Historically the Rivers Inlet fishery for sockeye salmon Oncorhynchus nerka was one of British Columbia's largest salmon fisheries. Suspecting that spawning escapements had declined to far below optimum levels, in 1979 the Canadian Department of Fisheries and Oceans initiated an adaptive management experiment to rebuild spawning runs in hopes of producing larger recruitments. The fishery was essentially closed from 1979 to 1984 and was allowed to increase gradually from 1984 to 1988 in expectation of higher recruitments following the closure. The higher recruitments have apparently not materialized, implying either that the stock was not so badly overfished in the first place, that there has been an unlucky run of poor years for ocean survival, or that the stock has responded but increases have not been detected due to poor spawner enumeration methods. Our inability to distinguish among these alternatives, even after a decade of experimentation, illustrates difficulties in designing effective plans for adaptive management. Industry and government have cooperatively developed a new strategy that they feel represents a better balance between short-term fishing opportunities and long-term information gathering, and that will be less demanding to implement in terms of in-season regulatory tactics.
A preliminary investigation of two mountain streams in Alberta was undertaken during 1968-69, in order to assess the effect of fluctuating stream flows on standing crops and drift of benthic organisms. One of these, the Kananaskis River, was subject to flow regulation for hydroelectric purposes, while the other, a tributary, Lusk Creek, was not. Several environmental factors known to affect these phenomena were also investigated. The life histories of some of the Ephemeroptera and Plecoptera, and emergence patterns of some Plecoptera in addition to a study of insect distribution at and below the surface of the substrate have been reported elsewhere (Radford & Hartland-Rowe 1971a, b, c). Except for studies by Neel (1963), Pearson & Franklin (1968), and Pearson, Kramer & Franklin (1968), little work has been done on rivers whose flow is regulated. Pearson & Franklin (1968) note that sudden flow increases caused rapid rises in the catastrophic drift of Baetis sp. and Simuliidae and found that artificial reduction of stream discharge also caused an increase in the drift, with virtually all bottom-dwelling forms being affected, as also did Minshall & Winger (1968). Neel (1963) states that daily fluctuations in reservoir releases discourage littoral stream life and may reduce a stream's carrying capacity for many organisms. Sedentary forms of insects, clams and fixed oligochaetes find survival very difficult under such conditions, but most insects (especially those making long mating and egg-laying flights) are apparently able to cope with controlled, fluctuating discharges. Also, the normal annual temperature cycle of streams can be disrupted under regulated flows since reservoirs delay the rise in river temperature in the spring and its decline in the autumn, because more time is required for their relatively great volumes of water to approach air temperature. Rawson (1948) undertook a biological investigation of the Kananaskis River after completion of the Upper Kananaskis Lake reservoir (Interlakes Dam), but before construction of the Lower Kananaskis Lake reservoir (Pocaterra Dam). He found a 'rich and varied fauna' (no quantitative data are given) in stream samples obtained below the Lower Kananaskis Lake. This was the only previous study of the benthic invertebrates in the Kananaskis River.
The first record of an American eel (Anguilla rostrata) is reported for Alberta. The specimen was collected in the South Saskatchewan River and probably originated from elvers stocked in Lac Pelletier in Saskatchewan in 1953.
A new subsurface sampling technique for collecting macroinvertebrates in gravel‐bottom streams is described. The cylinder sampler collects all species whose presence is indicated by a Surber sampler, but the percentage composition of the population sampled is different. With this method, a far larger number of benthic invertebrates is obtained, making it possible to reduce the number of samples to 10 or less and yet obtain estimates within 20% of the true mean of the benthic invertebrate population inhabiting the top 17.5 cm of substrate.
A t-test showed that actual and reported mean times spent angling by parties during each month of a creel survey on a lake in Alberta were not significantly different. A paired t-test showed no significant difference in means between the actual time and the reported time spent angling by parties which caught one or more fish and by parties which caught no fish. Any differences found are attributed to sampling. It is concluded that when one uses reported times in creel surveys, he must first determine if any significant difference exists between reported and actual mean times over an extended period of time before applying a correction factor to the reported catch ratio data.
The seasonal distribution of Plecoptera in two mountain streams in Alberta is presented and compared with emergence patterns in the northwestern United States and southern British Columbia. Differences between the emergence periods in our study are attributed to differences in the amount of heat the streams accumulated. Some general aspects of the emergence pattern peculiar to the region, and its relation to the interaction between photoperiods and water temperature are discussed.
Abstract The life histories of Nemoura besametsa , Epeorus deceptivus , Epeorus longimanus , and Ephemerella coloradensis are described as "fast seasonal" types and Arcynopteryx aurea , Nemoura cinctipes , Nemoura columbiana , Nemoura oregonensis , Cinygmula ramaleyi , Ephemerella doddsi , and Rhithrogena doddsi as "slow seasonal" types according to Hynes’ (1961) classification. All of the species are univoltine with the exception of N . cinctipes which may be bivoltine. There seems to be a correlation between life cycles and food availability. A means of ecological separation in the four Nemoura species is elucidated. Stream temperature was found to influence growth rates.
