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FISHERIES RESEARCH BOARD OF TECHNICAL REPORT NO. 273

1971 FISHERIES RESEARCH BOARD OF CANADA Technical Reports

FRS Technical Reports are research documents that are of sufficient importance to be preserved, but which for some reason are not appropriate for scientific pUblication. No restriction is placed on sUbject matter and the series should reflect the broad research interests of FRB.

These Reports can be cited in pUblications, but care should be taken to indicate their manuscript status. Some of the material in these Reports will eventually appear in scientific pUblication.

Inquiries concerning any particular Report should be directed to the issuing FRB establishment which is indicated on the title page. FISHERIES RESEARCH BOARD OF CANADA Technical Report No. 273

Oceanographic Features of and Biological Observations at Bowie , 14-15 August, 1969.

by

R. H. Herlinveaux Pacific Environment Institute 4160 Marine Drive West Vancouver. B.C.

September, 1971 TABLE OF CONTENTS

Page

Introduction .

Conclusions ·.·····.··· ..

Acknowledgements .

References .

Lis t of Figures .

Figures 1- 20 •••.•...... ••..•.....•.....•...... •. 8-27

Tables 1-3 •.•••....•..•...... •.•• ········•·· 29-33

Appendix 1 - Bathythermographs ....•.....•...... 35 Introduction

During August 14-15, 1969, an oceanographic program was carried out on and over Bowie Seamount as part of a co-operative study with the Defence Research Establishment Pacific to deter­ mine the feasibility of using this and other (eg. Union or Cobb)--Fig. l--as oceanic observation platforms. Data from hydrographic and biological sampling in this program are presen­ ted in this report. (A preliminary bathymetric study (Fig. 2) had been carried out earlier (March 25-29, 1969); the results have been reported by 5crimger and Bird (1969).

Physical

(a) Water Properties:

Data on salinity, , and nutrients--silicate (5i03), nitrate (N03), and phosphate (P04)--were gathered by hydrographic casts employing Nansen bottles, at stations along two transects over the seamount (Fig. 2). were obtained from deep-sea reversing thermometers attached to the bottles; bathythermographs were also employed. Salinity determin­ ations were carried out by means of an inductive-type laboratory salinometer (Brown and Hamon, 1961). The nutrient samples were frozen, and later analysed at the Laboratory, by means of an auto-analyser (Stephens, 1970). The results are presented in Table 1 and Appendix 1.

The vertical salinity and temperature structures of the waters overlying, and in the vicinity of the seamount are shown in Fig. 3. The vertical sections of temperature, salinity, density, and nutrients (P04, 5i03 , N03) to a depth of 250 m along the transects are presented in F1g. 4 and 5. The structures and distributions of properties reported here are consistent with those reported in earlier research (Bennett, 1959; Dodimead et al., 1963). The vertical ~emperature between-­ depths of 25 and 50 m defines the position and magnitude of the seasonal at the times of sampling (Fig. 4A). It basically denotes the limiting depth of surface-induced heating and mixing processes. Below the seasonal thermocline, a temperature-minimal stratum, with values ranging from 5.3 to 5.5 C., was present at about 109 m depth. The stratum is considered to represent the remnants of water cooled during the previous winter. (Dodimead, et al., 1963). A temperature-maximum stratum with values ranging trom5.8 to 6.0, at about 150 m depth, is evident on most of the bathythermograms (Appendix 1) as well as in Fig. 3. The maximum - 2 - is most pronounced at Station 4; in this instance it is located on the southeast side of the seamount (Fig. 4A). The temperature structure over the seamount itself has a different character; the minlmum- and maximum-temperature strata were found not to be con­ tinuous. The lowest minimum temperature occurred south of the seamount (Station 4 and 5); the highest maximum temperature on the southeast side (Station 4). Below 150 m the temperature decrea­ ses slowly with depth. In the vertical distribution of salinity (Fig. 3) two generally appear to be present. The shallower, smaller, , which is coincident in depth with the seasonal thermo­ cline, is a summer feature attributed to the addition of fresh water which is served in the 'surface layer' above the thermocline (Dodimead et al., 1963). The top of the permanent halocline occurs at a depthof"""'ibout 100 m and is coincident with the temperature minimum. The surface layer varies in depth between 17 and 30 m.; it was deepest at Station 4, and shallowest at Station 2 (Fig. 3). The sections involving the nutrients provide an indica­ tion of the gradients associated with these properties in the area. From the surface to about 30 m depth, nutrient concentra­ tions are low, probably as a result of utilization associated with primary production in this area. A relatively large increase in the amount of all nutrients measured occurs between 30 and SO m coincident WIth the thermocline and secondary halocline. Below SO m the nutrient increase more gradually with depth.

