7821

• UCREFRP Catalog Number: 7821
• Author: Hamilton, S. J., et al.
• Title: Evaluation Of Toxicity To Larval Razorback Sucker Of Selenium-Laden Food Organisms From Ouray NWR On The Green River, Utah.
• USFW Year: 1996.
• USFW - Doc Type: \
• Copyright Material: NO

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organisms/L, 37 mg in ponds with 24 organisms/L. and 45 mg in ponds with 43
organisms/L. Their results suggest that larvae in the present study and in the supplemental
feeding study did not grow as well as those in ponds where a greater variety of foods
including algae, sessile organisms, and detritus would be available. Other studies with larval
razorback sucker did not report weights (Papoulias and Minckley 1990, Marsh and Langhorst
1988, Langhorst and Marsh 1986). However, the length of larvae in the present study was
similar to that of larvae in the laboratory study of Papoulias and Minckley (1990), the
backwater site of Marsh and Langhorst (1988), and the supplement feeding study.

Survival of larvae in studies 1-4 was 0-27 %. Modde and Wick (1996) reported
survival of 1-2 year old razorback sucker in a 25-day cage study at Ouray NWR was 90-
100% at two wetland sites (Leota Bottom pond 7 and Sheppard Bottom pond 3), but
averaged 40% at three backwater sites on the Green River. They also reported 8-9% growth
in fish at the Sheppard wetland site and 2-3 % growth at the Leota site, but no or negative
growth in reference fish held at the Ouray Native Fish Facility and fish at the three
backwater sites. Survival of fish held at the wetland site in Old Charley Wash was 0-10%
due to a disease problem. The high survival of 1-2 year old fish at the two wetland sites
compared to our low survival rates with larval fish coincides with the generality that early
life stages of fish are more sensitive to environmental stresses than older fish (Rand and
Petrocelli 1985). No inorganic residues were measured in water, food organisms, or fish in
the study by Modde and Wick (1996).

Finger et al. (1995) conducted an on-site toxicity test at Ouray NWR (NR, SR, and
Leota Bottom pond 6) with 3-day old cladoceran (Daphnia ma!1:na), 3-day old fathead
minnow (Pimephales promelas), and 40-60 day old razorback sucker. The test involved only
waterborne exposure and no effects were observed in any of the exposures. The lack of
adverse effects was attributed to the relatively clean water used in the tests. Selenium
concentrations in water were 2-3 p.g/L in NR, 1-3 p.g/L in SR, and 0.1-0.8 p.g/L in Leota 6.
These concentrations in NR and SR seem abnormally low because Stephens et al. (1988,
1992) and Peltz and Waddell (1991) reported median selenium concentrations in outflow of
NR and SR were 40 p.g/L. Based on the low concentration of trace elements in water, the
advanced age of razorback sucker tested, and the water only route of exposure, it is not
surprising that no adverse effects were observed in their study.

Selenium

In the present study, S 1 was considered the reference site because it was believed to
be relatively uncontaminated, i.e., selenium concentrations in waterbird eggs were low
(Stephens et al. 1992, Peltz and Waddell 1991). However, selenium concentrations in larval
razorback sucker fed zooplankton from SI were extremely elevated in study 2 (14.3 p.g/g)
and near the lower end of the toxic threshold for adverse affects in larval fish (4 p.g/g; Lemly
1993) in study 3 (3.7 p.g/g). This lower value is almost two times the selenium
concentrations typically reported in control fish from laboratory studies with either water or
diet exposure or reference fish from field studies (0.4-2.0 p.g/g; Table 13). Although after

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