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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Mortality of fish was recorded daily and dead fish removed. At the termination of
studies 3 and 4, all live fish were measured for total length and weight and Fulton-type
condition factor was calculated as K = W x, where W is weight (g), L is length (mm), and
U
x is an arbitrary scaling factor (100,000) (Nielsen and Johnson 1983). No measurements of
fish size were made in studies 1 and 2.

Supplemental feedin~ study

A study was conducted at Yankton ERS in March-May, 1996, to determine the
influence of feeding density of live food organisms on survival and growth of larval
razorback sucker. One lot of fish was used in three tests. Eyed eggs were received from
Dexter National Fish Hatchery, NM, and were from brood stock from the Yampa River,
CO. Eggs and larvae were cultured in Yankton well water (hardness 292 mg/L as CaC03,
alkalinity 175 mg/L as CaC03, pH 8.2). Larvae were fed live nauplii of brine shrimp
(Artemia sp.) prior to testing.

Three tests were conducted; one with 5-day old larvae, a second with lO-day old
larvae, and a third with 24-day old larvae. Twenty-eight-day old larvae were not tested
because of their close proximity in age to 24-day old larvae. Ten fish were placed in each of
four replicate 2000-ml beakers containing 1600 ml of well water at room temperature.
Water in exposure beakers was aerated continuously with compressed air from an oil-less air
compressor. Beakers were held on a table and temperature in the room was maintained as
close to 200C as possible. The photoperiod was maintained at about 12 light: 12 dark.

Brine shrimp (24 hour old) were collected daily from a culture jar and diluted about
10-fold. Organisms were sampled with a 2-ml Hensen-Stempel pipette and counted with a
stereoscope microscope at 0.7x magnification and a Wards zooplankton counting wheel. The
number of organisms in three replicate counts were averaged and the volume calculated to
feed 20, 40, or 80 organisms per fish for the number of live fish in each exposure vessel.
Fish were fed once daily after water renewal and were fed for 20 days. Based on 1600 ml
test water volume and 10 fish per vessel, the 20 organism per fish feeding rate was
equivalent to 125 organisms/L, the 40 organism per fish feeding rate was 250 organisms/L,
and the 80 organism per fish feeding rate was 500 organisms/L.

Water quality characteristics were measured weekly in test water using standard
methods (APHA et al. 1989). Test water had corrected conductivity 824 jA.mhos/cm,
hardness 278 mg/L as CaC03, alkalinity 169 mg/L as CaC03, calcium 81 mg/L, magnesium
18 mg/L, cWoride 12 mg/L, and sulfate 242 mg/L. Dissolved oxygen concentrations were
greater than 8.4 mg/L in test vessels. Water temperature was measured daily in test vessels
and averaged 17.4, 17.6 and 16.60C in tests with larvae at 5, to, and 24 days old,
respectively.

Mortality was measured daily and dead fish removed. At the termination of each

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