Search

Understanding variability in growth patterns of marine mammals provides insights into the health of individuals and status of populations. Body growth of gray whales (Eschrichtius robustus) has been described for particular life stages, but has not been quantified across all ages. We derived a comprehensive growth equation for gray whales by fitting a two-phased growth model to age-specific length data of eastern North Pacific gray whales that were captured, stranded, or harvested between 1926 and 1997. To predict mass-at-age, we used the allometric relationship between mass and length. We found that on average (± SD), calves were 4.6 ± 0.043 m and 972 ± 26 kg at birth, and reached 8.5 ± 0.095 m and 6,019 ± 196 kg by the end of their first year of life (n = 118). Thus, calves almost double (2×) in length and octuple (8×) in mass while nursing, and are effectively about two-thirds of their asymptotic adult length and one-third of their maximum mass when weaned. The large sample of aged individuals (n = 730) indicates that gray whales live up to ~48 years and have a life expectancy of < 30 years. Adult females attain a mean (± SD) asymptotic size of 13.1 ± 0.048 m and 20,758 ± 222 kg, while the smaller males average 12.6 ± 0.048 m and 19,938 ± 222 kg at ~40 years of age. Females are thereby ~4% longer and heavier than males. These age-specific estimates of body size can be used to estimate food requirements and assess nutritional status of individuals.

Understanding variability in growth patterns of marine mammals provides insights into the health of individuals and status of populations. Body growth of gray whales (Eschrichtius robustus) has been described for particular life stages, but has not been quantified across all ages. We derived a comprehensive growth equation for gray whales by fitting a two-phased growth model to age-specific length data of eastern North Pacific gray whales that were captured, stranded, or harvested between 1926 and 1997. To predict mass-at-age, we used the allometric relationship between mass and length. We found that on average (± SD), calves were 4.6 ± 0.043 m and 972 ± 26 kg at birth, and reached 8.5 ± 0.095 m and 6,019 ± 196 kg by the end of their first year of life (n = 118). Thus, calves almost double (2×) in length and octuple (8×) in mass while nursing, and are effectively about two-thirds of their asymptotic adult length and one-third of their maximum mass when weaned. The large sample of aged individuals (n = 730) indicates that gray whales live up to ~48 years and have a life expectancy of < 30 years. Adult females attain a mean (± SD) asymptotic size of 13.1 ± 0.048 m and 20,758 ± 222 kg, while the smaller males average 12.6 ± 0.048 m and 19,938 ± 222 kg at ~40 years of age. Females are thereby ~4% longer and heavier than males. These age-specific estimates of body size can be used to estimate food requirements and assess nutritional status of individuals.

Ecosystem-based approaches to fisheries management to date have lacked a quantitative spatial understanding of habitat impacts from fishing. Understanding such ecological impacts in part requires knowledge of benthic structure and sensitivity. We compared two approaches to calculate and map spatially explicit habitat impacts for twelve different fisheries in 21 broad benthic classes in Canada's Pacific. By fishery, bottom trawling had the highest sum impact score across benthic classes, and bottom trawl and bottom longline generally scored highest per unit area. Soft shelf, which was the most extensively fished benthic class (33,373 km2 of a total 454,183 km2 study area), had the highest cumulative impact score, followed by the slope benthic classes (16,315 km2). Canyons and slope benthic classes had the highest impact scores per unit area. We recommend our approach as one that facilitates a regional understanding of benthic habitat impact by individual fisheries, as well as of cumulative impact for all bottom and demersal fishing activities. This assessment also highlights the regional paucity of habitat data required for more detailed analyses. Such habitat impact assessments have utility in informing fisheries assessments for eco-certification schemes, and in the mitigation of benthic habitat impacts through marine spatial planning efforts.

The rapidly progressing field of cumulative effects mapping is highly dependent on data quality and quantity. Availability of spatial data on the location of human activities on or affecting the ocean has substantially improved our understanding of potential cumulative effects. However, datasets for some activities remain poor and increased access to current, high resolution data are needed. Here we present an updated analysis of potential cumulative effects in Canada’s Pacific marine waters. New, updated datasets and methodological improvements over the previous analysis were completed, including a new index for land-based effects on marine habitats, updated habitat classes and a modified treatment of vulnerability scores. The results show increased potential cumulative effects for the region. Fishing remains the biggest overall impact amongst marine activities, while land-based activities have the highest impact per unit area in affected ocean areas. Intertidal areas were the most affected habitat per unit area, while pelagic habitats had the highest total cumulative effect score. Regular updates of cumulative effects assessments will make them more useful for management, but these require regularly updated, high resolution datasets across all activity types, and automated, well-documented procedures to make them accessible to managers and policy-makers.

