Translated by the Translation Bureau(LT)

ISSN 0704-3716
Y
j
CANADIAN TRANSLATION OF FISHERIES AND AQUATIC SCIENCES
No. 4802
Salmon smolt migration from Lule River
by
P.O. Larsson, and S. Ateshkar
Original Title:
From:
Laxsmoltens vandring fraan Lulealven
Fiskeritidskrift for Finland (1): 8 - 9, 1979.
Translated by the Translation Bureau(LT)
Multilingual Services Division
Department of the Secretary of State of Canada
Department of Fisheries and Oceans
Quebec Region
Quebec, PQ
1982
5
pages typescript
1
1:1EPARTMENT OF THE SECRETARY OF STATE
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INTO - EN
-nglish
Swedish
AUTHOR - AUTEUR
r.O. Iarsson and S. Ateshkar
TITLE IN ENGLISH - TITRE ANGLAIS
Salmon smolt migration from Luis River
TITLE IN FOREIGN LANGUAGE (TRANSLITERATE FOREIGN CHARACTERS)
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Laxsmoltens vandring fraan Lulealven
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Fiskeritidskrift for snlinland
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Fisheries Journal for Finland
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Fiskeritidskrift for Finland
Fishery Journal for Finland 1.1979
SALMON SMOLT MIGRATION FROM LULE RIVER
P-0. Larsson and S. Ateshkar,
Sâlmon Research Institute, Alvkarleby,
Sweden
When young salmon (smolt) migrate from a river to begin their life
in the sea, they are called post-smolt until they reach a commercial size.
As salmon oft}p post-smolt size are caught only occasionally by fishing
implements meant for other species, very little is known about their biology.
Therefore, an attempt has been made to gather information about post-smolt
from salmon smolt tagged by the Salmon Research Institute. The results below
deal with migrations in the sea during the first year after descent from
Lule River.
Material and methods
During the period 1963 - 1974, 449,108 tagged salmon smolt were
placed out at Boden in Lule River. About 3,000 (0.67%) were reported to
have been caught during the stocking year (post-smolt). Several hundreds
of these were found in the stomachs of burbot (Lota lota) and pike (Esox
lucius), in the excrements of Hydroprogne tschegrava and other gulls, etc.
r'-_. "1
nn
SEC 5-25T (Rev. 6/78)
-
2
These are not included in the study, since the time when the smolt had been
eaten is most frequently uncertain.
Due to some variation in stocking times, recovery times were recorded
as number of weeks after date of stocking. To make the material sufficiently
usually
reliable, the fairly small areas, where recoveries were -i— roade e were combined
to form larger units, seen in Figure 1.
Within each area, the chronological
distribution was calculated in percentages, until and including August for
two-week periods, and after August for one-month periods. Furthermore, the
average times (mean and median values) of migration into each area were
computed.
Results
Table 1 shows for each area:
distribution in % chronologically,
total number of recoveries, "average recovery time", and computed shortest
distance from stocking place to centre
of area .
Fig. 2 is a layout of main migration routes of post-smolt.
Discussion
The average migration times of salmon show surprisingly, that for
example area 9 on the Finnish side of the narrowest part of the Bay of
Bothnia seems to be reached sooner than areas 2 and 3 on the Swedish side
and areas 6, 7, and 8 at the Finnish shores of the Bay.
However, this is
explained by the distribution of recoveries over the year. The distribution
of post-smolt in the sea is naturally wide, 60 that some of them probably
3
,jL
mv -Qp
Lule HivèT,
6)
The
/ - i— Bay of
Bothnia
/
/
/8J
3
The
Sea of
Bothnia
1o ,
\J
\., ..
, --
4• -.1 ,,
_ .
,....
-,
The Baltic
.,
(f•
i
(
rl/(/11
1
Fig.
1.
Recovery areas for post-smolt from Lule River (see text).
Dashed lines: Areas not included due to too few recoveries.
migrate more or less directly eastward to the Finnish coast, while a majority
of the migrating salmon simply follow the dominant surface current and travel
south towards the narrowest part of the Bay, and most of them migrate
directly into the Sea of Bothnia. However, part of the surface current
swings back towards the north along the Finnish coast, to turn later toward
the Swedish coast again. Similar circling migration with the current takes
place in the Sea of Bothnia, which is shown by a late second peak in
recoveries in area
4.
4
Table 1.
Recoveries of post-smolt, distributed over the areas by percentages
(see Fig. 1) on several post-stocking dates.
Sea of
Bothnia
/ Baltic
Sea
No,. of-Weeks -------krea -We Fig. 7-1 --)
1
2
3
009
after stocking
_
•
'
66,4
9.3
6,2
4.9
4,5
3,7
3,6
0.5
0,5
0 -2
2--4
4--13
6--8
8--10
10- -12
12 - -16
16--20
20--24
21-28
No• of recove-ries
861
46,5
38,2
2,9
2,4
4,1
2,4
1,8
1,8
170
12
38
16
8
6
4
8
8
11,1
14,8
22,2
22.2
3,7
7,4
18,5
50
27
14
5
6
7
8
9
10
B
.._
3,4
3,4
31,0
13,8
20,7
3,4
20,7
3,4
4,7
4,7
20,3
12,5
21,9
10,9
12,5
12,5
29
(31
2,4
12,7
31,0
20,6
15,9
7,9
6,3
2,4
0,8
126
1,6
14,8
18,0
36,1
3.3
11,5
4,9
6.6
3,3
61
1,5
11,2
44,0
20,9
10,4
3,0
5.2
1.5
2,2
134
9,9
12,1
33,3
31,9
5,7
1,4
2,1
2,8
3,6
7,1
7,1
1,8
8.9
19.6
30,4
21,4
56
0,7
141
- 1 Ô
.
1,4
1,4
3,5
23,2
53,5
10,9
142
1.
_ ,_,
18,8
36,5
37,6
25,9
85
No. of weeks after stocking
lean
3,13
l'iledia_ri
___ ._
_____1:5
Distance from
20
3,13
2,2
50
6,16
4,0
125
9,40
8,2
230
9,47 11,86
7,22
?8107 . _ 6,4
380
000
190
8,95
6,9
200
18,54 21,03 20,74
6,01
6,76
22,6_ _
22.5
5,7 . . 5,7 . . 23
279
310
520
( (300)
. (>700)
stockihK blace;
During the first winter, a number of post-smolt stay in the Sea of
Bothnia, where they can be caught both coastally and out at the sea.
The average migration speed is difficult to determine with certainty,
since the exact migration routes of the fish are never known.
The variation
is wide; some fish may reach areas 4 and 9 (a minimum of 300 km) in less than
two weeks. However, migration speed in the sea seems to be on an average
50 km/week.
The above results are based solely on reports of recoveries of
tagged fish.
assistance.
Thanks are due to fishermen and others who offered their kind
..
5
.
I
Fig. 2. Sketch of main migration routes of post-smolt from Lule River.