The effects of population synchrony, life history, and access constraints on benefits from fishing portfolios

Abstract

Natural resources often exhibit large interannual fluctuations in productivity driven by shifting environmental conditions, and this translates to high variability in the revenue resource users can earn. However, users can dampen this variability by harvesting a portfolio of resources. In the context of fisheries, this means targeting multiple populations, though the ability to actually build diverse fishing portfolios is often constrained by the costs and availability of fishing permits. These constraints are generally intended to prevent overcapitalization of the fleet and ensure populations are fished sustainably. As linked human-natural systems, both ecological and fishing dynamics influence the specific advantages and disadvantages of increasing the diversity of fishing portfolios. Specifically, a portfolio of synchronous populations with similar responses to environmental drivers should reduce revenue variability less than a portfolio of asynchronous populations with opposite responses. We built a bioeconomic model characterized by the Dungeness crab (Metacarcinus magister), Chinook salmon (Oncorhynchus tshawytscha), and groundfish fisheries in the California Current, and used it to explore the influence of population synchrony and permit access on revenue patterns. As expected, synchronous populations reduced revenue variability less than asynchronous populations, but only for portfolios including crab and salmon. Synchrony with longer-lived groundfish populations was not important because environmentally-driven changes in groundfish early life survival were mediated by growth and natural mortality over the full population age structure, and overall biomass was relatively stable across years. Thus, building a portfolio of diverse life histories can buffer against the impacts of extremely poor environmental conditions over short time scales, though not for long-term declines. Increasing access to all permits generally led to increased revenue stability and decreased inequality of the fleet, but also resulted in less revenue earned by an individual from a given portfolio because more vessels shared the available biomass. This means managers are faced with a tradeoff between the average revenue individuals earn and the risk those individuals accept. These results illustrate the importance of considering connections between social and ecological dynamics when evaluating management options that constrain or facilitate fishers' ability to diversify their fishing.

Impact of the 2014–2016 marine heatwave on US and Canada West Coast fisheries: Surprises and lessons from key case studies

“…(2) continuing to refine entanglement prevention strategies that are co-developed with stakeholders and are proven to be effective, robust or adaptable to changing conditions, and minimally impactful on fishers (CDFW, 2015;Samhouri et al, 2021); (3) reforming the federal fisheries disaster program to provide fast, accurate, and equitable relief (Bellquist et al, 2021); and (4) easing access to alternative fisheries as a means of diversifying fishing opportunities (Oken et al, 2021) and potentially escaping the "gilded trap" presented by the lucrative, yet volatile, Dungeness crab fishery (Fisher et al, 2021).…”

Trends in Chinook salmon spawner abundance and total run size highlight linkages between life history, geography and decline

“…The negative effects of these disturbances and ecosystem shifts have been precipitated and intensified by more than two centuries of anthropogenic climate change, marine and watershed habitat alterations, and hatchery practices that have eroded the resilience and productivity of Chinook salmon (McClure et al, 2008; Satterthwaite & Carlson, 2015; Dorner et al, 2018; Beechie et al, 2021; Munsch et al, 2022). Chinook salmon are also getting smaller over time, with potentially serious implications for their demographic productivity and ability to support fisheries in the future (Ohlberger et al, 2018; Oken et al, 2021; Xu et al, 2020). These changes in size are likely driven by a multitude of factors including shifting climate and marine food webs, competition with pink salmon, and harvest; and much like survival trends these changes in size are shaped by life history, watershed of origin and marine distribution (Buckner et al, 2022).…”

“…Highly mobile species often exhibit diverse life histories, phenology and reproductive strategies that have evolved in response to the range of physical and biological conditions they confront during different stages of their lives. All told, this diversity can stabilize population and ecosystem dynamics, providing more reliable ecological, cultural and economic benefits in social‐ecological systems (Moore et al, 2014; Oken et al, 2021; Schindler et al, 2010). However, life histories may also influence the exposure, and thus vulnerability, of specific populations to different stressors.…”

Oceanographic drivers of legal-sized male Dungeness crab in the California Current System

“…After 1980, the trends in legal-sized male Dungeness crab abundance changed and do not appear to exhibit strong periodicity (Rasmusson, 2013;Richerson et al, 2020). Understanding the causes and consequences of fluctuations in Dungeness crab abundance and forecasting recruitment is important for fishers, processors, and managers of Dungeness crab and other fisheries to which crab fishers divert effort as crab catch rates decline during each season (Oken et al, 2020;Holland and Leonard, 2020;Fisher et al, 2021). In general, marine populations fluctuate due to 1) varying abiotic environmental conditions (Moran, 1953), 2) biotic interactions with other species (e.g., prey and predators), 3) fishing (Shelton et al, 2011), 4) dispersal (Bani et al, 2019), 5) nonlinear dynamics (Munch et al, 2020), and 6) other ecoevolutionary processes (Waples et al, 2010).…”