UVicSpace : Browsing by Author "Juanes, Francis"

Browsing by Author "Juanes, Francis"

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A tale of two surveys: Improving biodiversity monitoring through rapid baseline assessments
(University Of Victoria, 2025) Toma, Emily; Melchers, Grace; Dudas, Sarah E.; Hunt, Brian; Hessing-Lewis, Margot; Juanes, Francis; Cox, Kieran
Biodiversity monitoring is critical for understanding ecosystem condition and guiding conservation efforts. While the scale and scope of biodiversity data collection have expanded through novel techniques and citizen science initiatives, methods for integrating diverse datasets remain poorly developed. This has hindered our ability to leverage the full potential of modern biodiversity monitoring approaches. I address this gap by producing a framework for synthesizing data across multiple techniques, comparing rapid baseline assessments that emphasize expert identification with systematic surveys that prioritize replication over space and time. I use a multi-ecosystem approach, examining 3 distinct marine communities: soft-sediment bivalves, temperate kelp forests, and tropical coral reefs to test the broad applicability of this framework. Using species lists to develop a standardized framework for data integration, I address a fundamental challenge in biodiversity monitoring: how to effectively combine data from diverse sources to create more comprehensive and accurate biodiversity assessments. The results will inform the development of more efficient, ecosystem-specific monitoring.
Advantages and insights from a hierarchical Bayesian growth and dynamics model based on salmonid electrofishing removal data
(Ecological Modelling, 2019) Laplanche, Christophe; Leunda, Pedro M.; Boithias, Laurie; Ardaiz, Jose; Juanes, Francis
Growth is a fundamental ecological process of stream-dwelling salmonids which is strongly interrelated to critical life history events (emergence, mortality, sexual maturity, smolting, spawning). The ability to accurately model growth becomes critical when making population predictions over large temporal (multi-decadal) and spatial (meso) scales, e.g., investigating the e ect of global change. Body length collection by removal sampling is a widely-used practice for monitoring sh populations over such large scales. Such data can be e ciently integrated into a Hierarchical Bayesian Model (HBM) and lead to interesting ndings on sh dynamics. We illustrate this approach by presenting an integrated HBM of brown trout (Salmo trutta) growth, population dynamics, and removal sampling data collection processes using large temporal and spatial scales data (20 years; 48 sites placed along a 100 km latitudinal gradient). Growth and population dynamics are modelled by ordinary di erential equations with parameters bound together in a hierarchical structure. The observation process is modelled with a combination of a Poisson error, a binomial error, and a mixture of Gaussian distributions. Absolute t is measured using posterior predictive checks, which results indicate that our model ts the data well. Results indicate that growth rate is positively correlated to catchment area. This result corroborates those of other studies (laboratory, exploratory) that identi ed factors besides water temperature that are related to daily ration and have a signi cant e ect on stream-dwelling salmonid growth at a large scale. Our study also illustrates the value of integrated HBM and electro shing removal sampling data to study in situ sh populations over large scales.
Assessing Indices of Growth for Field Studies of Juvenile Salmon: An Experiment and Synthesis
(Marine and Coastal Fisheries: Dynamics, Management, and Ecosystem Science, 2018) Duguid, William D.P.; Iwanicki, Thomas W.; Journey, Meredith L.; Noel, Amanda L.; Beckman, Brian R.; Juanes, Francis
The hypothesis that size-selective mortality in the first marine year is a major regulator of recruitment in Pacific salmon Oncorhynchus spp. has led to interest in assessing the recent growth of field-caught fish. Understanding differences in relative growth across years, regions, habitats, and prey fields may provide insights into factors influencing survival. Plasma insulin-like growth factor 1 (IGF1), muscle RNA : DNA ratio (RD), and scale circulus spacing have all been used as indices of recent growth in juvenile salmonids. We concurrently assessed these growth rate indices in a laboratory study of postsmolt, young-of-the-year, ocean-type Chinook Salmon O. tshawytscha. We synthesized results with previous work to inform selection of appropriate growth rate indices for field studies on juvenile salmonids. Muscle samples suitable for RD analysis were obtained nonlethally and without subsequent growth impacts, even for very small juvenile salmon (75–99 mm FL). Plasma IGF1 concentration was strongly correlated with growth rate (R2 = 0.79), while loge(RD) and mean spacing of the outer two circuli were moderately correlated with growth rate (R2 = 0.47 and 0.44, respectively). Relationships between the two biochemical indices and growth rate were independent of body size at the start of the experiment. Conversely, initially larger fish formed wider circuli for a given growth rate. Insulin-like growth factor 1 and RD responded to a change in growth conditions within 4 and 6 d, respectively. Rate of circulus formation varied positively with growth rate, meaning that outer circulus spacing indexed shorter periods of growth in faster-growing fish. Our results confirm the value of plasma IGF1 as an index of recent growth in juvenile salmon. Although scales (marginal circulus spacing) and white muscle (RD) can both be sampled nonlethally, scale sampling presents a number of practical advantages.
