Pallard, J. (2022) Assessing the effects of non-native salmonids on Bull Trout (Salvelinus confluentus) in Alberta’s Rocky Mountain foothills.

Thesis Title:Assessing the effects of non-native salmonids on Bull Trout (Salvelinus confluentus) in Alberta’s Rocky Mountain foothills.

Author: Jacqueline Pallard

Abstract

The rapid decline in global biodiversity threatens the natural resources, food security, health, and livelihoods of current and future generations. Anthropogenic activities, including the introduction of non-native species, habitat fragmentation and alteration, and resource extraction, have exacerbated this decline. One such imperiled species are Bull Trout (Salvelinus confluentus), which have exhibited significant declines throughout their range and are expected to decline by >30% over the next 21 years in Alberta. While their decline is attributed to a myriad of threats, the degree to which non-native fishes contribute to their decline is uncertain. The objective of my thesis was to investigate the effects of Brook Trout (Salvelinus fontinalis) and Brown Trout (Salmo trutta), two non-native salmonids, on the habitat use and dietary niche of Bull Trout. To address the habitat component, I developed a multi-species N-mixture model using in-stream and land use derived characteristics to assess how Brook Trout and Brown Trout affect Bull Trout abundance in relation to habitat factors. I determined that Brook Trout negatively affect Bull Trout abundance when streams are <11°C and lack habitat complexity. Interactions between Brown Trout and Bull Trout are less certain, but larger, lower elevation streams are likely to see reductions in Bull Trout abundance where Brown Trout invasion is present and likely to occur. To address the dietary component, I employed stable isotope analysis to investigate how Brook Trout and Brown Trout interact with the dietary niche of Bull Trout. I determined that Bull Trout in sympatry with both Brook Trout and Brown Trout undergo a niche shift and are displaced from terrestrial-based resources. Furthermore, potential for competitive exclusion exists when resources are low given all species exhibit a high degree of niche overlap (>80%) when in sympatry and the amount of niche overlap does not decrease between allopatry and sympatry. The findings of my thesis suggest that both Brook Trout and Brown Trout interfere with the resource use of Bull Trout, on multiple levels, and provides practical guidelines for limiting future declines.

 

Medinski, N.A.*, Maitland, B.M.*, Jardine, T.D., Drake, D.A.R. and M.S. Poesch (2022) A catastrophic coal mine spill in the Athabasca River watershed induces isotopic niche shifts in stream biota including an endangered rainbow trout ecotype. Canadian Journal for Fisheries and Aquatic Sciences 79(8): 1321-1334.

Abstract:

Freshwater biodiversity is declining from impacts associated with anthropogenic stressors. Here, we use carbon (δ13C) and nitrogen (δ15N) stable isotopes to assess food web effects following a coal mine spill that displaced biota and altered biophysical stream characteristics. We compared isotopic niche metrics of benthic macroinvertebrates and the fish community, including non-native brook trout (Salvelinus fontinalis) and endangered Athabasca rainbow trout (Oncorhynchus mykiss), to infer spatial differences in site-specific resource use along a habitat disturbance gradient. Predatory benthic macroinvertebrate trophic position was elevated where impacts from the spill were most pronounced. Autochthonous carbon contribution to consumer diets was lowest in biota sampled at the most highly impacted site from the mine spill, leading to an unexpected expansion of the isotopic niche size of rainbow trout and the aquatic invertebrate community. Collectively, our results suggest spatial variation in trophic resource assimilation across multiple levels of the food web, fuelled by the allochthonous energy pathway in highly impacted study sites. We conclude this reflects a biotic response to altered basal aquatic resources following a major industrial disturbance.

Citation: Medinski, N.A., Maitland, B.M., Jardine, T.D., Drake, D.A.R. and M.S. Poesch (2022) A catastrophic coal mine spill in the Athabasca River watershed induces isotopic niche shifts in stream biota including an endangered rainbow trout ecotype. Canadian Journal for Fisheries and Aquatic Sciences 79(8): 1321-1334.

Also Read:

Nelson-Chorney, H.*, Carli, C.M., Davis, C.S., Vinebrooke, R.D., Poesch, M.S., and M.K. Taylor (2019) Environmental DNA in lake sediment reveals biogeography of native genetic diversity. Frontiers in Ecology and Evolution 17: 313-318.

*Lab members: Nathan Medinski, Bryan Maitland, Mark Poesch. Check out opportunities in the lab!

Banting, A.*, Vinebrooke, R., Taylor, M., Carli, C. and M.S. Poesch. (2021) Impacts of a regionally-native predator on littoral macrobenthos in fishless mountain lakes: implications for assisted colonization. Conservation Science and Practice 3(2): e344.

Abstract:

The intentional introduction of native cold-water trout into high elevation fishless lakes has been considered as a tool for building resilience to climate change (i.e. “assisted colonization”). However, ecological impacts on recipient communities are understudied. Our purpose was to inform native trout recovery by assessing potential consequences of translocating a regionally-native trout (Westslope Cutthroat Trout, Oncorhynchus clarkii) into fishless mountain lakes. We compared littoral benthic invertebrate richness, diversity, community structure, and density between three groups of lakes (native trout, nonnative trout, and fishless) in the Canadian Rocky Mountains. While richness and diversity was conserved across all lake groups, other lines of evidence suggested introducing native Westslope Cutthroat Trout into fishless lakes can alter littoral benthic invertebrate communities in similar ways as nonnative Brook Trout (Salvelinus fontinalis). The community structure of  Cutthroat Trout lakes resembled Brook Trout lakes in comparison to fishless lakes. For example, both trout lake groups contained lower density of free-swimming ameletid mayflies and a higher density of some burrowing taxa. Considering the alteration certain aquatic invertebrates can cause cascading trophic effects, we suggest risk assessments consider a broad range of taxa to mitigate risk of collateral damage from trout recovery actions.

Citation: Banting, A., Vinebrooke, R., Taylor, M., Carli, C. and M.S. Poesch. (2021) Impacts of a regionally-native predator on littoral macrobenthos in fishless mountain lakes: implications for assisted colonization. Conservation Science and Practice 3(2): e344.

Also Read:

Castaneda, R.A., Ackerman, J.D., Chapman, L.J., Cooke, S.J., Cuddington, K., Dextrase, A., Jackson, D.A., Koops, M.A., Krkosek, M., Loftus, K., Mandrak, N.E., Martel, A.L., Molnar, P., Morris, T.J., Pitcher, T.E., Poesch, M.S., Power, M., Pratt, T.C., Reid, S.M., Rodriguez, M.A., Rosenfeld, J., Wilson, C., Zanatta, D.T. and D.A.R. Drake. (2021) Approaches and research needs for advancing the protection and recovery of imperilled freshwater fishes and mussels in Canada. Canadian Journal of Fisheries and Aquatic Sciences 78 (9): 1356-1370.

*Lab members: Allison Banting and Mark Poesch. Check out opportunities in the lab!