2021

Permanent URI for this collectionhttps://hdl.handle.net/1807/104123

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Using diatoms to track road salt seepage into small, shallow, softwater Ontario lakes
(Canadian Science Publishing, 2021-12-24) Valleau, Robin E; Rühland, Kathleen M; Paterson, Andrew M.; Smol, John P
Since the 1950s, the widespread application of road salt for winter road maintenance and safety in cold regions has led to increased conductivity levels in many freshwater systems. Salting practices have adversely affected freshwater biota; however, the magnitude of ecological impacts may vary by species and ecosystem. Here, we examine diatom assemblage changes during the past ~200 years from sedimentary records from five impacted lakes (measured specific conductance values of 149 – 350 S/cm) and a reference lake (15 S/cm) located in the Muskoka River Watershed, south-central Ontario, Canada. Diatom compositional changes in the road-salt impacted sites were consistent with increasing conductivity and increased diatom-inferred conductivity was evident during the latter half of the 20th century, concurrent with known road salt application. The strongest predictor of DI-conductivity changes among the six lakes was the km equivalents of roads within the watershed (i.e. km of road x # of lanes). Similar to changes observed in a previous study focussing on cladoceran assemblages, we conclude that even modest applications of road salt have affected diatom assemblages in softwater lakes in south-central Ontario.
A catastrophic coal mine spill in the Athabasca River watershed induces isotopic niche shifts in stream biota including an endangered rainbow trout ecotype
(Canadian Science Publishing, 2021-11-21) Medinski, Nathan; Maitland, Bryan M; Jardine, Timothy D.; Drake, D. Andrew R.; Poesch, Mark S
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 variation in trophic resource assimilation across multiple levels of the food web, fueled 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.
Physical and biological constraints on the capacity for life-history expression of anadromous salmonids: an Eel River, California, case study
(Canadian Science Publishing, 2021-11-16) FitzGerald, Alyssa M; Boughton, David; Fuller, Joshua; John, Sara N; Martin, Benjamin T.; Harrison, Lee R.; Mantua, Nathan J
Recovery of anadromous salmonid populations is complicated by their complex life-histories. We examined the spatiotemporal interplay of stream temperature, geomorphic features, and a species’ thermal sensitivity mediated by biological interactions in a case study of steelhead trout (Oncorhynchus mykiss) and Chinook salmon (O. tshawytscha) in California’s Eel River watershed. We estimated habitat suitability and fish capacity for each salmonid run and freshwater life stage during average, cool, and warm years in each of the watershed’s subbasins, including a historically-occupied high-elevation subbasin upstream of an impassable dam. Our estimates varied depending on whether we accounted for exposure to the Sacramento pikeminnow (Ptychocheilus grandis), an introduced predator/competitor. Our results indicate that the dammed subbasin has substantial salmonid capacity relative to the rest of the watershed and could provide an important cool-water refuge during warm years and from pikeminnow, potentially improving the productivity and resilience of multiple anadromous salmonid populations. Our approach can be applied in any setting where spatially explicit habitat metrics can be estimated and population specific and life-stage specific habitat criteria can be specified.
Inuvialuit Knowledge of Pacific Salmon Range Expansion in the Western Canadian Arctic
(Canadian Science Publishing, 2021-11-09) Chila, Zander Kaleb Einar; Dunmall, Karen; Proverbs, Tracey; Lantz, Trevor; Hunters and Trappers Committee, Aklavik; Hunters and Trappers Committee, Inuvik; Hunters and Trappers Committee, Sachs Harbour; Hunters and Trappers Committee, Olokhaktomiut; Hunters and Trappers Committee, Paulatuk
Rapid climate change is altering Arctic ecosystems and significantly affecting the livelihoods and cultural traditions of Arctic Indigenous peoples. In the Inuvialuit Settlement Region (ISR), an increase in the harvest of Pacific salmon indicates largescale changes influencing Inuvialuit fisheries. In this project we recorded and synthesized Inuvialuit knowledge of Pacific salmon. We conducted 54 interviews with Inuvialuit fishers about the history of Pacific salmon harvest, how it has changed in recent decades, and concurrent changes to local environments and fish species. Our interviews show that historic, incidental salmon harvest in the ISR ranged from infrequent to common among western communities, but was rare or unprecedented among eastern communities. Participants in all six communities reported a recent increase in salmon harvest and attributed this shift to regional environmental change. Fishers were concerned that salmon would negatively affect their cultural traditions and preferred fish species. Given uncertainty about the effects of salmon on local fisheries, research on salmon diets in the Arctic, their subsidies to Arctic freshwater systems, and the likelihood of their establishment is vital.
