Vestnik MGTU (Jun 2019)
Distribution and spawning area of Atlantic salmon Salmo salar L. in the River Ura (the Murmansk Region)
Abstract
The development of measures to preserve the population of Atlantic salmon has been carried out on the basis of the results of studying the state of its habitat and the conditions of reproduction. During the survey of the habitat conditions of this species in the River Ura (the Murmansk region, Russia), the area of spawning and nursery fund has been determined, the qualitative and quantitative distribution of salmon in the river basin has been established, and the migration barrier (waterfall) and the bypass for this obstacle have been described. The data obtained during the calibration of spawning and nursery plots and juveniles fishing have indicated that Atlantic salmon Salmo salar L. is widely distributed in the River Ura and runs along the main watercourse, three tributaries of the 1st order and one inflow of the 2nd order. The waterfall located on the River Ura at the distance of 28 km from its mouth does not limit the distribution of salmon which has the ability to make spawning migration along the creek bending the waterfall. The total area of the spawning and nursery fund is 69.4 ha, 83 % of which are located in watercourses below the waterfall. Spawning and nursery habitat of the Atlantic salmon is represented by a variety of habitat conditions with various longitudinal relief of the lake - river system, and the fractional composition of the bottom substrate. During the studies it has been noted a relatively high content of gravel and cobble fractions forming the most important types of spawning and nursery grounds, most suitable for Atlantic salmon spawning. "Spawning-nursery" grounds (42 %), as well as "spawning-nursery grounds with spawning grounds predominance" (35 %) constitute the bulk of spawning and nursery fund of the Atlantic salmon in the River Ura basin. Nursery grounds play a smaller role in its formation. The role of the latter is more noticeable in the river reaches above the waterfall where their share reaches 50 %.
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