Spatial and temporal segregation of spawning habitat by catostomids in the Savannah River, Georgia and South Carolina, U.S.A.

Abstract

Spawning aggregations of five species of catostomids were observed on the two mid-channel gravel bars of the Savannah River, Georgia and South Carolina, in 2004 and to assess the degree of spatial and temporal overlap in the use of this habitat and determine the habitat preferences leading to segregation. Spawning catostomids showed a considerable amount of temporal overlap in their use of these mid-channel gravel bars. The observed temporal overlap was consistent between 2004 and 2005 and corresponded to temperatures at which species were present. The distribution of catostomids was not uniform at the upstream gravel bar. Carpsuckers Carpiodes sp., spotted sucker Minytrema melanops and robust redhorse Moxostoma robustum both demonstrated some spatial overlap with notchlip redhorse Moxostoma collapsum; however, their overall distributions were different from one another. Northern hogsucker Hypentelium nigricans was present across the gravel bars, apparently as an egg predator. Spawning catostomids segregated based on flow, depth, slope and substratum size. Whether due to limited habitat availability or changes in the timing of reproduction due to altered cues, temporal and spatial overlap occurs between spawning catostomids despite the apparent partitioning of available spawning habitat. It is unclear, however, if this overlap results in excessive mortality in the early life-history stages of these species. Results suggest spatial overlap among catostomid species was minimized due to species spawning in areas within a narrow range of conditions. Intraspecific interactions such as nest site superimposition or disturbance may be a concern.

Post‐release movements and habitat use of robust redhorse transplanted to the Ocmulgee River, Georgia

“…The radio-tagged robust redhorse above Juliette Dam did move upstream into Lloyd Shoals during spring. However, visual surveys by divers did not find suitable spawning habitat as described by Freeman and Freeman (2001) and Grabowski and Isely (2007) in the areas occupied by these individuals. This habitat in the form of mid-channel gravel bars is present above Juliette Dam; however, this study was conducted during a period of severe drought in central Georgia.…”

“…In addition to concerns about the arrival of flathead catfish in this portion of the river, results indicate that radio-tagged robust redhorse in this portion of the river did not spawn successfully. They did initiate upstream spring migrations, presumably in preparation for spawning, but the fish either did not find suitable spawning habitat as described by Freeman and Freeman (2001) and Grabowski and Isely (2007) or environmental cues necessary to trigger spawning were absent. In other systems, such upstream migrations end at a spawning aggregation (Grabowski and Isely, 2006), but whether such aggregations occur in the Ocmulgee above Juliette Dam is unclear.…”

“…This habitat in the form of mid-channel gravel bars is present above Juliette Dam; however, this study was conducted during a period of severe drought in central Georgia. Gravel bars upstream of Juliette Dam similar to those used by robust redhorse in other rivers (Freeman and Freeman, 2001;Grabowski and Isely, 2007) that potentially could have served as spawning habitat for robust redhorse were left exposed during spring and early summer. On the other hand, rocky shoal habitat similar to that used by spawning fish below Juliette Dam was readily available to the upstream individuals during the course of this study but did not seem to be used.…”

Brown trout Salmo trutta redd superimposition by spawning Lampetra species in a lowland stream

“…The striking overlap in spawning habitat preferences between the three species is the main explanation for the high occurrence of the phenomenon. Water depth, water velocity and sediment size are generally considered to be the most important in‐stream microhabitat variables in determining the spawning site selection of stream fishes (Manion & Hanson, 1980; Grabowski & Isely, 2007; Louhi et al , 2008), and these variables measured in spring 2008 overlapped for S. trutta , L. fluviatilis and L. planeri . Although measurements of hydraulic variables for S. trutta redds taken in spring may not represent the real spawning microhabitat preferences, these were consistent with spawning habitat criteria established for spawning females in autumn (Louhi et al , 2008).…”

“…Closely related sympatric fish species must have evolved mechanisms such as spatial and temporal segregation of spawning processes that limit negative reproductive interaction (Grabowski & Isely, 2007; Savvaitova et al , 2007). The spawning of sympatric S. trutta and Lampetra spp.…”