Accurately predicting errors related to preservation, lipid extraction, and lipid normalization on chemical tracers would enable the use of archived samples in long-term studies of trophic ecology and habitat use of aquatic species. We determined whether stable carbon and nitrogen isotope ratios and concentrations of 14 trace elements can be accurately predicted from dimethyl sulfoxide (DMSO)-preserved mammal skin, which would provide equivalent estimates to that from unpreserved tissue. We tested 3 lipid-correction approaches for applicability to cetacean skin, a largely unexplored taxon and tissue, and provide a model for evaluating impacts of errors from lipid extraction or normalization on diet composition estimated using isotopic mixing models. DMSO had unpredictable effects on trace element concentrations, rendering DMSO-preserved samples inefficient for retrospective studies. However, lipid extraction and DMSO preservation resulted in predictable and similar, although not identical, effects on isotopic signatures across 4 cetacean species with different skin structure and thickness, making correction for these effects a potentially viable alternative to lipid and DMSO extraction. Generally, lipid-normalization models were reliable when applied to cetacean skin, as errors were similar to those from other species or tissues. Because model fit generally improved with data specificity, developing tissue-and species-specific parameters and equations is probably more important than model choice, although the mass-balance model was considered the most robust across aquatic vertebrates and tissues. The effects of errors associated with the various treatments and lipid normalization on isotopic mixing results increased as the isotopic distance among prey sources decreased, suggesting that empirical corrections as an alternative to δ 13 C determination from lipid-extracted duplicate samples need to be evaluated a priori relative to study objectives and anticipated results.

Time-depth-speed recorders and stomach-temperature sensors were deployed on 11 harbor seals (Phoca vitulina) in the St. Lawrence estuary to examine their diving and foraging behavior. Fifty-four percent of dives were to depths of <4 m. Dives that were [Formula: see text] 4 m deep were classified into five distinct types, using a combination of principal components analysis and hierarchical and nonhierarchical clustering analyses. Feeding, indicated by a sharp decline in stomach temperature, occurred during dives of all five types, four of which were U-shaped, while one was V-shaped. Seals swam at speeds near the minimum cost of transport (MCT) during descents and ascents. V-shaped dives had mean depths of 5.8 m, lasted an average of 40 s, and often preceded or followed periods of shallow-water (<4 m) activity. Seals invariably dove to the bottom when performing U-shaped dives. These dives were to an average depth of 20 m during daylight and occurred in shallower waters (~8 m) at twilight and during the night. Once on the bottom, seals (i) swam at MCT speeds with occasional bursts of speed, (ii) swam at speeds near MCT but not exceeding it, or (iii) remained stationary or swam slowly at about 0.15 m/s, occasionally swimming faster. It is unlikely that all dives to depths [Formula: see text] 4 m are dedicated to foraging. However, the temporal segregation of dive types suggests that all types are used during foraging, although they may represent different strategies.

The trophic relationships of both the benthic and pelagic communities in the Estuary and Gulf of St Lawrence regions were examined, with a special focus on the trophic position (TP) and relationship(s) among harbour, grey, hooded and harp seals and beluga whales. A multiple stable isotope and multiple tissue approach, used in conjunction with conventional dietary information, suggested that marine mammals occupied the highest trophic positions in the food webs of both communities and that they overlapped with one another to some extent trophically. Harbour seals Phoca vitulina and hooded seals Cystophora cristata occupied the highest TP, grey seals Halichoerus grypus, Gulf harp seals Phoca groenlandica, and male beluga whales Delphinapterus leucas were intermediate, and Estuary harp seals and female beluga whales were at the lowest TP. A general pattern of increasing enrichment of 13 C or 15 N with age was observed in marine mammals (as well as fishes), although yearlings showed a decreased enrichment compared to both younger and older age classes. Sex also influenced δ 15 N values. Males were more 15 N-enriched than females, with the difference between the sexes increasing with age, and being most pronounced in species that are sexually dimorphic with respect to body size. Geographical location also influenced isotope abundance. Estuary organisms were generally 13 C-enriched relative to Gulf animals. δ 13 C values were on average lower in short-term diet integrators (blood serum) than in longer-term diet integrators (red blood cells) of harbour seals captured in April to June in the Estuary, which suggests that they probably did not move outside the Lower Estuary during the winter. Grey seals captured in the Lower Estuary did, however, show evidence of having been in the Gulf region some weeks or months before capture.

During June-July 1991, we monitored the vocal behavior of belugas before, during, and after exposure to noise from a small motorboat and a ferry to determine if there were any consistent patterns in their vocal behavior when exposed to these two familiar, but different sources of potential disturbance. Vocal responses were observed in all trials and were more persistent when whales were exposed to the ferry than to the small boat. These included (1) a progressive reduction in calling rate from 3.4-10.5 calls/whale/min to 0.0 or <1.0 calls/whale/min while vessels were approaching; (2) brief increases in the emission of falling tonal calls and the three pulsed-tone call types; ( 3 ) at distances <1 km, an increase in the repetition of specific calls, and (4) a shift in frequency bands used by vocalizing animals from a mean frequency of 3.6 kHz prior to exposure to noise to frequencies of 5.2-8.8 kHz when vessels were close to the whales.

