. Bulletin of the Museum of Comparative Zoology at Harvard College. Zoology. Effects of Expatriation in Fishes • O'Day and Nafpakfitis 83. Figure 4. The two-gyre system proposed by Worthington (1962). Reproduced from Deep-Sea Research. will remain in the Gulf Stream, while a few may follow the current until they return to the spawning grounds. In the expatriation area the young dojleini, apparently capable of adapting themselves to the physico- chemical factors, will grow to physical ma- turity. However, with ecological factors far from meeting the requirements of their reproductive physiology
. Bulletin of the Museum of Comparative Zoology at Harvard College. Zoology. Effects of Expatriation in Fishes • O'Day and Nafpakfitis 83. Figure 4. The two-gyre system proposed by Worthington (1962). Reproduced from Deep-Sea Research. will remain in the Gulf Stream, while a few may follow the current until they return to the spawning grounds. In the expatriation area the young dojleini, apparently capable of adapting themselves to the physico- chemical factors, will grow to physical ma- turity. However, with ecological factors far from meeting the requirements of their reproductive physiology, these fishes will fail to reproduce. There are remarkable differences between the temperature and salinity distributions in the expatriation area and the spawning area. Hjort {in Murray and Hjort, 1912: 444^45) wrote: "A peculiar feature is that all the [100 m] isotherms on the western side [of the North Atlantic] are quite close together, the water layers being squeezed between the oceanic subtropical waters from the south and the Labrador current from the north. All changes in temperature are therefore on the western side very sharp. On the eastern side the layers are spread out fan-wise, and as a consequence we may at a depth of 100 meters find the same temperature prevailing from north to south over wide areas . ." The average temperatures at a depth of 200 m in the North Atlantic (Fig. 5) show a pattern very similar to that described by Hjort for the 100-meter isotherms. A temperature profile across the Atlantic at 40°N shows that there is a sharp convergence of isotherms above 2,000 m in a westward direction (Fig. 6). At the same latitude, the isohalines show a marked convergence from east to west (Fig. 7). Briefly, then, the variation in both tem- perature and salinity with depth is much. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrati
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