Burke. Channel

~.. ~. HSHtRI tS atSu~R&' " . BGA'R~ ~f Cl~llA . .~ ~. - . ' ~ . B\OtOG\b~t ,Sl~l\Q~, .. , - '-. '.'· Sf. Jn1\tiJs.M£WfnU:Rnl~ND .., " ).0 '.;; I" . .' -... ... -.. - . IJI8:8 •••_$ _R_ . 8~~B~ (;P .·' BOA •• ," ' OF" CA -:N ' A:P&-~ " . :- ', ..~:ANJ1SCRIPT REP'O~T . SEItIES ,No. 976 .. .. " • j. _ ' - - . ' • I _I, ' . [ , '<" . ~ .. r, . Drift Card Beiea8e.8 ~ ~n, d .ReeQverielf . , .. , ... ..... • ' -' .0 >' In . '. , -,. 'Burke . Channel - .- \ . i j' , " >.- British ,Columbia, 1 1967 .. ,. 0 • b1 " ~"" 'It • ' .J 1t~1I~ ', Herlinveaq~ . .- , ~. :" . - , ", .BlQ1o.gical S-tat;on, NJlIi.tmo, B.C.; - .. i?~cifl~Qceanogr~phic Group ' . - , ' , ,~ ."~. March 1968 FISHERIES RE8EAR~B BOARD OF ~ANADA MANUSCRIPT REPORT SERIES No. 970 Drift Card Releases and Recoveries • In Burke Channel British Columbia, 1967 by R. H. Herlinveaux Biological Station, Nanaimo, B.C. Pacific Oceanographic Group March 1968 Programmed by The Canadian Committee on Oceanography Drift Card Releases and Recoveries in Burke Channel, British Columbi.a, 1967 by E..H. Herlinveaux INTRODUCTION Burke Channel is the main migratory route of the pink salmon moving into and out of the Bella Coola River system (Figure 1). On their way to the sea, the pink salmon spend approximately twq months (mid~April to mid-June) in the system, during which time a significant and variable mortality occurs. The mortality must be associated partly with environmental factors. among which water movements are considered to be most significant. Water movements may either directly tiansport the fish, or, by altering the salinity distribution, and! or by concentrating or dispersing food organisms, modify their travel. Furthermore , variation in water movements may change the nutrient supply, which in turn will alter production of food necessary for growth and survivaL An extensive 5=year study of the l!spring Qceanographic conditionsl! in the system was terminated in 1967. The analyses of the data for the period 1963-65 is complete and a report is in preparation, in which the general oceanographic features of the whole system from North Bentinck Arm to Nalau Pass~il1 be described. During 1966 oceanographic and meteorological conditions were monitored to confirm the early observations on property distribution. It also became evident that the system oscillated. apparently as a result of wind effect. Finally during 196'~ an extensive oceanographic, meteorological and biological sampling program was organized and carried out 9 in order to examine the oscillation in various 'recorded parameters. As an aid in the study of surface water movements, a drift card release was also carried out. The analysis of the oceanographic and meteorological data is far from complete. but some interesting relationships coming to light are presented here as background information. Figure 2 shows 10 sets of meteorological and oceanographic time~series observations recorded during the period April 15 to April 25, 1967, in North Bentinck Arm and at Bella Coola Wharf. It is evident that the properties oscillate in phase or out of phase, depending on the property being observed. The most important feature for this report is the fact that the net daily surface movements can be outward for several days. then reverse and be inward for a similar period (Fig. 2 I). The movements were recorded on continuous recording current meters (Neyrpic) which were suspended ( 2 metres) from surface,anchored buoys at a position shown in Figure 1. Twenty other positions were occupied through= out the system for varying periods of time which will be reported when the recorded data are analyzed. - 2 - DRIFT CARD PROGRAM The drift cards were the same as those used and reported by J.W. Martin (1967) of the U.S. Bureau of Commercial Fisheries, Biological Laboratory, Auke Bay, Alaska. Figure 3 shows the card in opened-up and in the folded position as used. The open card shown drifted for 34 days. The plastic eventually fractures and the card disintegrates. It is difficult to determine how long the cards remain intact in the marine environment. However, sufficient numbers did remain intact long enough to be retrieved. These are reported below. Seeding procedure The procedure usually varied from a line of ten cards released across channel daily to groups of ten released in certain locations. Numbers of cards were recorded for identification,and positions of release points were determined by sight of known landmarks. On the last seeding conducted on May 19, 200 cards were released in a group at the Labouchere Channel - Burke Channel position. Drift card releases and returns ' , Cards were released in North Bentinck Arm, in Burke Channel, inward and seaward of Labouchere Channel and in Dean Channel. The returns