Assessing Northwest Pacific Fishery Stocks Using Two New Methods: The Monte Carlo Catch-MSY (CMSY) and the Bayesian Schaefer Model (BSM)

Qing-qiang Ren,Min Liu

doi:10.3389/fmars.2020.00430

Abstract

The CMSY and Bayesian Schaefer model (BSM) methods were applied to assess data-limited fishery stocks in the Japan Sea and surrounding areas of the Northwest Pacific. Ten stocks including 4 fish species and 5 cephalopod species were assessed; the CMSY method was used in 3 stocks with catch data only, and the BSM method in 7 stocks with both catch time series and catch per unit effort (CPUE) data available. The two methods estimated the maximum intrinsic rate of population increase (r) and carrying capacity of each stock, which allowed the computation of maximum sustainable yield (MSY), and exploited biomass relative to the biomass at maximum sustainable yield (B/BMSY). All 10 stocks were overfished, if to a different extent, and one, the spear squid (Heterololigo bleekeri) has collapsed. The reference points estimated here may be used as indicator for fishery management in this ecoregion.

Highlights

Global marine fishery catches fluctuated from 75 to 85 million tonnes since the late 1980s (FAO, 2018)
The Bayesian state-space Schaefer surplus production model (BSM) (Meyer and Millar, 1999; Millar and Meyer, 1999) that is part of CMSY R-code was applied to account for variability in both population dynamics and measurement and sampling (Thorson et al, 2014; Froese et al, 2017)
The Okhotsk atka mackerel has been subject to ongoing overfishing since the early 1980s with B/BMSY reaching 0.76 at the end of time series (Figure 3C and Table 5)

Summary

Introduction

Global marine fishery catches fluctuated from 75 to 85 million tonnes since the late 1980s (FAO, 2018). Fishing fleets increased from 1.7 to 3.7 million vessels between 1950 to 2015, and effective catch per unit of effort (CPUE) has decreased substantially since 1950 (Rousseau et al, 2019). Due to excessive fishing effort, the percentage of fish stocks being overfished within a decade after a fishery was fully developed increased from 26% in the 1950s to 35% in the 1980s. 50% of 900 important exploited species were overfished, collapsed or abandoned due to overfishing in 1999 (Froese and Kesner-Reyes, 2002), and the number of sustainably exploited stocks decreased from 90% in 1974 to 67% in 2015 (FAO, 2018). Large predatory fishes are strongly depleted, with their current biomass at only 10% of their pre-industrial levels (Myers and Worm, 2003)

Methods

Results

Conclusion