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

I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I

EXECUTfVES~ARY

Many investigations have been conducted in recent years in an attempt to determine
what factors are causing the decline of threatened and endangered fish such as razorback
sucker. An on-site toxicity test was conducted at Ouray National Wildlife Refuge, Utah,
with larval razorback sucker to determine the effects of dietary selenium on survival, growth,
and whole-body residues. Studies were conducted with 5, 10, 24, and 28-day old larvae fed
food organisms collected from six sites. Site water where organisms were collected had
selenium concentrations ranging from < 0.4 to 78 fJog/L, and concentrations in food
organisms ranged from 2.3 to 91 fJog/g dry weight. Static renewal tests were conducted for
20 to 25 days using reference site water with selenium concentrations of < 1.1 fJog/L. In all
studies, nearly complete mortality occurred in 15 to 20 days. In study 4 with 28-day old
larvae, fish weight was significantly reduced in larvae fed organisms containing 12 fJog/g
selenium from Sheppard pond 5 compared to pond 3. Whole-body concentrations of
selenium ranged from 3.7 to 14.3 fJog/ g in fish fed organisms from the reference site
(Sheppard Bottom pond 1) up to 94 fJog/g in fish fed organisms from North Roadside Pond.
Limited information suggested that the Sheppard pond 1 site was relatively clean and suitable
as a reference treatment. However, the nearly complete mortality of larvae and elevated
concentrations of selenium in larvae and selenium and other inorganics in food organisms
indicated this site was also contaminated with selenium and other inorganics. Whole-body
residues of selenium in larvae and selenium concentrations in food organisms from all sites
were slightly lower or greater than thresholds where adverse effects occur in other fish
species. Larval razorback sucker seem to have a greater sensitivity than other species that
may have been due in part to the presence of other inorganics in the reference water used in
all exposures or to inorganics such as vanadium that were elevated in food organisms. Based
on this study, selenium concentrations of 2.3 fJog/ g or greater in food organisms, in
combination with other elevated inorganics in water and food organisms, may cause adverse
effects in larval razorback sucker. Evaluation of the enhancement or restoration potential of
nursery habitats for larval razorback sucker should incorporate evaluation of contaminant
concentrations in food organisms. Contaminant evaluation is being considered as a vital part
of screening floodplain habitats for enhancement or restoration in the Upper Colorado River
Basin Recovery Program. This study suggests that bioaccumulation and toxicity of selenium
at low concentrations in food chain organisms, in combination with other inorganics in water
and food, can result in high monality of larval razorback sucker. Enhancement or
restoration of floodplain habitats would be of little value in the recovery of the endangered
razorback sucker in areas containing high concentrations of contaminants.

Key words: Colorado River basin, razorback sucker, endangered fish, selenium, inorganics,
food chain, feeding study, survival, growth, residue

IX