This paper not to be cited without prior reference to the author.

International Council for the

~Exploration of the Sea

C.M. 1982/M:35

Anadromous and Catadromous

Fish Committee

Returns of microtagged Atlantic Salmon (Salmo Salar)

of Kollafjörour stock to three different salmon

ranching facilities.

by

Arni !saksson

(Institute of Freshwater Fisheries, Reykjavik Iceland)

Abstract

Salmon ranching from release sites which are not physically

tied to a salmon farm i5 gradually building up in Iceland.

The paper deals with experimental releases at Sugandafjörour and

Laros salmon ranching ~ites, using smolts f~om Kollafjörour

Fish Farm, where control releases have been performed. Return­

rates at the Sugandafjörour site have normally been one-half of

those at Kollafjörour but releases at Laros in the one year

discussed were considerably higher than at the control site.

This indicates that salmon ranching at release sites can become

a viable industry.

Returns to Sugandafjörour from comparable smolt releases,

have had higher proportion of two-sea-winter fish than at

Kollafjörour, especially when one-year smolts are released.

It is suggested that this may be primarily due to delayed smolt

migration as a result of lower spring temperatures as weIl as

a colder sea in that area. An.inference.can· be.made to great

differences in grilse-salmon ratio between rivers in Northern and

Southern Iceland.

•

-2-

Resume

Le "ranching" de saumon ä. des 1ieux de re1äche" qui sont

situes loin de 1a ferme de saumon, se construit progressivement

en Is1ande.

Ce rapport decrit 1es re1äches experimentales ä des 1ieux

de ranching a Sugandafjörour et a Laros en uti1isant des smo1ts

de 1a ferme experimentale de Ko11afjörour ou des re1äches de

contrö1e ont ete performe. Le taux de retour a Sugandafjöröur

est norma1ement 1a moitie des taux ä Ko11afjörour mais 1e taux

de retour ä. Laros est considerab1ement plus grand qu 'au 1ieu de

contrö1e. Ces donnees indiquent que ranching de saumon ä. des

1ieux de re1äche peut devenir une industrie viab1e •

Les retours ä Sugandafjörour, de re1äches de smo1ts

cornparab1es, ont une proportion plus grande de poisson de deux

hivers en mer qu 'ä Ko11afjörour, particu1ierement quand on

re1äches des srno1ts d run an.

I1 est suggere que ce1ä peut etre principa1ernent due aU

retard de migration des srno1ts ,ce qui resu1te d run temperature

de printemps inferieur cornrne d 'une mer plus froide dans cette

region. Une grande difference dans 1e rapport de 1 9ri1se" a~

saumon entre dans 1es rivieres dans 1e Sud et 1e Nord de ~'Islande

peut etre referee.

,.------------ ---- ------------ --

-3-.

Introduction

---- ---- ----------- ---

•

Salmon ranching experiments from a site where the smolts

were also reared have been conducted at ~he Kollafjörour Experimental

Fish Farm for over 15 years. It is very important for further

development of salmon ranching in Iceland if. it could be carried

out in release sites distant from the fish farm where the

smolts are reared. Suitable rearing sites are limited and only

in a few instances located close to the sea.

Ranching experiments from arelease site .were tiied at Laros

(fig~) in the 1960's,apparently with limited Success, using

Carlin-tagged two-year smolts. In the early 1970's ranching

was started at Sugandafjörour on a small scale, using one- and

two-year smolts~ Most of the smolts were untagged and success

was difficult to estimate but returns seemed to vary at lot

between years and were generally low. In 1978 Nordic Council

granted some funds to conduct salmon ranching experiments in

Iceland. Initially experimental releases were only done at

Kollafjörour and Sugandafjörour as weIl as at more distant release

sites on the north and east coast of Iceland where proper

facilities for ranching were not available and harvest of

salmon had to be done by seining. In 1980 the Laros site was

added into the program with funding from the Economic Development

Institute which has provided funding for the whole program

since 1981.

The smolt releases at Kollafjörour, Laros and Sugandafjörour

(figure 1) provided an excellent opportunity to study the return­

rates of identical smolts to different ranching sites and

observe whether there would be a reduction in the rate of return

with increased distance from the horne area as weIl as any changes

that might occur in the grilse-salmon ratio and possible reasons

for those changes. The following report gives abrief account

of the ranching experiments from 1978 through 1980.

•

-4-

Methods

All smolts released in the experiments have been microtagged

and adipose clipped. The use of this tagging technique : has

madeit possible to try different release techniques and

release times and still get return rates into freshwater which

are fairly representative of those observed for untagged smolts.

As seen in table 1, the release methods have varied considerably

from one site to another depending on the possibilities available.

