Hatchery Coho Research Articles

Estestvennaya i zavodskaya molod' kizhucha ozera Bol'shoj Vilyuj

Estestvennaya i zavodskaya molod' kizhucha ozera Bol'shoj Vilyuj

The Early Marine Biology of the Hatchery/Wild Juvenile Salmonid (Oncorhynchus sp.) Community in Barkley Sound, Canada

We conducted 11 purse seine/beachseine surveys over the summers of 2000 and 2001 to learn about the migration timing, distribution, and diet of hatchery chinook (Oncorhynchus tshawytscha) and coho (O. kisutch), and wild chinook, coho, sockeye (O. nerka) and chum (O. keta) juvenile salmon, in Barkley Sound, West Coast Vancouver Island. Juvenile salmon partitioned Barkley Sound by time and space, and by diet except for hatchery and wild coho. The analysis of migration timing included historic data for 1987-89, and results showed that timing differed between species and was consistent over years. Sockeye and chum dominated the juvenile salmon community until mid-June and hatchery and wild chinook dominated subsequently. Fish tended to be dispersed contagiously. Results of correlation analyses of catch suggested that fish of different origins and species did not co-occur. The euphausiid Thysanoessa spinifera was an important prey item but different fish species selected different sizes of T. spinifera at different times. The diet overlap between hatchery and wild coho did not affect return. Migration timing for sockeye and wild coho seems to reflect a strategy to enter the ocean when the biomass of the size fraction of T. spinifera that each species selects is likely to be maximal. Descriptions of migration timing, fish interactions, and diet provide information which appears to be useful for learning about the biological basis of salmon return variability.

The Effectiveness of Semi-Natural Rearing of Coho Salmon (Oncorhynchus kisutch) at the Nitinat River Hatchery, British Columbia

We compared: 1) rearing mortality, 2) size at release (mean length), 3) jack, male and female sizes, and 4) jack, female, and adult returns of coho salmon (Oncorhynchus kisutch) from three consecutive brood years reared at the Nitinat River hatchery using a conventional or a semi-natural rearing method. The semi-natural method included feeding restrictions, shading of the rearing ponds, lower rearing temperature and rearing densities, exposure to a predator and a volitional release. We found no significant effects of brood year or rearing method on rearing mortality; it was significantly lower during the marking to release phase than during the other two phases (eyed-egg to ponding, ponding to marking). Conventionally reared smolts were significantly longer. Conventionally reared males were longer. As a proportion of number of smolts released, semi-natural rearing produced 86% fewer jacks, the same proportion of females and 15% more adults. Adult production trends, described as marine survival rate (returning adults • smolt-1) for Nitinat River Hatchery coho, and as ln recruits • female spawner-1 for a nearby wild coho population, were similar. Jacking rates were lower in Nitinat River hatchery coho than for the nearby wild coho population. We concluded that the semi-natural rearing methodology produces adult fish more efficiently than the conventional rearing method does, and at 73% of the cost.

Copper-induced olfactory toxicity in salmon and steelhead: Extrapolation across species and rearing environments

Recent research has shown that hatchery coho salmon ( Oncorhynchus kisutch) are vulnerable to the olfactory neurotoxicity caused by copper from urban runoff, pesticide use, and mining activities. To explore the broader application of this data to salmonids living in the wild, we exposed naturally-reared steelhead ( O. mykiss) to copper (5 and 20 μg/L; 3 h) and measured losses in olfactory function via electro-olfactogram (EOG) recordings. Copper exposure disrupted the olfactory responsiveness of steelhead to an amino acid ( l-serine) in a dose-dependent manner that was equivalent to previously published data for hatchery coho. Our findings support extrapolation of copper toxicity data across species and from fish raised in hatcheries to fish in the wild.

