Date of Award

8-1-2002

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Biology

Abstract

Spawning habitat availability and reproductive timing are crucial factors that affect survival of larval fish. To understand temporal and spatial variation in larval fishes in the Red River, samples were collected from the Red River and North Dakota tributaries using ichthyoplankton nets. Collections were made during the spring and summer of 1999, 2000, and 2001. Spatial patterns were examined to uncover any variation in a cross section of the river. Common carp Cypritr j carpio, cyprinid spp. and white bass Morone crysops were more abundant near the surface than at mid-depth. Channel catfish Ictalurus pimctatus were more abundant at mid-depth than at the surface. There appeared to be no difference between the shore and midstream sampling stations for any species.

Densities of larval fish were compared between each of five tributaries and the Red River near each confluence to determine whether species have greater preference for or spawning success in tributaries versus the main channel. Moxostomo spp., white bass, Stizostedion spp. and Hiodontid spp. were more abundant in the main channel of the Red River than North Dakota tributaries. None of the species examined were more abundant in the tributaries selected for this study.

Reproductive timing of the most common species (carp, white sucker Catostomus commersoni, freshwater drum Aplodinotus gnmniens, and Stizostedion spp.) in the Red River was examined using larval fish density to indicate peaks in spawning activity and identify probable spawning dates. Density was compared with water temperature and discharge to determine which of these is the predominant synchronizing cue, triggering spawning behavior. In all years, water temperature regimes were similar; however, discharge hydrographs differed substantially. The years 1999 and 2001 were more typical where peaks in discharge occurred in April and were related to snow-melt and heavy spring precipitation. In contrast, the 2000 peak in discharge occurred during the third week of June. The timing in reproduction of white sucker and Slizosledion spp. appeared to be associated primarily with temperature or photoperiod. Spawning for these species occurred at the same time during all three years of the study. Spawning in freshwater drum could be either temperature or discharge related. Estimated spawning times for carp appeared to be associated primarily with peaks in discharge. Peaks in carp reproduction occurred as discharge rates began increasing in 2000, indicating that discharge may act as the primary synchronizing cue for carp. The relationship between discharge and the initiation of spawning in carp may stem from their requirement of submerged vegetation for spawning habitat.

Download

Share

COinS