7817

• UCREFRP Catalog Number: 7817
• Author: Tyus, H. M. and S. H. Severson
• Title: Growth and Survival of Larval Razorback Suckers Fed Five Formulated Diets
• USFW Year: 1990
• USFW - Doc Type: The Progressive Fish-Culturist
• Copyright Material: YES

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77It' Progrrss;W! Fish-Cui/uris/ S2: 197-200. 1990

Growth and Survival of Larval Razorback Suckers
Fed Five Formulated Diets

HAROLD M. Tyus AND
STEVEN H. SEVERSON

U.S. Fish and Wildlife Service
1680 West Highway 40, Room 1210
Vernal. Utah 84078, USA

Abstract.-Sac fry of razorback sucker (Xyrauchen
texanus) were reared from 5 to 45 d posthatching on
live commercial fry diets as first foods. Fish fed diets
UVand 8-250 had 78% survival, and fish on diets AP-
100, A-250, and 4200 had survivals of 59,32, and 20%,
respectively. Total lengths of fish at the completion of
the study ranged from II to 27 mm; mean fish weight
ranged from 0.026 to 0.092 g. Growth of fish fed a lim-
ited ration (1-5% of body weight per day) was compa-
rable to growth in other laboratory experiments with live
foods. We recommend use of the diets producing the
highest survival (LlV or 8-250) as first foods for razor-
back sucker.

The razorback sucker (Xyrauchen texanus), an
endemic Colorado River catostomid, is in danger
of extinction in native habitats due to population
decline and lack of recruitment (Minckley 1983;
Tyus 1987; Lanigan and Tyus 1989). Although
not currently protected under provisions of the
Endangered Species Act of 1973, this monotypic
genus is protected by: state statutes and is a can-
didate for federal listing by the U.S. Fish and
Wildlife Service (USFWS 1990).
Natural reproduction of razorback sucker oc-
e' curs in the upper Colorado River basin, but re-
00 cruitment is absent or severely curtailed (Tyus
o 1987). Efforts were initiated in 1987 to augment
a dwindling population of perhaps a thousand
o adults (Lanigan and Tyus 1989) through hatchery
: propagation. A small experimental fish hatchery
was constructed at 0 the Ouray (Utah) National
Wildlife Refuge under the auspices of a multi-
agency recovery implementation program
(USFWS 1987). .
Razorback suckers have been reared success-
fully at Dexter (New Mexico) National Fish
: Hatchery. Brood fish are stripped, eggs are fertil-
r ized and incubated, and the resulting fry are
i. stocked in ponds containing plankton and other
~.o. natural foods (Hamman 1987). In ponds, larval
:' razorback suckers feed on organisms less than 0.1
~. mm in width as first foods (rotifers and chiron-

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omids); organisms 0.3 mm in width are consumed
by larger fry (> 18 mm in total length [TL]; Pa-
poulias 1988).
Information about"mtensive culture of razor-
back sucker fry on dry, formulated foods is scant,
and comparisons between commercially available
diets for fry have not been published. Costs as-
sociated with construction and maintenance of
rearing ponds could be avoided ifrazorback suck-
er larvae could be intensively cultured with one
of the commercially available dry diets currently
marketed for the rearing of various coldwater and
warmwater fishes. Propagation of endangered
fishes may also require a diverse brood stock, and
rearing fry to a larger size would allow fish of dif-
ferent parental stocks to be marked at an early
age.
The objectives of this study were to evaluate
growth and survival of razorback sucker fry fed
five commercially available diets varying in in-
gredient composition and particle size.

Methods

Eggs and milt were collected from wild razor-
back suckers on the Green River near Jensen, Utah.
The eggs were fertilized with sperm from five males
and transported to the USFWS experimental
hatchery at Ouray, Utah. Fertilized eggs were
placed in Heath - incubators and held in flowing
water at 2O"C. Eggs began hatching 112 h postfer-
tilization, and all fry had emerged after 145 h. The
sac fry were held for 4 d in a 76-L aluminum tank
supplied with heated, degassed, aerated, single-
pass well water (80w, 18;95 Umin; average tem-
perature, 21"C; dissolved oxygen, 5.4 mglL; pH,
7.7; total hardness, 440'mglL). On the fifth day
after hatching, 40 fry were placed into each of
fifteen 2.5-L aquarium breeder baskets in a com-
pletely randomized design. Baskets were con-
structed of 1 O-~m-mesh nylon net on a plastic
frame and suspended in 29.1-L compartments.
Each compartment was supplied with heated, de-
gassed, aerated, single-pass well water (flow, 1.90
Umin; average temperature, 20.3"C; dissolved ox-
ygen, 6.1 mglL; pH, 7.7; total hardness, 440 mgl
L). Well water was introduced into the top of each
tank via a system of overhead pipes and was

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