Distribution, Age and Growth of Eastern Pacific Albacore (Thunnus alalunga Gmelin)

Abstract

Seasonal and regional variations in the abundance of albacore during the 1949, 1950 and 1951 British Columbia fishing seasons suggest that exploitable stocks occurred in increasingly northerly areas during July and August and in more southerly areas during late August, September and early October. Catches were composed of four length-groups with average lengths of 54.3, 62.9, 71.7 and 81.9 centimetres. These groups were sometimes fairly discrete, but usually overlapped broadly, so that it was necessary to plot frequency distributions on probability paper in order to choose the best points of separation.Concentric marks on the centra of vertebrae were used as indicators of the age of the fish. The relationship of body length to vertebral radius is rectilinear. There is good agreement between the estimated average length and standard deviation in length of the fish when grouped by length and when grouped by vertebral ring number. The ages indicated for the four groups are III, IV, V and VI; however the first vertebral ring is somewhat less clear than the others and if it were discounted these ages would be reduced by one year. The fish whose vertebrae were examined had almost completed a year's growth.The length-weight relationship is expressed by the formula, log W = −4.912 + 3.13 log L, where W is the weight in kilograms and L is the fork length in centimetres.