22 research outputs found

    Distribution, Abundance and Diversity of Benthic Macroinvertebrates on the Canadian Continental Shelf and Slope of Southern Davis Strait and Ungava Bay

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    Stations in a survey of benthic invertebrates on the Canadian continental shelf and slope of southeastern Baffin Island, in Ungava Bay, and on the northern Labrador Shelf, fell into definite groups as a result of an objective analysis of similarity in species composition. The groupings were shown to correspond to major water masses in the area. Groups corresponding to cold surface water masses, to the deep Irminger Atlantic water mass, and to mixtures of these with adjacent water masses were observed. The Irminger Atlantic group dominated on the Baffin Island continental shelf. Species diversity, also measured in the study, was high, with large numbers of species present in low abundance.Key words: marine, benthos, invertebrates, distribution, shelf, slope, Davis Strait, Ungava Bay, subarticMots clés: marin, benthos, invertébrés, distribution, plateau, versant, détroit de Davis, baie d'Ungava, subarctiqu

    Comparing the behavioural thermoregulation response to heat stress by Atlantic salmon parr ( Salmo salar ) in two rivers

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    Climate change is expected to increase the frequency and magnitude of extreme thermal events in rivers. The Little Southwest Miramichi River (LSWM) and the Ouelle River (OR) are two Atlantic salmon (Salmo salar) rivers located in eastern Canada, where in recent years, water temperatures have exceeded known thermal limits (~23°C). Once temperature surpasses this threshold, juvenile salmon exploit thermal heterogeneity to behaviourally thermoregulate, forming aggregations in coolwater refuges. This study aimed to determine whether the behavioural thermoregulation response is universal across rivers, arising from common thermal cues. We detailed the temperature and discharge patterns of two geographically distinct rivers from 2010 to 2012 and compared these with aggregation onset temperature. PIT telemetry and snorkelling were used to confirm the presence of aggregations. Mean daily maximum temperature in 2010 was significantly greater in the OR versus the LSWM (p = 0.005), but not in other years (p = 0.090–0.353). Aggregations occurred on 14 and 9 occasions in the OR and LSWM respectively. Temperature at onset of aggregation was significantly greater in the OR (Tonset = 28.3°C) than in the LSWM (Tonset = 27.3°C; p = 0.049). Logistic regression models varied by river and were able to predict the probability of aggregation based on the preceding number of hours >23°C (R2 = 0.61 & 0.65; P50 = 27.4°C & 28.9°C; in the OR and LSWM respectively). These results imply the preceding local thermal regime may influence behaviour and indicate a degree of phenotypic plasticity, illustrating a need for localised management strategies

    Climate-Driven Oceanic Range Shift of Saint John River Atlantic Salmon Revealed by Multidecadal Stable Isotope Trends

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    Publisher site: David X. Soto, Michael J. Dadswell, Kurt M. Samways, Richard A. Cunjak, and Tom McDermott "Climate-Driven Oceanic Range Shift of Saint John River Atlantic Salmon Revealed by Multidecadal Stable Isotope Trends," Northeastern Naturalist 30(4), 521-539, (2 January 2024). https://doi.org/10.1656/045.030.0414Marine migration patterns of unique or regional stocks of Salmo salar (Atlantic Salmon) are poorly known. Atlantic Salmon (AS) utilizing the North Atlantic Subpolar Gyre (NASpG) for foraging and growth consist of stocks from the United States (41°N) to Greenland (64°N) in the western Atlantic and from Spain (41°N) to Norway (70°N) in the eastern Atlantic. Wide latitudinal range and unique riverine characteristics probably result in stocks selecting differing suites of marine sea-surface temperatures (SST) within the species' known selection range (i.e., their Grinnellian niche). We analyzed trends in stable carbon isotope (ή13C) composition from archived scale tissues in relation to long-term variation of SST for the North Atlantic Ocean to identify marine feeding regions used by adult AS successfully returning to the Saint John River, Canada, during the period 1982–2011. Marine foraging regions were determined for individuals that spent 1 winter (1SW) or multiple winters (MSW) at sea. During 1982–1991 and 1992–2001, AS which successfully returned, exploited more southern regions of the NASpG, while returning adults from 2002–2011 exploited more northern regions. Historically presumed marine feeding regions, which were identified by the isotopic model as probable during 1982–2001, have experienced a warming trend, and data suggests that AS returning to the Saint John River have been migrating further north in the NASpG in response to recent global climate change. The northward range shift as the North Atlantic warmed is consistent with recent biogeographical changes found among other marine species also following their Grinnellian niche

    Ten practical realities for institutional animal care and use committees when evaluating protocols dealing with fish in the field

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    Institutional Animal Care and Use Committee’s (IACUCs) serve an important role in ensuring that ethical practices are used by researchers working with vertebrate taxa including fish. With a growing number of researchers working on fish in the field and expanding mandates of IACUCs to regulate field work, there is potential for interactions between aquatic biologists and IACUCs to result in unexpected challenges and misunderstandings. Here we raise a number of issues often encountered by researchers and suggest that they should be taken into consideration by IACUCs when dealing with projects that entail the examination of fish in their natural environment or other field settings. We present these perspectives as ten practical realities along with their implications for establishing IACUC protocols. The ten realities are: (1) fish are diverse; (2) scientific collection permit regulations may conflict with IACUC policies; (3) stakeholder credibility and engagement may constrain what is possible; (4) more (sample size) is sometimes better; (5) anesthesia is not always needed or possible; (6) drugs such as analgesics and antibiotics should be prescribed with care; (7) field work is inherently dynamic; (8) wild fish are wild; (9) individuals are different, and (10) fish capture, handling, and retention are often constrained by logistics. These realities do not imply ignorance on the part of IACUCs, but simply different training and experiences that make it difficult for one to understand what happens outside of the lab where fish are captured and not ordered/purchased/reared, where there are engaged stakeholders, and where there is immense diversity (in size, morphology, behaviour, life-history, physiological tolerances) such that development of rigid protocols or extrapolation from one species (or life-stage, sex, size class, etc.) to another is difficult. We recognize that underlying these issues is a need for greater collaboration between IACUC members (including veterinary professionals) and field researchers which would provide more reasoned, rational and useful guidance to improve or maintain the welfare status of fishes used in field research while enabling researchers to pursue fundamental and applied questions related to the biology of fish in the field. As such, we hope that these considerations will be widely shared with the IACUCs of concerned researchers

    Hierarchical model detects decadal changes in calibration relationships of single pass electrofishing indices of abundance of Atlantic Salmon in two large Canadian catchments

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    Electrofishing is a commonly used technique to assess freshwater fish population abundance and in many programs, there has been a shift in the sampling methodologies towards less laborious techniques. These new techniques usually only provide an index of abundance and require calibration with other sampling methods such as successive removal to be used for absolute abundance estimation. Using data for juvenile Atlantic Salmon collected in 400 sites sampled over 21 years in two large Canadian river catchments with a single sampling protocol, we developed a hierarchical Bayesian model to account for effort, day of sampling, area of the site, and catchment effects on the relationship between the single-pass index of abundance and the fish densities thereby illustrating the importance of carrying out a calibration exercise on a regular basis. Our work indicates that calibration relationships can change over time even with standardized sampling protocols and that these directional changes in important components of the sampling procedure can bias the estimate of population abundance and misinform the understanding of population dynamics.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author
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