CM_1982_M_7.pdf (688.6Kb)

International Council for the Exploration of the Sea

C oM. 19 8 2 /M : 7

Anadromous and Catadromous Fish Committee

BEHAVIOUR OF ATLANTIC SALMON SMOLTS DURING SEAWARD MIGRATION., I: PRELIMINARY REPORT ON ULTRASONIC TRACKING IN A NORWEGIAN FJORD SYSTEM.

by

l 2 3

Marianne Holm , Ingvar Huse , Erlend Waatevik , Kjell B. DØving4

and Jan Aure1.

l. Institute of Marine Research, Directorate of Fisheries, Pao.Box 1870, N-5011 Bergen-Nordnes, Norway.

2. Aquaculture Station Austevoll, N-5392 Storebø, Norway.

3. Directorate of Fisheries, P.o.Box 185, N-5001 Bergen, Norway.

4o Institute of Zoophysiology, University of Oslo, Blindern, Oslo 3, Norway.

ABSTRACT

In order to find the most effective releasing techniques for future ocean ranching programmes, the behaviour of wild and hatchery reared Atlantic salmon smolts during seaward migra- tion was studied by tracking fish tagged with acoustic trans- mitters. Four fish were tracked in 1981 and seven fish in 1982. Preliminary results are presented on vertical and horisontal migration. Some hydrographical data are also

presented and their influence on fish behaviour is indicated.

Afin de trouver la technique des lachers de smolts la plus efficace pour les programmes d'avenir de Sea Ranching, le comportement migratoire de smolts sauvages et de smolts elevees de saumon atlantique a ete etudie en suivant des pois-sons munis de transmetteurs acoustiques. Quatre smol ts ont ete suivi en 1981 et sept smolts en 1982. Des resultats preliminaires sont presentees sur des migrations verticales et horisontales. Quelques informations hydrologiques sont aussi donnees et leur signification pour le comportement des poissons sont discutees.

- 2 -

INTRODUCTION

Different types of transmitters attached to animals is today a widely used method of monitoring migratory behaviour of free living animalso The method is applicable also to fisho There- by valuable information can be obtained, that cannot be un=

covered by ordinary fish tagginge When working with small fish the method is hampered by the fact that the small acoustic trans~

ducers needed send on such high frequencies that give the trans~

mitters a very limited range, which makes tracking difficultø However the method has been quite successfully used on tracking Atlantic salmon smolts by among others La Bar et al. (1980) in

the UoS. and Tytler et al. (1978) and Ross (1981) in Scotlando In Norway experiments with tracking smolts could be started when the Technical University of Trondheim developed a minia-

ture version of their acoustic fish tag (Knutsson 1980, 1981).

The aim of the experiments is to find the most effective re- leasing techniques for future ocean ranching projects by collecting data on the migratory behaviour of smolts of At~

lantic salmon (Salmo salar L.) migrating seawards. The ex- periment started in 1978 focusing on the behaviour of migra- ting wild smolts in order to get some reference for comparing the migratory behaviour of hatchery reared smolts. The ex- periments were first carried out in the small river Lone, 35 km north of Bergen. In 1979 a cooperation was started with the Directorate of Wildlife and Freshwater Fish. In 1981 the experiments were transferred to the HØgsfjord area southeast of Stavanger where the Directorate of Wildlife and Freshwater Fish has its research hatchery and a smolt trap in the Imsa River. Thus wild smolt of suitable size as well as hatchery fish of desired age and origin could easily be obtained at the same time. The area is also interesting because of its topo- graphy, since i t is a large fjord system with a wast archipe- lago, giving the fish many possibilities of choosing its way

(or possibly drifting) out to the open sea.

The present paper gives preliminary results of the 1982 tracking and a few data from the 1981 experiment.

MATERIALS AND METHODS

In late May 1981 eight fish, one of which was a 2 year old hatchery reared smolt of Imsa origin, were tagged either by pushing the tag carefully down the pharynx into the stomach or attaching i t externally under the dorsal fin with a thin wire as shown in figure l.

Fig. l. Attachment of transmitters.

Four of these fish were tracked. Some data on these fish are given in table l.

The experiments were continued in 1982 (20-31 May) by tagging and tracking one wild smolt (Imsa) and eight hatchery reared 2-year old smolts. The reared smolts originated from Imsa

(no. 2, 6 and 7), the river Figga (no. 3, 4 and 5) located in Mid-Norway. The fish are presented in table l.

