Current projects

I am working on a variety of projects currently addressing different themes, aspects, and scale of the resilience and sustainability of complex social-ecological systems. If you have any thoughts or suggestions on these projects, I’m open to collaborating!

Some projects I am working on currently and some details below:

  1. Marine and freshwater regime shifts impact a community of migratory Pacific salmonids in decline
  2. Managing ecological surprises in metapopulations
  3. Life-history diversity in Canada’s lake trout
  4. Developing robust management for spatially structured fisheries
  5. Social-ecological resilience in changing fisheries

Marine and freshwater regime shifts impact a community of migratory Pacific salmonids in decline

The Keogh (Giyuxw) River is a 30-km long, rain dominated coastal third order river that flows north-westward on northern Vancouver Island, near Port Hardy. It is home to a wide variety of fishes including: Steelhead, Coho Salmon, Pink Salmon, Dolly Varden, and anadromous Cutthroat Trout. Populations on the Keogh have been under long-term monitoring through cooperative and collaborative research from provincial, federal, university, First Nations, and consulting biologists since the 1970s. This dataset is, arguably, one of the most important research sites for anadromous salmonids in the world, particularly for Steelhead, which are in decline across the Pacific Northwest.

The timing of adult steelhead migration runs on the Keogh River since 1976

We used the Keogh River as a reference site to unpack the role of density dependence, ecosystem trends, and stochasticity on productivity regimes for a community of five species of Pacific salmonids (Steelhead Trout, Coho Salmon, Pink Salmon, anadromous Dolly Varden, and anadromous Coastal Cutthroat Trout).In general, we identified three productivity regimes: an early regime (1976-1990), a compensatory regime (1991-2009), and a declining regime (since 2010) where large declines were observed for Steelhead Trout, Dolly Varden, and Cutthroat Trout, intermediate declines in Coho Salmon and no change in Pink Salmon. We tested potential explanations behind these changes for each species and particularly Steelhead, where the population remains at persistent low densities bordering on extirpation. This chronic condition emerged from cumulative effects across the salmon life cycle: increased seal densities and ocean competition were associated with lower adult marine survival, while watershed logging and earlier spawning runs were associated with lower freshwater productivity. Collectively, these changing environments limited juvenile production and lowered future adult returns. These results reveal how changes in freshwater and marine environments can jointly shape population dynamics among ecological communities, like Pacific salmon, with cascading consequences to their resilience.

Posterior predictive distribution (mean and 80% credible intervals (CI) indicated by lines and shaded polygon, respectively) of trends in intrinsic productivity (a) and emergent ecological regimes (a – shaded regions) for five salmonids through time. Mean effect sizes (panel b – points) and 80% credible intervals (panel b – line) of environmental drivers on recruitment productivity. Red points indicate covariates where 80% credible intervals do not cross 0. Posterior mean correlation between species’ intrinsic productivity through time (panels c).

Managing ecological surprises in metapopulations

Spatial recovery regime of heavily disturbed metapopulations with linear and dendritic topology through time (left panels) and space (right panels).

Spatially structured populations, like salmon watersheds, are composed of many interconnected local populations – called a ‘metapopulation’. Metapopulations can have strong patchiness in local processes, like dispersal, productivity, or mortality, which are often density-dependent, and these local processes feedback to structure aggregate dynamics. For resource populations, like fish and wildlife, management often works at the scale of the whole metapopulation whereas non-random stressors tend to work on a more local scale causing unpredictable patterns to emerge. This creates a mismatch between the scale of management and the scale of the problems. Together with the Salmon Watersheds Lab, we want to explore how spatial structure in local density-dependence drives surprising patterns at the metapopulation-scale ideas using (1) a conceptual model to illustrate this idea, (2) a theoretical model to quantify spatial patterns, and (3) review empirical case studies on a wide-variety of taxa to show how linkages between network structure, local density-dependence, and different stressors can create surprising patterns to emerge at the scale of resource management.

