The inland water system in our area has changed greatly during the faunal history of the Middle East. Rivers altered their flow direction and water links between various systems were formed and once again severed. Fish species of different origins expanded their distribution areas or were driven out by new invaders. These events shaped the fish fauna in our country.
Fish have penetrated Israel via diverse routes. African species arrived in several waves – most via the Pelusiac (or Pelusian) branch of the Nile River and some possibly via the Mediterranean (Cichlidae). Fish from the Tigris-Euphrates river system reached Mediterranean aquatic networks, such as the Orontes, at a time when these systems were linked. From there they spread to the Litani-Jordan river system when these were connected, which explains how fish from Asia Minor and the Levant penetrated into Israel. Aquatic systems in the western Arabian Peninsula were once much more plentiful than today and were inter-connected during certain periods. These links reached as far as the southern Dead Sea and were used as a passage route by fish.
In addition there are a number of freshwater fish of marine origin (species from the families: Blenniidae, Mugilidae and Anguillidae). Some consider Salaria fluviatilis, a freshwater species par excellence throughout the entire Mediterranean region, to be a relict from the Tethys Sea period.
B. The damage to inland water body habitats
Wetlands are considered extremely sensitive to development processes and are in danger of extinction throughout the world, particularly in arid or semiarid countries such as Israel. Threats to these habitats result from a number of factors:
» Increasing exploitation of water sources for human needs.
» Drainage of wetlands for agriculture or urban development.
» Accelerated exploitation of groundwater reservoirs that leads to the drying of surface water bodies.
» Processes of fragmentation and barrier creation between neighboring water bodies or water bodies that were previously linked by continuous flow.
» Discharge of effluents and wastewater into stream and riverbeds.
» Pisciculture in natural habitats and deliberate and accidental stocking of natural habitats with exotic fish species.
The effect of these factors on the populations of aquatic organisms is also amplified, among other reasons, by the following habitat characteristics:
a. the dimensions of most terrestrial water bodies are small, with corresponding small fish populations;
b. many water bodies are regularly or temporarily isolated from neighboring water bodies;
c. poisons and fertilizers are discharged into water bodies from agricultural and industrial areas and aquatic animals are affected instantly by pollution.
This combination of sensitivity to detrimental factors and to other side effects of anthropogenic activity has probably brought wetlands throughout the world closer to extinction than any other habitat.
C. Necessary conservation steps
Conservation steps for freshwater fish can only be taken by preserving their habitats from pollution, drainage and structural modifications. Establishing survival (or breeding) nuclei for some of the threatened species should be considered in cases where there is a chance of habitat improvement in the future. In addition, as a result of objective problems in assessing the dangers to or the status of the fish population in a changing environment, a regular fish monitoring system should be established in the entire Israeli aquatic system.
D. Status of the class species in Israel
Five fish species have become extinct from freshwater bodies during the 20th century.