Research

Coral reef network management
Predator-prey relationships and alternative harvest strategies
Juvenile life-history diversity
Food web effects of non-native species
Prioritizing restoration activities

Can managing for a diverse portfolio of coral reefs maintain reef function under a changing climate?

Collaborators: Daniel Schindler (UW), Malin Pinsky (Rutgers), Madhavi Colton (Coral Reef Alliance), Michael Webster (CRA), Adrian Stier (UC-Santa Barbara)

Recent coral bleaching episodes during warm sea temperature anomalies have increased concern about the ability of coral reef ecosystems to continue to provide valuable ecosystem services under changing climate conditions predicted to include warmer ocean temperatures. Strategies that have been suggested to increase the resilience and persistence of coral reefs under changing climate conditions have primarily focused on predict and prescribe tactics, where future environmental conditions are predicted from models and management/restoration activities focus on those species predicted to perform best under these new conditions. However, coral reef species have adapted to a broad array of abiotic and biotic conditions, and management/restoration strategies which focus on a limited set of climate variables may not provide the optimal protection for the reefs. Further, these strategies often ignore the ability of species to acclimatize or evolutionarily adapt to changes in their environment.

Instead of predicting who the winners will be under a changing climate, managers can alternatively leverage the vast diversity (genetic, population, species, and habitat) that is present is reef ecosystems to let nature pick the winners through repeated match-mismatch tests between the environment and coral reef species. By maintaining diversity, coral reef systems may be able to continue providing ecosystem services under changing climate conditions through either species turnover or evolutionary adaptation. We are using simulation models to examine the relative conservation value of different coral reef network management strategies (e.g., protect hot reefs, protect high coral density reefs, protect a diverse portfolio of reefs) under different assumptions about the level of adaptive capacity and dispersal of coral species in uncertain future conditions. Ultimately, these analyses can reveal management strategies that are robust to the vast uncertainty that exists around the adaptive capacity of corals and the rate, magnitude, and spatial heterogeneity of climate change.

Predator-prey relationships and the viability of alternative fishery harvest strategies

Co-authors: Daniel Schindler (UW), Tim Essington (UW)

Traditional fisheries management strategies focusing on single species have come under increasing scrutiny in recent decades.  One principal concern with single species management is that it ignores species interactions and ecosystem dynamics.  In this research, we are examining whether integrated management of a predator and prey species can improve performance of an ecologically, economically, and culturally important fishery.  The Chignik Lakes watershed on the Alaska Peninsula supports runs of sockeye and coho salmon.  Juvenile coho salmon have been demonstrated to consume a substantial proportion of emerging sockeye fry annually.  However, only the sockeye are targets of a directed commercial fishery.  Thus, predation by coho salmon may be limiting the productivity of sockeye populations.  We are examining whether predation pressure during early lie-stages is detectable in adult return data using historical escapement and harvest information for Chignik sockeye and coho. Additionally, we are using simulation models to examine how stochastic recruitment and observation error can mask predator effects.

A common impediment to moving management towards a more ecosystem based approach is the lack of knowledge about ecosystem structure (e.g., species interaction strengths). Active adaptive management has been repeatedly suggested as a method for managing ecosystems while learning about their structure through experiments. We are examining the effectiveness of adaptive management for learning about predation strength in a simulated salmon fishery, focusing on how long adaptive management strategies may need to be enacted before managers can learn about the ecosystem.

As the ultimate reason fishers participate in commercial fisheries is economic, an understanding of how different management strategies will influence fishers and processors is critical to any future management change. Using simulation models of the ecosystem and commercial fishery, we are examining the influence of a directed coho fishery on the overall performance of the salmon fishery at Chignik, across a range of potential biological and economic variables.

Relevant publications:

  • Walsworth TE, Schindler DE (2015) Coho salmon escapement and trends in migration timing to a data-poor river: estimates from a Bayesian hierarchical model.Canadian Journal of Fisheries and Aquatic Sciences. Accepted July 25, 2015. DOI: 10.1139/cjfas-2014-0554.
  • Walsworth TE, Schindler DE (In revision) Long time horizon for adaptive management to detect predation effects in in a salmon fishery. Goal for resubmission to Ecological Applications January 2016.