to date from these releases stand at 28 cards, which is 7% of the cards released. Table 1 shows a summary of drift card numbers, distance and direction travelled and average net speed. Figures 4 to 7 show the ,probable courses followed by the drift cards. The course of the drift card from the point of release was plotted along a reasonable path based on the distribution of the recoveries. Five were retrieved by fishermen and the remainder were retrieved by our scientific group. Most cards were found in the tide lines in areas such as at the junction of Burke Channel and Fitz Hugh So~nd and above the Burke Channel Narrows. The early returns from cards released April 21 to 24 suggest the movements tended to be inward, but from this period on, the movement appeared to be predominately seaward. The one exception was one card of a set of 200 released in the area below the Burke Channel - Labouchere Channel junction. This card was found at the mouth of South Bentinck Arm (Fig. 7). One card of a group of 10 released in Dean Channel was picked up above Burke Narrows (Fig. 6). DISCUSSION The drift cards released April 20-24 (Fig. 4) were released during a period of inward-blowing winds (Fig. 2 H). As a consequence, they were probably driven inward by the wind-driven surface currents. However, one card of these releases did move out of the system while one moved less than one mile away from release. The one that travelled such a short distance probably spent considerable time on the, beach. = . 3 = After April 26 (Fig. 5) . all c.ards moved persistently seaward towards the mouth of Burke Channel at speeds varying from a high of . 47 knots to as low as .06 knots with the mean being about . 14 knots . These drift=card movements indicate that even though the surface currents oscillate inwards and outwards the, net movement .was out. It is also possible for an object , to move against the apparent predominant net movement (Fig. 7) . This may occur if the object is moved into countercurrents or eddies near the southern . shore in Burke Channel. In. any inlet system where there is a predominance of runoff water in the surfa'ce layers, a definite cross=channel bias in surface movement may be observed. On the right, hand shore ' looking to seaward . ,there wi 11 be a net seaWard flow , while on the left hand shore there will be a smaller seaward flow . or in unusual circumstances , even a net inward flow. The dri,ft-card movement indicated that it is possible for .an object, in the surface layers to travel from Menzies Point into Labouchere Channel (Fig. 5) . It is also possible for an object to travel from Dean Channel down through Labouchere Channel into Burke Channe l (Fig . 6) . One card travelled out of Burke Channel into Fitz Hugh Sound , past Calvert Island (Fig . 7) . · . This is what would be expected if the, winds were predominately from northwest , as they were during May and. June 1967. It is speculated that during years when the winds are predominately from the southeast, the surface movements would be to the north through Fisher Channel (Fig. 1) . , CONCLUSIONS 1 . The North Bentinck Arm - Burke Channel system may go through periods of days when all surface movements are inward; then the surface currents reverse and for several days set outward . 2. ' An object in the surface layers may have a mean net movement of 3.4 miles per day seaward , but ' it ,coul d move 'at speeds as high as 11.3 miles per day for short periods. 3. When an objec t in the surface layer moves out of Burke Channel into Fitz Hugh Sound , the most important factor which determines whether or not an object will move southward or northward through Fisher Channel could be the local coastal winds . 4. The drift card returns for May 15 (Fig. 6) and April 26 (Fig. 5) indicate that there can be a definite movement from Dean Channel through Labouchere Channel into Burke Channe l. Also it is possible to have a movement from the mouth of South Bentinck Arm towards and into Labouchere Channel (Fig. 5). Further , a drift card movement indicated a surface current from Burke Channel (below Labouchere Channel) back up to South Bentinck Arm ( Fig. 7) . These three situations are separated in time and are indicative of an oscillating, cross=channel biased system, which is energized by meteorological forces . - 4 - Tab'leI. Drift Card Observations . Serial Time/Date Distance/Time Speed Direction No. F.S.T. Mile/Hrs (knots) 37 Apr 20-21 3.0 / 24 hr .13 Inward 62 Apr 23-24 2.0 / 24 hr .08 Across (south) 50 Apr 21-24 3.5 / 66 hr .05 Inward 41 Apr 20-24 3.5 / 90 hr .04 Inward 83 Apr 26-May 3 10.2 /132 hr ~ . 08 Outward 87 Apr 26-May 3 10.2 t132 hr .08 Outward 128 May :·6-May 9 ·.· 7~5 . I36 hr .21 Outward .

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