A slgnlflcant feature 15 the relatively marked downward slope of the Isopelths across the seamount, from Station 2 to Station 4, in the upper 100 'ro. This slope occurs at least over a distance of 2.5 miles and may be a result to some degree of associated with flow in the vicinity of and across the seamount.

(b) Observations:

The research ship was anchored by the bow about 60 m. over the seamount at a position (~) shown in Fig. 2. Three velocity profiles were obtained using a Hytech lISavonius-rotor" type current meter (Fig. 6). In addition, continuous observations of the currents at 20 m depth were made for approximately 11 hours; these data are presented in Fig. 7 and listed in Table 2, and were obtained from the Current meter recorder paper which had been di­ vided into 36 equal intervals. Also, the ships head was recor- ded in order to determine the direction of surface drift (Table 3) . The data indicate that the surface movement during the sampling period was easterly (roughly diagonally across the sea­ mount). Consistency is evident between values from ships head­ ing and from meter during the same time, ego Fig. 6B and 6C. At 20 m (Fig. 7) the current rotates anti-clockwise from NE through north-to-south over an II-hour period. The flow varied from 0.25 to 0.50 knots. Using the predicted times for flood and ebb at Tofino (Fig. 7C). it would appear that the flood sets general- ly northerly at about 0.5 knots, and the ebb generally southerly at about 0.4 knots at Bowie Seamount.

Satellite Navigation

The ship was anchored as previously mentioned in about 60 m with about 160 m of anchor chain out. The satellite naviga­ tion system (Magnavox Dual Channel 702 GA) was Tun continuously. The 10 positions computed during the period at anchor are dis­ played in Fi~. 8; the black dot encompasses three positions. The figure thus lndicates the scatter in computed positions that can be expected by one of these systems from ,a slowly-rolling ship at anchor.

Biological Oceanography

While the ship was anchored on the seamount, the ship's Simrad 11 kHz echo sounder was operated to observe echo character­ istics. At the same time the ship's crew fished with hand jigs. Examples of the echo sounder traces which indicate a shallow scattering layer are presented in Figure 9. A diurnal vertical migration of such a layer is usually noted in most areas of the ocean; however, it is not evident over Bowie Seamount (60 m in depth) . Several hundred pounds of fish were caught by the crew and frozen. They were later identified, and their stomach con­ tents analysed, by staff of the Fisheries Research Board, Biological Station, Nanaimo. The fish which were caught consisted primarily of three species: Sebastodes entomelas (widow rockfish), Sebastodes ruberrimus (red snapper), and Sebastodes prioriger (red stripped rockfish). Figure 10 shows the age- and length-frequency distri­ bution of Sebastodes entomelas, which suggests that these fish are a complete population, because there is a complete range of ages and sizes which brackets the known average length (400 mm) at maturity (Westrheim (private communication)). Further the age and length frequency distribution shown in Figure 10 are well with­ in the known size distribution of S. entomelas population for the coast of . (Westrheim et al .• 1968). The analysis of the stomach contents of the rockfisn-snow they are cannabalistic­ feeding predominately on juveniles. - 4 -