The ultrasonic tags used in 1981 were position only transmitterse They were 18-20 mm long, cylindricae with a diameter of 8.0 mm and weighed 3. 5 g in air (r-v-l. 5 g in water) , em i t ting different pulse rates at somewhat different frequencies in order to

distinguish one tag from another. In 1982 the Technical Uni- versity had developed miniaturized depth and temperature sensi- tive ult:r;:asonic tags. These were 22 mm long and 9 mm in dia- meter, weighing 4.0 and 2.5 in air and water respectively .. They were emitting at frequencies around 125KHZ. Changes in

pressure were transmitted by frequency modulation and changes in temperature as a change in pulse repetition rate. The range of

- 4 ~

the transmitters was 300~1 000 m depending on hydrographical conditions ~n the sea~ Expected battery life was 10-21 daysv A detailed description of tags is given by Holand (1982) .,

A highly directional hydrophone was mounted in the bow of the tracking vessel and connected to a receiver in the wheel=

houseo The hydrophone could be turned 360° horisontally by wires from the wheelhousee

Calibration of pressure to depth data was made by lowering the tag from 0-10 m into the sea and tuning the received signal to zero-beat frequency for each metre and noting the readouts for each receiver on its metere When tracking the fish the receiver was constantly to be tuned to Zero-beat when the fish moved up or down and the readouts were read into a tape=

recorder.,

After tagging the fish were left to recover from anestheti- zation (6-48 hours) and if they behaved normally they were

released either in fresh water in the river mouth or in brackish water a few hundred met.res away from the river mouth.

The intention was to follow the fish continuously for 2-3 days or until the fish disappeared or reached open sea. In a few cases the fish had to be given up as "non-migrants", but most fish started migration and were 'traced for shorter or langer distances until the signals disappeared~

The boats were positioned by taking fixes by the help of a radar (or sometimes by "common sense") which was considered to be accurate enough for our purposes. The direction of the fish relative to the boat could be fairly accurately estimated because of the hig~ly directional hydrophone. The distance to the fish was roughly estimated through experience of judging signal strength and the sector in which the tag could be heard when scanning (large sector - fish close by, narrow sector - fish far away) ^o

Buoys with instruments (Sensordata Ltd.) for automatic recording of temperatures, current speeds and directions every 20 minutes,

were located at stations I, II and III. At station I there were current meters also in 2 and 12 metres. In addition hydrographical stations 1-7 were sampled daily for tempera- ture and salinity profiles from 0-30 m. Stations 8-11 were taken especially when fish no 5 moved to the outer area.

The current speed and direction was also measured by 1.5 m cross waned drogues. The stations are shown in fig.9.

RESULTS AND DISCUSSION

Since a large amount of data from the 1982 cruise still remains to be thoroughly analysed, this paper presents only preliminary resu1ts focusing on a few points of interest.

Table 2 shows time and date of release, active migration time and distance from site of release when loosing the track. It must be mentioned that the tracking distance aften was sub-

stancially langer since the fish from time to time were milling around in coves and sounds befare continuing a more steady

migration. Langer periods of standing s~ill or milling around in one place is also deducted to get the active migration time.

Thereby a rough estimate of migrating speed is obtained. It should also be noted that all the smolts adapted to seawater some weeks prior to release migrated at least outside the small fjord between Imsa and AdnØy island.

Figures 2-9 present the migration routes of the fish. Areas where the fish showed active periods of vertical movements are indicated.

The diving activities of the fish are also roughly demonstrated in fig. 10 as number of dives per hour along the track.

The salinity data, fig. 11, show that in the fjord there was a clear stratification in the upper water masses. A 2-3 m layer of more brackish water was found above the more saline water masses beneath. This stratification could not be seen from the

temperature data. The stratification did not seem to exist in more coastal waters (outside Aamøy, see maps).

- 6 -

The depth data, although only tentatively treated, show that the smolt migrate in the upper brackish layer, but make short dives into the deeper more saline watere

CONCLUSIONS

Mc Cleave (1978) and La Bar et alo (1980) found clear coincidence between the direction of the tidal currents and direction of

fish movements. In the HØgsfjorden area the tidal currents are negligible, but there is a movement of the water masses in and out the fjord that is largely induced by winds and the coastal current. The tentative results of this study also indicates that the smolt follow the outgoing currents and that they tend to mill around and start diving activities when they come to areas with complicated current patterns~

The pressure sensing smolt tags were a valuable aid to the understanding of the smolts diving activities, but they still need some technical refinement since there was considerable

drift in the emitted frequencies, which makes the interpretation of the depth data difficult.

