CHAPTER XIII 

 DISTRIBUTION AND MIGRATIONS 



Science of Zoogeography. Marine and fresh-water fishes. Oceanic fishes. 

 Coastal fishes. Zones of distribution. Tropical Zone: Panama and 

 Suez Canals. South Temperate and Antarctic Zones. North Temperate 

 and Arctic Zones. Migrations of marine fishes: Tunny, Mackerel, 

 Pilchard, Herring, etc. Races of Herring. Origin of fresh-water fishes. 

 Catadromous and anadromous fishes. Distribution of Salmonidae. 

 Distribution of Ostariophysi. Zoogeographical regions. Australian 

 region: Wallace's Line. Madagascar. Neotropical region. Fishes of 

 South America and Africa compared. Ethiopian and Indian regions. 

 Palaearctic region. British fresh-water fishes. Nearctic region. 



The science of zoogeography or the geographical distribution of 

 animals presents many fascinating problems to the biologist, who 

 has to consider a variety of factors in order to understand the 

 almost cosmopolitan range of some species and the extremely 

 restricted habitat of others. In the case of terrestrial vertebrates, 

 the presence of such physical barriers as mountain ranges, arid 

 deserts, large stretches of water, and dense forests is generally 

 sufficient to explain the localisation of faunas into their own 

 particular regions. Similar physical factors probably serve to 

 limit the wanderings of many fresh-water fishes, but with all 

 the great oceans connected with one another, the dispersal of 

 marine fishes must be restricted by barriers of another kind. 

 The understanding of these involves the study of such diverse 

 factors as the temperature and salinity of the water, its chemical 

 properties, the nature and strength of the ocean currents, the 

 configuration of the coast-line, the presence of submarine 

 ridges and deeps, as well as the all-important subject of the 

 available food supply and its distribution. Nor is it sufficient 

 to consider only the barriers existing to-day, for the present 

 geographical range of many species has resulted from conditions 

 which exerted their influence in the more or less remote past, 

 when the disposition of the great land masses was quite different 

 (Fig. 97). A number of cases of apparently meaningless and 

 anomalous distribution became clear when considered in 

 relation to past history as unfolded by the geologist. 



The first and most obvious distinction which suggests itself is 



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