– The post smolt of anadromous Arctic charr (Salvelinus alpinus) from Lake Storvatn, northern Norway (70°39′48″), continued to feed and grow after their return to freshwater in late summer, but in late autumn (October) both their growth rate and feeding intensity ceased along with the drop in water temperature. In contrast, adult, sexually mature anadromous charr did not appear to feed during their freshwater residency. The stomach fullness of post smolts were similar to that of resident Arctic charr during early autumn, and their diets were similar, being dominated by pelagic prey such as surface insects, Holopedium sp., Bosmina sp. and chironomid pupae. Later in the autumn, the resident charr also included some more benthic prey, in particular gastropods, whereas the post smolts continued to feed predominantly on zooplankton and surface insects, but with a lower stomach fullness than the resident fish. This suggests that after arrival in freshwater, the post smolts continue their pelagic feeding behaviour displayed during the sea‐migration.
Following the 'Amoco Cadiz' oil spill, time-series sampling of the meiofauna was carried out from 1978 to 1984 in the intertidal zone of 3 sandy beaches on the northern Finistere coast (Brittany, France). Quantitative analysis documented 2 principal phases in the development of the main taxa (Nematoda and Copepoda). First came a degradation phase leading to impoverishment in density and diversity of the populations. Thls first phase could be subdivided into several stages corresponding mainly to the toxicity period and, on one beach (Kersaint), to a summer 'bloom'. Then came a recovery phase corresponding to a quantitative and qualitative reconstitution of the meiofauna. Each phase lasted a greater or lesser time according to station exposure and the considered taxon. A qualitative analysis of harpacticoid copepods illustrated the development of population dversity and 'ecological groups'. During the first phase, replacement of the original population by a substitute fauna was observed. Correspondence factorial analysis on the development of harpacticoid communities allowed a better understanding of the main pollution and recovery factors such as toxicity, organic matter, hydrodynamism and zoological groups. Meiofauna, particularly harpacticoid copepods, are significant bioindicators of ecological disturbances.
Smolt of anadromous Arctic charr Salvelinus alpinus (L.) migrating from Storvatn, northern Norway, had a similar feeding intensity as resident Arctic charr from the benthic-and pelagic zone in early summer in fresh water. While smolts fed mostly on surface insects, however, resident Arctic charr had a more broader diet consisting mostly of chironomids, Bosmina sp., benthic prey and surface insects. This indicates that Arctic charr smolts have adopted a surface oriented feeding behaviour prior to their sea migration.
The reproductive activity of eight harpacticoid copepod species (Canuella perplexa, Harpacticusflexus, Robertsonia celtica, Amphiascoides debilis, Amphiascoides debilis limicolus, Kliopsyllus constrictus, Paraleptastacus espinulatus and Asellopsis intermedia) was observed from 1978 to 1984 on three sandy beaches of Brittany (France) polluted by the 'Amoco Cadiz' oil spill. Species density, mean percentages of ovigerous females and of juveniles from the period of maximum pollution were compared to those of one or two years characteristic of the post-recovery period.During the year of maximum pollution (1979) the spring peak of density came often later than normal and was generally lower. The main effect of the pollution was on the reproduction cycles of the species. There was often a delay of one month or more in the appearance and peaks of both ovigerous females and juveniles. Moreover, the latter were often missing during strategic months of the usual reproduction period. The recovery generally occurred in 1980 or 1981.
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