Ernest L. Brannon

The influence of dietary lipid source and alpha-tocopheryl acetate level on product quality of rainbow trout (Salmo gairdneri)

Abstract Rainbow trout ( Salmo gairdneri ) were fed practical diets containing either fish oil or swine fat and supplemented with 0, 50, 500, or 1500 mg of alpha-tocopheryl acetate per kg of diet for 4 months prior to harvest. The effects of diet on sensory attributes, fatty acid composition, tissue alpha-tocopherol level, and lipid oxidation during forzen storage were determined. Dietary fat source or alpha-tocopheryl acetate did not significantly affect sensory attributes of trout fillets evaluated fresh or after prolonged frozen storage. The fatty acid composition of the muscle and viscera were influenced by dietary fat source, most markedly in the levels of n −3 and n −6 fatty acids. Tissue alpha-tocopherol levels were significantly increased at dietary levels of 500 and 1500 mg alpha-tocopheryl acetate per kg diet. The dietary level of alpha-tocopheryl acetate required to prevent vitamin E deficiency signs was higher in fish fed the fish oil diet than in the fish fed the swine fat diet. Fish fed diets containing 500 and 1500 mg alpha-tocopheryl acetate had lower levels of malonaldehyde after frozen storage at −80°C for 4 months, but not after frozen storage at −20°C for 10 months.

The use of celestial and magnetic cues by orienting sockeye salmon smolts

Summary1.Yearling sockeye salmon (smolts),Oncorhynchus nerka, trapped at the outlet of Babine Lake, Canada, on their way from the lake downstream to the ocean were tested in round orientation tanks. With a view of the sky, the smolts oriented towards the lakes outlet in the normal magnetic field (Fig. 3) and in a field rotated 90 ° counterclockwise (Fig. 4).2.Under opaque covers, the smolts displayed a bimodal distribution. In the normal magnetic field, they oriented towards or away from the lakes outlet (Fig. 5). In the altered field, the axis of the distribution was rotated 56 ° away from the axis in the normal field (Fig. 6).

Population Structure of Columbia River Basin Chinook Salmon and Steelhead Trout

The population structure of chinook salmon and steelhead trout is presented as an assimilation of the life history forms that have evolved in synchrony with diverse and complex environments over their Pacific range. As poikilotherms, temperature is described as the overwhelming environmental influence that determines what life history options occur. The different populations represent ecological types referred to as spring-, summer-, fall, and winter-run segments, as well as stream- and ocean-type, or stream- and ocean-maturing life history forms. However, they are more correctly described as a continuum of forms that fall along a temporal cline related to incubation and rearing temperatures that determine spawn timing and juvenile residence patterns. Population structure of chinook salmon and steelhead in the Columbia Basin, therefore, is the reflection of the genetic composition of the founding source or sources within the respective region, shaped by the environment, principally temperature, that defines life history evolutionary strategy to maximize fitness under the conditions delineated. The key in developing an effective recovery program for chinook salmon and steelhead is to recognize that measures taken must address the genetic and biological requirements of the population unit within the environmental template identified.

The Controversy about Salmon Hatcheries

Abstract The use of hatcheries has been a subject of lengthy debate in the management of salmon and trout resources in the Pacific Northwest. The problem has resulted in part from the wide distribution of hatchery fish in circumstances where natural populations were disadvantaged by management policy involving hatchery fish and the confusion of the effects of management with the effects of artificial propagation. Recently, the controversy has been epitomized by the recommendations to fisheries management agencies that excess hatchery fish should not be allowed to spawn in the wild, and hatchery fish should be excluded from salmon populations listed under the Endangered Species Act. The authors of the present article disagree with those recommendations and conclude that hatchery fish have an important role in recovery and supplementation of wild stocks. The present article is an attempt to help give balance to the discussion by providing a different perspective on hatchery fish and the literature pertainin...

Artificial Selection and Environmental Change: Countervailing Factors Affecting the Timing of Spawning by Coho and Chinook Salmon

Abstract Spawning date is a crucial life history trait in fishes, linking parents to their offspring, and it is highly heritable in salmonid fishes. We examined the spawning dates of coho salmon Oncorhynchus kisutch and chinook salmon O. tshawytscha at the University of Washington (UW) Hatchery for trends over time. We then compared the spawning date patterns with the changing thermal regime of the Lake Washington basin and the spawning patterns of conspecifics at two nearby hatcheries. The mean spawning dates of both species have become earlier over the period of record at the UW Hatchery (since the 1950s for chinook salmon and the 1960s for coho salmon), apparently because of selection in the hatchery. Countering hatchery selection for earlier spawning are the increasingly warmer temperatures experienced by salmon migrating in freshwater to, and holding at, the hatchery. Spawning takes place even earlier at the Soos Creek Hatchery, the primary ancestral source of the UW populations, and at the Issaquah ...

