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168
<br />the 13.1 g 1-' value found for squawfish in this
<br />study.
<br />Colorado squawfish tested in this study are ap-
<br />parently not suited for culture in undiluted
<br />Glen-60 water. However, dilution of saline waters
<br />like Glen-60 may provide suitable culture condi-
<br />tions,particularly at salinities in the range of 1-5 g
<br />1-'. Further studies are needed to define the sa-
<br />linity range and ionic composition of acceptable
<br />saline water for squawfish production and repro-
<br />duction.
<br />For risk assessment purposes, it would appear
<br />that exposure of Colorado squawfish, of the size
<br />tested, to salinities <_ 9.? g 1-', for short periods
<br />of time, would not result in direct mortality. In-
<br />direct mortality, however, may occur because of
<br />salinity effects on organisms that young squaw-
<br />fish feed upon. EPA (1988), and Hart et al. (1991)
<br />have compiled material showing that inverte-
<br />brates, which make up the bulk of young squaw-
<br />fish diets, are generally more sensitive than ver-
<br />tebrates to salinity changes. Hart et al. (1991)
<br />suggest that adverse effects on freshwater inver-
<br />tebrates occur at salinities as low as 1000 mg 1-'.
<br />In order to predict effects of increased salinity on
<br />squawfish in the basin, it may be necessary to
<br />study salinity effects at a lower trophic level.
<br />Acknowledgements
<br />We thank Steve Grabowski, Robert Behnke, and
<br />Donald Klein for providing assistance and sup-
<br />port, and the National Fish Hatchery in Dexter,
<br />New Mexico for providing fish. Del Nimmo and
<br />Tom Jackson reviewed an early draft of the paper
<br />and their comments were greatly appreciated.
<br />Funding for the project was provided by the
<br />United States Bureau of Reclamation.
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