Interbreeding with Domestic Strain Increases Foraging under Threat of Predation in Juvenile Steelhead Trout (Oncorhynchus mykiss): An Experimental Study

1991 ◽  
Vol 48 (2) ◽  
pp. 243-247 ◽  
Author(s):  
Jörgen I. Johnsson ◽  
Mark V. Abrahams
Keyword(s):  
Experimental Study ◽  
Rainbow Trout ◽  
Oncorhynchus Mykiss ◽  
Foraging Behaviour ◽  
Wild Population ◽  
Mortality Rates ◽  
Wild Fish ◽  
Risk Exposure ◽  
Steelhead Trout ◽  
Safe Area

The foraging behaviour of laboratory-reared juvenile steelhead trout (Oncorhynchus mykiss) and steelhead/domesticated rainbow trout hybrids were compared. In 10 replicate experiments, 10 fish from each strain were allowed to choose between foraging in a safe area or an area containing a predator. The hybrid trout were significantly more willing to risk exposure to the predator than were the steelhead. It was possible that differences in the relative willingness to risk exposure may have reflected differences in their susceptibility to predation. A second experiment measured the susceptibility of these two strains to the predator by simulating standardized encounters between predator and prey. Both strains suffered identical mortality rates and therefore were considered to be equally susceptible to the predator. This experiment confirmed that the hybrid trout were significantly more willing to take risks than the wild steelhead. These results indicate that interbreeding between escaped hatchery and wild fish may have a potentially damaging effect on the wild population.

Effect of Stocking Density on the Survival, Growth, and Dispersal of Steelhead Trout Fry (Salmo gairdneri)

1987 ◽  
Vol 44 (2) ◽  
pp. 271-281 ◽  
Author(s):  
Jeremy M. B. Hume ◽  
Eric A. Parkinson
Keyword(s):  
British Columbia ◽  
Overall Survival ◽  
Stocking Density ◽  
Mortality Rates ◽  
Wild Fish ◽  
Density Effect ◽  
Salmo Gairdneri ◽  
Steelhead Trout ◽  
Density Dependent ◽  
Coastal British Columbia

In a coastal British Columbia stream a stocking density of between 0.3 and 0.7 fry/m2 maximized the production of steelhead trout (Salmo gairdneri) parr and smolts. A severe autumn flood doubled the mortality rates of fry stocked at densities of 0.7 fry/m2 or higher but had little effect on fry stocked at lower densities (<0.15 fry/m2). Overall survival to smolts appeared to be lower than measured elsewhere for wild fish (2 vs. 4.5 – 18%). The proportion (<10%) of surviving fry found below the stocked sections was considered to be an indicator of potential displacement mortality in streams with no vacant downstream areas. This downstream dispersal was not density dependent and was small in comparison with the mortality of nondispersing fish. Although initial fry and parr sizes were density dependent, there was no detectable density effect on older parr or smolt sizes.

Experimental study of the connections of the gustatory system in the rainbow trout,Oncorhynchus mykiss

2003 ◽  
Vol 465 (4) ◽  
pp. 604-619 ◽  
Author(s):  
Mónica Folgueira ◽  
Ramón Anadón ◽  
Julián Yáñez
Keyword(s):  
Experimental Study ◽  
Rainbow Trout ◽  
Oncorhynchus Mykiss ◽  
Gustatory System ◽  
Rainbow Trout Oncorhynchus Mykiss

Hybridization with Domesticated Rainbow Trout (Oncorhynchus mykiss) Reduces Seasonal Variation in Growth of Steelhead Trout (O. mykiss)

1993 ◽  
Vol 50 (3) ◽  
pp. 480-487 ◽  
Author(s):  
Jörgen I. Johnsson ◽  
W. Craig Clarke ◽  
Ruth E. Withler
Keyword(s):  
Growth Rate ◽  
Seasonal Variation ◽  
Rainbow Trout ◽  
Oncorhynchus Mykiss ◽  
Natural Waters ◽  
Salt Water ◽  
Feeding Activity ◽  
Steelhead Trout ◽  
Rainbow Trout Oncorhynchus Mykiss ◽  
Winter Conditions

We tested the hypothesis that hybridization with domesticated rainbow trout (Oncorhynchus mykiss) reduces the seasonal variation in growth in both fresh and salt water in anadromous steelhead trout (O. mykiss). The seasonal variation in freshwater growth was more pronounced in the steelhead trout than in the hybrid and domesticated trout. Consequently, differences in growth rate among groups were considerably higher during winter than in fall or spring. We suggest that high feeding activity during unfavourable winter conditions in natural waters is maladaptive, but is not selected against in protected hatchery environments with a continuous food supply. This may lead to genetic divergence in feeding physiology and/or behaviour between steelhead trout and domesticated rainbow trout. Growth rates in experimental groups transferred to seawater in December relative to groups transferred in April were faster in rainbow and hybrid trout than in steelhead trout. The results support the hypothesis that seasonal variation in seawater growth in steelhead trout is reduced by crossing with domesticated rainbow trout.

