Graduate Thesis Or Dissertation
 

Distribution of Euphausiacea and Copepoda off Oregon in relation to oceanographic conditions

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https://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/7p88cj517

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  • Fifty-two one-meter plankton net samples from four stations off Newport, Oregon, were examined for composition and abundance of euphausiids and copepods. They provided data on dominance, species associations and environmental relationships. The euphausiid-copepod population off Oregon is composed of 12 numerically dominant species. These species occurred in most of the samples regardless of season or location. In order of their percentage contribution these species were Euphausia pacifica, Metridia pacifica, Calanus finmarchicus, Calanus pacificus, Eucalanus bungii, Calanus plumchrus, Calanus A., Metridia lucens, Thysanoessa spinifera, Acartia longiremis, Aetideus armatus and Calanus tenuico rnis. Sixty-seven other species were collected, several undergoing distributional changes in response to changing oceanographic conditions. Three species, Nematoscelis difficilis (d), Rhincalanus nasutus and Acartia danae are associated with the fall influx of water from the south . Tessarabrachion oculatus, Eucalanus elongatus hyalinus, Pseudocalanus minutus and Oithona spinirostris were primarily summer species. Eighteen other species occurred consistently at NH-45 and beyond throughout the year with an occasional shoreward extension in distribution during the winter. Two methods of association analysis were used. The Fager- McConnaughey method, which utilizes only presence or absence, produced 47 separate associations. Most of these were determined by a few infrequent or rare species. The Sanders method, which utilizes relative abundance, produced six basic associations which differed mainly in the proportions of the dominant species rather than major changes in species composition. Neither method revealed well defined communities off Oregon, probably because of the absence of rapid or extreme fluctuations in the environment or because of the small geographical area sampled. The similarity between species associations were compared with the temperature and salinity relationships indicative of changes in the physical environment. Higher affinities occurred between samples taken under similar temperature and salinity conditions than occurred between samples from different conditions.
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