ISSN:
1095-8649
Quelle:
Blackwell Publishing Journal Backfiles 1879-2005
Thema:
Biologie
Notizen:
To examine the larval competition between wild and hatchery ayu in the culture ponds, mixed rearing of 580 000 wild and 520 000 hatchery larvae was carried out in two 25-m3 ponds for 3 months, in contrast to the control in which 860 000 wild larvae were reared in another pond.The number of wild larvae in the mixed-rearing treatments decreased rapidly 20 days after the start of mixed rearing, in contrast to hatchery larvae. Mortality of wild larvae was almost 100% at the end of the experiment (3 months), while the hatchery larvae showed the usual survival rate of 15–16%. In the control pond, however, 16% of the wild larvae survived. The wild larvae grew much slower (0.10mmday -1) than the hatchery larvae (0·26 mm day -1) in the mixed-rearing ponds, whereas the wild larvae in the control pond showed almost the same growth rate (0·24 mm day -1) as hatchery larvae. On day 6 the gut fullness of wild larvae was only 30% of that of the hatchery larvae in the mixed-rearing experiments. On day 46 the wild larvae occurred deeper in the mixed-rearing ponds than the hatchery larvae. This depth difference in vertical distribution appeared to cause a disadvantage for the wild larvae in the competition with hatchery larvae, since the food was supplied at the surface. Thus, the wild larvae starved and died.
Materialart:
Digitale Medien
URL:
http://dx.doi.org/10.1111/j.1095-8649.1989.tb03322.x
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