7315 - Laserfiche WebLink

Home Browse Search

. REFERENCE NUMBER: CITATION: 027 Hamman, R.L. 1986. Induced spawning of hatchery-reared Colorado squawfish. The Progressive Fish-Culturist 48(1):72 - 74. SPECIES AND LIFE STAGE: cs, CS_EGG, CS_LAR TOPICS: Culture, Production, Temperature, Research KEYWORDS: COLORADO SQUA WFISH, INDUCED SPAWNING, EGGS, INCUBATION TEMPERATURE, INCUBATION APPARATUS, DEXTER NATIONAL FISH HATCHERY, PITUITARY, FECUNDITY SUMMARY: Hatchery-reared squawfish were successfully induced to spawn during 1983 - 1984 at Dexter National FISh Hatchery, NM. The brood stock during 1983 and 1984 consisted of 24, 9-year old females and nine 10-year old females, respectively. These fish were 1974 year-class progeny from wild adults collected from the Yampa River and spawned at Willow Beach Hatchery. . Ovulation was induced with injections of acetone-dried carp pituitary at the rate of 4 mg/kg body weight at 24-h intervals. Fish were anesthetized before the intraperitoneal injection, and then placed in a 2. 7S x: 0.7S x: 0.75 m holding tank and held until they were stripped. Cool water at 17 -18 C flowed through the tank at 90 - 130 VmiD. When eggs could be expelled with slight pressure, a female was anesthetized. and rinsed, and the eggs were stripped into a pan containing water and diluent. Milt from two or three hatchery-reared males was added, and the eggs were gently stirred with a feather. A bentonite clay solution was then added to counteract egg adhesiveness. Eggs were then washed and placed in a 31 x 31 x 18 -em floating basket and allowed to water harden for approximately 30 miD. Eggs were placed in either Heath incubators or hatching jars for incubation (20 - 22 C at 4 _ lll.Jmin). After hatching, fry were transferred to 2.75 x 0.75 x 0.75 - m tanks (20 - 22 Cat 15 - 23 l.Jmin) and held until swim-up occurred. In 1983, all 24 females owlated 18. - 20 h after receiving one carp pituitary injection. Fecundity averaged n,4OO; average number of eggs per kilogram body weight was 55,533. Eggs commenced hatching at 100 h and were completely hatched by 144 h. Numbers of fry following swim-up in Heath and jar incubators were 283,017 and 34,855, respectively. In 1984, all nine females ovulated 20 - 24 h after receiving two hormonal injections. Fecundity averaged 66,185; average number of eggs per kilogram body weight was 45,451. All eggs were incubated in hatching jars. Hatching began at 96 h and ended by 144 h. Actual numbers of swim-:up fry were 118,157. . A-28