Oncorhynchus mykiss mykiss (Walbaum, 1792)

在自然環境下，多棲息於冷而清澈的上游源頭、小溪、小河到大河或湖泊等，亦可見於溯河產卵的沿海小河，幾乎在水溫9-18℃的水體都可見其族群，但在夏季溫度超過25℃以上的水體及含氧量低的池塘則少見其族群。性情極為活潑，能跳躍攝餌，以陸生昆蟲、水生無脊椎動物及其他小型魚類為食；在海裡生活時則以小魚及頭足類為食。會進行小距離的遷移，如果是溯河產卵型或是湖泊型的魚種則會進行長距離的遷移。

Fish respond to magnetic fields: rainbow trout
 

The trigeminal cranial nerve of rainbow trout helps them detect magnetic fields by containing magnetosensitive nerve fibers.

 
  "In 1997, the first known magnetoreceptors -- directly linking magnetite to neural connections and activity -- were found in vertebrates. A team of zoologists from Auckland University, led by Dr. Michael Walker, had been studying this mysterious sense in trout, and knew that a region of its skull contained magnetite.

"Recording neural activity from that region, they discovered that a specific subgroup of nerve fibers within a branch of the trigeminal cranial nerve called the ros V nerve fired in response to changes in the surrounding magnetic field. They also found magnetite in a tissue layer directly beneath the trout's olfactory (smell) organs. When they injected a colored dye into the ros V nerve's newly exposed magnetosensitive fibers, the dye revealed that the fibers terminated and ramified all around the magnetite-containing cells within the trout's olfactory tissue." (Shuker 2001:46)
  Learn more about this functional adaptation.

Global Range: (>2,500,000 square km (greater than 1,000,000 square miles)) Native to streams along the Pacific coast of North America from the Kuskokwim River, Alaska, south to northern Baja California; also the upper Mackenzie River drainage (Arctic basin), Alberta and British Columbia, and endorheic (i.e. having no outflow of water) basins of southern Oregon (Page and Burr 1991). The species has been widely introduced and established in suitable habitats all over the world (Lee et al. 1980). At sea, O. mykiss occurs throughout the North Pacific above 40° N from the North American coast to the Sea of Okhotsk (Burgner et al. 1992); it is most abundant in the Gulf of Alaska and eastern part of the North Pacific, conforming to the 5°C isotherm in the north and 15°C isotherm in the south. Seasonal shifts in distribution are correlated with changes in water temperature (Sutherland 1973).

Enteric Redmouth Disease. Bacterial diseases