Assessing the effect of aquatic noise on fish behavior and physiology: a meta-analysis approach
(Proceedings of Meetings on Acoustics, 2016) Cox, Kieran D.; Brennan, Lawrence P.; Dudas, Sarah E.; Juanes, Francis
Due to the extreme distance that sounds can travel through water, many marine species rely on the soundscape for auditory information regarding predator or prey locations, communication, and habitat selection. These species not only take advantage of the prevailing sounds but also contribute to the soundscape through their own vocalizations. Certain sounds have been shown to have negative effects on marine species, resulting in disrupted communication and unbalanced predator-prey interactions. Unfortunately, the vast majority of soundscape studies are biased towards marine mammals, and only recently has attention been directed towards the potential repercussions for fishes. In an attempt to determine the implications that changes to the soundscape may have on the fishes, a meta-analysis was conducted focusing primarily on the role that anthropogenic noises may play in altering fish behavior and physiology. The review identified 3,174 potentially relevant papers of which were 27 used. The analysis indicates that anthropogenic noise has an adverse effect on marine and freshwater fish behavior and physiology. These findings suggest that although certain species may be more susceptible to anthropogenic noise than others, the vast majority of fish have the potential to be negatively affected by noise pollution.
Boat noise reduces vocalization rate and alters vocal characteristics in wild plainfin midshipman fish
(Marine Pollution Bulletin, 2025) Woods, Mackenzie B.; Halliday, William D.; Balshine, Sigal; Juanes, Francis
Anthropogenic noise pollution has been accelerating at an alarming rate, greatly altering aquatic soundscapes. Animals use various mechanisms to avoid acoustic masking in noisy environments, including altering calling rates or the frequency (pitch) of their vocalizations or increasing the amplitude (loudness) of their vocalizations (i.e., exhibiting the Lombard effect), but few studies have examined this vocal plasticity in fishes. We tested the effects of in situ motorboat noise on the agonistic and mating vocalizations of nesting plainfin midshipman fish (Porichthys notatus), and found that midshipman fish reduce and alter their vocalizations in the presence of boat noise. During boat noise, fish produced four times fewer agonistic vocalizations compared to ambient control periods. The fish also increased the frequency of mating hums and the amplitude of grunts and growls during boat noise. This study is the first to experimentally demonstrate the Lombard effect in fishes using real motorboat noise.
Boats, drones and tides: Evaluating effective methods for surface monitoring of kelp-encrusting bryozoans
(University of Victoria, 2026) Van Haren, Scott; Bergman, Jordanna; Juanes, Francis; Costa, Maycira
As increasingly frequent marine heatwaves reshape coastal ecosystems, the development of new monitoring tools is essential to track existing and emerging threats. During a recent coast-wide marine heatwave, an unprecedented outbreak of kelp-encrusting bryozoans, or "KEB", was observed on the Central Coast of British Columbia (BC), alarming First Nations and resource managers and spurring interest in monitoring future outbreaks. Here, we evaluated the use of drones to monitor KEB by comparing data collected in tandem from novel drone methods to established canoe surveys. Across 21 sites along the coast of BC, we compared KEB detection and tested the ability of both methods to detect a settlement pattern of KEB throughout kelp forests. Drone surveys prove to be an accessible and efficient alternative to the time-intensive canoe-based surveys that are currently used, providing similar data with less time on the water. Tide is a major constraint of both surveys, with KEB detection rates falling rapidly as the tide rises, especially for drone surveys. We discuss the strengths and limitations of this new approach to better inform resource managers in efforts to understand their waters.