Growth and Habitat Occupancy of Hatchery Coho Salmon in an Engineered Stream

AbstractWe designed and constructed a natural channel (hereafter, engineered stream; length = 284 m, flow rate = 0.08 m3/s) and compared weight, length, and condition factor between hatchery coho salmon Oncorhynchus kisutch (brood years [BYs] 2000 and 2002) reared in the engineered stream and those reared at Dungeness Hatchery, Washington, under similar temperature regimes. In addition, we compared rearing density, egg‐to‐smolt survival, smolt density, and smolt capacity in the engineered stream with reported reference values for wild coho salmon in rivers. Mean weight and length of fish reared in the engineered stream were 8‐32% and 39‐154% less, respectively, than those of fish reared in the hatchery. Mean condition factor was 1.6‐3.1% greater for fish reared in the engineered stream than for fish reared in the hatchery. Mean monthly growth differed between the engineered stream and hatchery treatment groups; fish in the engineered stream lost weight during the winter, and those in the hatchery gained weight. Rearing density (245%), smolt density (93‐209%), egg‐to‐smolt survival (61‐158%), and smolt capacity (219‐411%) in the engineered stream were greater than reported reference values for wild coho salmon in natural systems. The BY 2000 return rate was 2.61% for hatchery‐reared fish versus 2.55% for fish from the engineered stream. The BY 2002 return was 0.38% for hatchery fish versus 0.12% for fish from the engineered stream. The most important findings of this study are that engineered streams (1) produce smaller fish exhibiting condition factors and smolt‐to‐adult return rates similar to those of fish produced by hatcheries, (2) have a greater rearing capacity than natural habitat, and (3) may be an important approach for restoring the rearing capacity of rivers.

Comparison of genetically based antipredator behaviour in hatchery and wild coho fry from a coastal Oregon river: interpreting a negative result

Coho salmon Oncorhynchus kisutch fry derived from wild and hatchery stocks demonstrated no difference in responsiveness to an overhead fright stimulus in laboratory experiments.

Comparison of Midsummer Survival and Growth of Age-0 Hatchery Coho Salmon Held in Pools and Riffles

Abstract Habitat use studies have shown that juvenile coho salmon Oncorhynchus kisutch select pools over riffles. However, stream alterations have caused pool habitat to be lost or degraded throughout the Pacific Northwest. This study compared the growth and survival of age-0 coho salmon in riffles and pools in four streams in the South Umpqua River basin, Oregon. Hatchery coho salmon were stocked in block-netted riffles and pools. At the end of the study, the fish were recovered in order to measure their growth and survival in each habitat type. The survival of coho salmon was significantly higher (P 0.05) between pools and riffles. The condition factor of the coho salmon was significantly (P 0.05). The results of this study suggest that...

BREEDING COMPETITION IN A PACIFIC SALMON (COHO: ONCORHYNCHUS KISUTCH): MEASURES OF NATURAL AND SEXUAL SELECTION.

In the breeding system of Pacific salmon, females compete for oviposition territories, and males compete to fertilize eggs. The natural selection in females and sexual selection in males likely has been responsible for their elaborate breeding morphologies and the dimorphism between the sexes. We quantified direct-selection intensities during breeding on mature coho salmon (Oncorhynchus kisutch), measured for seven phenotypic characters, including three secondary sexual characters. Wild and sea-ranched hatchery coho were used to enhance the range of phenotypes over which selection could be examined. The fish were allowed to breed in experimental arenas where we could quantify components of breeding success as well as estimate overall breeding success. We found that without competition, natural selection acts only on female body size for increased egg production; there is no detectable selection on males for the phenotypic distribution we used. Under competition, the opportunity for selection increased sixfold among females. Natural selection favored female body size and caudal-peduncle (tail) depth. Increased body size meant increased egg production and access to nesting territories. The caudal peduncle, used in burst swimming and nest digging, influenced both successful egg deposition and nest survival. Increasing density increased competition among females, though it did not significantly intensify natural selection on their characters. In males, competition increased the opportunity for selection 52-fold, which was nine times greater than for females. Sexual selection favored male body size and hooked snout length, both characters directly influencing male access to spawning opportunities. Selection on male body size was also affected significantly by breeding density. The ability of large males to control access to spawning females decreased at higher densities reflecting an increase in the operational sex ratio. Further, the relative success of small males, which could sneak access to spawning females, appeared to increase as that of intermediate-sized males decreased. Such disruptive selection may be responsible for the evolution of alternative reproductive tactics in salmon.