Response of Juvenile Rainbow Trout to Turbulence Produced by Prismatoidal Shapes

Abstract Water velocity is a common measure of habitat suitability for salmonids. It is often noted that salmonid focal positions occur in low-velocity areas adjacent to high-velocity ones. Such locations are associated with increased turbulence. Turbulence in the stream regions typically occupied by salmonids is produced by flow separation around large objects such as rocks or on the riverbed. Turbulence has also been shown to increase the energetic cost of swimming for salmonids. Despite the link between cover and turbulence, no measurements of turbulence at the focal positions of juvenile salmonids have been reported in the literature. We measured turbulence at the focal positions of juvenile rainbow trout Oncorhynchus mykiss in a laboratory flume and found that those focal positions were characterized by low turbulence levels across a range of average velocities. Fish occupied highly turbulent locations if excessive average velocities were present. Eddy size, measured as the autocorrelation function o...

Use of the Average and Fluctuating Velocity Components for Estimation of Volitional Rainbow Trout Density

Abstract The relationship between discharge and fish density in streams is commonly accepted to be curvilinear, progressing from low discharge and low fish density to a peak and then declining to high discharge and low fish density. Discharge is related to water velocity; in general, as discharge increases velocity increases. Habitat complexity is an important aspect of salmonid ecology; more complex habitats support higher fish densities. Habitat complexity also influences the flow of water through the process of flow separation and turbulence production. More complex habitats generally exhibit higher levels of turbulence even though both may have similar average velocities. We tested whether the physical link between habitat complexity and turbulence was correlated with fish density. Turbulent kinetic energy and average velocity for three different levels of discharge and habitat complexity were measured in a flume. Turbulent kinetic energy was found to predict fish density, whereas average velocity did...

An Assessment of Oil-Spill Effects on Pink Salmon Populations Following the Exxon Valdez Oil Spill—Part 1: Early Life History

This paper discusses results of field programs initiated within a few days of the spill and designed to assess spill effects on critical early life stages of pink salmon in postspill years. Samples of water and stream sediments from throughout the spill area were used to define the exposure of pink salmon to residual hydrocarbons from the spill. Mean sediment concentrations of polycyclic aromatic hydrocarbons (PAH) up to 300 ppb were measured in oiled streams in 1989 and generally followed a downward trend toward background in 1990 and 1991. These PAH concentrations were then used in regression analyses of potential effects on key early life stages of pink salmon. Water samples taken from both nearshore feeding and rearing areas and offshore migratory areas show that hydrocarbon concentrations were from one to four orders of magnitude lower than concentrations reported in the literature to cause acute or chronic effects on fish species. The postspill field and laboratory studies of pink salmon early life stages included examination of potential effects on 1989, 1990, and 1991 eggs, fry, and juveniles. 28 refs., 8 figs., 8 tabs.

University of Washington zero-age coho salmon smolt production

Abstract Accelerated incubation and rearing of coho can result in the production of zero-age smolts and a return of 2-year old adult spawners. Sex ratio of returning adults is biased toward males. Size at return depends on marine residence location. Good smolt survival can be attained if release size is in excess of 10 cm, but the best criterion for migratory readiness is believed to be volitional migratory behavior.

Influence of Suspended Volcanic Ash on Homing Behavior of Adult Chinook Salmon

Abstract Adult male chinook salmon Oncorhynchus tshawytscha were tested for behavioral responses to suspended volcanic ash from Mount St. Helens, Washington. Chinook salmon exhibited a strong baseline preference for clean (ash-free) home water over a clean non-natal water source. The addition of ash to the home water significantly reduced preference for home water, apparently because of an avoidance response to ash, not an inability to identify home water. The ash also reduced upstream movement in the testing apparatus. The homing performance of displaced chinook salmon was assessed after a 7-day exposure to an ash suspension of approximately 650 mg/liter. The ash did not affect the proportion of fish that homed.