(figure 2). Releases at Laros have entirely been from floating pens,

some of wnich have been in brackish water. Sugandafjörour releases

have been both from release ponds and pens but Kollafjörour

releases only from release ponds, where salinity adaption has

been used as a control for freshwater release (Isaksson 1982).

All smolts released in these experiments have been adapted

and fed a dry diet for one month before release. The smolts

released at Kollafjörour were put into release ponds in the

middle of May and released after June 10th. Smolts released

at Laros have been trucked. to the site in oxygen inflated

plastic bags in early May and released in the middle of June.

Smolts have been transported in plastic bags by plane to the

Sugandafjörour site in late May and released in early July,'

2-3 weeks later than at the other sites. The reason for this is

a colder climate and lot of melting snow in the river used

for ranching.

The returning salmon are eithertaken from a fish trap

located at each site or seined below the structure when water

conditions discourage active migration. Microtagged salmon,

recognized by the adipose~clip are 'inspected with a magnetic

detector at Kollafjörour and a core removed from the snout of

the salmon. At the other sites a detector has not been

available and the microtag..has been removed fnom adipose clipped

salmon by cutting off apart of the snout up to the eyes and the

actual coring has been done at the Institute of Freshwater

Fisheries in Reykjavik.

•

-5-

Results

The returns of grilse and salmon in the ranching experiments

are shown in table 1. Both one and two year smolts were released

in the 1978 and 1980 experiment but only one-year smolts in the

1979 experiment.

1. The 1978 release experiment.

Total returns at Kollafjörour from the 1978 release experiment

were 5-8% or 150-200 kilograms per 1000 smolts released. The

percent returns of two-year smolts were considerably higher than

for one year smolts, but' the.latter group hadmuch higher returns

in the second year which reduced the difference in weight returns.

The returns of comparable smolts to Sugandafjörour release site

were 2,0-4,5% or 65-130 kilograms per 1000 released smolts. This

is approximately one-half of the return-rates observed in the area

of origin and rearing at Kollafjörour. All releases in this

experiment were from freshwater release ponds.

2. The 1979 release experiment.

The returns at Kollafjörour from the 1979 release experiment

were 7,5-9,0%, corresponding to approximately 200 kilograms per

1000 smolts released (table 1). High proportion of these returns

was as grilse. Comparable smolts at Sugandafjörour had retur~­

rates of 2,5-3,4% or ca 100 kilograms per 1000 smolts. On a per­

cent basis the returns are only one-third of those at Kollafjörour,

but on weight basis approximately one-half, due to higher returns

at Sugandafjörour in the second year.

Kollafjörour smolts were in 1979 partly released after

salinityadaption (Isaksson 1982). This treatment did not seem

to have any effect on return-rates compared to a conventional

freshwater release. Releases at Sugandafjörour, however, when

performed from floating pens instead of freshwater release ponds

increased percent returns of grilse and salmon by one-third and

had twice the return~rate on grilse basis only. This will be

further discussed in the section dealing with grilse-salmon ratios.

•

-6-

3. The 1980 release experiment.

Comparable releases at Kollafjörour and Sugandafjöröur

in 1980 involved both one- and two~year smolts but releases at

Laros and controls at Kollafjörour c6nsisted of one-year smolts

only (table 1).

Returns in the 1980 release experiment are only available

for grilse. At Kollafjörour the returns of one- and two-year

smolts were identical, close to 6% and releases from freshwater

release pond and those involving salinity adaption turned out

the same.

Grilse returns at Sugandafjörour were close to 3,5% and

thus little over one-half of those observed at Kollafjörour.

Differences between one- and two-year smolts were not obvious since

different release methods, gave contradictory.results.

One-year smolts showed almost .twice as high returns, when released

from a freshwater pond compared.to,afloating.. pen~bu~ two~year .sx,n0lts

ret':lrned better from. a floating pen' r~.lease.·~The t:roe~'meaning of

this can·not be evaluate~ before two-year sea'salmon have returned.

At Laros three release methods were tested. One involved

a months adaption period in a floating pen in freshwater, another.group got similar adaption in saltwater and the third group

got no adaption or feeding and was released directly into the

lake after transport (figure 2). It goes without saying that

all analysis of these data at this point is preliminary, since

two-year salmon returns are not available, but according to

the material available (table 1) the releases from floating

pens gave identical returns, close to 11%,unaffected by whether

they were.adapted in fresh- 'or salt-water. This was a little

surprising since the growth rate of the smolts adapted in

freshwater was considerably higher during the feeding period.

Second-year returns, however, might change the picture. Smolts

released without adaption had less than half the return-rate of

the adapted groups (4%), stressing the importance of adaption

and feeding before release.

