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Some features of the life history of the cockscomb prickleback : Anoplaruchus purpurescens Gill Peppar, John Lovell

Abstract

The cockscomb prickleback, Anoplarchus purpurescens Gill, family Stichaeidae, ranges from Attu Island and Pribilof Islands, Alaska, to central California. In British Columbia coastal waters it is a bottom-dwelling intertidal species, geographically sympatric with A. insignis, which appears to prefer deeper water than A. purpurescens. A. purpurescens was collected and studied at an intertidal site at Second Narrows, Burrard Inlet, Vancouver, British Columbia. Morphological variation within the population studied, was examined by both measurements and meristic counts. Data obtained were used to differentiate the population of A. purpurescens used in the study, from its sibling species A. insignis. Food and feeding habits were studied over a wide range in size, with emphasis on habitat and seasonal differences shown. Relative importances of various food items reflected differences in availability of organisms utilized as food at various tide levels. Food intake is curtailed in adult fish approaching and during the breeding season. Marking experiments were designed to examine movements, territoriality and homing behaviour. They showed movements of Anoplarchus to be rather restricted. Fifty-eight percent of recaptured marked fish showed a homing tendency. Marked fish were seldom found more than 50 feet from where originally captured. Territoriality was of the home-range type during non-breeding times of the year. With the beginning of pair formation in advance of spawning, defended territoriality is shown. Behaviour associated with courtship, parental care and interaction between the sexes subsequent to spawning, is described. Eggs were successfully hatched and the young are described. Spawning takes place in the months of January and February. The female Anoplarchus guards and tends its eggs. The newly hatched larvae show marked positive phototaxis for three to five days, suggesting a planktonic existence during this period; they then become negatively phototactic and seek the bottom. Age and growth were examined by the length-frequency method and otolith analysis. The population was found to be composed of individuals from less than one year of age, to greater than five years of age; representing year classes 1959 to 1963. Females show a slightly faster rate of growth than males and are larger than males at every year of age. The sex ratio favours females over almost the entire range in length exhibited. The value of exponent n, in length-weight relationship, W = c Lⁿ, was found to be 2.98585; log c, -5.31565. The sexes show a similar trend in values of coefficient of condition. The coefficient was at its lowest for specimens collected during the first month of the spawning season. Condition was examined on a size, sex and seasonal basis.

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