A fish out of water?
Massive engineering works block some of the world's most powerful river systems to transform water energy into electricity. Industry uses water to cool manufacturing processes, and returns it to the river from which it was extracted perhaps hotter, perhaps dirtier, perhaps more toxic than it should be. Fishers, hurling dynamite onto coral reefs to blast their way to a quick haul, destroy the tender habitat upon which their livelihood depends. No wonder then that fish are running out of water and fish genetic diversity is under threat.
Aquatic resources are threatened by a growing level of human interference in order to meet human needs, not just for fish but also for water. On land it is the water that is running out as rivers fail to reach the sea and lakes contract, leaving erstwhile fishing ports high and dry. At sea it is the fish that are running out, the remaining stocks still over exploited, risking the life of the fishing industry and the life of the fish species.
Aquaculture, despite the threats to genetic diversity, is expanding rapidly. Nevertheless, barriers, both real and metaphorical, disrupt aquatic resources and the potential for aquaculture development. Water is required for irrigation as well as energy and many natural floodplains, which once provided a natural spawning ground for fish, are now dry as a result of high dykes or levées, conserving the water for more controllable distribution. This not only destroys an important fish habitat but the now-protected agricultural land may be a source of toxic agrochemicals, seeping back into the river system, yet further threatening the wild fish.
Habitats of wild, freshwater fish are destroyed not only because rivers no longer flow unimpeded but because exotic species are accidentially, or sometimes intentionally, introduced to water courses with unforeseen environmental consequences. Nile perch was introduced some years ago into Lake Victoria in Africa, the world's largest freshwater lake. The species proved too well suited to its new surroundings and fed on, and destroyed, indigenous fish species, disrupting the food webs of which these species formed an essential component.
While many environmental factors impinge on the potential for inland aquaculture, fish farming itself is often the source of its own destruction. Pollution arises from fish faecal waste and uneaten food. This excess nutrient in the water reduces oxygen levels and, therefore, productivity. Effluent discharges may be contaminated by antibiotics and disinfectants with unknown consequences for the natural environment. Farmed fish inevitably escape from time to time and may flourish, once free, eating smaller wild fish, or consuming their food, eventually taking over.
Aquatic diversity is sinking fast and species are disappearing when efforts at domestication have hardly begun. Aquaculture is seen as the main hope for increasing the world supply of fish but, with each species lost, there is also the loss of genetic material that could make that hope more realistic. Compare the modern hybrid fowl to its wild, totally undomesticated relatives. Or match, size for size, wild maize from the Andean hills with that grown under today's industrialized farming systems. Domestication demands diversity and that is no less true for fish than for poultry or maize. Tilapia, for example, is a fish species that has been greatly improved through this domestication process and is now farmed in some 80 countries, bringing benefits to producers and consumers. But consumers like variety and so does nature.
