Are 20% B0, 20% Bunfished, and BMSY Valid as Reference Points for Fisheries Resource Management?

Abstract

The aim of this paper is to discuss the validity of 20% B0, 20% Bunfished and BMSY as reference points for managing fisheries resources. I reanalyzed eight stock-recruitment relationship (SRR) sets of data that were analyzed by Myers et al. in 1994, and showed that the theory proposed by Sakuramoto could be applied to the above SRR data. The results showed that: 1) clockwise loops or anti-clockwise loops emerged in the plots of SRR, and the results coincided well with those of 25 stocks that lived around Japan and the stock of Pacific bluefin tuna; 2) the slopes of the regression lines (b) drawn on SRR planes for above 34 stocks had a negative relationship with the age-at-maturity (m). That is, b = 0.995 - 0.211·m. Therefore, the results of this paper indicate that the SRR is governed by a mechanism that is quite different from that which has been traditionally accepted, and in which the main factor is believed to be a density-dependent effect. The results also indicated that 20% B0, 20% Bunfished and BMSY, which are derived from traditional SRR models, do not have any scientific basis as reference points for managing fisheries resources. Empirical reference points seem to be more reasonable measures as Hilborn and Kevin emphasized in 2010.