Threatened endemic freshwater fishes of western greece and peloponnese-distribution, abundance, threats and conservation measures.
A research programme was undertaken with the three-fold objective to identify threatened freshwater fishes in western Greece and Peloponnese and to discuss the problems of fish conservation, especially with regard to anthropogenic influences on their habitats. The conservation status of the freshwater fish living in the study areas is reviewed. Some of these species are protected by national and international legal instruments.
However, conservation has proved difficult because of paucity of appropriate life-history and ecological data. Bearing in mind that management/conservation actions may fail if not based on sound biology, the research framework included distribution surveys, assessments of abundance, ecological description of habitats, collection of life-history and ecological data, identification of habitats that contain threatened species or are suitable for re-establishments, artificial breeding, analysis of the nature of threats, and suggestions for possible management actions.
Three species with restricted geographical distribution and low local densities were characterised as critically endangered, and a number of other species were characterised as locally threatened. Water abstraction for irrigation was ranked as the factor causing the most adverse impacts on the fish fauna. Swamp drainage has also caused the loss of many fish habitats. Other harmful impacts have been generated from dam operation and various water supply schemes, that have modified the flow pattern and have acted as barriers to dispersal. In addition, the irregular release of water through the dams causes erosion of the banks and damage to the aquatic vegetation and benthic invertebrate fauna.
Abstraction of pebbles and engineering works, such as bridges and river management for flood mitigation, have altered dramatically many riverine habitats and caused a destruction of spawning sites and nursery areas. The effects of pollution were difficult to be evaluated, due to that most of the endangered species live away from large centres of urban, agricultural and industrial development.
In the future, dangers may arise from the uncontrolled introduction of alien species that may interact with the indigenous fishes through predation and competition or cause harmful hybridisations.