Graduate Thesis Or Dissertation
 

Biology of the ratfish, Hydrolagus colliei (Lay and Bennett)

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https://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/k643b424z

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  • In the fall and winter of 1965, 1966, and 1967, 298 ratfish (180 males, 118 females) were collected off the Pacific coast of Oregon and Washington and examined for food habits , parasites, growth relationships and a method of age determination. The following food organisms were found to be the most important in the collection; Pandalus, Crag o, Musculus, Amphissa, Pecten, and Brisaster. Two occurrences of cannibalism were found in ratfish collected off Cape Arago, Oregon. The parasite Gyrocotyle occurred in from 29. 2% to 65. 8% of the ratfish from the four collections made off Oregon. The copepod, Acanthochondria sp. , was found attached to the pelvic claspers of seven male ratfish from Cape Arago, Oregon. Age appears to be related to body length, with females growing faster and to a larger size than the males. The eye lens weights (wet and dry), vertebral radii, and body weights were compared to body lengths (S-V). General equations for body weight-body length (S-V) relationships (metric system) are Log weight = Log -4. 3217 + 3. 0546 Log length for the males and Log weight = Log -4. 1692 + 2. 9720 Log length for the females. No accurate method of determining age of the ratfish was found, although the body parts examined showed an increase in size with increase in body length. Ridges on the posterior side of the upper dental plate offer a promising indicator of age, but the relationship could not be confirmed.
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