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Diet‐tissue isotopic fractionation of carbon (C) and nitrogen (N) isotopes in short‐ and longer‐term diet integrators of diet (i. e., blood serum and red cells), that involve non‐invasive sampling techniques was examined using three species of phocid seals (harbor seals, gray seals, and harp seals) fed a known diet. Variability in diet‐tissue fractionation values within and between species was also scrutinized to determine the legitimacy of using values obtained from one species to explore trophic positions and diets of other related species. All captive seals raised on a constant diet had tissues enriched in 13C and 15N relative to their diet. Diet‐tissue isotopic fractionation values were generally consistent among conspecifics and among phocid species for a given tissue. Trophic isotopic enrichment in 13C was significantly higher in red blood cells (+1.5%±) than in blood serum (+0.8%±), whereas the reverse was observed for nitrogen isotopes (+1.7%± in red cells vs. +3.1%± in serum). However, 13C‐depleted lipids were not extracted from blood tissues in this study. This results in a downward bias in the diet‐tissue fractionation factors for carbon for both red cells and blood serum, particularly the latter because of their significantly higher lipid contents (x̄± SD = 14.6 ± 2.3%; n= 20; red blood cells 3.8 ± 0.9%±; n= 50, muscle 7.7 ± 2.0; n= 21) in marine mammals.

Ecologically similar species may coexist when resource partitioning over time and space reduces interspecific competition. Understanding resource use within these species assemblages may help predict how species relative abundance might influence ecosystem functioning. In the Gulf of St. Lawrence, Canada, 4 species of rorqual whales (blue Balaenoptera musculus, fin B. physalus, minke B. acutorostrata and humpback Megaptera novaeangliae) coexist during the summer feeding period. They can be observed within hundreds of meters of one another, suggesting an overlap in ecological niches; yet fine-scale habitat use analyses suggest some resource partitioning. While major ecological changes have been observed in marine ecosystems, including the Gulf of St. Lawrence, we have little understanding of how the removal of predatory fish might cascade through ecosystems. Here, we take advantage of a 19 yr tissue collection subsequent to a fishery collapse (which occurred in 1992) to investigate trophic niche partitioning within a guild of rorqual whales following the loss of a key ecosystem component, groundfish. We analyzed stable isotope ratios for 626 rorqual individuals sampled between 1992 and 2010. Using Bayesian isotopic mixing models, we demonstrated that the 4 rorqual species segregated trophically by consuming different proportions of shared prey. An overall increase in δ 15 N values over the study period (post groundfish collapse), particularly for fin and humpback whales, suggested a progressive use of higher-trophic level prey, such as small pelagic fish, whereas the stability of blue whale diet over time confirmed their specialized feeding behaviour. This study provides the first longterm assessment of trophic ecology among rorqual populations on this Northwest Atlantic feeding ground, and evidence for differential resource use among large marine predators following ecosystem change.

Evaluating and understanding biodiversity in marine ecosystems are both necessary and challenging for conservation. This paper compiles and summarizes current knowledge of the diversity of marine taxa in Canada's three oceans while recognizing that this compilation is incomplete and will change in the future. That Canada has the longest coastline in the world and incorporates distinctly different biogeographic provinces and ecoregions (e.g., temperate through ice-covered areas) constrains this analysis. The taxonomic groups presented here include microbes, phytoplankton, macroalgae, zooplankton, benthic infauna, fishes, and marine mammals. The minimum number of species or taxa compiled here is 15,988 for the three Canadian oceans. However, this number clearly underestimates in several ways the total number of taxa present. First, there are significant gaps in the published literature. Second, the diversity of many habitats has not been compiled for all taxonomic groups (e.g., intertidal rocky shores, deep sea), and data compilations are based on short-term, directed research programs or longer-term monitoring activities with limited spatial resolution. Third, the biodiversity of large organisms is well known, but this is not true of smaller organisms. Finally, the greatest constraint on this summary is the willingness and capacity of those who collected the data to make it available to those interested in biodiversity meta-analyses. Confirmation of identities and intercomparison of studies are also constrained by the disturbing rate of decline in the number of taxonomists and systematists specializing on marine taxa in Canada. This decline is mostly the result of retirements of current specialists and to a lack of training and employment opportunities for new ones. Considering the difficulties encountered in compiling an overview of biogeographic data and the diversity of species or taxa in Canada's three oceans, this synthesis is intended to serve as a biodiversity baseline for a new program on marine biodiversity, the Canadian Healthy Ocean Network. A major effort needs to be undertaken to establish a complete baseline of Canadian marine biodiversity of all taxonomic groups, especially if we are to understand and conserve this part of Canada's natural heritage.