Three real-world examples for how metapopulations collapse and are slow to recover.

Life-history diversity in Canada’s lake trout

In 2008-2009, BC FLNRO sampled 30 lake trout populations that ranged from larger, exploited lakes to pristine, backcountry, and high-alpine lakes. From this, they collected back-calculated size-at-age from 1,100 lake trout. These fish ranged drastically in maximum body size (several > 100cm in fork length) and age (many were born in the 1950s!). Throughout their range, lake trout are known to have several large- v. small-bodied morphs typically associated with variation in their diet and/or their post-glacial evolution. These “polymorphs” may represent a unique contribution both to fisheries and to biodiversity conservation. We can use this dataset to ask several intriguing questions on the ecology of lake trout:

Lake Trout Growth
Example growth trajectory of a lake trout captured at age 56 and born in 1953 that reached 91 cm in length and weighed 9 kg. Here, we see evidence of rapid growth in the first 10 years with growth slowing (but still continuing!) with age. Some years provided much more growth than others. What explains these patterns?
  • Are their polymorphs present in these 30 lakes?
  • If so, how many morphs are there?
    • Use bioenergetics von Bertalanffy model to ask does a fish belong to one particular morph or another?
  • What drives variation in their growth over time?
    • Use time-series of climate and fishery infrastructure development to determine when, at age or in years, growth conditions change

Developing robust management for spatially structured fisheries

Lake trout in western Canada face a variety of challenges: some lakes are warming, and some are targeted for exploitation from a variety of commercial, recreational, or subsistence fisheries. Many of these populations seem quite limited in their resilience. I am collaborating with BC FLNRO, BC MOE, and Environment Yukon to apply the landscape-scale model developed in my past research and input variation in several potential drivers in fishery dynamics. Our aim is to develop scientifically-based management that is robust to potential climate changes and accounts for the diverse fishery needs across many of these lakes. Our hope is to harmonize regulations to balance the complexity of co-managing such a large and diverse fishery across several political jurisdictions.

Social-ecological resilience in changing fisheries

Fisheries are complex social-ecological interactions between people and nature, and they provide subsistence, cultural, and leisure opportunities for billions of people. Many fisheries are collapsing from overfishing and ecosystem changes, yet some fisheries remain resilient to these threats. Biodiversity may help foster resilience via the ‘portfolio effect’, analogous to how financial managers select portfolios composed of diverse assets to stabilize their returns. Hence, fisheries with high diversity (some populations ‘boom’ when others ‘bust’) appear more stable than fisheries with low diversity (populations ‘boom’ or ‘bust’ at the same time). However, fisheries are also diverse socio-culturally, yet current research exploring fishery portfolio effects has ignored these human dimensions. This research aims to illuminate the processes that underpin resilience in one complex social-ecological systems by integrating diversity in biological and social processes to understand how interactions between these dimensions contribute to the stability and resilience of fisheries. To answer this, we will first contrast the contributions of diverse people and their behaviours with fish biodiversity in a theoretical model. As not all fisheries have high biodiversity to conserve, these results can be used to determine how social-ecological diversity drives portfolio effects, and whether fishery managers can increase social well-being to manage for resilience.

SES portfolio diversity
Fishery portfolio effects (a) depended on social and ecological diversity. Social-ecological feedbacks occurred across a watershed network (b) connecting people (square node) with nature (circle nodes). Diverse peoples exploited diverse fish populations over time leading to asynchronous fishery dynamics (c) that depended on harvest, fish migration, and locally adapted demographic traits.

These concepts will then be applied to British Columbia steelhead: a migratory Pacific salmon recommended for emergency-listing as an at-risk species that supports dozens of fisheries worth $33 million CAD·yr-1 to BC’s economy. This work aims to integrate steelhead life-cycle dynamics with fisher diversity to determine policies that best realize resilience of BC fisheries and beyond, to help manage both existing biodiversity and the vast range of human interactions with that diversity.

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