Survival, Contribution, and Return of Hatchery Coho Salmon (Oncorhynchus kisutch) Released into Freshwater, Estuarine, and Marine Environments

We released six groups of marked yearling hatchery coho salmon (Oncorhynchus kisutch) in six locations each year for five years beginning with the 1981 brood. Fish were released immediately below Bonneville Dam (control), at the Tongue Point Coast Guard Station (head of saltwater intrusion in the Columbia River), between the jetties at the Columbia River bar, in the Columbia River plume water, in coastal water approximately 19 km north and 19 km offshore of the mouth of the river, and in oceanic water approximately 38 km offshore. We found a 1.6-fold increase in the survival index (ocean catch through September 18 each year) for the fish released at Tongue Point compared with the control group. After adjusting for differences in the survival index between release groups, we found a 2.5-fold increase in the contribution to the Columbia River gillnet fishery from the fish released at Tongue Point compared with the control group. We found no significant difference between survival of the other release groups and survival of the control group. We also found that the percentage of adult fish that returned to locations other than the Columbia basin increased as the distance the fish were transported offshore increased.

Survival, Ocean Growth, and Ocean Distribution of Differentially Timed Releases of Hatchery Coho Salmon (Oncorhynchus kisutch)

Estimates of growth rates in early ocean life and length frequency distributions at time of release for adult survivors were inferred from scale measurements for lots of coho salmon (Oncorhynchus kisutch) released at several dates from a Columbia River hatchery (Big Creek) and a southern Oregon hatchery (Coos Bay). Analysis of these measurements failed to support either of two literature-suggested hypotheses for the variability of marine survival of hatchery coho by date of release: (1) intraseasonal variability of food supply during early marine life; and (2) intraseasonally improving ability of smaller individuals within release lots to convert to salt water. Marine survival improved substantially with date of release at both hatcheries. However, fish released earliest, which survived relatively poorly, grew as fast in early marine life as fish released later, which survived better. Thus, poor survival of the early released fish did not appear related to lack of food at early ocean life. For the Big Creek hatchery, no significant differences were seen between the mean lengths at date of release and the mean release-date lengths of adult survivors back calculated from their scales, for lots released on May 5, June 3, and July 2. Apparently, small and large fish of each lot survived with equal probability. For the Coos Bay hatchery, the mean release-date lengths of adult survivors were significantly larger than the mean lengths of all fish released, for each of six lots released between early June and late July. Thus, large fish apparently survived better than small ones within each of these six lots. But there was no seasonal trend in survivability of small fish relative to large ones, contrary to hypothesis (2)

Effects of Dietary Clinoptilolite on Levels of Effluent Ammonia from Hatchery Coho Salmon

Abstract The addition of 5 and 10% clinoptilolite to the diet ofcultured coho salmon (Oncorhynchus kisutch) did not cause a significant reduction in effluent water ammonia concentrations compared to effluent water from fish fed control diets. Growth rate was not affected by the addition of clinoptilolite to diets.

Relation between Distance Transferred from Natal Stream and Recovery Rate for Hatchery Coho Salmon

Distance transferred from the natal stream was negatively related to recovery rate (recruits per gram of juveniles released) for hatchery-reared coho salmon Oncorhynchus kisutch. This relation, which reflects the important influence of genetic adaptation and genetic differences among stocks on recovery rates and survival, should be useful in deciding whether or not to transfer fish.

Factors Affecting Puget Sound Coho Salmon (Oncorhynchus kisutch) Runs

Summer streamflow, apparently affecting survival of zero-age coho salmon (Oncorhynchus kisutch), is shown to be an important determinant of Puget Sound run strength since 1952. Recently, hatchery production has also been a significant factor. Earlier studies indicated a relationship between rearing flows and coho run strength beginning in 1935. The persistence of the correlation between streamflow and run strength for more than 40 yr is noteworthy. Although the mechanism is unclear, survival of hatchery coho may also be positively dependent upon the same environmental conditions that affect stream-reared coho; a depensatory mortality relationship between abundance of hatchery coho and abundance of stream-reared coho is postulated.Key words: coho salmon, survival, run prediction, hatchery contribution