After sampling the fish in the scattering layer the Navy divers carried by the ship, swam down to a peak of the seamount at about 90 to 120 feet depth to collect samples of rocks and bottom organisms, to photograph the fish life in the scattering layer and the bottom forms, to observe and describe the topography and note characteristics near the bottom. Their findings are presented. (a) Rock samples, floral and faunal forms: Several large rock samples collected on the seamount were covered with floral and faunal forms. Dr. D. B. Quayle. Biological Station. Nanaimo. B.C. took samples of the forms for analysis and reporting. The rock samples were sent to Mr. R. H. Herzer. University of British Columbia. who has been working on the geology of Bowie Seamount and his results are being prepared for publication. Dr. R. F. Scagel. University of British Columbia is preparing a brief note on the floral forms found on the sea­ mount; the interest in these samples is due to the fact that the forms at 100 feet are usually those found in the . The fact that these forms occur at this depth could be due to one or more factors·-such as secular changes in . or the clarity of the water, which permits penetration of the sunlight to the top of the seamount. (b) Fish-life photographs: Examples of the fish comprlslng the scattering layer and of bottom forms are shown in Fig. 11 to 19. For a comparison of spring and summer populations. bottom· life photos taken in March, 1969 are included. Layers of fish, 30 to 40 feet in depth. were encountered on ascent and descent. The divers reported the "natives" were friendly--as 'a matter of fact. the divers had to push fish out of the way to obtain photographs. Fish species intermingled; however. the smallest fish were usually found at shallow depths. the large fish in deeper waters. A few 6-foot and many l-foot eel-like fish were noted. Several sturgeon-like fish were also observed. Numerous star­ fish, some white and some purple, were observed on the bottom. Many colored bottom forms were seen. The water at all depths was very clear and visibility on the bottom was extremely good. The combination of clear water and large numbers of fish suggests that the primary production in the area must he closely cropped. Several flat areas were observed by the divers which were also observed on the echo sounder traces. On leaving the seamount to take the oceanographic stations, the ship's sounder was operated to obtain the bottom features around the seamount. Examples of these echo sounder traces are shown in Fig. 20. - 5 -

Conclusions:

Bowie Seamount appears to be a very suitable "pedestal ll upon which to anchor or install continuous recording equipment because of its position in open ocean and topographic features consisting of flat areas. Further, although fouling organisms are present in the area proper selection of anti-fouling paints can overcome this problem. Bowie Seamount also appears to be extreme­ ly interesting ecologically because of the large year-around complete population of fish. Further study is necessary to deter­ mine the reason for and whether or not other seamounts exhibit similar ecological features.

Acknowledgements

The author acknowledges the support provided by Captain Colin Angus, the officers and crew of CSS PARI ZEAU , and by the fol­ lowing Navy divers: Master Warrant Officer R. Larsen, and Leading Seamen G. Benjamin, E. Phal, T. Vipond, and R. Ganner. W. R. Harling and D. Davenport of the Biological Station, Nanaimo iden­ tified the fish and analysed the stomach contents. A. J. Dodimead and L. F. Giovando reviewed the manuscript.

References

Bennett, E. B. 1959. Some oceanographic features of the northeast Pacific Ocean during August 1955. J. Fish. Res. Bd. Can. 16 (5): 565-633.. Brown, N. L., and B. V. Hamon. 1961. An inductive salinometer. Deep-Sea Research, 8 (1): 65-75. Dodimead, A. J., F. Favorite, and T. Hirano. 1963. Review of oceanography in the Subarctic Pacific Regio~. Int. North Pac. Fish Comm. Bull. No. 13. 195 p. Scrimger, J. A., and J. Bird. MS, 1969. Bowie Seamount Preliminary survey for instrument package placement. Defence Research Establishment Pacific. Tech. Memoran­ dum 69-7. Westrheim, S. J., W. B. Harling, and D. Davenport. MS, 1968. Preliminary report on maturity, spawning season and larval identification of rockfishes (Sebastodes) collected off British Columbia in 1967. Fish. Res. Bd. Canada, MS. Rept. Ser. (BioI.) No. 951, 23 p. - 6 -

List of Figures

Figure Location of Bowie, Union and Cobb Seamounts. Figure Topographic features of Bowie Seamount. Figure Vertical distribution of salinity and temperature of the waters overlying and in the vicinity of Bowie Seamount. Figure Vertical sections of temperature, salinity, phosphate, silicate and nitrate. Figure Density distribution over Bowie Seamount. Figure 6 Current profiles on Bowie Seamount. Figure Comparison of currents observed on Bowie Seamount with predicted tide for Tofino, B.C. Figure The computed positions from Magnovox satellite navigation system while ship was at anchor.

