Research and Teaching Interests
My research program focuses on investigating recruitment dynamics of key forage fish species and how these dynamics shape trophic and food web interactions in northern marine ecosystems. Forage species lie at the core of complex marine food webs, providing essential linkages among trophic levels. These short-lived fish species are characterized by high natural fluctuations in population size (~± 40%), driven by annual variability in the number of individuals surviving to reproduce, or recruitment. Mechanisms underlying recruitment dynamics are often unclear. Despite their critical role, forage fish comprise a third of the global marine fish catch, revealing an imminent need to identify factors driving recruitment dynamics as well as predator and food web responses to varying forage fish biomass. Many aspects of marine predator biology are influenced by forage fish biomass (e.g., foraging efficiency, reproductive success), but food web responses are less clear. Species interactions may change as forage fish biomass decreases, whereby a predator species’ ability to shift foraging strategies may be constrained by both direct and indirect interactions with other species. My lab investigates interactions of forage fish and multiple marine predators (seabirds, whales, fish) to understand predator-prey and food web dynamics. This research will increase our ability to maintain the long-term productivity of northern marine ecosystem to sustain fisheries yields and conserve marine biodiversity.
Marine ecology, species interactions, food web dynamics, foraging ecology, life history, habitat selection, fisheries oceanography, marine conservation biology, movement ecology, remote sensing, seabirds, whales, forage fish
Graduate Positions Available
I typically accept new graduate students into my lab in May/September. STUDENTS MUST APPLY FOR SCHOLARSHIPS TO COVER ALL OR PART OF THEIR STIPEND. The University of Manitoba Graduate Fellowship (UMGF) application is typically due in February.
For available graduate positions, please see https://davorenlab.wixsite.com/research/graduate-opportunities
Current Research Projects
Forage Fish Ecology
I have sustained a long-term interest in capelin (Mallotus villosus), a key forage fish species in northern marine ecosystems, and capelin-predator interactions. Since 2000, my lab has discovered and described deep-water (15-40 m) spawning sites of capelin on the exposed northeast Newfoundland coast, where this species is considered to primarily spawn on or adjacent to beaches. We found that capelin select spawning habitat based on temperature, supported by limited evidence of genetically differentiated populations. Although both spawning habitats have similar egg densities, temperature-dependent egg development, and larval condition, some researchers have suggested that deep-water habitat contributes little to recruitment. As a higher occupation of deep-water habitat is predicted with climate warming, it is critical to determine if this habitat represents an ecological trap. We use the chemistry of otoliths (metabolically inert ‘ear stones’) as a natural tag of capelin natal habitat. As larvae disperse immediately upon hatch, chemical signatures in the pre-hatch otolith region indicate natal habitat. Despite our finding of distinct maternally-derived chemical signatures in this pre-hatch region, our experiments have shown that chemicals are incorporated into otoliths during incubation and field-reared eggs/larvae have habitat-specific chemical signatures. We are current conducting research to quantify the relative contribution of spawning habitats and regions to recruitment in eastern Canada, as well as investigating the bio-physical factors (i.e. prey, predators, temperature) underlying capelin larval survival.
Since 1990, capelin have undergone major changes in distributional and density patterns in eastern Canada. First, this sub-Arctic species’ abundance increased in Arctic regions, where it was historically rare, possibly due to northerly range expansions or more favourable, warmer conditions. My lab has documented capelin spawning in Arctic regions, divergent Arctic life history traits, and high dietary niche overlap with key Arctic forage fish, Arctic cod (Boreogadus saida), illustrating potential competitive interactions. Impacts on Arctic food webs depend on persistent conditions resulting in high recruitment, but capelin Arctic environment-recruitment relationships are unknown. We are currently conducting research on capelin ecology in the eastern and western Canadian Arctic.
Predator Ecology (Seabirds, Whales, Fish)
My lab has found that annually persistent deep-water spawning sites of capelin result in the predictable formation of multi-species biological hotspots, or areas where high abundances of marine predators aggregate. Varying capelin biomass within hotspots, due to dynamic annual biomass and timing of spawning, is associated with changing predator ecology, including shifts in diet, foraging effort, and foraging strategies to minimize energetically costly search activities. Predator dietary and spatial overlap is low under low capelin biomass, but increases with capelin biomass, suggesting release from competitive interactions. Although predators are highly aggregated at hotspots, they primarily forage alone to capture solitary capelin, possibly due to intra- and inter-specific interactions (e.g., fighting, food stealing) that lower species-specific foraging success. These findings suggest that the costs and benefits of group foraging vary under dynamic prey and predator densities. We are currently integrating ship-based surveys, with at-sea experiments, animal-borne data loggers and dietary metrics (stomach contents, stable isotope analysis, fatty acid signature analysis) to further investigate marine predator-prey and food web interactions within a long-term, multi-species context.
Tripp A (2018-present) Factors influencing capelin (Mallotus villosus) recruitment on the Newfoundland Shelf. PhD, Biological Sciences.
Epp M (2017-present) Comparisons of humpback whale non-song vocalizations across their North Atlantic foraging grounds. MSc, Biological Sciences. NSERC PGS.
Mikhailitchenko A (2017-present) Diel patterns of three common non-song call types of humpback whales, Megaptera novaeangliae, on their Newfoundland foraging grounds in relation to prey availability. MSc, Biological Sciences. NSERC PGS.
Bliss L (2017-present) Predicting spatial distribution of marine predators using habitat characteristics in two marine ecosystems, Atlantic Canada and the California Current. PhD, Biological Sciences. University of Manitoba Graduate Fellowship.
Zhao S (2017-present) Weaning age and diet variation in narwhals (Monodon monoceros) determined using stable isotope analysis (δ13C and δ15N) of dentine. MSc, Biological Sciences (co-supervised with Dr C Watt).
For a full list of previous graduate and honours students, please see https://davorenlab.wixsite.com/research/people
BIOL 4220 Marine Biodiversity
BIOL 1030 Biological Diversity, Function and Interactions