Seasonal and geographical distribution of pelagic copepods in Oregon coastal waters

• Main Author: Cross, Ford A.
• Other Authors: Oceanography, Oregon State University. Graduate School
• Format: Master Thesis
• Language: English; unknown
• Published: Oregon State University
• Subjects: Copepoda; Pseudocalanus minutus; Copepods
• Online Access: https://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/vq27zr456

The copepod population in Oregon coastal waters was examined from 116 oblique plankton tows taken during 1962. Quantitative Clarke- Bumpus samplers were used and stations ranged from 5-105 miles from shore along four hydrographic lines. Forty-six species of copepods were identified. The total adult population varied according to distance from shore, season and hydrographic line sampled. Populations in neritic regions reached highest abundance during the spring and summer months while offshore populations reached peaks only during April and May. Two unusually high populations recorded during July appeared to be linked to the effects of upwelling and/or discharge from the Columbia River. Population diversity indices were calculated to show temporal and spatial change in percent species composition. The seasonal and spatial abundance of the total copepodite population was very similar to that of the adult population. Oithona similis Claus was the dominant cyclopoid species, and often the most abundant of all species. Pseudocalanus minutus (KrOyer) was the most abundant calanoid copepod. Acartia longiremis (Lilljeborg) was an important member of the copepod community during the summer months, and only in neritic areas. It is suggested that Acartia danae Giesbrecht and Centropages mcmurrichi Willey may be used as reciprocal indicators of seasonal change in surface current movement off Oregon. Their distributions appeared to correlate closely with surface water characteristics during different seasons of the year.