Red and white Chinook salmon: genetic divergence and mate choice.

Chinook salmon (Oncorhynchus tshawytscha) exhibit extreme differences in coloration of skin, eggs and flesh due to genetic polymorphisms affecting carotenoid deposition, where colour can range from white to bright red. A sympatric population of red and white Chinook salmon occurs in the Quesnel River, British Columbia, where frequencies of each phenotype are relatively equal. In our study, we examined evolutionary mechanisms responsible for the maintenance of the morphs, where we first tested whether morphs were reproductively isolated using microsatellite genotyping, and second, using breeding trials in seminatural spawning channels, we tested whether colour assortative mate choice could be operating to maintain the polymorphism in nature.

Upper thermal tolerance of wild-type, domesticated and growth hormone-transgenic coho salmon Oncorhynchus kisutch.

In coho salmon Oncorhynchus kisutch, no significant differences in critical thermal maximum (c. 26·9° C, CTmax ) were observed among size-matched wild-type, domesticated, growth hormone (GH)-transgenic fish fed to satiation, and GH-transgenic fish on a ration-restricted diet. Instead, GH-transgenic fish fed to satiation had significantly higher maximum heart rate and Arrhenius breakpoint temperature (mean ± s.

Selection for upper thermal tolerance in rainbow trout (Oncorhynchus mykiss Walbaum).

Rainbow trout (Oncorhynchus mykiss Walbaum) in southern Western Australia have undergone passive selection for over 19 generations to survive high water temperatures. Based on the conceptual model of 'oxygen- and capacity-limited thermal tolerance', we measured critical thermal maximum (CTmax), maximum heart rate (fH,max) and aerobic scope to test the hypothesis that these rainbow trout can maintain aerobic scope at high temperatures through a robust cardiac performance supporting oxygen delivery. Across five family groups CTmax averaged 29.

Altered expression of growth hormone/insulin-like growth factor I axis hormones in domesticated fish.

There are genetically based differences in growth and behavior between domestic and wild (W) trout and salmon, although the molecular underpinnings of the physiological alterations have not been identified. To test for genetically based alterations in the GH/IGF-I axis, which is thought to mediate some of the differences in growth and behavior, we measured circulating concentrations of GH, IGF-I, and thyroid hormone (T(3)), as well as mRNA levels for GH, IGF-I, and GH receptor, from multiple tissues and from fish reared under different environments. Both age-matched and size-matched individuals were examined to overcome difficulties examining strains with inherently different growth rates (and, thus, body size at age).

Effect of an acid mine drainage effluent on phytoplankton biomass and primary production at Britannia Beach, Howe Sound, British Columbia.

We investigated the effect of acid mine drainage (AMD) from an abandoned copper mine at Britannia Beach (Howe Sound, BC, Canada) on primary productivity and chlorophyll a levels in the receiving waters of Howe Sound before, during, and after freshet from the Squamish River. Elevated concentrations of copper (integrated average through the water column >0.050 mgl(-1)) in nearshore waters indicated that under some conditions a small gyre near the mouth of Britannia Creek may have retained the AMD from Britannia Creek and from a 30-m deep water outfall close to shore.