Fishing triggers trophic cascade in terms of variation, not abundance in an allometric trophic network model
(Canadian Science Publishing, 2021-11-09) Uusi-Heikkilä, Silva; Perlälä, Tommi; Kuparinen, Anna
Trophic cascade studies often rely on linear food chains instead of complex food webs and are typically measured as biomass averages, not as biomass variation. We study trophic cascades propagating across a complex food web including a measure of biomass variation in addition to biomass average. We examined whether different fishing strategies induce trophic cascades and whether the cascades differ from each other. We utilized an allometric trophic network (ATN) model to mechanistically study fishing-induced changes in food-web dynamics. Different fishing strategies did not trigger traditional, reciprocal trophic cascades, as measured in biomass averages. Instead, fishing triggered a variation cascade that propagated across the food web including fish, zooplankton and phytoplankton species. In fisheries that removed a large amount of top-predatory and cannibalistic fish, the biomass oscillations started to decrease after fishing was started. In fisheries that mainly targeted large planktivorous fish, the biomass oscillations did not dampen, but slightly increased over time. Removing species with specific ecological functions might alter the food web dynamics and potentially affect the ecological resilience of aquatic ecosystems.
Opposing trends in survival and recruitment slow the recovery of a historically overexploited ﬁshery
(Canadian Science Publishing, 2021-12-22) Phillips, Joseph S.; Gubergsson, Guni; Ives, Anthony R
Quantifying temporal variation in demographic rates is a central goal of population ecology. In this study, we analyzed a multidecadal age-structured time series of Arctic charr (Salvelinus alpinus) abundance in Lake Mvatn, Iceland, to infer the time-varying demographic response of the population to reduced harvest in the wake of the fishery's collapse. Our analysis shows that while survival probability of adults increased following the alleviation of harvesting pressure, per capita recruitment consistently declined over most of the study period, until the final three years when it began to increase. The countervailing demographic trends resulted in only limited directional change in the total population size and population growth rate. Rather, the population dynamics were dominated by large interannual variability and a shift towards an older age distribution. Our results are indicative of a slow recovery of the population after its collapse, despite the rising number of adults following relaxed harvest. This underscores the potential for heterogeneous demographic responses to management efforts due to the complex ecological context in which such efforts take place.
The effect of sea surface temperature on the structure and connectivity of species landings interaction networks in a multispecies recreational fishery.
(Canadian Science Publishing, 2021-12-10) Blincow, Kayla Mackenzie; Semmens, Brice X
Multispecies fisheries, particularly those that routinely adapt the timing, location, and methods of fishing to prioritize fishery targets, present a challenge to traditional single-species management approaches. Efforts to develop robust management for multispecies fisheries require an understanding of how priorities drive the network of interactions between catch of different species, especially given the added challenges presented by climate change. Using 35 years of landings data from a southern California recreational fishery, we leveraged empirical dynamic modelling methods to construct causal interaction networks among the main species targeted by the fishery. We found strong evidence for dependencies among species landings time series driven by apparent hierarchical catch preference within the fishery. In addition, by parsing the landings time series into anomalously cool, normal, and anomalously warm regimes (the last reflecting ocean temperatures anticipated by 2040), we found that network complexity was highest during warm periods. Our findings suggest that as ocean temperatures continue to rise, so too will the risk of unintended consequences from single species management in this multispecies fishery.
Detecting Population Regulation of Winter Flounder from Noisy Data
(Canadian Science Publishing, 2021-12-02) Langan, Joseph A.; Collie, Jeremy S.; Minto, Ciln
Year-class size of marine fish is thought to be determined during the first year of life, with density-dependent mortality during the larval or juvenile stages. However, investigations of such dynamics are often limited by data availability. To test this paradigm for winter flounder (Pseudopleuronectes americanus) in Narragansett Bay, Rhode Island, the abundances of 29 year classes moving through seven life stages were analyzed with a novel extension of key-factor analysis. Evidence of density dependence was identified between the egg and July young-of-the-year stages and high process-error variance was detected throughout the life cycle, suggesting year-class size is not fully determined until age-2. However, the first summer appeared to be a critical life stage for winter flounder, during which high temperatures, hypoxia, and predator abundance contributed to increased mortality rates behind a long-term population decline. Due to its general data requirements, the key-factor analysis method developed here may be applied to other marine populations to identify the impacts of external stressors at particular life stages and the degree to which they are compensated by density-dependent processes.
