Preliminary Categorization of the Productivity of 37 Coastal and Skeena River System Lakes in British Columbia

We carried out limnological surveys of 37 lakes on British Columbia's north coast and Skeena River system. Limnological data collected on these surveys enabled us to make preliminary estimates of the lakes' trophic status and productive capacity for juvenile sockeye. Of the 37 lakes, one (Moore) was meromictic and one other (Tsimtack) was more properly termed a tidal lagoon than a lake. Thermal structure of the lakes ranges from warm monomictic (18 lakes) to dimictic (13 lakes) to cold polymictic (6 lakes). Euphotic zone depths ranging from 0.4-23m. Total phosphorus concentrations ranged from 1.4-16.5 μg/L, indicating a wide range in trophic status in the surveyed lakes. Phytoplankton photosynthetic rates (PR) ranged from the lowest (8 mg C m-2 d-1) to among the highest (387 mg C m-1 d-1) yet recorded for a BC sockeye nursery lake. We categorized the lakes based on water type (glacial, organically stained, clear) and found significant differences in physical, chemical, and biological variables between the three lake types. In most cases, stained lakes had lower values for chemical variable and had less abundant plankton communities than clear lakes. Preliminary estimates of productive capacity indicate that sockeye escapements (normalized to lake area) needed to maximize sockeye smolt biomass ranged from 2-89 spawners/ha.