Capture severity, infectious disease processes and sex influence post-release mortality of sockeye salmon bycatch
(Conservation Physiology, 2017) Teffer, Amy K.; Hinch, Scott G.; Miller, Kristi M.; Patterson, David A.; Farrell, Anthony P.; Cooke, Steven J.; Bass, Arthur L.; Szekeres, Petra; Juanes, Francis
Bycatch is a common occurrence in heavily fished areas such as the Fraser River, British Columbia, where fisheries target returning adult Pacific salmon (Oncorhynchus spp.) en route to spawning grounds. The extent to which these encounters reduce fish survival through injury and physiological impairment depends on multiple factors including capture severity, river temperature and infectious agents. In an effort to characterize the mechanisms of post-release mortality and address fishery and managerial concerns regarding specific regulations, wild-caught Early Stuart sockeye salmon (Oncorhynchus nerka) were exposed to either mild (20 s) or severe (20 min) gillnet entanglement and then held at ecologically relevant temperatures throughout their period of river migration (mid-late July) and spawning (early August). Individuals were biopsy sampled immediately after entanglement and at death to measure indicators of stress and immunity, and the infection intensity of 44 potential pathogens. Biopsy alone increased mortality (males: 33%, females: 60%) when compared with nonbiopsied controls (males: 7%, females: 15%), indicating high sensitivity to any handling during river migration, especially among females. Mortality did not occur until 5-10 days after entanglement, with severe entanglement resulting in the greatest mortality (males: 62%, females: 90%), followed by mild entanglement (males: 44%, females: 70%). Infection intensities of Flavobacterium psychrophilum and Ceratonova shasta measured at death were greater in fish that died sooner. Physiological indicators of host stress and immunity also differed depending on longevity, and indicated anaerobic metabolism, osmoregulatory failure and altered immune gene regulation in premature mortalities. Together, these results implicate latent effects of entanglement, especially among females, resulting in mortality days or weeks after release. Although any entanglement is potentially detrimental, reducing entanglement durations can improve post-release survival.
Cataloging fish sounds in the wild using combined acoustic and video recordings
(The Journal of the Acoustical Society of America, 2018) Mouy, Xavier; Rountree, Rodney; Juanes, Francis; Dosso, Stan E.
Although many fish are soniferous, few of their sounds have been identified, making passive acoustic monitoring (PAM) ineffective. To start addressing this issue, a portable 6-hydrophone array combined with a video camera was assembled to catalog fish sounds in the wild. Sounds are detected automatically in the acoustic recordings and localized in three dimensions using time-difference of arrivals and linearized inversion. Localizations are then combined with the video to identify the species producing the sounds. Uncertainty analyses show that fish are localized near the array with uncertainties < 50 cm. The proposed system was deployed off Cape Cod, MA and used to identify sounds produced by tautog (Tautoga onitis), demonstrating that the methodology can be used to build up a catalog of fish sounds that could be used for PAM and fisheries management.
Centering relationships to place for more meaningful research and engagement
(Proceedings of the National Academy of Sciences, 2024-06-03) Beaty, Fiona; Domínguez-Sánchez, Pablo Santiago; Nalven, Katy; Palacios-Abrantes, Juliano; Oken, Kiva; Ban, Natalie; Nickols, Kerry; Juanes, Francis; Okey, Thomas; Spalding, Ana K.; Morzaria-Luna, Hem Nalini; Jenkins, Lekelia; Tulloch, Vivitskaia; McKechnie, Iain
Research has the potential to simultaneously generate new knowledge and contribute meaningful social–ecological benefits; however, research processes and outcomes can also perpetuate extractive patterns that have manifested the climate, biodiversity, and social justice crises. One approach to enhance the societal value of research processes is to strengthen relationships with places of study and the peoples of those places. Deepening relational engagement with the social–ecological context and history of a place can lead to more accurate results and improved public trust in the scientific process and is particularly important for natural scientists who work at the interface of nature and society. We provide three actionable pathways that range from individual to systemic change to enhance place-based relationships within research systems: 1) deepen reflection and communication about relationships with places and peoples; 2) strengthen collaboration among research teams and partners; and 3) transform systems of knowledge creation to foster place-based roots. Action on any of these proposed pathways, but especially action taken across all three, can build empathy and connections to place and people, strengthening the meaningful impact of research both locally and globally.
