Evaluating a multispecies adaptive management framework: must uncertainty impede effective decision‐making?

Abstract

Summary1. Application of adaptive management to complex natural resource systems requires careful evaluation to ensure that the process leads to improved decision-making. As part of that evaluation, adaptive policies can be compared with alternative nonadaptive management scenarios. Also, the value of reducing structural (ecological) uncertainty to achieving management objectives can be quantified. 2. A multispecies adaptive management framework was recently adopted by the Atlantic States Marine Fisheries Commission for sustainable harvest of Delaware Bay horseshoe crabs Limulus polyphemus, while maintaining adequate stopover habitat for migrating red knots Calidris canutus rufa, the focal shorebird species. The predictive model set encompassed the structural uncertainty in the relationships between horseshoe crab spawning, red knot weight gain and red knot vital rates. Stochastic dynamic programming was used to generate a statedependent strategy for harvest decisions given that uncertainty. In this paper, we employed a management strategy evaluation approach to evaluate the performance of this adaptive management framework. Active adaptive management was used by including model weights as state variables in the optimization and reducing structural uncertainty by model weight updating. 3. We found that the value of information for reducing structural uncertainty is expected to be low, because the uncertainty does not appear to impede effective management. Harvest policy responded to abundance levels of both species regardless of uncertainty in the specific relationship that generated those abundances. Thus, the expected horseshoe crab harvest and red knot abundance were similar when the population generating model was uncertain or known, and harvest policy was robust to structural uncertainty as specified. 4. Synthesis and applications. The combination of management strategy evaluation with state-dependent strategies from stochastic dynamic programming was an informative approach to evaluate adaptive management performance and value of learning. Although natural resource decisions are characterized by uncertainty, not all uncertainty will cause decisions to be altered substantially, as we found in this case. It is important to incorporate uncertainty into the decision framing and evaluate the effect of reducing that uncertainty on achieving the desired outcomes.

Conservation status of the American horseshoe crab, (Limulus polyphemus): a regional assessment

“…Several efforts have occurred to develop horseshoe crab population models useful for assessing population viability (Gibson and Olszewski 2001;Grady and Valiela 2006;Davis et al 2006;Sweka et al 2007;McGowan et al 2011b;Smith et al 2013). Modeling studies have focused on horseshoe crab populations in Rhode Island (Gibson and Olszewski 2001), Cape Cod , and Delaware Bay (Davis et al 2006;Sweka et al 2007;McGowan et al 2011b;Smith et al 2013).…”

“…Modeling studies have focused on horseshoe crab populations in Rhode Island (Gibson and Olszewski 2001), Cape Cod , and Delaware Bay (Davis et al 2006;Sweka et al 2007;McGowan et al 2011b;Smith et al 2013). All analyses concluded that while high harvest results in population depletion, some Additional details can be found in Sweka et al (2013: Appendix B) Rev Fish Biol Fisheries (2017) 27:135-175 159 levels of reduced harvest can be compatible with maintenance of a viable population.…”

A Full Annual Cycle Modeling Framework for American Black Ducks

“…[]; Smith et al. []; McGowan []). The framework presented here provides a tool that can be used in conservation decision making, but should also be continuously refined and tested as more information becomes available.…”

The Role of Horseshoe Crabs in the Biomedical Industry and Recent Trends Impacting Species Sustainability

“…Once in the Delaware Bay, red knots and other shorebirds feed predominantly on the eggs laid by spawning horseshoe crabs while they are available (Tsipoura and Burger, 1999;Mizrahi and Peters, 2009;McGowan et al, 2011;Smith et al, 2013). It is unlikely that other food sources found at shorebird stopover sites would be as widely available or as nutritionally dense as horseshoe crab eggs (Mizrahi and Peters, 2009).…”