It is interesting, that camparable smolts released at

Kollafjörour Fish Farm,where the smoltsoriqinated and were reare~

only had about 6% returns as grilse. It.is very encouraging

-7-

for those involved in salmon ranching at release sites in Ieeland

to see that return-rates can be realized which are considerably

better than those obtained in the home-stream' .50-100 kIn'away. It

is difficult to explain this difference but it seems likely that

this might, either be due to difference inbhe abundance of

predators feeding on~.the smolts after release or feeding conditions

for the smolts just after they enter the sea. It may also be

noted that the smolts leavingthe Laros area are entering relatively

open and deep sea but the smolts leaving Kollafjöröur have to

migrate out through a narrow passage, sometimes over a shallow

beach on the low tide.

4. Grilse~salmon ratio.

The 1978 and 1979 releases revealed.some interesting

differences in grilse-salmon ratio between Kollafjöröur and

Sugandafjöröur. As a rule in Ieeland there is a reduction in the

fraction of the PJpulation returning as grilse, as one goes further

north. It seems likely that these differences might be partly

due to colder ocean temperatures, later sea-ward migration:of

smolts and possibly slower growth in freshwater. Salmon stocks

with genetic tendencies towards high ocean age are found both

in Southern and' .'Northern Ieeland (Isaksson 1982) ~

In general there seem t6 be tendencies towards a higher

ratio of salmon vs. grilse at Sngandafjöröur compared to

Kollafjöröur in the 1978 and 1979 release experiments. Due to

relatively small numbers returning at Sugandafjöröur it seemed

4t very important to inspect how consistent these trends were in

individual replicates which then could be pooled in the final

analysis. Chi-square analysis of these data ;is shown in table 2.

Low Chi-square values in 1978-79 replicate comparisons indicate

that replicate returns are very similar and can be pooled for

the analysis of grilse-salmon ratio.

a) Difference between release sites.

In table 2 there are' showndifferences in grilse-salrnon

ratio between Kollafjöröur and Sugandafjöröur in the 1978 and

79 release experiments. Looking at releases of one year smolts

in both years it seems clear that comparable smolts have greater

tendencies to return as two-year salmon at Sugandafjöröur. Similar

trend is clear for two-year' smolts, although less pronounced.

-8-

The reasons for these differences might be colder climate at

Sugandafjöröur which results in later smolt-migration as weIl

as colder sea-temperatures than in the Kollafjöröur area.

b) Difference between smolt age-groups.

Similar comparison of the grilse-salmon ratio between one­

and two-year smolts released'at Kollafjöröur and Sugandafjör~ur

in 1978 (table 2) shows significantly,:: higher grilse ratio in

two-year smolts on both locations. ~his is in good,agreement.

with previous findings at the Kollafjöröur Fish Farm. (tsaksson 1982)

and has also been suggested to be true forhatchery smolts.in

Canada (Ritter and Carey 1980).

c) Difference between release methods.

At Kollafjöröur there was no difference in grilse-salmon

ratio which could be related to whether the smolts were released

in freshwater or adapted to sea water before release. At

Sugandafjöröur, however, there were marked differences in grilse­

salmon ratio depending on whether the smolts were released from a

release pond or a floating pen on a freshwater lagoon (figure 2).

Smolts released form the release pond which normally has colder

water temperatures during the adaption period had significantly

higher ratio of two-sea-winter fish returning than those released'

from the floating pen. One is tempted to relate this to delayed

smoltification and outmigration from the release pond due to

colder water temperatures in the pond. This conf6rms to the

hypothesis that higher-:proportion of two-sea-winter salmon

in most north-coast rivers in Iceland might be partly due to

late spring, delayed migration of smolts due to cold freshwater

temperatures as weIl as lower sea-temperatures than in Southwestern

Iceland.

Summary of results

1. Smolts of Kollafjöröur stock had 5~9% total returns when

released in .the horne area, which corresponds to ca 200 kg

per 1000 smolts released. Comparable smolts released at

Sugandafjöröur had 2-4% returns or ca 100 kg per 1000 released.- .Comparablereturns:.,tb the Laros 'ranching site were 11 %" on

grilse basis only I which ..corresponds to 250 kilograms of

salmon per 1000 released smolts.

-9-

2. Returns at Laros on gri1se basis were over 50% higher than

the returns to the home area at Ko11afjöröur. Returns at

Sugandafjöröur were on1y one-ha1f of those in the home-site.

3. Returns as gri1se,of smo1ts released directly into Laros

Lake without any adaption were only 4% compared to 11%

returns for smo1ts which were adapted and fed for a month

in floating pens.

4. One-year smo1ts had clear1y greater tendencies to return

as salmon rather than gri1se at Sugandafjöröur compared

to Kollafjöröur.