Coherent population dynamics associated with sockeye salmon juvenile life history strategies
(Canadian Journal of Fisheries and Aquatic Sciences, 2018) Freshwater, Cameron; Trudel, Marc; Juanes, Francis; Burke, Brian; Scheuerell, Mark; Grant, Sue
We examined how individual processes contribute to a latitudinal gradient in body size within populations of migrating juvenile Sockeye Salmon (Oncorhynchus nerka) while simultaneously testing for size-selective mortality, a potentially confounding population scale process. Using otolith microstructure techniques and structural equation modeling, we determined that ocean entry size and phenology had strong, direct effects on size at capture. Population identity and freshwater age also had strong indirect effects, moderated by size at entry. Conversely, marine growth rates immediately after entry or before capture were relatively weak predictors of size during migration. We next tested for shifts in size distribution indicative of selective mortality, but detected no evidence of smaller individuals experiencing lower survival during early marine migrations. These results indicate that the migratory distributions of juvenile Sockeye Salmon are influenced by body size and that this variation is predominantly driven by traits present prior to freshwater outmigration, rather than marine growth or differential survival. We suggest integrating individual variation in migratory characteristics with the effects of environmental conditions experienced en route to provide an improved understanding of migratory species.
Community assessment techniques and the implications for rarefaction and extrapolation with Hill numbers
(Ecology and Evolution, 2017) Cox, Kieran D.; Black, Morgan J.; Filip, Natalia; Miller, Matthew R.; Mohns, Kayla; Mortimor, James; Freitas, Thaise R.; Greiter Loerzer, Raquel; Gerwing, Travis G.; Juanes, Francis; Dudas, Sarah E.
Diversity estimates play a key role in ecological assessments. Species richness and abundance are commonly used to generate complex diversity indices that are dependent on the quality of these estimates. As such, there is a long-standing interest in the development of monitoring techniques, their ability to adequately assess species diversity, and the implications for generated indices. To determine the ability of substratum community assessment methods to capture species diversity, we evaluated four methods: photo quadrat, point intercept, random subsampling, and full quadrat assessments. Species density, abundance, richness, Shannon diversity, and Simpson diversity were then calculated for each method. We then conducted a method validation at a subset of locations to serve as an indication for how well each method captured the totality of the diversity present. Density, richness, Shannon diversity, and Simpson diversity estimates varied between methods, despite assessments occurring at the same locations, with photo quadrats detecting the lowest estimates and full quadrat assessments the highest. Abundance estimates were consistent among methods. Sample-based rarefaction and extrapolation curves indicated that differences between Hill numbers (richness, Shannon diversity, and Simpson diversity) were significant in the majority of cases, and coverage-based rarefaction and extrapolation curves confirmed that these dissimilarities were due to differences between the methods, not the sample completeness. Method validation highlighted the inability of the tested methods to capture the totality of the diversity present, while further supporting the notion of extrapolating abundances. Our results highlight the need for consistency across research methods, the advantages of utilizing multiple diversity indices, and potential concerns and considerations when comparing data from multiple sources.
Comparing the use of red-edge and near-infrared wavelength ranges for detecting submerged kelp canopy
(Remote Sensing, 2022) Timmer, Brian; Reshitnyk, Luba Y.; Hessing-Lewis, Margot; Juanes, Francis; Costa, Maycira
Kelp forests are commonly classified within remote sensing imagery by contrasting the high reflectance in the near-infrared spectral region of kelp canopy floating at the surface with the low reflectance in the same spectral region of water. However, kelp canopy is often submerged below the surface of the water, making it important to understand the effects of kelp submersion on the above-water reflectance of kelp, and the depth to which kelp can be detected, in order to reduce uncertainties around the kelp canopy area when mapping kelp. Here, we characterized changes to the above-water spectra of Nereocystis luetkeana (Bull kelp) as different canopy structures (bulb and blades) were submerged in water from the surface to 100 cm in 10 cm increments, while collecting above-water hyperspectral measurements with a spectroradiometer (325–1075 nm). The hyperspectral data were simulated into the multispectral bandwidths of theWorldView-3 satellite and the Micasense RedEdge-MX unoccupied aerial vehicle sensors and vegetation indices were calculated to compare detection limits of kelp with a focus on differences between red edge and near infrared indices. For kelp on the surface, near-infrared reflectance was higher than red-edge reflectance. Once submerged, the kelp spectra showed two narrow reflectance peaks in the red-edge and near-infrared wavelength ranges, and the red-edge peak was consistently higher than the near-infrared peak. As a result, kelp was detected deeper with vegetation indices calculated with a red-edge band versus those calculated with a near infrared band. Our results show that using red-edge bands increased detection of submerged kelp canopy, which may be beneficial for estimating kelp surface-canopy area and biomass.
