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Environmental features influencing the non-reproductive distribution and success of riverine populations of Salmo trutta Linnaeus (brown trout) : a review of the literature.
thesisposted on 2023-05-27, 06:24 authored by Andrew, J. (Jane)
Abstract taken from part of the introduction: Despite past controversy, it is now agreed that there is one species of trout native to north-western Europe - Salmo trutta. As the ice retreated at the end of the last ice age the rivers of northern Europe were colonised via the sea by two successive forms of trout. Both of these forms gave rise to brown trout which lived wholly in fresh water. Some of their modern descendants migrate to the sea but no consistent morphological criteria have been found to distinguish sea-run from non-migratory brown trout. It is still common for sea-run trout to be called Salmo trutta trutta and freshwater brown trout to be called Salmo trutta fario (MacCrimmon and Marshall, 1968; LeCren, 1984). For the purposes of this review, both forms will be considered, but only in the freshwater resident phase. The brown trout (Salmo trutta Linnaeus) is native to the European coast of the Atlantic Ocean and to the coast of the Mediterranean Sea. Its natural distribution includes Iceland, the Scandinavian countries, northern Europe, Great Britain, the Mediterranean countries including northern Africa and the countries of the Middle East whose rivers drain into the Mediterranean Sea. The Caspian, Aral and Black Seas and their tributaries also contain natural populations of brown trout (MacCrimmon and Marshall, 1968). Stocking of waters around the world has taken place since 1852 and there are now self-sustaining populations of brown trout on all continents with the exception of Antarctica (MacCrirnmon, Marshall and Gots, 1970). Brown trout are now found in a wide range of lotic and lentic environments throughout temperate regions.In considering the wide variety of riverine environments available to fish populations, one must examine the basic factors causing variation. Geomorphological _ features including stream order, basin area, basin relief ratio (elevation of source divided by length of river), position of groundwater input and the level of the water table interact with the amount and variability of rainfall to create variations in the velocity of riverine waters (Hynes, 1970; Lanka et al., 1987). These occur on both a general (i.e. longitudinally from headwater to estuary) and localised basis and affect a range of stream features, such as channel morphology, temperature regime, turbidity, and sedimentation. The flow rate is thus largely determined by topographic and climatic conditions external to the river and can be considered as the major feature through which variation in the stream habitat is mediated.
Rights statementDept. of Zoology M.Sc. (qual.) Thesis, 1990