Figure Examples of echo sounders tracer recorded while ship was at anchor. Figure 10 The age- and length-frequency distributions of Sebastodes entomeZas.

Figure 11 Rockfish and plant life at about 100 feet, probably Sebastodes 2ecentrus or flavidus~ August 14, 1969. Figure 12 Intermingling of species of Sebastodes (1) entomeZas (2) panci8pini8 and others, August 14, 1969.

Figure 13 Intermingling of species Sebastodes (1) rubberrimus and (2) Priorigen, August 14, 1969. Figure 14 of fishes around Bowie Seamount, August IS, 1969. Figure IS Concentrations of fishes near the Bowie Seamount, (100-110 feet), August 14, 1969. Figure 16 Concentration of fish when looking up from about 100 feet, August 14, 1969.

Figure 17 Plant life and schooling fish at about 100 feet, August 14, 1969.

Figure 18 Plants and fish life at about 100 feet, August 14, 1969. - 7 -

Figure 19 Plant and fish life at about 100 feet, during March, 1969. Figure 20 Echo sounder traces over and on Bowie Seamount, August 14, 1969. - 8 -

130 0

55 0 U-----t.l,.---J'-,-..(tJ~~~~

, -. I"'l -

oBO IE -<'\: .. ';>' c..' ( --\--- \

500~--+----

oUNION

o B i-...... " .I\ ' I

1350 1300 125 0 Figure 1: Location of Bowie. Union and Cobb Sea.aunts. 135°39.200'W

_3

0 I ~ ~ ~ \5317.853' N

5- zov o I IIILES 2

Figure 2: Topographic features of Bowie Seamount. - 10 -

Salinity %. 32.0 325 330 335 340 Omfli~--""':--_---:~---':':':'---

60

80

~ Q) Q; E 120

.c g. 140 o

160

5 6 7 8 9 10 II 12 13 14 Temperature ·C Figure 3: Vertical distribution of salinity and te.perature of the vaters overlying and in the vicinity of Bowie Sea.ount. 11-

~w. RL , STATIONS , .go IZ" l' X 00

'00 100 ~

'00 '00 200 200 '----- ,oo,L__jj;~~~~~==J '00 0',-,.------,-----,---, 0

____12~-- ~O 00 -----""---- 100 '00 '00

200 200

'00 0

00 ~'1RE= 0 ;;" --'7~ '00 E "" -:.00 - '00 '00 ::t: .... '00 '00 n- Ul 0'00 0

00 "" '00 "0 "0 200 200 L_~

Figure 4: Vertical sections of temperature, salinity, phosphate, silicate and nitrate. 12 -

N.W. SIn. 2 SIn. I SIn. 4 S. E. 0'..-----'------'------'-----, :...-- =..::::...=..:- - 24.2 __ 25.0 24.5- - - -- 50 -255

----- 26.0-__ 100

150

200

250 :! :! ..E 300 Stn.3 N.E Sin. 1 S.W.Sln.5 :r 0 ~ ....ll. 0 _---- __24.2 __ 50 ----24.5 25.0 25.5 100

150

200

250

Figure 5: Density distribution over Bowie Seamount. - 13 -

DIRECTION (0 true I VELOCITY (ktlJ 0°i-_-,9",0,---,I-,:80"--.£f"C--"';>'-"I-_~0)';'i'-5_--,;1.0

10

20

30

40 1912113/811969 O.I-'-"'-I---+--+---+-:+.-4--+;r--I

10

• 20 E

:r.... 30 0- W C 40 2030/13/8/1969

30

40 2210/13/811969

50L._...J..-l._-'--_--'-_----'~L-_-l.-_...J

Figure 6: Current profiles on Bowie Seamount. ------

- 14 -

TI ME (hour) 23 24 2 3 4 5 6 7 8 0; 1.0 '0 ..c

?: 0.5 00 0 00 u 0 0 0 °0 0 00 0000000 000 000 o 0000 0 0° ...J UJ 20 m > 0

~360 ~ ~ z ------§0180 a: ap,m is o ---- /'r-- 5 ., :!: 10 V- :I: a.f­ ~ UJ -- o 5 ~ t------o T~FINO TI DAL IHEIGHT