Decrease in recreational fisher compliance during the COVID-19 pandemic: The case of Rockfish Conservation Areas
(ICES Journal of Marine Science, 2022) Ban, Natalie C.; Miltner, Chessi; Matthews, Charlotte; Ankenman, Madeleine; Stelte, Sarah; Haggarty, Dana; Davies, Hailey L.; Venturelli, Paul A.; Juanes, Francis
Little is known about the effect of the COVID-19 pandemic on recreational fisheries compliance. Starting in 2015, we monitored recreational fishing activity in Rockfish Conservation Areas (RCAs) with trail cameras overlooking RCAs around Galiano Island, Canada. We also carried out in-person surveys with recreational fishers at marinas and docks to assess recreational fisher compliance with RCAs. Questions included asking fishers whether they had accidentally or intentionally fished inside RCAs with prohibited techniques in the past two years. The number of suspected or confirmed angling incidents that we observed on the trail cameras declined steadily from 2015 to 2019, and then increased significantly during the pandemic to the highest levels seen during our eight years of data collection. The number of fishers who admitted to intentionally or accidentally fishing in RCAs in the past two years with prohibited gears did not change during the pandemic, although there was an apparent but not statistically significant increase in the number of respondents who personally knew someone who intentionally fished in RCAs. Our study corroborates other research that showed a response of pandemic lockdowns on illegal activities. High non-compliance highlights the ongoing need for education, outreach, and increased enforcement.
Deep-sea cabled video-observatory provides insights into the behavior at depth of sub-adult male northern elephant seals, Mirounga angustirostris
(PLoS ONE, 2024) Frouin-Mouy, Héloïse; Rountree, Rodney; Juanes, Francis; Aguzzi, Jacopo; De Leo, Fabio C.
The Ocean Networks Canada (ONC) cabled video-observatory at the Barkley Canyon Node (British Columbia, Canada) was recently the site of a Fish Acoustics and Attraction Experiment (FAAE), from May 21, 2022 to July 16, 2023, combining observations from High-Definition (HD) video, acoustic imaging sonar, and underwater sounds at a depth of 645 m, to examine the effects of light and bait on deep-sea fish and invertebrate behaviors. The unexpected presence of at least eight (six recurrent and two temporary) sub-adult male northern elephant seals (Mirounga angustirostris) was reported in 113 and 210 recordings out of 9737 HD and 2805 sonar videos at the site, respectively. Elephant seals were found at the site during seven distinct periods between June 22, 2022 and May 19, 2023. Ethograms provided insights into the seal’s deep-sea resting and foraging strategies, including prey selection. We hypothesized that the ability of elephant seals to perform repeated visits to the same site over long periods (> 10 days) was due to the noise generated by the sonar, suggesting that they learned to use that anthropogenic source as an indicator of food location, also known as the “dinner bell” effect. One interpretation is that elephant seals are attracted to the FAAE site due to the availability of prey and use the infrastructure as a foraging and resting site, but then take advantage of fish disturbance caused by the camera lights to improve foraging success. Our video observations demonstrated that northern elephant seals primarily focused on actively swimming sablefish (Anoplopoma fimbria), ignoring stationary or drifting prey. Moreover, we found that elephant seals appear to produce (voluntary or involuntary) infrasonic sounds in a foraging context. This study highlights the utility of designing marine observatories with spatially and temporally cross-referenced data collection from instruments representing multiple modalities of observation.
Disentangling individual- and population-scale processes within a latitudinal size-gradient in Sockeye Salmon
(Canadian Journal of Fisheries and Aquatic Sciences, 2015) Freshwater, Cameron; Trudel, Marc; Beacham, Terry; Godbout, Lyse; Neville, Chrys-Ellen; Tucker, Strahan; Juanes, Francis
We examined how individual processes contribute to a latitudinal gradient in body size within populations of migrating juvenile Sockeye Salmon (Oncorhynchus nerka) while simultaneously testing for size-selective mortality, a potentially confounding population scale process. Using otolith microstructure techniques and structural equation modeling, we determined that ocean entry size and phenology had strong, direct effects on size at capture. Population identity and freshwater age also had strong indirect effects, moderated by size at entry. Conversely, marine growth rates immediately after entry or before capture were relatively weak predictors of size during migration. We next tested for shifts in size distribution indicative of selective mortality, but detected no evidence of smaller individuals experiencing lower survival during early marine migrations. These results indicate that the migratory distributions of juvenile Sockeye Salmon are influenced by body size and that this variation is predominantly driven by traits present prior to freshwater outmigration, rather than marine growth or differential survival. We suggest integrating individual variation in migratory characteristics with the effects of environmental conditions experienced en route to provide an improved understanding of migratory species.
