Rainbow trout (Parasalmo mykiss)
Mikizha (mykyz) is the native Kamchadal name of the brightly colored resident fish that bears the name “rainbow trout” on the American side of the Pacific. Lots of the Russian scientists do not agree that both this trout and steelhead belong to the genus Oncorhynchus; they place the “noble Pacific salmon” into the Parasalmo genus, relative to Salmo. This genus contains steelhead, rainbow, and cutthroat trout.
Rainbow trout as a species can occupy a very broad ecological niche and are represented by four main forms: river-resident, lake-resident, coastal (estuarine), and sea-run (anadromous). The true sea-run form is called steelhead (see previous chapter). The range of the resident trout in Asia is much bigger than the anadromous form (steelhead). They are present in most rivers of Kamchatka with the exception of its northern part at the narrow neck of the peninsula. Besides Kamchatka, the only part of Asia where you can catch “wild” natural rainbow trout is the Bolshoi Shantar Island in the western part of the Sea of Okhotsk.
Kamchatka trout is silvery high-bodied fish with bright pink stripe on its sides, the same pink color on the gill covers, and many black, often X-shaped spots on the head, body and fins. On the island of Bolshoi Shantar, the species is mostly quite dark in color – gray-pink with a crimson stripe and a very dark back. The general tone of her body is most often not white, but yellow, gray-yellow or pinkish-gray.
In some rivers of Kamchatka (for instance, the Tigil) a small percentage of trout specimens have red marks below the gills. On the Bolshoi Shantar Island, such dots were observed on all specimens of the local rainbow trout. These red “cutthroat” marks are an important distinguishing peculiarity of another American salmonid fish — the cutthroat trout. Probably the Asian trout, which has both pink stripes and red cutthroat marks, is related to the ancestral form of these two American species.
In river drainages as a whole, different ecological forms of Parasalmo mykiss form a joined stock or population; this is a flexible system, which can fine-tune itself for optimal use of available food resources. In the rivers with abundant food, most small trout will stay in freshwater. In streams with low productivity, they will go out into the sea to feed. In the upper reaches of big rivers situated further than 200 km from the ocean and in the tributaries to productive lakes, most of the trout are resident and there is no anadromous form. In many rivers of the Kamchatka Peninsula the average weight of trout in catches is 0.8–1.2 kg; in the best streams the 2–3 kg specimens are common.
In medium-sized streams (for instance, in the Utkholok River of the northwestern Kamchatka) different ecological forms are present. Here you can catch typical river-resident trout, “coastal” trout, and the true anadromous form — steelhead. Coastal trout behave similar to chars: in summer this fish goes out into the estuary or sea, and in the fall enters the river for spawning and wintering. This coastal form of rainbow trout can often be bigger than 2 kg; its body is much heavier and more round than the rather flat resident fish. The maximum weight of the coastal or estuarine trout (or of resident fish in big rivers and lakes) can be up to 7–8 kg.
From the small streams of the Western Kamchatka the absolute majority of the mikizha parr go out into the sea (become steelhead), with only a few males staying in freshwater. Spawning of all forms of Asian rainbow trout occurs in the spring, in May (in the south of the range) or in beginning of June (in the northwest of the Peninsula). Spawning “dress” of all these different fish is very similar: they become dark and their gill plates and pink stripes are bright crimson.