7133 - Laserfiche WebLink

Home Browse Search

Only recently has sexual maturation of razorback sucker been reported in the literature. Minckley (1983) reported that razorback suckers reared at Willow Beach NFH attained sexual maturity in six years when the fish were 14 to 16 inches total length. Two-year-old male razorbacks (15.6 inches, 1.6 pounds) reared at Dexter were sexually mature in the spring of 1983; microscopic examination of the milt showed it contained motile, thus presumably viable, spermatozoa. Ovaries from two-year-old female razorbacks (I6.2 inches, 1.9 pounds) contained developing ova. Three-year-old razorbacks spawned successfully in 1984 (Ham man 1985). Sexual maturation of razorback sucker is more closely related to size (15") than age (2-6 years). Female razorback suckers held at Dexter NFH become gravid and spawn when the water temperature approaches 55° F. Females are injected with hormone to stimulate final maturation and ovulation of eggs. Inslee (1982) determined that 100 International Units (IU) of chorionic gonadotropin (CG) per pound of body weight injected intramuscularly was the preferred hormone, dosage, and site of injection for female razorback suckers. Male razorback suckers receive intramuscular CG injections at 300 IU/pound ~o stimulate and/or maintain gamete production. Utilizing the wet method, eggs are handstripped into pans, milt added from two or more males and eggs stirred gently with a feather to ensure adequate mixing of sexual products. Razorback sucker eggs are very adhesive so they are "clayed" with slurried bentonite following fertilization. The clayed-eggs are poured into floating egg baskets, gently washed to remove the bentonite, allowed to water harden, enumerated gravimetrically, and placed in Heath trays and in jars. Water flow through the incubators is regulated at three gpm. At 70° F razorback sucker eggs begin hatching at about 96 hours and continue through 144 hours; peak hatching occurs at about 120 hours. Frq are held in tanks until swimup and are then stocked in rearing ponds at rates ranging from 100,000 to 150,000/surface acre. A total of 134 three and four-year-old domestic razorback sucker averaging 3.2 pounds were spawned in 1985. These fish gare a total of 8,714,114 eggs fora mean egg take of 65,030 and 19,887 eggs per pound of body weight. Egg viability averaged 62.5% and swimup fry ,numbered 2,853,872, 52.4% of _expected fry. Eggs were hatched both in Heath trays and jars. Although egg viability was similar for both hatching techniques (62.3% for Heaths and 63.2% for jars), swimup fry numbered only 46.7% of expected for jars while they constituted 54% of expected for Heaths. Data indicates that Heath trays are the superior technique for incubating razorback sucker eggs. -37-