REFERENCES

Knutsson, S. 1979. Utvandring av laksesmolt. Årsmelding 1978 t i l NFFR ..

1980 Utvandring av laksesmolt. Årsmelding 1979 t i l NFFR.

(Migration of salmon smolts. Annual reports 1978 and 1979 to the Norwegian Council for Fisheries Research).

La Bar, G.W., McCleave, J.D. and Fried, S.M. 1980. Seaward migration of hatchery-reared Atlantic salmon (Salmo salar) smolts in the Penobscot River Estuary, Maine: Open water movements. J.Cons.

Int.Explor.Mer. 38:257-269.

McCleave, J.D. 1978. Rhytmic aspects of estuarine migration of hatchery-reared Atlantic salmon (Salmo salar) smolts. J.Fish.Biol. 12:559-570.

Tytler, P., Thorpe, J.E. and Shearer, W.M. 1978. Ultrasonic

trac.king of the movements of Atlantic salmon smol ts (Salmo salar L.) in the estuaries of two Scottish rivers. J.Fish.Biol. 12:575-586.

Ross, L.G. 1981. Smolt acoustic tracking in a lake, in Report of meeting on Practical Aspects of Fish Tracking.

Dec.l981. Leatherhead, U.K.

Table 1 .. Orig in ^y lengthb' weight, tagging method and releasing site of smolts in 1981 pnd 1982~

Fish Orig in Length Weight Sea Re leasing Tagg ing Transmitter

no .. cm g water si te method type

ada ted 1981

2 Wild~ Imsa 21 .. 5

- ^-

River mouth Internal position only

4 ^{n vv} 19 .. 5

- -

^iV " ⁿ

5 ^{n Vi} 22.2 82

-

^Estuary Ex terna l temperature

7 Hatchery, Imsa 22 .. 7 89

-

River rnouth ^{n n}

1982

l Wild, Imsa 20.1 63

-

^{VI IV} pressure and

ternperature

co 2 Hatchery, Imsa 30 .. 5 259

-

^VI " "

3 ^QU Figg.a 36.5 393 y es Estuary ^{IV i l}

4 ^Di " 34 .. 0 326 " ⁿ " "

5 ^{DV IV} 28.4 216 ^{vv VI} " ⁿ

6 ^vv Imsa 29.,5 281

-

" " ¹¹

7 ^{Vi U i} 29.0 195

-

ⁿ In terna l position only

Tab le 2. Data on tracking in 1981 and 1982G

Fish Rele as ed Active Migra- Track Speed no. Date Time t i on time

1982 - l

l 20.5 22.45 5 .. 5 h 3.5 km 17.6 cm/s 2 22 .. 5 10 .. 00 0.8

"

^{0.7 11 24.8 "}

3 24.5 00.15 32.0 " ^27.7 " ^23.0 "

4 25.5 21 .. 08 9.0 ¹¹ 12.0 " ^37.0 "

5 26.5 21.20 40.0 42.5 ¹¹ 29.5 "

6 29.5 11.15 18.0 ¹¹ 14.0 ¹¹ 21.0 ¹¹

7 30.,5 13.35

1981

2 21.5 17.20 12.5 " ^{12.9 11 28.8 11}

4 23 .. 5 10.00 ("\../24.0 " impossible to calculate 5 26.5 23.56 ("\./21.5 ¹¹ 16.6 " ^21.4 "

7 29.5 23.12 22.5 ¹¹ 20.5 " ^25.9

"

1. 21/5 2o ¹⁰ 3. "

4 . . . 5 . . . 6. ..

7 ^{c . ,}

8 . . . 9. ..

o

kl .17. 2o-17. 55 k.l.18.52 kl.l9.05 J<.l.l9.45 kl.23.07 kl. OL 13-02.15 k.l.03.0S kl.04. 49 kl.05.SS

Hem

Fig. 2e Track of fish noe 2 (1981)

1.23/5 kl. 10.05-24/5 00.35 2.24/5 kl. 01.14 fisken borte 3. .. kl. 02.13 fisken funnet 4. • · kl. 02.45 fisken borte 5. • kl. 05.47-21.57

6. • kl. 22.40

7. 25/5 kl. 06. 30 fisken borte 8., • kl. 09.45 fisken funnet 9. • kl. 20.45

10.26/5 kl. 01.46 11. ~ kl. 02.30

O O;.m

Fig. 3. Track of fish noe 4 (1981)

TA VANG

58.58~N 5•44~E

l. 26/5 i<l.23.56

4 . 27/5 .. _00.45

3. .. _04.28

4. .. ₁₁ o 2 9

s.