Figure 7: Comparison of currents observed on Bowie Seamount with predicted tide for Tofino, B.C. - 15 -

41' 135°40' W 39' 38' I

, 19

1mile sq. N ,

, 17

, 16

Figure 8: The computed positions from Magnovox satellite navigation system while ship was at anchor. - 16 -

4() :.':'*----...... ------l 100

.0 40 60 80

Figure 9: Examples of echo sounder tracer recorded while ship was at anchor. - 17 -

30,..------,.---.,.----,..-----.------,

20

a: w CD :;; ::;) z 20

10

o 0 o L~o~o~~~~~~::...:~:....::_._::c::!-_=_.::..-~:....:~~~__.:;,_f.

LENGTH

Figure 10: The age- and length-frequency distributions of Sebastodes entomelas. '"""'

Figure 11: Rockfish and plant life at about 100 feet, probably S.bostodss

28centrus or flaviduB J August 14, 1969. .... ""

Figure 12: Intermingling of species of Sebastodes (1) entomeZas (2) pancispinis and others, August 14, 1969. N o

Figure 13: Intermingling of species Sebastodee (1) rubberimu8 and (2) priorigen, August 14, 1969 ....N

Figure 14: Concentrations of fishes above Bowie Seamount, August 15, 1969 N N

Figure 15: Concentrations of fishes near the Bowie Seamount (100-110 feet), August 14, 1969. N '"

Figure 16: Concentration of fish when looking up from about 100 feet, August 14, 1969. ...N

Figure 17: Plant life and schooling fish at about 100 feet, August 14, 1969. N '"

Figure 18: Plants and fish life at about 100 feet, August 14, 1969. - 26 -

.. ..." o o .-<

..~ o .0 '" - 27 -

20 40 60 00 _ '00 ... . " '20 j '40 : ~ 20 40 60 80 100 '20 >40

20 40 60 80 100 '20 '40

~igure 20: Echo sounder traces over and on the Bowie

Seamount J August 14, 1969. - 28 -

TAB LES - 29 -

Table 1.

Station 11 Date: 14 Aug. 1969 Latitude: 53° 18.01' N Time: !.g£ Longitude: 135° 39.6' W

Temperature Salinity Si0 N0 P04 3 3 Depth (oC) (%0) (ug.at./1) (ug.at.!l) (ug.at./1)

0 12.6 32.051 .69 7.6 .22 10 12.84 32.049 .59 7.6 .12 20 12.76 32.059 .62 8.1 .17 30 11. 68 32.152 .67 9.0 1. 00 50 6.53 32.508 1. 33 18.9 10.5 75 5.90 32.746 1. 54 26.0 14.6 100 5.72 32.930 1.66 29.5 22.0

Station '2 Date: 14 Aug. 1969 Latitude: 53° 19.1' N Time: 1548 Longitude: 135° 41.' W

Temperature P0 Si0 N0 Salinity 4 3 3 Depth (oC) (%0) (ug.at./l) (ug. at ./1) (ug.at.ll)

0 12.5 32.028 .67 7.4 .22 7 12.70 32.013 .64 8.2 .37 17 12.55 32.029 .56 8.5 .22 27 8.67 32.333 1. 03 15.5 6.0 47 6.02 32.638 1. 44 23.4 14.0 72 5.86 32.796 1. 62 27.0 16.0 97 5.80 32.027 1. 84 33.0 19.0 123 5.89 33.394 2.00 41. 3 24.4 147 5.91 33.549 2.13 46.4 26.8 172 5.62 33.706 2.36 52.6 31.0 247 5.04 33.841 2.49 66.2 35.0

continued - 30 -

Table 1. - cont'd.

