Biology subjects

Armstrong, J. B.

Publications and source records attributed to Armstrong, J. B..

3 recordsLinked to original sources

bioRxiv2025

Fish spawning events stimulate trophic hotspots across freshwater food webs

1.0Mass reproductive events, where large numbers of organisms aggregate for synchronous reproduction, are often captivating and ecologically significant, boosting offspring survival and reducing time spent searching for mates. However, mass reproduction can also instigate cryptic but consequential responses across entire food webs. Reproductive materials are abundant and accessible resources that can attract mobile consumers from up to thousands of kilometers away. Yet, their consumption, especially in aquatic systems, is difficult to detect and rarely characterized. Here, we combine molecular techniques with acoustic telemetry, literature review, and extensive natural history observations to investigate the food web consequences of synchronized reproduction in freshwater fishes. First, we demonstrate that a common but underappreciated fish species, white sucker, creates a resource pulse used ubiquitously by consumers, from local invertebrates and fishes to mobile predatory fishes, birds, and terrestrial mammals. Spawning white sucker create trophic hotspots that attract consumers across trophic levels and ecosystems to feed on eggs, spawning adults, and aggregated egg predators. Then we show that egg provisioning and predation is widespread among north-temperate freshwater fish species, highlighting that resource pulses instigated by mass reproduction may play a critical but underappreciated role in freshwater and terrestrial ecosystems.

ecology↗

bioRxiv2023

Foodscapes for Salmon and Other Mobile Consumers in River Networks

Mobile consumers track fluctuating resources across heterogeneous landscapes to grow and survive. In river networks, the abundance and accessibility of food and the costs of foraging vary between habitats and through time, providing a shifting mosaic of growth opportunities for mobile consumers. However, a framework integrating the spatiotemporal dynamics of growth potential within riverscapes has been lacking. Here we present the concept of "foodscapes" to depict the dynamic changes in food abundance, food accessibility, and foraging costs that contribute to spatial and temporal variation of fish growth in rivers. Drawing on case studies of salmonid fishes from Alaska to California, we illustrate that "healthy" foodscapes provide a plethora of foraging opportunities--promoting diverse life history strategies that potentially enhance population stability. We identify knowledge gaps in understanding foodscapes, and approaches for management that focus on restoring trophic pathways which support diverse foraging and growth opportunities for fish in river networks.

ecology↗

bioRxiv2020

Missing pieces in the full annual cycle of fish ecology: a systematic review of the phenology of freshwater fish research

In recent decades, fish ecologists have become increasingly aware of the need for spatially comprehensive sampling. However, a corresponding reflection on the temporal aspects of research has been lacking. We quantified the seasonal timing and extent of freshwater fish research. Since reviewing all prior work was not feasible, we considered two different subsets. First, we compiled the last 30 years of ecological research on juvenile Pacific salmon and trout (Oncorhynchus spp.) (n = 371 studies). In addition to the aggregate, we compared groups classified by subject matter. Next, to evaluate whether riverscape ecology has embraced space at the expense of time, we compiled research across taxa in which fish were enumerated in a spatially continuous fashion (n = 46). We found that ecological Oncorhynchus spp. research was biased towards summer (40% occurred during June-August) and the month of June in particular, at the expense of winter work (only 13% occurred during December-February). Riverscape studies were also biased toward summer (47% of studies) and against winter (11%). It was less common for studies to encompass multiple seasons (43% of ecological Oncorhynchus spp. studies and 54% of riverscape studies) and most were shorter than 4 months (73% of ecological Oncorhynchus spp. studies and 81% of riverscape studies). These temporal biases may cause researchers to overemphasize ecological phenomena observed during summer and limit our ability to recognize seasonal interactions such as carry-over effects or compensatory responses. Full year and winter studies likely hold valuable insights for conservation and management.

ecology↗