Dynamics of juvenile salmon and forage fishes in nearshore kelp forests
(Aquatic Conservation: Marine and Freshwater Ecosystems, 2023) Shaffer, Anne; Gross, Justin; Black, Morgan; Kalagher, Amelia; Juanes, Francis
1. North-east Pacific juvenile salmon and forage fishes, including the endangered salmon species Chinook (Oncorhynchus tshawytscha), coho (Oncorhynchus kisutch), chum (Oncorhynchus keta), and pink (Oncorhynchus gorbuscha), and the forage fishes species of Pacific herring (Clupea pallasi), surf smelt (Hypomesus pretiosus), and sand lance (Ammodytes hexapterus), utilize kelp environments. Many details of the kelp forest ecosystem function for these fishes are lacking. 2. Kelp forests, salmon, and forage fishes are declining precipitously as the global climate shifts and developments along coastal shorelines expand. It is therefore essential to understand kelp forest function for these species. 3. Analysis of 7 years of snorkelling survey videos indicates that both forage fishes and salmon use kelp forests throughout the outmigration season, and that their interactions occur in small and large groups, primarily along the outer edge of kelp beds. Over the course of outmigration, juvenile Chinook and coho salmon encounter sand lance first, followed by smelt and herring. The majority of interactions are intermingling, in which a subset proceed to predation, primarily on herring. 4. It is important to develop and implement specific fishery and habitat conservation measures to preserve and restore these functions. Long-term research has shown that intact, conserved nearshore habitats function better ecologically than restored habitats, and individual kelp forests can function differently for forage fishes and salmon. Therefore, conservation plans should be developed to conserve wild kelp forests which are documented to provide ecosystem function for salmon and forage fishes, by protecting them from various development impacts, including dredging, filling, and water-quality decline. 5. Coastal restoration is often only successful when ecosystem-limiting factors that result in a loss of habitat are resolved. Kelp forest restoration, therefore, should be prioritized for regions of known high historical kelp forest importance, with restoration actions focused on correcting the limiting factors that caused loss and/or degradation.
Eelgrass as Valuable Nearshore Foraging Habitat for Juvenile Pacific Salmon in the Early Marine Period
(Marine and Coastal Fisheries: Dynamics, Management, and Ecosystem Science, 2018) Kennedy, Laura A.; Juanes, Francis; El-Sabaawi, Rana
The early marine period is a critical life history stage for growth and survival of anadromous juvenile Pacific salmon. The integrity of nearshore ecosystems where juvenile salmon reside and the capacity of these habitats to provide prey can thus influence overall salmon returns. Eelgrass Zostera marina beds in particular are considered critical nearshore habitat. By examining how juvenile salmon use this habitat during their early marine life, we gain insight into the trophic dynamics in these ecosystems and help gauge the effects of accelerating eelgrass loss and nearshore habitat development on juvenile salmon. This project investigated the role of eelgrass as juvenile salmon foraging habitat. We compared juvenile Chum Salmon Oncorhynchus keta and juvenile Chinook Salmon O. tshawytscha diets to prey availability in zooplankton tows and in epifaunal eelgrass samples across a gradient of eelgrass density in the Comox Estuary, British Columbia. Harpacticoid copepods dominated the diets of both juvenile Chum Salmon and Chinook Salmon and were found in abundance in eelgrass blades. We complemented diet analysis with carbon (δ13C) and nitrogen (δ15N) stable isotope analysis to examine the relative contribution of zooplankton, eelgrass epifaunal invertebrates, and terrestrial invertebrates to the diet of juvenile Chum Salmon. Juvenile Chum Salmon isotope ratios closely reflected those of eelgrass invertebrates, suggesting that eelgrass invertebrates made up approximately 80% of the diets of juvenile Chum Salmon. Our results highlight the value of eelgrass in providing nearshore foraging opportunities for juvenile salmon and suggest that eelgrass habitat protection and restoration may provide critical support for growth, thereby easing the transition of juvenile salmon from freshwater to the marine environment.
