Species Life-cycle Analysis Modules (SLAM): A flexible tool for evaluating species management scenarios applied to a threatened Pacific salmon case study

Background/Question/Methods . The Species Life-cycle Analysis Modules (SLAM) program is a flexible tool for exploring population consequences of changes in life-stage survivals and capacities under different management scenarios. The program is not species-specific and allows users to specify almost any life-cycle structure, from simple two-stage semmelparous species, to iteroparous species with dozens of distinct life-stages. Although we have used SLAM to look at a variety of species, we present an example focused on threatened Pacific salmon. Alternative management scenarios for Pacific salmon included changes in freshwater habitat, harvest and hatchery regimes, future climate conditions and marine survivals, which are modeled in SLAM as different life-stage transition functions with different survival, capacity and environmental forcing parameters. A key feature of SLAM is that these input parameters can be entered as probability distributions rather than as point estimates. This produces output distributions, which provide more information to managers than simple point estimates. SLAM has built in sensitivity analysis capabilities, which include a global sensitivity variance partitioning module to identify critical parameters influencing model behavior. These critical parameters can be targets for improved field monitoring. Although transition parameterization is external to SLAM, the model can be fit to empirical life-stage specific survival and capacity time series data as a form of model calibration. Model output consists of predicted time series distributions for all life stages.

Results/Conclusions . For our Pacific salmon example, findings relevant to management include: 1) juvenile over-wintering capacity in freshwater provides a limit on population abundance, 2) delays in restoration lead to substantially increased short-term population risk, 3) predation of hatchery produced fish on wild fish can reduce overall population resilience and 4) size selective harvest has a greater effect on extinction risk than harvest that is not size selective.