Direct Exploitation of Prey on an Inundated Floodplain by Cherryfin Shiners (Lythrurus roseipinnis) in a Low Order, Blackwater Stream
Riverine fishes may benefit from moving onto inundated floodplains and directly exploiting floodplain resources. Studies of floodplain ecology for smaller streams have focused primarily on how fishes benefit indirectly from flooding (e.g., cycling of allochthonous nutrients). In a second order, blackwater stream in southern Mississippi, more food was available for cherryfin shiners (Lythrurus roseipinnis) on an inundated floodplain than was available in the low water stream. The floodplain drift of prey items consisted of significantly higher densities of terrestrial arthropods (Collembola, terrestrial Acariformes) and aquatic organisms associated with floodplain pools (Oligochaeta, larval Chironomidae, Anomopoda). While on the floodplain, L. roseipinnis ate significantly more food and consumed a significantly different diet than did L. roseipinnis in the stream. The difference in diets between the two habitats was because of the predominance of a terrestrial arthropod (Collembola) in the diet of L. roseipinnis on the floodplain. These results demonstrate that fishes in small streams can directly exploit floodplain food resources of briefly inundated floodplains. If stream-floodplain connectivity is eliminated in small streams through anthropogenic activities (e.g., channelization, riparian destruction), then L. roseipinnis and other small stream fishes will have limited access to invertebrate food resources.Abstract
Number of drift items per m3 collected downstream of enclosures containing different densities of fish (Lythrurus roseipinnis) for all flood and low water sampling periods. Each sample represents the data from either five drift nets (13 and 17 February) or six drift nets (remaining samples). The densities of fish in enclosures were: no fish (white bars), one fish (light gray bars), and five fish (dark gray bars). The location of the enclosures (floodplain versus low water stream) is indicated above each set of bars. Data are untransformed. Horizontal black lines represent mean values and vertical bars represent 95% confidence intervals
Mean adjusted dry weight of gut contents for Lythrurus roseipinnis from enclosures on the inundated floodplain (gray bars) and the low water stream (striped bars). Horizontal black lines represent mean values and vertical bars represent 95% confidence intervals. Dry weights were adjusted using fish standard length (SL) as a covariate. (A) Adjusted dry weight of gut contents of L. roseipinnis at fish density 5 (natural density). (B) Adjusted dry weight of gut contents of L. roseipinnis at fish density 1 (one fish per enclosure). Dashed lines represent the mean adjusted dry weight of gut contents from control enclosures at fish density 5 (n = 15 for both A and B). Dotted lines represent the mean adjusted dry weight of gut contents from control enclosures at fish density 1 (n = 3 for both A and B)