Short-Term Pain and Long-Term Gain: Using Phased-In Minimum Size Limits to Rebuild Stocks-the Pacific Bluefin Tuna Example

Like many stocks, the Pacific Bluefin Tuna Thunnus orientalis has been considerably depleted. High exploitation rates on very young fish have reduced the spawning stock biomass (SSB) to 2.6% of the unexploited level. We provide a framework for exploring potential benefits of minimum size regulations as a mechanism for rebuilding stocks, and we illustrate the approach using simulations patterned after Pacific Bluefin Tuna dynamics. We attempt to mitigate short-term losses in yield by considering a phased-in management strategy. With this approach, the minimum size limit (MSL) is gradually increased as biomass rebuilds, giving fishing communities time to adjust to new restrictions. We estimated short- and long-term effects of different MSLs on yield and biomass by using data from the 2016 assessment. A variety of scenarios was considered for growth compensation, discard mortality, and interest rates. The long-term value of the fishery was maximized by setting an MSL of 92 cm FL, which resulted in a 70% loss in yield during the first year (short-term pain). By implementing the MSL in two phases (64 cm FL in year 1; 92 cm FL in subsequent years), the long-term value of the fishery was maintained, and the short-term pain was reduced to a maximum 46% loss in yield during any 1 year. Under a three-phase implementation (55 cm FL in year 1; 77 cm FL in year 2; and 92 cm FL in subsequent years), the short-term pain was further reduced to a maximum loss of 30% during any 1 year. With no discard mortality, long-term yield increased by 165% and SSB increased 13-fold (to 33% of virgin SSB), regardless of the number of phases used. Long-term benefits were quickly diminished with increasing discard mortality. This simulation approach is widely applicable to cases where minimum size changes are contemplated; for Pacific Bluefin Tuna, our simulations demonstrate that size limits should be considered

Modeling for policy change: A feedback perspective on improving the effectiveness of coastal and marine management

Those advocating for effective management of the use of coastal areas and ecosystems have long aspired for an approach to governance that includes information systems with the capability to predict the end results of various courses of action, monitor the impacts of decisions and compare results with those predicted by computer models in order to suggest alterations in the actions needed if the goals are not being achieved. This dissertation draws on system dynamics modeling, content analysis and professional experience to explore four decades of experience in the United States as well as international cases to reveal lessons and strategies for putting into practice the systematic approach sought by advocates of ecosystem-based management of the nation's, and the worlds coasts and marine areas. Simulations are used to examine the implications of program structure and policy choices in state-level coastal regulatory programs, decisions on a controversial use of marine areas: offshore fish farming, and the ongoing quest for more effective approaches to attaining local success in the sustainable use of coastal resources in poor countries. The models presented here draw upon structures used in variety of business management cases. These reveal the impacts of delay, the value of acting early on to set policies, and the danger of taking half-measures. Sufficient effort must be mobilized to enforce policies and change behavior patterns before coastal resource scarcity drives up the price of protection as well as the resistance to stringent rules. Development assistance places great emphasis on short term, high impact projects, but local success depends on steady long term support to overcome the barriers to attaining better management. Fish farming is controversial for environmental reasons, but seemingly stable operations such as bluefin tuna ranching in Mexico are highly sensitive to market fluctuations, the migration patterns of juvenile bluefin tuna and dependent on the abundance of sardine stocks. Many management failures can be traced to policy resistance and problems of informatics whose solutions include endogenous strategies. Our failures are often generated by ourselves, not by outsiders or by big, surprising shocks to the governance system

Population, health, and environment situational analysis for the Saadani National Park Area, Tanzania

This study provides a snapshot of the population, health, and environment situation and practices in the villages surrounding the Saadani National Park (SANAPA) and demonstrates the utility of a transdisciplinary systems perspective to evaluate population-health-environment linkages (PHE). Analyzing survey data from eight villages, this paper shows that in the SANAPA area, livelihoods are highly dependent on natural resources, but both agriculture and fisheries are experiencing a decline in productivity and profitability. Population stressors include a high population momentum, early marriages, teenage pregnancies, and migration. Women bear a heavy workload, while having little or no say in decision-making. The public health situation is severe with health facilities few and far in-between; lack of access to clean water and safe sanitation; and many households suffering from diarrhea, malaria, pneumonia, skin diseases, and HIV/AIDS. Environmental protection arrangements are in place in all sites, however, the awareness of protected areas and their benefits is low and many feel helpless in protecting the environment. Climate change-increasing periods of drought and irregular rainfall-contribute to food insecurity and health problems. The interconnectedness between these stressors reinforces the need for an integrated approach to addressing coastal conservation and community development in the SANAPA area. © 2012 Elsevier Ltd

WTO must ban harmful fisheries subsidies

Sustainably managed wild fisheries support food and nutritional security, livelihoods, and cultures (1). Harmful fisheries subsidies—government payments that incentivize overcapacity and lead to overfishing—undermine these benefits yet are increasing globally (2). World Trade Organization (WTO) members have a unique opportunity at their ministerial meeting in November to reach an agreement that eliminates harmful subsidies (3). We—a group of scientists spanning 46 countries and 6 continents—urge the WTO to make this commitment..