Management Strategy Evaluation of Fisheries Resources in Data-poor Situations Using an Operating Model Based on a Production Model

Abstract

The allowable biological catch (ABC) in Japanese fishery management is currently determined by applying harvest control rules, which are categorized into two types depending on whether or not stock-size information is available. We evaluate management procedures (MPs) in data-poor situations using an operating model (OM) based on a production model. The OM incorporates uncertainties regarding its assumptions and the process and observation errors of population dynamics and fishing processes, while the values of the MP parameters are determined to avoid stock collapses and low catches. We evaluated the MP formulationwhere δ is a coefficient dependent on the stock status level on the stock size, C t is the catch in year t, k is the weight coefficient, b reflects the trend in stock abundance index over time, and Iˉ is the mean of the stock abundance index I. This study shows that smaller values of k reduce the frequency of substantially low catches, particularly when there is significant uncertainty surrounding the stock status. In addition, the value of δ affects both the frequency of fishery collapse as well as stock and catch sizes. We conclude that more reliable stock abundance indices are necessary if the stock size and catch are to stabilize and MPs become more robust to uncertainties.

Validation of a feedback harvest control rule in data-limited conditions for managing multispecies fisheries

“…Therefore, the present study attempted to accomplish fisheries management under a default HCR, which complies with data-limited and mixed-species conditions. A straightforward validation of mixed-species data was generated by comparing the default feedback HCR and its alternates in terms of their performances with single-species data, which have been validated previously (Ohshimo and Naya 2014;Ichinokawa et al 2015). Under these circumstances, an ideal HCR would be a tool for limiting the frequency of overfishing, maintaining biomass, and generating more stable catches for mixed-species stocks-goals that were reflected in the five performance measures.…”

“…6 Some studies evaluated the robustness of the feedback HCR through several models that used single-stock data (Hurtado-Ferro et al 2010;Hoshino et al 2012;Ohshimo and Naya 2014;Ichinokawa et al 2015), but none considered validating the robustness of the feedback HCR for a mixed-species fishery. Such validation would be a valued response to recent calls for fishery management approaches under data-limited conditions and applicable to most countries.…”

“…The feedback HCR evaluated in this study is called the ABC rule 2-1 in the Japanese TAC system (Fisheries Agency and Fisheries Research and Education Agency of Japan 2017) and was previously validated for single-species stock data (Hiramatsu 2004;Ohshimo and Naya 2014;Ichinokawa et al 2015). The formulas used for the ABC rule 2-1 are as follows:…”

“…where is a random number with standard normal distribution, and is the scale of variance for the ε σ process error. To cover various changes in stock size in the pre-management period, three scenarios were considered, following the method of previous simulation studies (i.e., Hiramatsu 2004;Ohshimo and Naya 2014;Ichinokawa et al 2015). Exploitation histories for the pre-management period were reflected in the value of the initial biomass (B 1 ) and the value of the terminal biomass (B 21 ), which was defined as either high (B H ), medium (B M ), or low (B L ) biomass at 75%, 50% and 30% of total carrying capacity, respectively.…”

“…The catch of each species in the total σ catch quota is allocated as proportional to the biomass of each species, which reflects a non-selective multispecies fishery. To evaluate the robustness of the HCR, the magnitude for and was assumed as 0.2 for the default, as was applied in former studies (i.e., Hiramatsu 2004;Ohshimo and Naya 2014;Ichinokawa et al 2015). Additionally, = 0.4 was tested, and the results are provided in Supplementary, Figs.…”