Jack M. Tipping

Evaluation of Visible Implant and Sequentially Coded Wire Tags in Sea-Run Cutthroat Trout

Abstract Sea-run cutthroat trout Oncorhynchus clarki were tagged with visible implant (VI) tags inserted into the transparent periocular tissue. Sequentially coded wire tags were placed in the snout of the same fish to evaluate long-term retention and visibility of VI tags. Fish ranged from 200 to 307 mm fork length at the time of tagging. Tags were recovered 3–21 months after tagging through voluntary returns from anglers and from hatchery rack returns. Ninety-four percent of the 156 tagged fish recovered from the hatchery rack retained the VI tag. All but one of the VI tags were visible and readable in situ after recapture.

Effect of Smolt Length at Release on Adult Returns of Hatchery-Reared Winter Steelhead

Abstract Smolts of hatchery-reared steelhead Oncorhynchus mykiss were tagged by length-group and released in 1983 and 1984 on the Cowlitz River, Washington. Recovery of adults was significantly greater for smolts 190 mm and larger compared with returns of smaller fish.

Use of Demand Feeders on Large Steelhead Rearing Ponds

Abstract Demand feeders were installed on 5-acre rearing ponds for fingerling steelhead (Salmo gairdneri) to replace truck-mounted feed blowers. Because the demand feeders could dispense dry feed, substantial savings in feed costs were realized. The demand feeders supported acceptable fish survival and feed conversion rates, and they removed the uncertainty of feed calculations associated with large populations that cannot be monitored between stocking and harvest.

Reducing Feed Levels during the Last Month of Rearing Enhances Emigration Rates of Hatchery-Reared Steelhead Smolts

Abstract Downstream migration of hatchery-raised smolts of steelhead Oncorhynchus mykiss maintained on a reduced-feed diet during the last month of rearing was compared with migration of fish fed to satiation (control diet) before release. Five releases were made in two streams over 3 years. Fish on the reduced diet averaged 7 mm shorter and 21 g lighter than control fish at release and had an average condition factor (K = 105 [weight,g]/[length,mm]3) of 0.92, versus 1.03 for control fish. An average of 57.5% of reduced-diet fish were recaptured, compared with 49.4% recapture of control fish; recoveries favored the test group for each release, and the difference was significant for three releases. Fish on the reduced diet generally arrived at traps 1–2 d sooner than control fish. Savings in fish feed costs were also realized with the reduced diet strategy.

Communications: Length and Condition Factor of Migrating and Nonmigrating Hatchery-Reared Winter Steelhead Smolts

Abstract Effects of length and condition factor on emigration rates of hatchery-reared smolts of winter steelhead (Oncorhynchus mykiss) stocked 4.7 km upstream of a permanent fish trap were examined. For three releases, an average of 19.8% of fish did not emigrate past the trap. Fish with fork lengths of 190 mm or more and condition factors (K = 105 [weight, g]/[length, mm]3) of 0.90–0.99 generally migrated at higher rates than other fish.

Ozone control of ceratomyxosis: survival and growth benefits to steelhead and cutthroat trout.

Abstract Tests with ozone to control infective Ceratomyxa shasta in cutthroat trout (Oncorhynchus clarki, formerly Salmo clarki) successfully established the minimum effective ozone treatment, the product of ozone concentration (mg/L) and minutes of ozone contact with water, of 0.84. Summer steelhead (O. mykiss, formerly S. gairdneri), reared in raw water or ozonated water from August 1985 through March 1986 and released in May 1986, had 81.2 and 1.4% mortality, respectively. The mean lengths of steelhead reared in ozone-treated water were significantly larger than those of control fish. In 1986–1987, summer and winter steelhead and sea-run cutthroat trout were reared in ozonated water from July through mid-November and thereafter in raw water until April. Fish reared in ozone-treated water again had significantly less mortality and were significantly larger than control fish.

Effect of Condition Factor at Release on Smolt-to-Adult Survival of Hatchery Sea-Run Cutthroat Trout

Abstract To determine if condition factor of migrating smolts influenced subsequent survival to adulthood, sea-run cutthroat trout (Oncorhynchus clarki) from two releases at Cowlitz Hatchery were measured for length and condition factor and then marked individually with visible implant tags. Sport and hatchery recoveries indicated condition factor did not statistically influenceadult returns, although no smolts with a condition factor of 1.14 or greater were recovered as adults. Smolts over 210–220 mm fork length had higher return rates than smaller fish.

Use of Size for Early Detection of Juvenile Hatchery Steelhead Destined to Be Precocious Males

Abstract At two Washington State hatcheries in August 1999–2002, juvenile steelhead Oncorhynchus mykiss were size-graded and the largest fish (4.8–9.2% of the population) were coded-wire-tagged and mixed with small fish to determine whether the large fish were those that became precocious males. The results showed that the large fish in August at Merwin Hatchery tended to become precocious, although the mean lengths of the precocious and nonprecocious fish were similar at their time of release in April. At Abernathy Fish Technology Center (FTC), the large fish in August did not disproportionately become precocious, and the nonprecocious fish were significantly larger than the precocious fish at release. We suggest that precocious fish at Abernathy FTC may have committed to precocity before August whereas fish at Merwin Hatchery committed to precocity in August. Because only 0.82% of the large fish became precocious, removing the 5–10% largest fish in August at the Merwin Hatchery would be marginally succe...

Return Rates of Hatchery-Produced Sea-Run Cutthroat Trout Reared in a Pond versus a Standard or Baffled Raceway

Abstract Sea-run cutthroat trout Oncorhynchus clarki were reared in and released from a pond with a gravel–earth bottom, a standard concrete raceway, and a raceway with baffles at the Cowlitz Trout Hatchery, Washington. Adult returns from two release years showed that significantly more fish from the rearing pond survived (3.2%) than fish reared in standard raceways (2.0%) and that significantly more fish returned from the standard raceway than from the baffled raceway (1.7%).

Effect of Release Size on Return Rates of Hatchery Sea-Run Cutthroat Trout

Abstract Optimum release size for Cowlitz, Washington, hatchery sea-run cutthroat trout (Salmo clarki) was determined for the 1982 and 1983 year classes by tagging smolts at release. Hatchery returns and sportfishing harvest indicated fish released when they were 21 cm in fork length or larger averaged 12.8% return compared to 2.3% return for smelts less than 21 cm. Based on returns, initial migrant maturity was about 85% for males and 69% for females. Sportfishing harvest accounted for 23.5 and 48.6% of tag returns for each year class, respectively. Nonmigrating cutthroat trout were significantly smaller than smelts and were predominately females.