Sea-run Cutthroat Trout Research Articles

Adult Returns of Hatchery Sea-Run Cutthroat Trout Reared in a Seminatural Pond for Differing Periods prior to Release

Abstract I compared the postrelease survival of sea-run cutthroat trout Oncorhynchus clarki reared in a seminatural rearing pond for 4–7 months before release with that of fish raised in the pond for 1 month before release. Fish reared in the pond for 4–7 months averaged 31% more returns, suggesting that hatchery managers could enhance adult returns by moving fish from raceways to rearing ponds early rather than at the end of the rearing term.

Adult Returns of Hatchery Sea-Run Cutthroat Trout Fed by Hand versus Demand Feeders

Abstract Postrelease survival of hatchery sea-run cutthroat trout Oncorhynchus clarki reared on demand feeders was compared with survival of fish fed by hand. For 3 years of releases, demand-fed fish averaged 10% greater adult returns than hand-fed fish, but the difference was only significant in 1 year, indicating both feeding methods affect fish survival similarly after release.

Fishes and the Forest

E very year, millions upon millions of anadromous fish come from the oceans to spawn in freshwater streams. In Southeast Alaska alone, these fish spawn in over 5000 streams (Halupka et al. in press). The best-known anadromous on the Pacific coast are the seven species of Pacific salmon of the genus Oncorhynchus (including steelhead, Oncorhynchus mykiss, and sea-run cutthroat trout, Oncorhynchus clarki). Other, less-publicized and less well studied anadromous species include the chars (Salvelinus spp.) and smelt, such as the eulachon (Thaleichthys pacificus). In addition to anadromous species, several species of fully marine forage fishes use interand subtidal zones. For example, along the north Pacific coast, Pacific herring (Clupea harengus pallasi) spawn on rocky coastlines, and Pacific sand lance (Ammodytes hexapterus) can be found buried in soft sands, often near the mouths of streams. These teeming hordes of fish fall prey not only to marine hunters, such as other fish, whales, and sea lions, but also to numerous terrestrial predators and scavengers. Historically, the predators were seen as competing with human harvesters of fish, and predator-control programs aimed at reducing the number of

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%).

Status of Anadromous Salmon and Trout in British Columbia and Yukon

Abstract Using fisheries agency databases and files, we assembled a summary database on the status of anadromous salmon stocks (genus Oncorhynchus) from British Columbia and Yukon streams. We then collected supplementary information by circulating the database among fisheries professionals and interest groups throughout British Columbia and thus identified 9,662 anadromous salmon stocks. These stocks included 866 chinook, 1,625 chum, 2,594 coho, 2,169 pink, 917 sockeye, 867 steelhead and 612 sea-run cutthroat trout stocks. We assessed the status of anadromous stocks by employing a classification scheme similar to that of Nehlsen et al. (1991). Assessments were possible for 5,487 (57%) of all stocks and included all large, commercially important stocks. The assessments found 624 stocks were at high risk, 78 were at moderate risk, 230 were of special concern, and 142 were extirpated in this century. We were unable to classify 4,172 (43%) of the stocks because of an absence of reliable data. Due to their sma...

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.

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.

Use of Electronic Fish Counters for Coho and Chinook Salmon, Steelhead, and Cutthroat Trout Smolts

Abstract Electronic fish counters produce accurate counts, are less stressful to fish, and require fewer personnel than traditional methods of counting smolts of coho salmon (Oncorhynchus kisutch), Chinook salmon (O. tshawytscha), steelhead (O. mykiss), and sea-run cutthroat trout (O. clarki) released from hatcheries.

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 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.

Age, Food, and Migration of Sea-run Cutthroat Trout, Salmo clarki, at Eva Lake, Southeastern Alaska

Abstract Information was collected on sea-run cutthroat trout (Salmo clarki) from the Eva Lake system on Baranof Island, Southeastern Alaska. Migrations of 1,210 to 1,594 out-migrants and 1,203 to 1,682 in-migrants were recorded at a weir across the outlet of Eva Lake. Migration peaks occurred in mid-May (out-migrants) and mid-September to early October (in-migrants). No movement of cutthroat was noted at the weir from December through February. Ages of out-migrant cutthroat ranged from 3 to 10, with the majority showing 5, 6, and 7 annuli on their otoliths. The numbers of annuli considered to be formed prior to smolt migration were 2 (3%), 3 (80%) and 4 (17%). Stomach contents consisted primarily of salmon young and insects during the summer and stickleback and insects during the winter in Eva Lake. The fish fed mostly on insects during their out-migration and amphipods and salmon young in salt water. Results of the Eva Lake study and other studies on sea-run cutthroat are compared.