Roy M. Martin

Adult Production of Chinook Salmon Reared at Different Densities and Released as Two Smolt Sizes

Abstract Chinook salmon (Oncorhynchus tshawytscha) were reared at densities of 6.6–24.3 kg/ m3 and released as small (9.7–10.3 g) or large (28.2–31.8 g) smolts to determine the effects of fish size at release and rearing density on postrelease growth and adult return rate. Density did not affect survival during rearing, but mean weights for both size-classes were significantly lower at the highest rearing densities (P < 0.05). Density and size at release affected adult return rates, which were lower for fish reared at high densities for both size-classes. However, the increased number of smolts produced at higher densities compensated for the reduced return rates by yielding a higher number of returning adults per unit volume of rearing space. The estimated costs for each adult produced were US

Early male maturity in two stocks of chinook salmon (Oncorhynchus tshawytscha) transplanted to an experimental hatchery in southeastern Alaska

11.10–12.00 for small smolts and

Survival of coho salmon (Oncorhynchus kisutch) cultured in fresh water and in estuarine net pens

13.10–23.80 for large smolts. The lowest costs were projected at the second-highest density (18.6 kg/m3) for small smolts and at the highest density (20.3 kg/m3) for large smolts.

Floating vertical raceway to culture salmon (Oncorhynchus spp.)

Progeny of 1976-brood chinook salmon (Oncorhynchus tshawytscha) from the Chickamin and Unuk rivers in southeastern Alaska were reared to the smolt stage in a hatchery 250 km northwest of their natal streams. As fingerlings, the fish were separated into eight groups to test the effect of stock, time of release, smolt size at release, and culture salinity on marine survival and rates of early male maturity (mature males returning earlier than the youngest mature females; i.e., ≤4 years in age). A total of 13 397 Chickamin River and 22 508 Unuk River smolts were tagged and released from the hatchery in 1978. From 1978 to 1982, 1373 fish from the Chickamin River and 1634 fish from the Unuk River stock were recovered in fisheries or as maturing fish returning to the release site. Age-5 chinook salmon of both sexes from the Chickamin River were larger than those from the Unuk River stock (P < 0.05), but age-6 fish of both stocks were similar in size, regardless of sex. Rates of early male maturity were 5.4–16.7% in the Chickamin River stock and 70.6–96.0% for the Unuk River stock, and stock was significant (P < 0.030) in determining early-male maturity. Smolt size at release, culture salinity, and time of release did not affect maturation age of males in either stock.

Culture of sockeye salmon (Oncorhynchus nerka) smolts in estuarine net pens and returns of adults from two smolt releases

Abstract Growth, survival during culture, and subsequent marine survival are compared for two broods of juvenile coho salmon ( Oncorhynchus kisutch ) cultured in freshwater raceways or in net pens suspended in a highly stratified estuary. Two strategies for use of estuarine net pens were examined: (1) transfer as subyearlings from fresh water to net pens in fall, and (2) transfer as presmolt yearlings to net pens in early spring, prior to their normal migration or release time. Overwinter survival of juveniles cultured in net pens exceeded 90% and was only slightly lower than that of fish cultured in fresh water; however, fish cultured in fresh water were slightly larger at release. Time of release had a much greater effect on subsequent adult return than did culture environment. Return rates were significantly higher for fish released in late spring than for fish released in fall or early spring. Return rates of fish cultured in net pens were similar to or greater than that of fish cultured in fresh water. Results demonstrated that juvenile coho salmon can be cultured overwinter in estuarine net pens, thereby freeing rearing units for culture of subsequent broods and increasing the number of yearling smolts that can be produced in a hatchery.

Successful Maturation and Spawning of Captive Chinook Salmon Brood Stock

Abstract A floating vertical raceway was developed to culture salmon ( Oncorhynchus spp.), and tested for 12 years. The structure is composed of a durable, impervious liner suspended from a rigid flotation collar. Notable features of the raceway include low construction and maintenance costs, adaptability to sites that are remote or without suitable area for shore-based raceways, and high water quality in the rearing environment.

Growth and Survival of Alaska Stream-Type Chinook Salmon Cultured in Estuarine Net-Pens or Freshwater Raceways

Abstract In 1973, adult sockeye salmon, Oncorhynchus nerka , were transported from Nakvassin Creek, Baranof Island, southeastern Alaska, to a nearby research station and hatchery at Little Port Walter. Progeny from these fish were used for the study. The fry were initially cultured in freshwater, then transferred to an estuarine net pen as fingerlings (6.7 g) on 31 October 1974 for overwinter culture in seawater. Survival of the fingerlings from transfer until 21 April 1975 was 97%. Two groups of smolts were released from the net pen in 1975: an early group on 22 April and a late group on 7 June. The age, sex ratios, and size of returning adults from the two releases were similar. The proportion of the returning adults from each group, however, was significantly different ( P

Growth and Survival to Adulthood of Chum Salmon Vaccinated as Juveniles against Vibriosis

Abstract Brood stock of chinook salmon (Oncorhynchus tshawytscha) cultured from egg to maturity had low prespawning mortality and highly viable offspring when fed a formulated brood diet and matured in a seawater net-pen with a surface freshwater lens. The brood fish were cultured in freshwater raceways as fry, reared in seawater net-pens from the juvenile (4.7 g) stage until 2 months before spawning, and then transferred into the seawater net-pen modified with a 1-m-thick freshwater lens. Diet was changed 12 months before spawning from a basic formulated commercial diet to a commercial brood-fish diet. The average egg viability to the eyed stage (72% for the progeny of nine females, each crossed with a single male) compared favorably with that of anadromous fish produced at the same facility. Although cultured fish matured younger and smaller, and thus produced smaller eggs and fry, than did wild or anadromous fish of the same stock, juvenile size did not differ after 6 months of freshwater rearing.

Short-term Rearing of Pink Salmon (Oncorhynchus gorbuscha) Fry: Effect on Survival and Biomass of Returning Adults

Abstract The overwinter survival and growth and the subsequent marine survival of stream-type chinook salmon Oncorhynchus tshawytscha were compared between fish cultured in marine net-pens and their siblings cultured in freshwater. The net-pens were suspended in a stratified estuary with a low-salinity lens; the lens provided osmotic relief to the fish, and its depth and salinity varied seasonally. The median overwinter survival for chinook salmon from six brood years was 89.1% for the net-pen groups, significantly (P = 0.009) less than the median survival of 99.0% in freshwater. The median overwinter growth rate was 0.5% of body weight/d for the net-pen groups, significantly (P = 0.013) higher than the median growth rate of 0.2% for freshwater groups. The median marine survival of smolts from net-pen and freshwater groups was similar, 5.6% and 5.3%, respectively. These results demonstrate that juvenile stream-type chinook salmon can be cultured successfully over winter from the subyearling to smolt stage...

Viability of Gametes from Adult Anadromous Coho Salmon Ripened in an Estuarine Pen

Abstract Three consecutive year classes of juvenile chum salmon Oncorhynchus keta were vaccinated with Vibrio spp. bacterin, marked, and released into the marine environment. The return rates of adults from these releases were similar to those of unvaccinated control groups for two of the three year classes and were significantly lower for one of the year classes. There was no difference in size or age distribution at return between the vaccinated and control groups; thus, vaccination procedures did not increase survival or growth of these freely migrating chum salmon.