Summer stream habitat preferences of Nunavik anadromous Arctic char (Salvelinus alpinus) fry and parr
(Canadian Science Publishing, 2021-12-13) Dubos, Vronique; St-Hilaire, Andr; Bergeron, Normand E
Arctic char is a fish species known to occupy diverse habitats within the Arctic region. However, summer habitat use during the juvenile stage of the anadromous form is largely unknown. The present study aims to characterize fry and parr summer habitat preferences. Surveys were conducted by electrofishing, associated with physical habitat characterization on several rivers of the Ungava Bay, Nunavik, Canada. At the microhabitat and station scales, fry showed significant habitat preferences for shallow water and slow velocity. At the mesohabitat scale, fry showed a significant habitat selectivity for riffles. This habitat selectivity implies that habitat models can be built to evaluate the potential of habitat suitability for Arctic char fry. However, no significant habitat selectivity was found for parr. Parr size was nonetheless positively correlated with velocity, which was found to be a limitative factor for juvenile habitat use. This first attempt at modeling juvenile anadromous Arctic char habitat in rivers emphasizes the importance of selecting an appropriate spatial scale and reiterates the fact that parr showed relatively high plasticity in stream habitat selection.
Spatial and Temporal Differences in Fecundity of Atlantic Herring (Clupea harengus) off Nova Scotia and Consequences for Biological Reference Points
(Canadian Science Publishing, 2021-12-22) Barrett, Timothy J; Hordyk, Adrian R.; Barrett, Melanie A; van den Heuvel, Michael R
The relationships between fecundity and size of Atlantic herring (Clupea harengus) were estimated within five different spawning areas off the coast of Nova Scotia in 2019 and 2020. Statistically significant differences in fecundity relative to body weight were observed among spawning areas and between years. Fecundity-at-length on the German Bank spawning ground was 29-36% and 22-28% lower than estimates from 2001 and 1970, respectively. Temporal changes in weight- and relative fecundity- at-age resulted in a decrease in the number of eggs-per-recruit (in an equilibrium unfished state) by 50% and a decrease of 27% in the egg production per tonne of spawning stock biomass (SSB) in 2020 relative to 1970. Decreases in SSB-per-recruit and eggs-per-recruit over time resulted in proportional decreases in equilibrium SSB at maximum sustainable yield (MSY); however, the fishing mortality rate (F) at MSY remained relatively stable over time. Total egg production was shown to be disproportional to SSB. Equilibrium SSB at MSY was greater (and F at MSY lower) when estimated using eggs-per-recruit compared to SSB-per-recruit. Failing to account for fecundity and assuming that egg production is proportional to SSB resulted in an overestimate of stock status
Inclusion of recreational fishing in data-limited stocks: a case study on Norway lobster (Nephrops norvegicus) in Norway
(Canadian Science Publishing, 2021-11-15) Zimmermann, Fabian; Kleiven, Alf Ring; Ottesen, Merete Vik; Svik, Guldborg
Recreational and semi-subsistence fisheries are challenging to monitor but can act as precursors of developments in commercial fisheries, contributing information in data-limited situations. We compared trends in commercial landings of Norway lobster (Nephrops norvegicus) with data collected through a citizen science project by recreational fishers in Norway during a period that coincided with the onset of a commercial trap fishery. The results show that trap fishing for Nephrops emerged recently in Norway, with significant regional differences in size composition and catch rates. Comparable patterns in catch rates between regions were found in commercial landings during the same period, suggesting that landings per boat trip may provide a suitable abundance index in a severely data-limited fishery. Our study indicates that recreational fishing acted as trailblazer for a surge in fishing with lower-impact gear along the Norwegian coast, underscoring the fact that non-commercial fisheries may act as early indicators of emerging commercial fisheries. Collecting information through citizen science projects targeting non-commercial fishers can therefore provide baseline data, especially from the earliest, unmonitored stages of fisheries, and contribute to stock assessment.
Monitoring the water balance of seepage lakes to track regional responses to an evolving climate
(Canadian Science Publishing, 2021-11-17) Watras, Carl J; Michler, James R; Rubsam, Jeff
Understanding the causes of large fluctuations in lake water levels is important for adaptive resource management. The relatively simple water budgets of small seepage lakes make them potentially useful model systems, provided that key water balance components can be well constrained. Here, spatial variability in measured rates of evaporation (E) and precipitation (P) at the whole lake scale was investigated, and the effect on daily and seasonal water balance estimates was quantified. To estimate spatial variability, triplicate sensor platforms were deployed on and near an 18 ha seepage lake. Lake stage (S) was monitored at a single node in the lake. The water balance was closed by estimating net groundwater seepage (Gnet) analytically as Gnet = ∆S – (P – E). Instrumentation on a second seepage lake was maintained by citizen scientists to assess the potential for more widespread sensor deployments. Data were collected every 30-minutes for six months. The results indicate that low-cost sensor networks with single nodes to measure E, P and ∆S provide well-constrained water budgets at daily and seasonal time scales.
