In-season Forecast of Chum Salmon Return Using Smoothing Spline

Kyuji Watanabe

doi:10.4172/2150-3508.1000173

Abstract

We developed an in-season forecast model of return of chum salmon for the population off the Honshu region in the Sea of Japan using the smoothing spline based on catch data obtained in fishing season. The optimal in-season model was constructed using adult return in season 8 (middle October) as an explanatory variable. Residual sum of squares of the optimal in-season model was lower than that of the pre-season forecast (sibling) model, indicating the former was more accurate than the latter. The relationship between forecast error rate in the optimal model and the cumulative proportion of return until season 8 (middle October) was positive. Yearly variation in the forecast error rate may be affected by variability in the timing of return. We provide a new and accurate forecast model of chum salmon return.

Highlights

Mature chum salmon (Oncorhynchus keta) migrate from offshore into coastal waters and natal rivers to breed [1,2]
As the fishing season proceeds the cumulative proportion of returning adults gradually increases (Figure 1)
We focused on the relationship between forecast error rate and the cumulative proportion of the adult return

Summary

Introduction

Mature (adult return) chum salmon (Oncorhynchus keta) migrate from offshore into coastal waters and natal rivers to breed [1,2]. Spawning season spans approximately 7 months, from August to February [3]. In Japanese waters, returning adults are caught mainly by set-nets in coastal waters off natal rivers, and by gill- and purse-seine nets within rivers. The number of returning adults is defined as the sum of numbers caught coastally (coastal catch) and numbers caught in rivers (river catch). As the fishing season proceeds the cumulative proportion of returning adults gradually increases (Figure 1). We can view in-season catch data as a kind of relative density index obtained by in-season survey

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Results