Understanding Habitat Needs for Rare Fish with Long Term Telemetry Studies

Restoration and management of the Lower Missouri River (LMOR) to support recovery of the endangered pallid sturgeon (Scaphirhynchus albus) requires quantifying habitats used during all life stages in order to isolate specific habitats, if any, that present bottlenecks to reproduction and survival. All life stages of the pallid sturgeon take place in rivers where depth and turbidity are prohibitive to direct observation of movement, behavior, and habitat selection. Female pallid sturgeon reproduce only once every 3-5 years, but during a reproductive season they may migrate 10's to 100's of kilometers to spawn in patches of only 100's of square meters over a period of several hours. The broad ranges of spatial and temporal scales involved in understanding how particular life stages relate to their environment, as well as the technical challenges of working in a large river, dictate application of a multi-scale, remote sensing approach. At the scale of the entire LMOR (1300 km), extensive hydroacoustic mapping using single and multibeam bathymetry, acoustic Doppler current profiling (ADCP), and substrate classification has been used to quantify the fundamental biophysical capacity of river segments in terms of frequency distributions of hydraulic variables. Coordinated telemetric tracking of reproductive fish provides an understanding of home range and habitat selection at reach to segment scales, over timescales commensurate with 3-5 year reproductive cycles. Intensive reach-scale hydroacoustic mapping using multibeam bathymetry, ADCP, and high-resolution sidescan sonar, combined with intensive telemetric tracking, provide coincident measures of habitat availability and selection for upstream-migrating and spawning fish during reproductive seasons. These assessments measure habitat variables at sub-meter to bed form scales, commensurate with the scale at which fish occupy their habitat. For example, dual-frequency identification sonar imagery indicates that during spawning, sturgeon occupy the lee slopes of dunes facing upstream (presumable to minimize energetic expenditure) but episodically move out of dune fields and into deep, fast water over coarse substrate (presumably to release eggs or milt). Data recording tags implanted in the fish provide complementary data on depth and temperature at very fine temporal resolution (15-minute intervals) and can be associated with contemporaneously collected spatial information. This multi-scale, multi-instrument remote-sensing approach is essential for improving understanding of the linkages between life stages of the pallid sturgeon and its environment.