Effects of anthropogenic noise on fishes at the SCaan Kinghlas-Bowie Seamount Marine Protected Area
(Proceedings of Meetings on Acoustics, 2016) Riera, Amalis; Rountree, Rodney A.; Mouy, Xavier; Ford, John K.; Juanes, Francis
Underwater noise from anthropogenic sources has been increasing dramatically for the past few decades and little is known about its effects on fishes. The objective of this study is to describe the occurrence and characteristics of fish sounds in the SGaan Kinghlas-Bowie Seamount Marine Protected Area (SK-B MPA, British Columbia, Canada) and to correlate them with the corresponding anthropogenic soundscape. Here we present preliminary results of the detection of fish sounds at SK-B MPA between July 2011 and July 2013. An automatic detector was used on nearly 40,000 acoustic samples (4,754.5 hours in total) to search for fish sounds. About 1.2% of the data were highlighted as containing fish-like signals. Manual verification of these detections revealed that 95.5% were false positives and the remaining sounds were of unknown origin. Eighty detections were highly stereotyped and are suspected to be produced by fish, but no identification has been confirmed yet. Systematic manual inspection of sub-sampled acoustic data is yet to be performed to determine if the detector missed any fish sounds. Future deployments should select areas based on the presence of known fish habitat occurrence, and install autonomous recorders optimized to reduce equipment self-noise and flow noise biases.
Effects of temperature and ration on the otolith-to-somatic size relationship in juvenile Chinook salmon (Oncorhynchus tshawytscha): a test of the direct proportionality assumption
(Marine and Freshwater Research, 2016) Stormer, David G.; Juanes, Francis
Fish otoliths are commonly used to estimate somatic growth rate, but this depends on the assumption that the otolith and body grow in direct proportion. Environmental conditions contribute to variability in somatic growth and can result in deviations from direct proportionality in the otolith-to-somatic size relationship. In the present study we examined the otolith-to-body size relationship for juvenile Chinook salmon (Oncorhynchus tshawytscha) subjected to simulated seasonal (summer, autumn and winter) water temperatures and feeding rations. The otolith-to-somatic size relationship became uncoupled during summer between fish subjected to the cool (158C) and hot (218C) water temperatures. A food ration effect was also observed during the summer, such that fish fed an unlimited ration had smaller otoliths than equivalently sized fish fed a limited ration. The effects of water temperature and ration disappeared by the end of autumn, indicating that a seasonal compensatory response occurred in the otolith-to-somatic size relationship after the extreme temperatures and food limitations were alleviated. In winter, this relationship became uncoupled again, but only between fish that were fed throughout the winter and fish that were starved during the 3-month experimental period. The effects of water temperature and rations on the otolith-to-somatic size relationship of juvenile Chinook salmon could have implications for accurately estimating somatic growth from otolith growth in natural populations and should be incorporated into back-calculation techniques.
Exposure of satellite tagged bowhead whales (Balaena mysticetus) to transiting vessels in the Eastern Canadian Arctic
(Marine Mammal Science, 2024) Martin, Morgan; Halliday, William; Ferguson, Steven H; Young, Brent G.; Charish, Rachel; Dawson, Jackie; Fortune, Sarah M. E.; Juanes, Francis; Qaunaq, Levi; Insley, Stephen J.
Climate change poses new challenges to Arctic marine mammals, with increasing vessel traffic and associated underwater noise pollution emerging as significant threats. The bowhead whale (Balaena mysticetus), an endemic Arctic cetacean, faces these new threats. The Eastern Canada-West Greenland (ECWG) bowhead whale population migrates through areas with the highest levels of vessel traffic in the Canadian Arctic. Here, we document the spatial and temporal overlap between 36 satellite-tagged ECWG bowhead whales and vessels equipped with Automatic Identification System (AIS) transponders during 2012–2017. We report 1,145 instances where vessels were within 125 km of a tagged whale, with 306 occurrences within distances ≤50 km. Overlap between vessels and tagged bowhead whales was quantified monthly within years to investigate individual whale encounter rates. Results indicate that ECWG bowhead whales encounter the majority (79%) of vessels annually during August–October, with the highest number of encounters (42%) observed in September. Encounter rates ranged from 0.25 to 0.51 vessels encountered per day per whale during August–October compared to <0.07 vessels per day in all other months in this study. To better inform conservation strategies, further research is required to assess bowhead whale behavioral responses relative to distance from vessels.

Browsing by Author "Juanes, Francis"

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