RESTRICTED Material in this report AVa is not to be quoted with- » V)- out explicit permission. Fisheries Research Board of Canada ANNUAL REPORT OF THE BIOLOGICAL STATION London, Ontario for the period APRIL 1, 1961 to MARCH 31, 1962 BY W. A. KENNEDY Director With Investigators' Summaries as Appendices FLSHERIES RESEARCH BOARD OF CANADA ANNUAL REPORT of the BIOLOGICAL STATION LONDON, ONTARIO for the period April 1, 1961 to March 31, 1962 by W. A. Kennedy, Director With Investigators' Summaries as Appendices 1 3 4 "Open House" at the Station Nov. 29-30, 1961 1. Biologist D. Dodge discusses wall charts with Messrs. Werner and Davis of the Ontario Department of Lands and Forests. Z. Pulse height analyzer and other apparatus used to develop a technique for tagging with radioactive elements. 3. Technician G. McRae demonstrates ta,gging techniques used at Heming Lake. 4. Biologist R. McCauley adjusts a microscope on the stage of which are par- tially developed Lamprey eggs. 1 Fisheries Research Board of Canada Report of the Biological Station, London for 1961-62 by W. A. Kennedy The Éiiological Station at London is concerned with freshwater fisheries problems in central Canada. Its research program is primarily directed at establishing the basic biological principles requisite to the sound manage- ment of inland fisheries. In fulfillment of a contractual arrangement between the Fisheries Research Board and the Great Lakes Fishery Commission, the Station also carried out work on sea lampreys in the Canadian waters of the Great Lakes during 1961. The administrative headquarters of this Station are in a rented two- storey building at 539 Richmond Street, London, Ontario, which is shared with the London Technological Unit. To expedite the analysis of data and the conduct of experimental work, facilities include a library, I.B.M. equip- ment to punch and sort data cards, equipment for determining the ages of fish from their scales, several laboratories suitable for experimentation with live fish, and associated shops. The building serves as a base for most field parties, although satellite field stations are also maintained for this purpose. A relatively large warehouse and workshop at Sault Ste. Marie, Ontario is used for storage and maintenance of equipment used in the lamprey control experiment, and about half of the men on that project are permanently stationed there. A sizeable field station at Heming Lake in northern Manitoba is occupied seasonally for research on fish populations. A field station at Hay River, N.W. T. , is permanently occupied by two men in connection with research on Great Slave Lake. In addition to a number of small boats, the Station has two 45-foot, steel-hulled, diesel-powered motor vessels. M. V. Cottus is used on Lake Superior in lamprey and fishery problems, and M.V. Stenodus is used in a study of the Great Slave Lake fisheries. HEM ING LAKE Population Studies: In their attempts to predict fishery yields under various conditions, fishery scientists use mathematical models of fish populations. These models are essentially equations whose terms are manipulated to represent various sets of conditions which might influence a fish population, so that the theoretical effect of various changes might be studied. All concerned have long realized that it would be most advantageous to test the validity of such mathematical models by attempting to apply them to an actual fish population. Heming Lake has been chosen as such a testing ground. It is small enough that relatively few men can apply sufficient fishing pressure to greatly affect the population and can tag a sizeable proportion of the fish present. It is remote enough that outside interference with the experiment is unlikely. At the same time, a good deal is known about the lake and its biota because of a previous study conducted there on Triaenophorus crassus, and the physi- cal plant used for that study is available. Although there was preliminary work on populations in 1960, serious work started for the first time in 1961. Construction of barriers to fish mi- gration both downstream and upstream, which was begun in 1960, was com- pleted in early 1961. The fish of Heming Lake are now isolated from all other fish populations. Especially designed trap nets were used for the first time in 1961 to take fish for tagging. Six different variations of tags were used and nearly 5, 000 fish were tagged and released. The disease of fin rot caused some difficulty during tagging, but techniques were worked out to minimize this difficulty. The experiment consists mainly of recording the time and place of re- capture and other particulars about recaptured fish, and of using this infor- mation to assess various population parameters, .Data are forwarded to London weekly and transferred to I.B.M. cards. This method of handling data has greatly facilitated operations. The experiment must run at least ten years before enough data is accu- mulated to test mathematical models in the intended fashion. However, one minor but important fact has already emerged. Evidence has been produced that the colour of the tag has an effect on the tagging experiment; fish with yellow tags appear to be much more susceptible to predation than do fish with clear (uncoloured) tags. Triaenophorus crassus; The Triaenophorus experiment has been terminated, but some informa- tion concerning it is still being collected. A heavy mortality fishery is avoided because of the requirements of the population study. For the fourth successive year the intestines of all pike examined have been completely de- void of Triaenophorus. Other Observations; The occurrence of black spot disease in various species of fish was noted and is being investigated. The collection of Eirnnological data has con- tinued. Data on the age and growth of burbot have now been worked up and a published paper is expected shortly. Two new species of minnows were iden- tified at Heming Lake for the first time in 1961. 3 GREAT SLAVE LAKE FISHERY The fishery of Great Slave Lake has been studied continuously since commercial fishing first began in 1945. The study has served to document the effect of fishing on the fish populations and the effect of the changes in the fish populations on the fishery. The resulting information has been used by the Department of Fisheries which manages the lake, and in most cases where pertinent information is available the fisheries regulations are based on the results of the study. But more important than this use of the data is the fact that information gathered from such an intensive study has wide application. Great Slave Lake is particularly appropriate for an in- tensive study because (a) the collection of data began with the unexploited condition and has not been interrupted, (b) the catch is landed at very few places, (c) there are relatively few species in the lake and only two are important in the commercial catch, (d) only one type of fishing gear is used, and (e) the lake is entirely under federal jurisdiction, which eliminates some pl'oblems which would arise in a similar study of any other Canadian lake of comparable -size. The main source of data has been, and remains, the commercial fishery. Samples are exarnined regularly from the fishermen's catches to get information on sizes of fish caught and their ages. Daily interviews of the fishermen produce information on catch per effort and on places fished. Data on total commercial catch is accumulated by officers of the Department of Fisheries and made available to us, but it is necessary to supplement this data with information gathered by other means in order to arrive at a true figure of biomass removed from the lake. Data from sources other than the commercial fishery have played a minor but important part in the general study. Early in the history of the fishery the Department accepted our re- commendation that the permitted catch from Great Slave Lake be consider- ably greater than had been contemplated. Because of fears that this in- creased catch might be too large, it was for several years necessary to close- ly follow the effects of the fishery on the fish as a precaution against overfishing. During this period changes in the average size of fish, in catch per effort and in age structure were closely followed. However, it was eventually established: that average size is a reliable and sufficient in- dex of the effect of removing fish from the lake; that all over the lake average size, after an initial decrease, has become stable at a slightly lower level, indicating equilibrium between the fish population and the fishery; and that this equilibrium level is far above the overfishing level. Having thereby demonstrated that fears of overfishing are unfounded, it has been possible in recent years to suspend the time-consuming anhual compu- tation of these indices and to concentrate on a more detailed analysis of the data in order to derive more useful basic information. The major work in 1961 has been translating data to punch cards in pre- paration for a much more thorough-going analysis than has been practical with the data processing methods used to date. Because this has required concentration on the development of appropriate techniques, there are relatively few results to report from Great Slave Lake. The data have been scanned sufficiently, however, that had there been any indication of over- fishing it would have been noted. In the field more emphasis was placed on taking observations on board fishing vessels. As a result of these extra observations, we have gained considerable confidence in our previous estimates of fish discarded "at s'ea".