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Joseph M. Hennessy

Publications and source records attributed to Joseph M. Hennessy.

4 recordsLinked to original sources
USGS2025

RAD (Resist-Accept-Direct) switch points and triggers for adaptation planning

Climate change is transforming ecosystems globally. The Resist-Accept-Direct (RAD) framework has gained traction within many natural resource management institutions to help consider the decision space in response to this transformation. Because RAD helps manage for directional change, RAD choices entail considering which RAD pathway to implement and for how long. For example, one may accept a slowly changing ecosystem, but at a certain point, decide to begin resisting or directing the change an ecosystem is experiencing. Alternatively, one may begin resisting an ecosystem transformation, but ultimately realize resistance is no longer feasible based on cost or efficacy. These choices are challenging and encompass broad domains of cultural, ecological, financial, organizational, public, regulatory, and technological considerations to determine when to switch RAD pathways. We introduce the concepts of RAD switch points and triggers to help support these decision processes. We illustrate these concepts using case studies on walleye ( Sander vitreus ) stocking decisions in Wisconsin, wildfire response in the Greater Yellowstone Ecosystem, and bull trout ( Salvelinus confluentus ) management in Oregon, USA. Synthesizing across these examples, we delineate key points for decision makers as they (iteratively) reevaluate among the RAD pathways as conditions continue to change.

Journal of Environmental Management↗
USGS2021

Recruitment bottlenecks for age-0 walleye in northern Wisconsin lakes

Some northern Wisconsin lakes have shown declines in catches of age-0 Walleye Sander vitreus in standardized fall electrofishing sampling, suggesting that recruitment bottlenecks are occurring in the first several months of life. In 2016 and 2017, we sampled six lakes with declining trends in natural Walleye recruitment (D-NR lakes) and seven lakes with a history of sustained natural recruitment (S-NR lakes) to determine if timing of potential recruitment bottlenecks for age-0 Walleye were consistent among D-NR lakes and if abiotic and biotic metrics differed between D-NR and S-NR lakes. We also examined diets of larval Walleye to assess prey items that may be important to early growth and survival and to determine if occurrence of piscivory was related to larval Walleye total length. Differential patterns in the presence and absence of age-0 Walleye at different life history stages in the first 6 months of life suggested that recruitment bottlenecks in D-NR lakes were consistently occurring before mid-July (five of six lakes). Mean Secchi depth, surface conductivity, abundance of larval Yellow Perch Perca flavescens , and most metrics of zooplankton abundance and mean size were similar between D-NR and S-NR lakes. Log 10 transformed number of adult Walleye per hectare was lower and adult mean total length was higher in D-NR lakes. Across all lakes, diets of larval Walleye consisted of zooplankton and larval fish and the occurrence of piscivory was higher than reported in previous studies and was positively related to total length of larval Walleye. Causes of recruitment bottlenecks in D-NR lakes remain unclear, making it difficult to identify management actions that might be implemented to circumvent these bottlenecks. However, our results indicate that future research should focus on the period between egg deposition and mid-July.

Wisconsin↗
USGS2017

Defining a Safe Operating Space for inland recreational fisheries

The Safe Operating Space (SOS) of a recreational fishery is the multidimensional region defined by levels of harvest, angler effort, habitat, predation and other factors in which the fishery is sustainable into the future. SOS boundaries exhibit trade-offs such that decreases in harvest can compensate to some degree for losses of habitat, increases in predation and increasing value of fishing time to anglers. Conversely, high levels of harvest can be sustained if habitat is intact, predation is low, and value of fishing effort is moderate. The SOS approach recognizes limits in several dimensions: at overly high levels of harvest, habitat loss, predation, or value of fishing effort, the stock falls to a low equilibrium biomass. Recreational fisheries managers can influence harvest and perhaps predation, but they must cope with trends that are beyond their control such as changes in climate, loss of aquatic habitat or social factors that affect the value of fishing effort for anglers. The SOS illustrates opportunities to manage harvest or predation to maintain quality fisheries in the presence of trends in climate, social preferences or other factors that are not manageable.

Fish and Fisheries↗