Length-weight Relationship, Food Habits, Parasites, and Sex and Age Determination of the Ratfish, Hydrolagus Colliei (lay and Bennett)'

In the fall and winter of 1965-1967, 292 ratfish (Hydrolagus colliei) Wi!re collected from four locations off the Pacific coast of Oregon. Specimens were examined for length-weight relationships, food habits, parasites, and a method of sex and age determination. Equations describing the body weight-body length (snout to vent) relationships were log weight = log -4.3217 + 3.0546 log length for males, and log weight = log -4.1692 + 2.9720 log length for females. The food organisms most important to ratfish were shrimp (Pandalus and Crago), mollusks (Musculus and Amphissa), and echinoderms (Brisaster). Two occurrences of cannibalism were found in ratfish collected off Cape Arago, Oreg. Infestations by Gyrocotyle ranged from 29 to 66% among samples from the four locations. The copepod, Acanthochondria sp., was attached to the claspers of seven males from Cape Arago. EYi!-lens weights (wet and dry), vertebral radii, basal sections of the dorsal spine and left pectoral fin, and body-length frequencies were studied, but no accurate method of age determination was found. Tritors on the posterior side of the vomerine dental plate may be indicative of age, but the precise relationship was not determined.