With increasing human population, large scale climate changes, and the interaction of multiple stressors, understanding cumulative effects on marine ecosystems is increasingly important. Two major drivers of change in coastal and marine ecosystems are industrial developments with acute impacts on local ecosystems, and global climate change stressors with widespread impacts. We conducted a cumulative effects mapping analysis of the marine waters of British Columbia, Canada, under different scenarios: climate change and planned developments. At the coast-wide scale, climate change drove the largest change in cumulative effects with both widespread impacts and high vulnerability scores. Where the impacts of planned developments occur, planned industrial and pipeline activities had high cumulative effects, but the footprint of these effects was comparatively localized. Nearshore habitats were at greatest risk from planned industrial and pipeline activities; in particular, the impacts of planned pipelines on rocky intertidal habitats were predicted to cause the highest change in cumulative effects. This method of incorporating planned industrial development in cumulative effects mapping allows explicit comparison of different scenarios with the potential to be used in environmental impact assessments at various scales. Its use allows resource managers to consider cumulative effect hotspots when making decisions regarding industrial developments and avoid unacceptable cumulative effects. Management needs to consider both global and local stressors in managing marine ecosystems for the protection of biodiversity and the provisioning of ecosystem services.

Much knowledge is emerging about the past and potential effects of climate change on the unique and complex marine ecosystems of Canada's Pacific, including variations in the resilience, sensitivities, responsiveness, and non-stationarity of the biota. Such knowledge, however, is rarely synthesized or summarized with any overall integrated analyses that could guide the development of proactive planning for the effects of climate change. Regional and local planning of climate adaptation strategies, for example, requires an examination of ecological sensitivities and vulnerabilities at relevant spatial resolutions. We developed an illustrative example of a habitat-based ecological vulnerability assessment for the whole of Canada's Pacific marine area using existing spatial information from this region and from the California Current ecosystem. Potential climate impacts were calculated as the product of estimated exposure (E) of habitats to multiple dimensions of changing climate variables and expert-derived sensitivity (S) ratings of those habitats to changes in those climate variables. Vulnerability was then derived as the product of the estimated potential climate impacts in a location and the estimated cumulative impacts (CI) of non-climate stressors there, which we considered to be an inverse proxy of the adaptive capacity (AC) of the biota in those habitats. We found considerable spatial variability of potential climate impacts and vulnerability on the scales of the 12 Ecosections of Canada's Pacific, 25 habitat categories, and at finer scales. We produced maps of ecological vulnerability to climate change as an example output for use in spatially-oriented adaptation planning. Our initial assessment indicated that the Strait of Georgia in particular followed by Queen Charlotte Strait, Juan de Fuca Strait, Vancouver Island Shelf, and Johnstone Strait have relatively high vulnerabilities to climate change, in part due to concentrations of local stressors there. On a coast wide basis the habitats that were indicated as most vulnerable are shallow rocky reefs, seagrass habitats, kelp habitats, and deep rocky reefs. This approach for mapping vulnerability to climate change could be improved with finer scale climate data, additional climate variables, and stressor-habitat sensitivity estimates derived specifically for this system. We provide a stepwise manual for policy-makers, managers, or other practitioners to map ecological vulnerability to climate change in other marine settings.

The Arctic is one of the fastest-changing parts of the planet. Global climate change is already having major impacts on Arctic ecosystems. Increasing temperatures and reductions in sea ice are particular conservation concerns for ice-associated species, including three endemic cetaceans that have evolved in or joined the Arctic sympagic community over the last 5 M years. Sea ice losses are also a major stimulant to increased industrial interest in the Arctic in previously ice-covered areas. The impacts of climate change are expected to continue and will likely intensify in coming decades. This paper summarizes information on the distribution and movement patterns of the three ice-associated cetacean species that reside year-round in the Arctic, the narwhal ( Monodon monoceros ), beluga (white whale, Delphinapterus leucas ), and bowhead whale ( Balaena mysticetus ). It maps their current distribution and identifies areas of seasonal aggregation, particularly focussing on high-density occurrences during the summer. Sites of oil and gas exploration and development and routes used for commercial shipping in the Arctic are compared with the distribution patterns of the whales, with the aim of highlighting areas of special concern for conservation. Measures that should be considered to mitigate the impacts of human activities on these Arctic whales and the aboriginal people who depend on them for subsistence include: careful planning of ship traffic lanes (re-routing if necessary) and ship speed restrictions; temporal or spatial closures of specified areas (e.g. where critical processes for whales such as calving, calf rearing, resting, or intense feeding take place) to specific types of industrial activity; strict regulation of seismic surveys and other sources of loud underwater noise; and close and sustained monitoring of whale populations in order to track their responses to environmental disturbance.