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Effects of Variable Flows on Water Chemistry Gradients and Fish Communities at the Hillsborough River, Florida
 

Summary: Effects of Variable Flows on Water Chemistry Gradients and Fish
Communities at the Hillsborough River, Florida
MATTHEW J. CATALANO,* MICHEAL S. ALLEN, AND DEBRA J. MURIE
Department of Fisheries and Aquatic Sciences, University of Florida, 7922 Northwest 71st Street,
Gainesville, Florida 32653-3071, USA
Abstract.--We evaluated the effects of variable flows on water chemistry and fish communities to
recommend biologically based minimum flows that protect low-salinity zones for freshwater­oligohaline
(FO) fishes below the Hillsborough River Dam, Tampa, Florida. We plotted the distributions of hypoxic
(dissolved oxygen [DO] 4 mg/L) and meso- and polyhaline (salinity . 5%) habitats and evaluated changes
in species richness and spatial distributions of FO fishes on five sampling dates from October 2002 to July
2004. During low flows (0.12 m3
/s; ,25th percentile) in May 2004, oligohaline habitat was reduced as a salt
wedge (.5%) migrated upstream to within 1,300 m of the dam and DO decreased to less than 4 mg/L in the
lower part of the reach. However, intermediate (1.19­2.18 m3
/s; 25th­50th percentiles) and high flows (5.49
m3
/s; 50th­75th percentiles) on four of the five sampling dates maintained oligohaline salinities (i.e., 5%)
and DO greater than 4 mg/L throughout most of the reach. Using fyke net data, we found no flow-related
trends in FO fish species richness. However, spatial occurrence data indicated that the distribution of FO
fishes shifted upstream to within 1,660 m of the dam during a low flow in May 2004. Thus, FO fishes may

  

Source: Allen, Micheal S. - Department of Fisheries and Aquatic Sciences, University of Florida

 

Collections: Environmental Sciences and Ecology