The groundfish trawl fishery operating off the coasts of Oregon
and Washington 1985-1987 caught six major assemblages of species
which could be treated as units in developing mixed-species
management plans. Eighty-one percent of the tows observed on
commercial vessels were consistently placed in one of the assemblage
designations using three multivariate techniques. Two of the
assemblages were dominated by a single species, pink shrimp (Pandalus
jordani) or widow rockfish (Sebastes entomelas). The other
assemblages identified were: a deepwater rockfish assemblage, a
deepwater Dover sole assemblage, a nearshore mixed-species
assemblage, and a bottom rockfish assemblage. The assemblage
designations of the consistently placed tows were predicted with an
estimated 85% average accuracy using discriminant functions based on
the gear used and bottom depth fished. Fishermen had different
targets (intended catch) for each assemblage caught. The mixed-species
assemblages had several targets, representing at least some
of the dominant species in the assemblage. Targeting and discarding
information indicated that fishermen did not always intend to catch
the species together; there were unintentional or unavoidable catches
of all the major species except for shrimp in the shrimp assemblage.
Discarding occurred in all the assemblages, primarily due to
unmarketable species or fish that were too small to market.
Monitoring the assemblages over time could be accomplished by using
the defined strategies with logbook data, particularly if the large
and small rockfish categories were used to consistently separate
shelf and deepwater rockfish. The defined strategies could not
effectively predict the research cruise assemblages or catches;
research data do not accurately describe commercial catches. / Graduation date: 1994
| Identifer | oai:union.ndltd.org:ORGSU/oai:ir.library.oregonstate.edu:1957/35586 |
| Date | 23 February 1994 |
| Creators | Rogers, Jean Beyer |
| Contributors | Pikitch, Ellen K. |
| Source Sets | Oregon State University |
| Language | en_US |
| Detected Language | English |
| Type | Thesis/Dissertation |
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