Juvenile life-history diversity within sockeye salmon spawning populations

Co-authors: Daniel Schindler, Jennifer Griffiths (UW) and Christian Zimmerman (USGS-Anchorage)

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The life-history of Pacific salmon is well known, and the diversity between populations is well appreciated.  Such diversity has been demonstrated to confer stability on salmon stocks, providing more reliable benefits to human, wildlife, and plant communities that rely upon the annual subsidy of salmon nutrients.  However, less is understood about the diversity of life-history behaviors within populations.

By analyzing otolith microchemistry (the chemicals incorporated into the ear bones) of sockeye salmon from a single spawning population, we are able to determine where each sockeye was located in the watershed throughout their life.  This analysis revealed a diversity of life-history strategies based on location and duration of residence in freshwater.  As these were detected in spawning adult salmon, each of these life-history strategies contributes to the spawning population.

Relevant Publications:

  • Walsworth TE, Schindler DE, Griffiths JR, Zimmerman C (2015) Diverse juvenile life-history behaviors contribute to the spawning stock of an anadromous fish population. Ecology of Freshwater Fish 24 (2): 2014-213DOI: 10.1111/eff.12135

Effects of non-native species on desert stream food web

Co-authors: Phaedra Budy (Utah State University – MS Advisor), Gary P. Thiede (USU)

Freshwater ecosystems have been heavily impacted by anthropogenic activities, due to the simultaneous concentration of biodiversity in freshwaters and human activities along waterways. The Colorado River Basin has been heavily impacted by human activity, and many of the basin’s native fish species have experienced dramatic reductions in range and abundance. For my Master’s research, I examined the impacts of non-native species on the food web structure in the San Rafael River, in southeastern Utah, and any subsequent effects on the growth of a complex of three imperiled native fishes.  I used a combination of stable isotope techniques and back-calculation of length-at-age from fin ray sections to determine the influence of non-native fishes on the food web structure and on the growth of native species.

Relevant publications:

  • Walsworth TE, Budy P, Thiede GP (2013) Longer food chains and crowded niche space: effects of multiple invaders on desert stream trophic structure. Ecology of Freshwater Fish 22: 439-452. DOI: 10.1111/eff.12038

Modeling limiting factors and restoration potential for native desert fishes

Co-authors: Phaedra Budy (USU), Gary P. Thiede (USU), Jared Bottcher (USU), Dave Speas (US Bureau of Reclamation)

Every species has a certain range of environmental conditions under which it can maintain populations, often referred to as its ecological niche.  As ecological niches are generally preserved across the geographic distribution of a species, models can be developed to predict the presence or abundance of a species based on the environmental factors limiting it’s niche.  In the second chapter of my thesis work at Utah State University, I used random forest models to determine the limiting factors on populations of the ‘three species’ (roundatil chub Gila robusta, bluehead sucker Catostomus discobolus, and flannelmouth sucker C. latipinnis) from reach specific measurements of both abiotic and biotic variables.  I then used these models to predict the distribution of the ‘three species’ along the continuum of the lower San Rafael River under both current conditions and simulated restoration conditions.  The models developed in this research can provide a framework for management agencies to prioritize their restoration activities to provide the greatest benefit to the ‘three species’ throughout their range.

Additionally, we examined the habitat use of endangered Colorado River fishes. Colorado River endangered fishes are primarily thought to inhabit large river ecosystems, and habitat protection and monitoring efforts therefore focus on mainstem habitats. However, we detected the use of small tributary habitats by endangered fishes, suggesting that these smaller tributaries may be important habitats for endangered fishes, at least during some portion of their lie-history. These findings have implications for conservation efforts, suggesting that restoring tributary habitats may benefit populations of these endangered fishes.

Relevant publications:

  • Walsworth TE, Budy P (2015) Integrating non-native species in niche models to prioritize  native fish restoration action locations along a desert river corridor. Transactions of the American Fisheries Society 144 (4): 667-681.
  • Bottcher JL, Walsworth TE, Thiede GP, Budy P, Speas D (2013) Tributary usage by the endangered fishes of the upper Colorado river basin: A case study from the San Rafael River, UT. North American Journal of Fisheries Management 33: 585-594.
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