Occurrence, abundance and biomass of fish in rivers of Latvia in accordance with river typology

Abstract

This study analyses the structure of fish communities in 201 Latvian rivers: the number of species, their diversity, abundance and biomass of fish in accordance with the nationally accepted river typology and its parameters, i.e. the river basin area and the average slope. The number of species and their diversity as well as the abundance and biomass of fish vary significantly in rivers with different basin areas and temperature regimes. Latvian rivers can be classified into the following types based on the fish communities therein: (I) small coldwater rivers with trout and stone loach as dominant species, (II) small warmwater rivers dominated by stone loach, minnow, pike and perch, (III) medium coldwater rivers with such dominant species as brook lamprey, trout, minnow, stone loach and sculpin, (IV) medium warmwater rivers with pike, roach, gudgeon, minnow, stone loach and perch as dominant species, and (V) large potamal warmwater rivers dominated by pike, roach, chub, gudgeon, minnow, riffle minnow, ble...