Food for thought: pretty good multispecies yield

Abstract

MSY principles for marine fisheries management reflect a focus on obtaining continued high catches to provide food and livelihoods for humanity, while not compromising ecosystems. However, maintaining healthy stocks to provide the maximum sustainable yield on a single-species basis does not ensure that broader ecosystem, economic, and social objectives are addressed. We investigate how the principles of a “pretty good yield” range of fishing mortalities assumed to provide >95% of the average yield for a single stock can be expanded to a pretty good multispecies yield (PGMY) space and further to pretty good multidimensional yield to accommodate situations where the yield from a stock affects the ecosystem, economic and social benefits, or sustainability. We demonstrate in a European example that PGMY is a practical concept. As PGMY provides a safe operating space for management that adheres to the principles of MSY, it allows the consideration of other aspects to be included in operational management advice in both data-rich and data-limited situations. PGMY furthermore provides a way to integrate advice across stocks, avoiding clearly infeasible management combinations, and thereby hopefully increasing confidence in scientific advice.

System-level optimal yield: increased value, less risk, improved stability, and better fisheries

“…In practice OY has played out as being applied on a stock-by-stock basis, but it does not have to be done that way. Several jurisdictions are exploring or have proposed a systems approach to broaden the stock-specific application of OY (e.g., Mueter and Megrey 2006;Fogarty et al 2012;Fogarty 2014;Rosenberg et al 2014;Gaichas et al 2017;Rindorf et al 2017aRindorf et al , 2017b. When I advise governments and engage with counterparts in countries all around the world, for example, Norway, Canada, Australia, South Africa, New Zealand, Japan, the EU, Iceland, etc.…”

“…(cf. Mardle et al 2002;Marchal et al 2009;Dichmont et al 2010;Mesnil 2012;Patrick and Link 2015b;Rindorf et al 2017a), and broach the topic, not one has objected nor indicated that considering OY in aggregate is not allowed; rather, they typically tend to simply not think of it. This is also true in numerous intergovernmental organizations, such as the International Council for the Exploration of the Sea, Food and Agricultural Organization of the United Nations, or other regional fisheries management organisations -not one objects to aggregate OY on a legal basis.…”

“…), one can execute commonly available models, simply ignore the stock or species delineations, combine the data into an aggregate group, and obtain model outputs for the group as a whole. Several theoretical, simulation, and contextual considerations have explored this approach Link 2009, 2012;Worm et al 2009;Bundy et al 2012;Fay et al 2013Fay et al , 2015Fogarty 2014;Gaichas et al 2017;Rosenberg et al 2014;Rindorf et al 2017a) and found the method performs as one would expect from hierarchy theory, namely that resulting model outputs are consistent with the portfolio effect Jin et al 2016). Many works (e.g., Mueter and Megrey 2006;Fogarty et al 2008Fogarty et al , 2012Christensen et al 2009;Gaichas et al 2012;Lucey et al 2012;Rosenberg et al 2014;Rindorf et al 2017aRindorf et al , 2017b have examined these approaches, tested the analytical methods, explored the robustness and vagaries of the results, and generally arrived at the conclusion that at the very least, the analytical methodologies and considerations are not a limitation for the adoption of this systems approach.…”

“…These discussions typically revolve around both how to define it and how to achieve it. Often associated with maximum sustainable yield (MSY) and related proxies (Restrepo et al 1998;Rindorf et al 2017a), the concept of yield has engendered considerable debate in the discipline (Schaefer 1954;Larkin 1977;Sissenwine 1978;Mace 2001;Hilborn 2010;Legovic et al 2010;Finley 2011;Finley and Oreskes 2013;Rindorf et al 2017a). The debate over whether OY should be measured as MSY or something else aside, and the debate over the politics of how the science to support and implement it arose also aside, the simple fact is that we need to have some concept -or preferably some type of measure -of the amount of fish biomass that is harvestable at any given place and time (Mace 1994;Fogarty 2014), an estimate that is loosely associated with the productivity of the fishes involved and the carrying capacity of the ecosystem that limits such productivity (Graham and Edwards 1962;Gulland 1970;Ryther 1969;Iverson 1990;Pauly and Christensen 1995;Ware 2000;Friedland et al 2012;Heath 2012;Fogarty 2014).…”

“…The debate over whether OY should be measured as MSY or something else aside, and the debate over the politics of how the science to support and implement it arose also aside, the simple fact is that we need to have some concept -or preferably some type of measure -of the amount of fish biomass that is harvestable at any given place and time (Mace 1994;Fogarty 2014), an estimate that is loosely associated with the productivity of the fishes involved and the carrying capacity of the ecosystem that limits such productivity (Graham and Edwards 1962;Gulland 1970;Ryther 1969;Iverson 1990;Pauly and Christensen 1995;Ware 2000;Friedland et al 2012;Heath 2012;Fogarty 2014). Most countries with any fisheries jurisdiction at all have some form of OY espoused in their fisheries polices (Mardle et al 2002;Marchal et al 2009;Dichmont et al 2010;Mesnil 2012;Patrick and Link 2015b;Rindorf et al 2017a). The reality is that the concept of OY can be applied to a population, a guild of species, an entire biotic community, or a fishery or group of fisheries or even an entire ecosystem.…”