Fish fauna rivers

Grande, L. (1984). Paleontology of the Green River formation with a review of the fish fauna. Geological Survey of Wyoming Bulletin, 63 1-333. 

In alpine regions, especially in maritime climates, snow depths may be considerable. This insulates the stream environment from subzero temperatures. River ice is an important environmental component of alpine rivers and has resulted in adaptive mechanisms among the fauna [50, 51]. Despite these adaptations, winter conditions inevitably cause high mortality to stream invertebrates and fish, especially in reaches with unstable snow and ice cover and thereby susceptible to formation of frazil and anchor ice. The lack of winter ice cover in lake outflows and groundwater-fed reaches provides a favourable environment for primary producers and those benthic invertebrates utilising primary production [52]. 

The river mouth area usually has a specific soil and vegetation cover with predominately boggy and meadow soils, aquatic or hygrophilous plants it has peculiar and rich fauna (fish, fowl, fur-bearing animals, etc). The landscape of land patches within the river mouth area sometimes differs radically from the surrounding area landscape and is azonal, particularly in geographical zones insufficiently wet (steppes, semideserts, and deserts). 

Many parasite pathogens are transferred to fish stocks via indigenous fish, ubiquitous in the local natural aquatic environment, and thus farm site selection should take this into account in disease prevention. Knowledge of pathogens in the ecosystem of the culture site and their seasonal dynamics would be a valuable weapon in the armoury against epizootics of cultured fish, yet this is rarely included in the preliminary surveys. Lakes, rivers, inshore and offshore waters have characteristic faunas which, known and understood, enable the analysis of risk of transfer of parasites into farm fish and for effective methods to be put into place to minimise or prevent introductions, e.g. fallowing, filters etc. to minimise the threat of epizootics. 

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