Station 13 Date: 14 Aug. 1969 Latitude: 53° 19.3' N Time: 1638 Longitude: 135° 35.6' W

Si0 N0 Temperature Salinity P04 3 3 Depth (oC) (%0) (ug.at./l) (ug.at.ll) (ug.at.ll)

0 13.3 32.077 .69 8.6 .07 10 13.02 32.042 .56 8.9 20 12.82 32.045 .79 7.8 .07 30 10.00 32.291 .61 7.9 .07 50 6.91 32.470 .92 16.8 9.0 75 5.91 32.588 1. 41 22.6 13.0 100 5.71 32.886 1. 74 30.2 18.3 125 5.86 33.167 1.92 36.7 22. 5 150 5.82 33.561 2.10 44.1 26.0 175 5.80 33.639 2.18 50.0 27.5 250 5.18 33.822 2.44 60.5 33.8

Station 14 Date: 14 Aug. 1969 Latitude: 53° 17. 0' N Time: !Z1P- Longitude: 135° 38.9' W

Temperature P0 N0 Salinity 4 Si03 3 Depth (oC (% 0 ) (.g.at./l) (.g.at./l) (.g.at./l)

0 13.4 32.088 10 13.13 32.041 20 13.00 32.041 30 12.96 32.058 50 6.89 32.448 75 5.58 32.602 100 5.46 32.927 125 5.89 33.261 150 6.01 33.507 175 5.81 33.607 250 5.32 33.836

continued . ... - 31 -

Table 1 cont'd.

Station 15 Date: 14 Aug. 1969 Latitude: 53° 157' N Time: 1828 Longitude: 135° 45.6'W

Temperature Salinity P04 Si0 N0 Depth 3 3 (oC) (0fool (.g.at.!l) (.g.at.ll) (.g.at.!l)

0 13.3 32.112 10 13.3 32.098 20 12.96 32.135 30 10.80 32.262 50 6.45 32.438 75 5.6 32.584 100 5.3 32.781 125 5.86 33.187 150 5.90 33.551 175 5.86 33.696 250 5.06 33.853 Table 2. Current velocity and direction at 20 m and bO m (3.86 intervals/hr).

20 m !O m True True Time Date Item Velocity Time Date Item Velocity Direct 10n Direction 2223 13 Aug.69 1 .50 047 25 .34 256 2 .47 040 26 .36 238 3 .42 036 27 .38 226 4 .39 032 28 .38 226 5 .36 025 6 .34 018 7 .32 018 0527 14 Aug.69 28.5 8 .31 011 29 .38 226 .... 9 .30 007 30 .36 220 N 10 .30 004 31 .36 220 11 .30 011 32 .30 220 12 .30 032 33 .38 184 13 .28 34 .44 191 14 .27 025 35 .40 191 15 .26 011 36 .36 148 16 .26 349 17 .26 334 60 m 18 .26 320 19 .28 316 1953 13 Aug.69 1 .22 147 20 .27 310 2 .24 134 21 .29 295 3 .28 147 22 .30 291 4 .20 134 23 .32 284 5 .24 126 24 .32 270 6 .25 126 .25 140 .24 126 .25 126 Table 3. Ship's heading while anchored on Bowie Seamount 13-14 Aug. 1969.

Current Current Time Heading Time Heading Direction Direction 13 Aug. 2000 230 050 14 Aug. 0100 Z55 075 2010 250 070 0115 240 060 2020 242 062 0130 235 055 2030 220 040 0145 250 070 2035 237 057 0200 245 065 2040 243 063 0215 255 075 2045 248 068 0230 260 080 2050 235 055 0245 255 075 2055 225 045 0300 255 075 2100 218 038 0315 255 075 2110 230 050 0330 255 075 2115 245 065 0345 265 085 2120 242 062 0400 267 087 2125 240 060 0422 271 091 '" 2130 238 058 0442 284 104 2140 245 065 0200 228 048 2150 230 050 0220 227 047 2200 228 048 0240 217 037 2210 240 060 0600 232 052 2220 240 060 0620 228 048 2230 240 060 0640 222 042 2240 240 060 0702 214 034 2250 255 075 0720 214 034 2300 250 070 0740 218 038 2315 245 065 2330 240 060 2340 245 065 2350 245 065 2400 248 068 2415 250 070 2430 235 055 2445 240 060 - 34 -

Appendix I

Bathythermographs - 35 ­

Temperature (Oe)

SIn. I

,. 2.'<: ,.

~ '" '"E

Q. '"

Stn.2 3 4

2.,<: ,.

10

H.

2 •• 21. Stn. 5