LGL (Canada)

Abstract Objective The Fraser River in British Columbia, Canada, historically supported productive Indigenous, recreational, and commercial fisheries for Eulachon Thaleichthys pacificus. Although Eulachon spend most of their lives in the marine environment, they spawn in freshwater and it is hypothesized that habitat degradation in the Fraser River has contributed to population decline. A greater understanding of Eulachon life history strategies is necessary to develop species recovery strategies. The purpose of this study was to provide insight into population demographics, migration timing, residence time, travel speed and distance, and movement patterns of Eulachon traveling in the Fraser River by conducting index netting and acoustic telemetry. Methods In total, 244 Eulachon were acoustically tagged at the mouth of the Fraser River, and their movements were monitored using acoustic receivers in the lowermost 70 km of the Fraser River and in the Pitt River (a tributary to the Fraser River) over a 2-year period. Result Tagged Eulachon displayed heterogeneous movement behaviors and a protracted migration period between February and May. Eulachon index gill netting revealed three discrete migration groups matching traditional ecological knowledge from Indigenous knowledge holders. There were shifts in population demographics, with sex ratios changing from predominately males to females throughout the migration. Residence time within the estuarine salt wedge and river was short. Upstream travel speeds varied significantly between sexes and slowed as fish traveled upstream. Conclusion Overall, Eulachon travel speeds, travel distances, and residence times, along with size and sex effects, provided insights into movement patterns. These results will increase our understanding of sex-specific risks related to instream disturbance, harvest, and predation and will inform management decisions regarding protection of critical habitats. The observed patterns highlight the need for stock assessment methods to consider all discrete migration groups and will assist in prioritizing species recovery efforts.

Changing climate patterns strongly influence marine ecosystems across the Pacific Arctic region creating significant ecosystem transitions and change. Macrobenthic species are essential prey for numerous marine mammals and seabirds but the influence of climatic drivers that control macrobenthic community population dynamics are poorly known in critical prey habitats. We investigated associations of environmental, temporal, and climatic covariates with the biomass concentrations of six prey groups (Actinopterygii, Amphipoda, Bivalvia, Cumacea, Isopoda, and Polychaeta) in essential habitats for Korean-Okhotsk (western) gray whales adjacent to northeastern Sakhalin Island in the Sea of Okhotsk. Prey community biomass concentrations were correlated with water depth, year, and climate indices reflecting oceanographic and climatic patterns associated with macro-scale climatological effects. The correlation of prey biomass with water depth and year accounted for ∼90% of total variation in canonical correlation analyses (CCor). Climate indices accounted for ∼10% of total variation in CCor. Water circulation in winter may be particularly important for maintaining populations through the advection of particulate organic carbon entrained in winter currents. Overall, temporal trends in the biomass concentrations of gray whale prey resources appear to reflect climatic and oceanographic factors that are driving ecosystem changes across the Sea of Okhotsk and the Pacific Arctic region.

This paper presents a new, simple and generalized approach to calculate flying capacitor currents for an n-level flying capacitor converter without the use of look-up tables. The performance of the proposed method has been studied for a three-, four- and five-level flying capacitor converter in MATLAB/Simulink environment.

The diet and feeding behaviour of harp seals, Phoca groenlandica, was examined in two high arctic locations. Fish otoliths were used to evaluate dietary composition and aspects of the population dynamics of the major prey species, arctic cod, Boreogadus saida. Harp seals, primarily adults, arrive in the high arctic in mid to late June and depart by early October. Their migration is undertaken specifically for feeding. Harp seals feed intensively on arctic cod, often occurring in dense multispecies aggregations in late summer. The average weight of harp seal stomach contents was high; glutted individuals contained as much as 6% of their body weight in food. Although arctic cod declined in abundance between years, size of cod ingested was similar between areas and years, and overlapped completely with cod taken by other marine mammals. Age/size segregation of arctic cod may account for poor representation of fish <3 years old in the seal diet. Widespread reproductive failure of arctic cod could have a profound influence on the energy balance of adult harp seals since there does not appear to be an alternate food source of equivalent energy value and abundance in arctic waters. Increasing harp seal populations will likely result in increased competition with a host of arctic cod predators, particularly ringed seals.