Backwaters in the Upper Reaches of Reservoirs Produce High Densities of Age‐0 Crappies

Abstract

Reservoir backwaters are aquatic habitats in floodplains of reservoir tributaries that are permanently or periodically flooded by the reservoir. Like many reservoir arms, backwaters are commonly shallow, littoral habitats, but they differ from arms in various respects, including their support of primarily wetland plant assemblages that are tolerant to flooding. Elsewhere, the reservoir floods mainly upland plants that are less tolerant to flooding, producing a band of barren shoreline along the fluctuation zone. We investigated differences in relative abundance of age‐0 crappies Pomoxis spp. in backwaters and arms of widely fluctuating flood control reservoirs, examined the effect of water level, and estimated the likelihood and timing with which these habitats are flooded annually. Higher catch rates of age‐0 crappies were obtained in backwater habitats than in arm habitats. When inundated during the crappie spawning season, backwaters provided vegetated habitat at lower water levels than arms. Backwaters flooded earlier than arms and remained flooded longer to provide prolonged nursery habitat. Whereas vegetated habitat was inundated almost yearly in backwaters and arms, inundation that was timed to the onset of spawning occurred less regularly. Because of differences in water elevation, vegetated habitats were flooded in time for crappie spawning about every other year in backwaters but only every third year in arms. Recruitment of age‐0 crappies was inversely correlated with high water levels during the months preceding the spawning period, perhaps because early flooding degraded the vegetation. Our results suggest that water levels may be managed during late winter and spring to regularly flood wetland vegetation communities in backwaters; however, water levels should be maintained at or below normal pool and should only irregularly flood upland vegetation in reservoir arms to promote the preservation of such vegetation. Furthermore, management efforts to enhance crappie recruitment should consider the enhancement and preservation of backwaters. Received June 15, 2011; accepted February 7, 2012

Intra-Annual Variation in River-Reservoir Interface Fish Assemblages: Implications for Fish Conservation and Management in Regulated Rivers

“…Examples of species known to use floodplain habitats in unregulated river reaches included centrarchids, gizzard shad, threadfin shad, inland silverside, freshwater drum, and western mosquitofish (Kwak, ; Winemiller et al ., ; Galat et al ., ). Previous work suggests that centrarchids in particular may use littoral habitats of RRIs for spawning (Meals and Miranda, ; Slipke et al ., ; Dagel and Miranda, ). Migratory species (white bass and longnose gar; Riggs, ; Netcsh and Witt, ; Webb and Moss, ; Johnson and Noltie, ) observed in RRIs were likely travelling to spawning sites in upstream riverine habitats or returning to the reservoir following such migrations.…”

Importance of Canals for Florida Largemouth Bass: Lake Griffin, Florida

“…Some bodies of water have sections (e.g., canals, marshes, tributaries, and sloughs) that are important to the fishery but that are often excluded from sampling for several reasons (e.g., difficult access, gear restrictions, time or budgetary constraints). Studies have shown that additional sections provide critical biological habitat to various freshwater fish species (Holland and Huston 1984;Sheaffer and Nickum 1986;Nack et al 1993;Zorn et al 1998;Dagel and Miranda 2012), including essential spawning and nursery area for Largemouth Bass Micropterus salmoides (Nack et al 1993). These sections, even if they are small, may support similar amounts of angler effort (total hours) as the main section of a lake, and understanding their contribution may be important in monitoring sport fish populations and in making management decisions about the system.…”

Reservoir Floodplains Support Distinct Fish Assemblages

“…Our fish sampling in these reservoirs has shown that in years when water reaches spawning temperature but water level is not high enough to expand into the floodplain, some fish species congregate in the river channel adjacent to a floodplain (Miranda et al ., ). Concurrent research in the study reservoirs has also shown that juvenile recruitment increases in years when water level is low during the months preceding the spawning period and high during the spawning period (Dagel and Miranda, ). Also, for some species, the advantages of floodplain macrohabitats may be blurred when water levels are high and inundated vegetation is available throughout the reservoir (Dagel and Miranda, ).…”