..

_12.07

6. " l 3. 53

7.

..

_14.14

8.

..

_15.48

9.

lO. 28/5

..

_01.13

11. " 03.20

12. " 04.15

13.

..

_04.44

14. .. _05.07

15. " 06.00

Fig~ 4. Track of fish no. 5 (1981)

Borge fjord

l -~-

G~

29/5 kl 23. 2 ^\

2. 30/5 " . 03.14-22.5 3- 31/5 " 04.28

4. .. _06.21

5. 08.05

6. " lo.OO

... l . .. _12.15

8. " 14.04

9. "'15.45

o 2 km

Fig. 5. Track of fish no. 7 (1981)

... ,

2-o.s ' 2245

24/5

- 12 -

l km

Fig. 6. Track of fish no. l (1982). Arnow indicates releasing site. Open square indicates start of active migration~

Black square indicates disappearing point.

Fig. 7. Trade of fish

:mm;

^{no. 3 (1982}

dr i vin

~ . g activitv

V WJ.lld d ·

~

~ lrection

current direct' J.on in l rn depth

- 14 -

:3'

o 5 km

FigQ 8. Track of fish noe 4 (1982 legends see previous figures

...

=::::::::

dr i ving a c ti vi ty

/ currant direction in l m depth

Il)

~

28o5 Sta J 11 I 6 3 O

®·

n

_~ ^~

...

',

~

o c;:>

Stil. vanner

o

o~~

Sta. 8

..

^-~.-

~ ^. .

C3

®

vtfo.

Sta· 9 • 6 • ,

~t

Q

^o

~· ^o

~ l}

~

\)

(),

c:j

o.

I ms;

26.5 2IIO

fl

30

Ul

~.

20

·rl V'(j 4-U o

H lO

(})

§ _o;

z

\.0 Ul

~;20

M

·ri

l

ro

lH

o 10

~ ())

~ ^o

z

0-1 rn

~

Fish no. 3

l-2m

l

Fish disappeared

lrn ^{A Jl,}

0-1 m Increasing

hours

00 ⁰⁰ 22

00

24o5 25.5 date 25a5

Fish no. 5

Fish stavs in 2.- 3m deoth 4- 5 ^m

l

04 08 12 16 20.

00 00

26a5 27o5 28o5

..

• l

.Pig., 10., Diving activity per hour and a crude indication of swimming depthe

Fish no .. 4.

04 26.5

1-2m

~

08 hours date

r~~:= ... ^l

9~ i

^!,· ---It---... _ ^{0,5 /}

l , / ^l

.2

l

²

/

El r

x---- -x 24.

5

^l

:S

^{3 3 J l}

~

^{4 - - 25.5 4}

Jf

^X---X 26.5 stn. 7

5 5 29.5 stn. 7

temperature salinity

8 9 10 11 12 t⁰e 8 9 lO 11 12 13 t⁰e

o

^{16 18 20 22 24 26 28} 30 S o/oo

o

14 19 l? 2p ... 212 241 ~6 48 . 3Q s ojoo

l<"; l

^{l l}

·c:::· ^.,

^{l l l l l Lo}

^{.. ·-}

o,5i ^JL, 0,5

l ^\.._ l

2 ^l 2

3 ^{~ l} 3

El ^{l l}

4 ^l

:L

:S

^{~ l}

f

^{)E-- _ -x} 26.5 stn. 2

l x--^-4C 24.5 stn. 2

~

⁵

^t

- - - 25.5 stn. 2 - 2 7 . 5 stn. 4

r-- 7 7

~

ro

lO

temperature salinity

8 9 lO 11 12 t⁰e 8 9 10 11 12

o

^{16 18 20 22 24 26 28} 30 S o/oo

o

^{14 16 18 20 22 24 26 28} 30 S o/oo

0,5 0,5 r

l l ^~ _\

El 2 2 ^\ _~'

' ,,

:S

³ _l 3 ^... 'l<,

~

5 4 ^l >E---~

---

25.5 stn.. 26.5 stn.. 4 5 4 28.5 stn. 8 28.5 stn. 11 ^{\ \ \ l( \ t '}

7 7

lO lO

temperature salinity 15

Fig. 11. Salinity and ternperature 24.-29.5. at stations 2, 4, 7, 8 and 11.