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781.
Zooplankton from coastal/continental margin environments can be transported long distances seaward into the subarctic North
Pacific by the large (100–200 km diameter) anticyclonic eddies that form annually in late winter along the eastern margin
of the Alaska Gyre. One recurrent region for eddy formation is off the southern tip of the Queen Charlotte Islands (near 52°N
132°W). Eddies from this source region (termed ‘Haida eddies’) propagate westward into open ocean waters during the subsequent
1–3 years, often to about 140°W, occasionally to mid gyre. Each eddy contains a core of anomalously low density water, and
produces an upward doming of the sea surface detectable by satellite altimetry, thereby aiding repeated ship-based sampling.
The zooplankton community in the eddies is a mixture between shelf/slope species (transported from the nearshore formation
region) and subarctic oceanic species (which colonize the eddy from the sides and below). This paper reports sequential observations
(late winter, early summer and fall seasons of 2000, and early summer and fall of 2001) of the abundance and distribution
of continental-margin zooplankton in the Haida eddies that formed in late winters of 2000 and 2001. Shelf-origin species declined
in abundance over time. Species that appeared to have a continental slope origin sometimes declined but sometimes persisted
and flourished. Transport and retention within the eddy appeared to be especially effective for species that undergo diel
vertical migration.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
782.
In 1978 the food and habitat resource partitioning of three small and common fish species, viz. Pomatoschistus microps (Krøyer), Gasterosteus aculeatus (L.) and Pungitius pungitius (L.) were studied in river Broälven estuary on the Swedish west coast (58°22′N, 11°29′E). The area was divided into three habitats, based on environmental features. In July, September, and October stomach contents and size distribution of each species present were analysed.In July there was high food and habitat overlap between the species. Interference interactions probably occurred between some size classes of P. microps and the other two species. P. pungitius was exposed to both intra- and interspecific interactions. In September the food and habitat overlaps between G. aculeatus and P. pungitius were high, while both had low food and habitat overlaps in relation to P. microps. Interactions between G. aculeatus and P. pungitius were probably influenced by more severe abiotic conditions in one habitat, which caused lower abundances there, and higher abundances in the other two habitats. In October no interactions were observed. These results indicate that competition for food at least temporarily determines the species distribution in a temperate estuary, and that estuarine fish populations are sometimes food limited. 相似文献
783.
784.
Since the 1970s, small-scale fisheries have had an important place in fisheries social science and in fisheries management. While there has been substantial discussion of what constitutes the category of small-scale fisheries, its considerable ambiguity is nevertheless often passed over. This paper argues that while the category of scale fisheries can be best understood in terms of scale, the underlying reason for the power of the category lies in the values of social justice and ecological sustainability that it has come to represent in response to dominant high modern narratives of change. Fisheries governance may better be served by prioritising these values rather than by making a fetish out of small-scale fisheries. 相似文献
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