Based on the concept of adaptive management, the Commission for the Conservation of Southern Bluefin Tuna (CCSBT) had been using a management procedure (MP) called Bali Procedure to set total allowable catches (TACs) since 2011. The MP is defined as a harvest control rule that applies pre-agreed procedures (algorithms) and fishing/survey data to specify the TAC. The MP is often developed through an extensive computer simulation called Management Strategy Evaluation (MSE) that tests its robustness to uncertainties about fisheries/fish populations and its performance in achieving management objectives. The scientific aerial survey to obtain recruitment data needed for Bali Procedure was discontinued in 2017. In 2019, the CCSBT redeveloped a replacement MP called Cape Town Procedure (CTP), which utilizes alternative recruitment data. This paper overviews the MSE process for the development of the CTP (the construction of the operating model, the development of candidate MPs, performance comparison among the candidate MPs, and final selection from the candidate MPs) and how the CTP has recently been applied to the management of southern bluefin tuna. Lessons learned from the authors’ experience through the MSE process in the CCSBT and issues related to MP development are discussed.

In Kumihama Bay (Kyoto Prefecture), an enclosed sea area, monthly longitudinal and vertical observations and automatic vertical observations at fixed points were carried out to investigate the cause of the recent poor growth of cultured bivalves. The spatial and temporal distribution of chlorophyll, a food indicator, was investigated. The results showed that chlorophyll was distributed in layers regardless of season, and the depth of the maximum layer changed with the season. The chlorophyll maximum layer was the deepest at 6–10 m in April and shallowest at less than 5 m in November and December. When hypoxic water masses developed in the lower layer from June to August, a chlorophyll maximum layer was formed in the middle layer directly above it. At that time, nutrients were depleted and the chlorophyll concentration was generally below 5 μg·L^-1 in the upper layer, corresponding to the layer where shellfish are cultivated. Throughout the year, the chlorophyll distribution in the bay strongly depended on the seasonal dynamics of hypoxic water masses. Because the high primary productivity in the bay is concentrated in specific layers, it is plausibly not being fully utilized for bivalve aquaculture.

The levels of nutrients (TN and TP) and chlorophyll-a (Chl-a) required for the success of the Manila (Asari) clam fisheries in Mikawa Bay were discussed based on the results of fishing ground surveys and long-term water quality monitoring data. The correlation coefficient between the change in abundance and water quality during fall and winter was positive and was particularly significant with Chl-a in summer. Long-term water quality data showed extremely low CPUA (clam catch per unit fishing area) below threshold values (TN: 385–417 μg∙ L^-1, TP: 40–42 μg∙ L^-1, Chl-a: 10.7–12.2 μg∙L^-1, all annual means). Based on the logistic regression analysis, the concentration thresholds at which the risk of resource collapse increases were calculated to be 364 μg∙L^-1 for TN, 39 μg∙L^-1 for TP, and 9.3 μg∙L^-1 for Chl-a, while the concentrations for the achievement of the clam fishery level were 457 μg∙ L^-1 for TN, 54 μg∙L^-1 for TP and 14.4 μg∙L^-1 for Chl-a. These water quality concentrations were higher than the reference concentrations of environmental standard type II applied to the bay area including the clam fishing grounds in Mikawa Bay, which suggests that appropriate nutrient management is necessary for clam stocks to recover.