Post-settlement abundance, condition, and survival in a climate-stressed population of Pacific cod
(Canadian Science Publishing, 2021-11-21) Abookire, Alisa A.; Litzow, Michael A.; Malick, Michael J.; Laurel, Benjamin Jeffrey
The Pacific cod (Gadus macrocephalus) fishery recently collapsed in the Gulf of Alaska after a series of marine heatwaves that began in 2014. To gauge the likelihood of population recovery following these extreme warming events, we investigate potential thermal stress on age-0 cohorts through a comprehensive analysis of juvenile cod abundance, condition, growth, and survival data collected from 15 years of beach seine surveys. Abundance was strongly negatively related to ocean temperature during the egg and larval phase (winter/spring), but age-0 cod were larger in the early summer following warm winter/spring temperatures. Body condition indices suggest that warm summers may improve energetic reserves prior to the first winter; however, there was no summer temperature effect on post-settlement growth or survival. Spatial differences in abundance, condition, or growth were not detected, and density-dependent effects were either weak or positive. While the positive effects of increased summer temperatures on juvenile condition may benefit overwintering survival, they cannot compensate for high pre-settlement mortality from warming winter/spring temperatures. We conclude the critical thermal bottleneck for juvenile abundance occurs pre-settlement.
The timing of spring warming shapes reproductive effort in a warm-water fish: the role of mismatches between hepatic and gonadal processes
(Canadian Science Publishing, 2021-10-25) Fernandes, Timothy J.; Shuter, Brian J.; Ihssen, Peter E; McMeans, Bailey C.
Spring-spawning fishes native to northern environments rely on both increasing temperature and lengthening photoperiod to cue reproduction and may thus be particularly sensitive to rapid warming earlier in the year while day lengths remain short. We investigated the reproductive response of pumpkinseed sunfish Lepomis gibbosus to spring warming commencing at a range of day lengths (9 – 15 hours), corresponding to various calendar days (January 10 – May 22). In both the laboratory and field, both male and female fish that experienced early warming while day lengths were
Interspecific competition reduces the performance of Atlantic salmon, Salmo salar: implications for restoration programs
(Canadian Science Publishing, 2021-10-31) Grant, James W A; Weir, Laura K.
Competition from non-native salmonids is potentially impairing efforts to restore Atlantic salmon (Salmo salar) to parts of their historical range. In three separate meta-analyses, we collected 104 effect sizes from 25 published papers to quantify the effect of both native and non-native salmonids on the performance (i.e. behaviour, habitat use, growth and survival) of Atlantic salmon. The presence of other species had negative effects on the performance of Atlantic salmon; in particular, non-native species and brown trout (Salmo trutta), whether native or non-native, had the most negative effects. Contrary to our predictions, the negative effects of other species were not exacerbated in laboratory compared to field studies, and did not increase with total salmonid abundance, or the relative body size of the competitors. However, most studies in our analysis were conducted under laboratory conditions and at densities much higher than found in nature. Thus, a realistic assessment of the potential success of restoration programs when interspecific competitors are present should include more studies conducted under natural conditions.
Retrospective analysis of marine growth and relationships to return rates of Penobscot River Atlantic salmon
(Canadian Science Publishing, 2021-10-05) Barajas, Miguel Fillion; Sheehan, Timothy F; Haas-Castro, Ruth; Ellingson, Brandon; Mills, Katherine
Beginning in the 1980s, return rates of Atlantic salmon to the Penobscot River, Maine U.S.A. declined and have persisted at low levels. This downturn coincided with similar declines in North American and European Atlantic salmon stocks and with changes in the Northwest Atlantic ecosystem. Previous studies investigated whether early marine growth explained the declines, but results varied, with decreased growth associated with declines in European stocks but not North American stocks. In this study, we evaluate whether growth over the entire marine stage is related to Atlantic salmon marine survival. We constructed a growth time series from scales of returned Penobscot River Atlantic salmon spanning periods of varying marine survival. We used ANOVA and post-hoc tests to quantify seasonal growth increment differences and principal component analysis to characterize variability among the suite of growth increments. We observed reduced growth during the second winter and second marine year starting in the 1990s, with compensatory seasonal growth relationships. These results indicate that diminished growth during late marine stages is associated with low return rates in this population.
