a non-native but commercially important species.…”

“…Indexed mass of the fourth trophic level increased significantly; likely due to the increase in visual predators (especially northern pike and largemouth bass) experiencing increased feeding efficiency with greater water transparency (Killgore et al 1989;Grimm & Backx 1990;Bettoli et al 1993). Additionally, many of the top trophic-level species (northern pike, longnose gar and bowfin, specifically) are also phytophilic spawners, so they may have benefited both from increased clarity and increased vegetation abundance (Parks et al 2014).…”

Ecological impacts of winter water level drawdowns on lake littoral zones: a review

“…For example, macrophyte assemblages offer a variety of meso-and microhabitats including transient heterogeneous DO and temperature refugia (Miranda et al 2000) that can harbor distinct fish size-classes (Chick and McIvor 1994;Yamanaka 2013), high fish densities (Keast 1978;Hugh Barwick 2004;Randall et al 2012), and high species richness (Keast 1978;Pratt and Smokorowski 2003;Hugh Barwick 2004) compared to other littoral mesohabitats. Declines in fish diet, growth rate, biomass, and abundance correlate with reduced littoral physical habitat complexity (Bettoli et al 1993;Sass et al 2006). Anthropogenic regulation of water level regimes is a primary threat to fish species that use the littoral zone for all or part of their lives (Winfield 2004;Miranda et al 2010;Strayer and Findlay 2010).…”