Comparisons between hatchery and wild steelhead trout (Oncorhynchus mykiss) smolts: physiology and habitat use

2006 ◽  
Vol 63 (7) ◽  
pp. 1627-1638 ◽  
Author(s):  
Megan S Hill ◽  
Gayle Barbin Zydlewski ◽  
William L Gale
Keyword(s):  
Habitat Use ◽  
Atpase Activity ◽  
Oncorhynchus Mykiss ◽  
Plasma Osmolality ◽  
Wild Fish ◽  
Microhabitat Use ◽  
Steelhead Trout ◽  
Hatchery Fish ◽  
Before And After ◽  
Seawater Challenge

Hatchery steelhead trout (Oncorhynchus mykiss) smolts, progeny of a newly founded native origin broodstock, were released into Abernathy Creek, Washington, in 2003 and 2004. After release, saltwater tolerance, gill Na+,K+-ATPase activity, and habitat use were compared. A subsample of hatchery and wild steelhead trout were implanted with 23 mm passive integrated transponder (PIT) tags each year. PIT-tagged migrants were used for physiological comparisons. Hatchery fish were significantly larger than wild fish. Hatchery migrants expressed significantly lower levels of gill Na+,K+-ATPase activity than wild migrants. After a 24 h seawater challenge, hatchery migrants had significantly higher plasma osmolality and [Na+] than wild migrants. Microhabitat use of PIT-tagged hatchery and wild individuals in a control (wild fish only) and effect (hatchery and wild fish) site were compared before and after the introduction of hatchery fish. No difference was detected in hatchery and wild smolt habitat use. Wild fish did not change their habitat use after the introduction of hatchery fish. Although hatchery and wild fish differed in smolt physiology, differences in short-term use of freshwater habitat were not detected, and hatchery fish did not appear to displace wild fish.

Comparison of Three Anadromous Rainbow Trout (Oncorhynchus mykiss) Populations Using DNA Fingerprinting and Mixed DNA Samples

1994 ◽  
Vol 51 (S1) ◽  
pp. 252-257 ◽  
Author(s):  
Paul Spruell ◽  
Shawn A. Cummings ◽  
Yousok Kim ◽  
Gary H. Thorgaard
Keyword(s):  
Image Analysis ◽  
Genetic Variation ◽  
Rainbow Trout ◽  
Oncorhynchus Mykiss ◽  
Dna Fingerprinting ◽  
Steelhead Trout ◽  
Rainbow Trout Oncorhynchus Mykiss ◽  
Oligonucleotide Fingerprinting

DNA fingerprinting of 15 individuals from three populations of steelhead trout (Oncorhynchus mykiss) was compared with DNA fingerprinting of mixtures of 15 individuals from the same populations. Three oligonucleotide fingerprinting probes were used to detect genetic variation in individuals and mixtures. Scanning image analysis coupled with customized software was used to assign band identity. The degree of band sharing of individuals within and between populations was then determined. Although band-sharing estimates were similar within and between populations, bands found predominately in one population were identified. DNA fingerprinting of mixtures detected bands found only in the majority of the individuals in the mixture, allowing differences between populations to be more readily identified.

Bias and significance of relative reproductive success estimates based on steelhead trout (Oncorhynchus mykiss) data: a Bayesian meta-analysis

2011 ◽  
Vol 68 (10) ◽  
pp. 1827-1835 ◽  
Author(s):  
Shuichi Kitada ◽  
Hirohisa Kishino ◽  
Katsuyuki Hamasaki
Keyword(s):  
Reproductive Success ◽  
Oncorhynchus Mykiss ◽  
Meta Analysis ◽  
Wild Fish ◽  
Steelhead Trout ◽  
Bayesian Hierarchical ◽  
Hatchery Fish ◽  
In The Wild ◽  
The Mean ◽  
Log Normal

The evaluation of the reproductive success (RS) of hatchery fish in the wild is one of the most important issues in hatchery supplementation, aquaculture, and conservation. Estimates of the relative reproductive success (RRS) have been used to evaluate RS. Because RRS may vary greatly depending on cross, years of release, and environmental conditions, we introduced a log-normal distribution to quantify the variation. The classical estimator of RRS based on multiple measurements is contrasted with the mean of this distribution. We derived the mean, variance, and relative bias and applied our Bayesian hierarchical model to 42 empirical RRS estimates of steelhead trout ( Oncorhynchus mykiss ) in the Hood River, Oregon, USA. The RRS estimate generally had an upward bias. Although the average level of RRS implied the reproductive decline of hatchery fish and wild-born hatchery descendants, we could not reject the null hypothesis that hatchery fish and their descendants have the same chance of having smaller RS than wild fish as they do of having larger RS than wild fish.

Seasonal Changes in Osmoregulation, Cortisol, and Cortisol Receptor Activity in the Gills of Parr/Smolt of Steelhead Trout and Steelhead-Rainbow Trout Hybrids, Oncorhynchus mykiss

1994 ◽  
Vol 93 (1) ◽  
pp. 103-113 ◽  
Author(s):  
J.M. McLeese ◽  
J. Johnsson ◽  
F.M. Huntley ◽  
W.C. Clarke ◽  
M. Weisbart
Keyword(s):  
Rainbow Trout ◽  
Oncorhynchus Mykiss ◽  
Seasonal Changes ◽  
Receptor Activity ◽  
Steelhead Trout

Hybridization with domesticated rainbow trout reduces seasonal variation in seawater adaptability of steelhead trout (Oncorhynchus mykiss)

Aquaculture ◽  
1994 ◽  
Vol 121 (1-3) ◽  
pp. 73-77 ◽  
Author(s):  
Jörgen I. Johnsson ◽  
W.Craig Clarke ◽  
John Blackburn
Keyword(s):  
Seasonal Variation ◽  
Rainbow Trout ◽  
Oncorhynchus Mykiss ◽  
Steelhead Trout
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