Assessing the ability of the growing degree-day metric to explain variation in size-at-age and duration-to-moult of lobsters and crabs
(Canadian Science Publishing, 2021-10-25) Steele, Reid William; Neuheimer, Anna B
Environmental temperature directly controls the rate at which ectotherms grow and develop. The growing degree-day metric (GDD, C∙d) scales time by temperature to create a thermal time scale relevant to ectothermic organisms. Here we assess the ability of GDD to model size-at-age and duration-to-moult in 15 datasets (9 size-at-age, 6 duration-to-moult) comprising 7 species of lobsters and crabs. We applied generalized linear models to assess the ability of GDD vs. “calendar” time to explain growth and development observations within and across trials. Best-fit models included GDD with fewer parameters in 6 of 9 size-at-age and 5 of 6 duration-to-moult datasets, and a better fit to the data in 6 of 9 size-at-age datasets. Our results show that the individual growth of lobster and crab species can be modelled using thermal time models. Such models can be used to identify thermal tolerance limits, predict growth under varying temperature conditions and disentangle temperature effects from those of other factors affecting individual growth and development, resulting in improved growth models for field conditions including fisheries management.
High prevalence of basin fidelity and homing by lake trout, Salvelinus namaycush, in a small northern lake
(Canadian Science Publishing, 2021-10-21) Gallagher, Colin P; Guzzo, Matthew M; Dick, Terry A
Identifying how habitat structure influences the spatio-temporal movements of fishes is important for conservation, population assessment, and management purposes. Here, we determined whether acoustically tagged lake trout, Salvelinus namaycush, from a 305 ha lake exhibited homing behaviour and lake basin fidelity over multiple seasons and years. The lake has two distinct deep basins (‘north’ and ‘south’) connected by a shallower centre basin. Fifteen lake trout captured during the spawning season from both deep basins were tagged and released in the south basin. All translocated north-basin fish quickly returned to the north basin (median= 1.85 d, range= 0.36–4.5 d), apart from one fish that returned 41 d post-release, while none from the south ventured into the north basin during this time. After translocated individuals returned, all fish demonstrated high basin fidelity among years as >90% of detections were from the same basin fish were captured, while
Food web incorporation of marine-derived nutrients after the reintroduction of endangered inner Bay of Fundy Atlantic salmon (Salmo salar)
(Canadian Science Publishing, 2021-10-25) Bryson, Grace Elizabeth; Kidd, Karen A; Samways, Kurt M
Inner Bay of Fundy Atlantic salmon (Salmo salar) are endangered anadromous fish that have the potential to provide marine-derived nutrients (MDNs) to freshwater ecosystems depending on their population abundance. Salmon have been reintroduced to the Upper Salmon River, but not the adjacent Point Wolfe River, in Fundy National Park, New Brunswick, Canada. This study determined whether stocking of adult salmon increased the productivity of the river. To examine the incorporation of MDNs, biofilm, leaf litter, Perlidae, Heptageniidae and brook trout (Salvelinus fontinalis) were sampled pre- and post-spawning in 2015-2017 from down- and up-stream of a natural barrier in both rivers and analyzed for carbon (δ13C) and nitrogen (δ15N) isotopes. After salmon spawning in each year, all organisms at the downstream site of the stocked river increased in δ13C and δ15N, with the greatest enrichment in brook trout (δ13C -23.97 to -21.10‰, δ15N +6.36 to +10.73‰). The proportion of MDNs in brook trout after salmon spawning (2015: 23.4%, 2016: 40.7%, 2017: 37.4%) also increased with higher numbers of released adult salmon. Results support the importance of salmon restoration for increasing the proportion of MDNs and productivity in rivers in Atlantic Canada.
The role of hatcheries in the decline of Lake Ontario Atlantic Salmon
(Canadian Science Publishing, 2021-11-02) Morrison, Brian P; Peiman, Kathryn
Lake Ontario Atlantic Salmon were one of the first species of fish to be cultured in Canada. Their story goes from abundance in the 1700s to protective legislation in 1807, then hatchery culture in 1866 and finally ends in extirpation in 1898. The standard narrative is that Samuel Wilmot’s hatchery efforts briefly staved off their loss from the Lake Ontario basin. However, that story is replete with inaccurate assumptions, unfounded faith in technological solutions, and a belief that numbers of fish released was an accurate measure of success. We challenge the narrative around the perceived benefits of these hatchery efforts and suggest instead that they contributed to the decline of Atlantic Salmon in Lake Ontario through the mining of wild gametes, transferring eggs out of basin, mixing locally-adapted populations across streams, and the negative genetic effects of releasing hatchery fish.

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