obtained from sturgeon broodstock raised at five
commercial farms in Northern California and at the
University of California, Davis research facilities.
plied by irrigation water, rearing temperature fluc-
tuated seasonally (10–12°C in the winter and 16–
18° C in the summer). Commercial facilities were
supplied by underground water with a constant
temperature of 20°C. Ripe broodfish raised on
commercial farms were transferred to cooler water
(10–14º C) 3–6 months before spawning, to prevent
ovarian atresia and testicular regression. Fish were
held in artificially chilled tanks or transported to
other facilities with a supply of cool reservoir water.
To examine reproductive cycles, gonadal develop-
ment of marked fish was monitored by tissue biopsy
starting at age 3–4 years. Commercial broodstock
were sampled annually in the fall, and the ripe fe-
males were re-sampled before spawning (March-
May). In the experiments conducted at the universi-
ty, fish were sampled several times per year. Ani-
mals were anesthetized in a 100 ppmMS- 222 bath, 7
ml of blood was drawn with a vacutainerfromthe
caudal vein. centrifuged. and plasma was stored fro-
zen for the analyses of reproductive hormones and
metabolites. Gonads were biopsied (1cm^3 frag-
ment through a small abdominal incision. and tis-
sue was fixed in 100% buffered formalin. As fish
reached full sexual maturity, ovulation and sper-
miation were induced by the administration of
mammalian GnRH analog. GnRHa ([D-Ala^6 , Pro^9
N-Et]-GnRH, Sigma) and extracts of dried com-
mon carp pituitary glands (Stoller Fisheries). Al-
though optimal hormonal induction protocols are
still being investigated. the most common hormonal
treatment Tor ovulation was a ‘priming’ dose of 10
μg kg-1of GnRHa followed by intramuscular injec-
tion of 4.5 mg kg–1carp pituitary material 12 hours
later. To induce spermiation. sturgeon were given a
single injection of 1.5 mg kg–1carp pituitary, and se-
men was collected by catheter 30–32 hours later.
Additional procedures for hatchery breeding of
sturgeon were described by Conte et al. (1988) and
Doroshov et al. (1993).
Stages of gametogenesis were examined on par-
affin sections stained by periodic acid Schiff (PAS)
or by hematoxylin and eosin (H&E) stains (Do-
roshov et al. 1991). The pre-ovulatory ovarian stage
was detected by germinal vesicle migration (mea-
suring distance of the nucleus from the animal pole
of boiled and bisected eggs) and by the in vitro oo-Broodfish and methods
White sturgeon live along the Pacific coast of North
America and in watersheds of the Fraser, Colum-
bia, and Sacramento-San Joaquin rivers (PSMFC^1 ).
It is a semi-anadromous species, with landlocked
populations in freshwater reservoirs and tributaries
of the Columbia River basin. In the wild, males
reach first sexual maturity at age 10–12 years and
females at 15–32 years (PSMFC^1 ). River migrations
and spawning exhibit seasonal patterns. In the Sac-
ramento River peak spawning was observed in
April, at water temperature 14–15°C (Kohlhorst
1976), while in the lower Columbia River major
spawning activity occurred in May at water temper-
ature 12–14°C (McCabe & Tracy 1994). The com-
mercial fishery and hydroconstruction at the turn of
the century severely depleted and fragmented wild
stocks (Skinner^2. Semakula & Larkin 1968, Gal-
breath 1985). The restricted sport fishery is current-
ly the major harvester of stocks in the Columbia
River and San Francisco Bay (PSMFC^1 ). Artificial
propagation of white sturgeon was established dur-
ing the 1980's (Conte et al.1988),and the offspring
were used by aquaculturists for raising domestic
broodstocks and production of sturgeon for the
rood market (Logan et al. 1995).
The broodfish studied were 3–14 year old first-
hatchery generations of wild sturgeon originated
from the Sacramento and Columbia rivers. They
were raised in freshwater tanks and fed a commer-
cial salmonid diet at a rate of 0.5–2.0% body weight
per day. Most rearing faclities were large (6–9 m
diameter and 1.5 m depth) outdoor tanks exposed
to natural photoperiod. In the research facility sup-
(^1) Pacific States Marine Fisheries Commission (PSMFC). 1992.
White sturgeon management frameworkplan.Portland, Ore-
gon. 201 pp.
(^2) Skinner, J.E. 1962. An historical review of the fish and wildlife
resources of the San Franciso Bay area California Department
ofFish& Game. Water Project Branch Report No. I. 226pp.