Aquarium Fish of the World [antikvár]

Preface TROPICAL FISH HABITATS Of our sun's nine planets, the earth on which we live, with its blue brilliance and teeming with life, is the most beautiful. Since its origin, the sea has been the cradle of life, nursing innumerable forms. Among the most successful are the fishes, whose present numbers may exceed three hundred thousand species. Of these, nearly one hundred thousand species live in fresh water. A large number of these inhabit the tropical and subtropical waters of South America, Africa and Southeast Asia. Many are remarkably specialized, as the photographs on the following pages will attest. Fish are all nature's gifts, living treasures of the tropical lands and waters of our bright blue planet. South America When I visited the Amazon, an exporter who obtains fishes from throughout the region said that each tributary river has its own distinct varieties of fishes. This explains how the waters of the Amazon can support 2,500-3,000 fish species, and why within the South American region, the total number of freshwater fish species approaches 5,000. The Amazon has its origins in the Andes, flowing rapidly down meandering valleys on the eastern slope of this enormous mountain chain, its volume increasing as it receives the waters of its many tributaries. Its flow velocity suddenly slows down as the Amazon crosses an almost flat plain which extends some 3,000 miles (4,800 km) to the Atlantic. Dropping only about 650 ft (200m) over this distance, the plain has a grade of but Va inch/mile (4 mm/km). Close to 1,000 mapped tributaries drain the approximately 2,4 miUion square mile (6.3 million square kilometer) Amazon Basin. Rainy and dry seasons alternate in the northern and southern portions of the Amazon Basin which straddles the Northern and Southern Hemispheres. Thus for one period of the year, water runs in from the north, and the following period, the Amazon's volume is swollen with water flowing in from the south. It is said that the waters of the Amazon equal two-thirds the volume of water carried by all the rivers of the world. The waters of the Amazon include innumerable swamps, springs, jungle brooks, as well as larger streams filled with exposed tree roots and fallen timber. This diversity of habitats affords ample scope for the evolution of specialized life-styles, resulting in the present assemblage of more than 3,000 species. It would not be an understatement to say that almost all the fishes living within the Amazon system are fantastic. These include some of the world's largest freshwater fishes such as the Pirarucu and many of the giant predatory cat-fishes that live in the main channels of the larger rivers. Small forest brooks support dozens of colorful characins, while the "king" of tropical fishes, the discus, lives in oxbow lakes. The Amazon is also a treasury of fish of peculiar habits and shapes, exemplified by the mimicry of the leaffish, the flat-bodied freshwater rays and many species of knifefishes. The bountiful "mother" Amazon promises to remain a treasury of aquarium fishes forever, if protected. Africa Another big river well worth the aquarist's attention is the Zaire (Congo) River in Africa. More than 500 species have been reported from this river which stretches 2,700 miles (4,400 km) from source to mouth. As the Zaire Basin has not been fully explored by ichthyologists, the inventory of its fishes remains incomplete. Many colorful fishes also live in the brooks and rivers of the tropical rain forests or jungles stretching from the estuary of the Zaire, northwestwards to that of the Senegal. Among these are the vividly colored cichlids called "Jewel Fish" by aquarists, upside-down catfish with their peculiar swimming orientarion and the weakly electric, elephant-nose fishes or mor-myrids. Their mysterious behavior and morphology are no less fascinating than those of the Amazon fishes. Fishes of western Africa are not exported in numbers to compare with those of Amazonia, but aquarists' interest in this region will no doubt increase as more of its attractive fish are introduced to the hobby. The most interesting African fishes at present available to aquarists are the cichlids native to the Great Rift Valley lakes of Tanganyika and Malawi in eastern Africa. These lakes were formed relatively recently, sometime between ten and two million years ago. So far, about 500 species in Lake Malawi and 200 in Lake Tanganyika have been recognized, and these along with the approximately 300 in nearby Lake Victoria represent the better part of around 2,000 cichlids known globally. It is certain that unknown species remain to be discovered there, and it appears likely that in many instances several distinct species have been lumped under a single name. The evolution of new species is actively in progress, so that several steps in this process may actually be observed. Accordingly, these lakes may be considered a treasury for both ichthyologists and aquarists. Another inviting group of African fishes are the rivuUns. These wonderful fishes include many species with brilliant coloration and elegant finnage. Many are annual killifishes whose eggs have the marvelous ability to survive the African dry season buried in the mud of their seasonally flooded habitats.