A Model for Predicting Pacific Herring (Clupea harengus pallasi) Spawn Density from Diver Observations

A series of mathematical models were examined to predict the density of Pacific herring (Clupea harengus pallasi) spawn in 1-m2 quadrats from diver observations of the dominant vegetation substrate, the number of layers of eggs on the vegetation, and the density of the vegetation in the quadrat (percent cover). The most appropriate model was chosen statistically and used to make predictions for comparison with egg counts. Outliers were identified and if a plausible biological interpretation was found, these were deleted from the data series. The model provides an efficient and precise means for estimating herring spawn density from diver observations and could be incorporated into a sampling survey design for estimating spawn abundance for stock assessment.Key words: mathematical model, Pacific herring, Clupea harengus pallasi; spawn density, stock assessment