A STATISTICAL STUDY OF THE ESTIMATION OF ABUNDANCE OF SARDINE (SARDINOPS CAERULEA) EGGS

Abstract

The reliability of the estimation of abundance of sardine (Sardinops caerulea) eggs is examined from two points of view. Analysis of egg observations collected on spawning surveys off southern California in 1941 indicates that the counts are consistent with the hypothesis that the egg population is distributed according to the negative binomial contagious distribution. Calculation of 95% confidence limits shows that the cruise estimates are subject to a variation of one‐half or double the estimate on the average. A seasonal estimate is probably subject to wider variation than the cruise estimates. Sardine egg observations collected from a 400 square mile grid of 25 stations off Baja California in 1952 over five days show important time and spatial variations. The coefficient of variation of an estimate of abundance of the egg population within the grid for the five day period from a single observation is estimated to be 31.1. The corresponding coefficient of variation of a sum of 40 counts from the grid is 4.9. The implications of this variability for the design of egg sampling surveys are discussed. © 1960, by the Association for the Sciences of Limnology and Oceanography, Inc.