5. Compared to two-year smo1ts, one-year smo1ts return in

higher proportion after two years in the sea at Ko11afjöröur

and Sugandafjöröur.

References

!saksson Ärni 1982: "Returns of microtagged At1antic Sa1mon

(Salmo sa1ar) to the Kollafjöröur Experimental Fish Farm

in 1976-79 Tagging Experiments", lCES C.M.-1982/M:34.

Ritter J.A. and T.G. Carey 1980. "Sa1mon ranching in the Atlantic

Maritime Provinces of Canada",in "Sa l mon Ranching", ed.

John Thorpe, Academic press. p.109-130.

oI

SCALE

50km ·100kmI

S}:

Figure 1. Location of the Kollafjöröur Experimental Fish Farm and

the salmon ranching sites at Laros and Sugandafjöröur.

Arrows indicate the transport of smolts of Kollafjöröur

stock to the release sites where they were adapted and

fed for a month before release.

KOLLAFJöRDUR FISH FARM

LARDS SALMON RANCHING SITE

"" LAGOON

SAND BAR

SOGANDAFJÖRDUR SALMON RANCHING SITE

Eä1 =SEA-WATER EIl; FRESH-WATER

Figure 2. Diagram of the three salmon ranching sites

discussed in the paper,showing location ofrelease and recapture facilities.

Tab1e 1. Returns cf rnicrotagged sa1Jron to various salnon-ranehing sites in the 1978-80 release experiIrent

Year of Plaoe cf h:]e cf ~th:x1 cf NuITber l'Eight cf . Returns as grUse Returns as salnon Total Ret:ums 2)release release SITOlts release re1eased SITOlts (grans) Nllllber , N1.mter , , Kg/1CX:X> SITOlts

O1e-year Release pond 2002 20 82 4.1 23 1.2 5.3 153YollafjBröur

1978~year freshwater 1045 30 79 7.6 3 0.3 7.9 . 198

Q1e-year Release pond. 2cx:x> 20 19 1.0 17 0.8 1.8 65SUgandafjBröur

~}"ear freshwater 1039 30 38 3.7 8 0.8 4.5 131

Release pond 2162 30 ISO 7.0 42 1.9 8.9 230Yollafjöröur Q1e-year

freshwaterRelease pond

1979 saltwater adaptlan 2099 30 130 6.2 30 1.4 7.6 200

Release p::md 2012 30 22 1~1 30 1.5 2.6 90SÜgandafjBrÖIJI cne-year freshwaterFloating pen 2116 30 49 2.3 23 1.1 ·3.4 120freshwaterRelease pond 204L 25 130 6.4 Serond year returns not avai1ab1efreshwater

Q1e-year Release FOfIdYollafjöröur sa1twater adaptien 2023 25 125 6.2 " " "

Release pond 1955 35 120 6.1 " • "~year

freshwaterRelease pond

1980 a saltwater adaptien 1806 35 115 6.4 • " "Release pcnd 2004 25 75 3.7 • " •

cne-year freshwaterFloating pen -

SÜgandafjöröur freshwater 1986 25" 40 2.0 • " ". Release pond 925 35 24 2.6 • " "

~freshwaterFloaUng penfreshwater 935 35 36 3.8 • • ".Release pond 2cx:x> 20 112 5.6 • " "Yollafjöröur cne-year freshwater .Release pondsaltwater adaptien 2034 20 128 6.3 • " •

, Floating pen 3400 20 1) 372 10.9 .. " ".

1980 b IAr6s, cne-year freshwater

Floating pen 20 1)sa1twater 3100 337 10.9 • " "No adapticn 1200 20 48 4.0 • • •, ---

1) Stolt weights are at the t.i.Ire cf tagging, L!r6s SllOlts reached 30-40 grams after a m:nth in release pens•.

2) 'Ihe average weights cf grUse and salm::n are considered to be 2.4 kg and 5 kg ~vely.

Table 2. Chi-square analysis of returns after one and two years

in the sea to Kollafjöröur and Sugandafjöröur ranching

sites. Low chi-square values in replicate comparisons

at the .05 level indicate that replicates can be pooled

for further analysis.

1978 releases.' COMPARISON OF REPLlCATES.

SEA-AGE Stat-o YEAR 1 YEAR 2 YEAR 1stics.

Kollafjör6ur stock.u........

OBS. EXP. OBS. EXP. OBS EXP V =.2REl.EASED

l-year-srolts 1013 960 937.1 41 41.5 12 11.6 !x2-o.04Kollafjör6ur release 989 937 959.9 41 40.5 11 11.4 P(x).0.02

2-year-srolts 522 481 481.0 41 39.5 0 1.5 X.2.3.11

Kollafjör6ur release 523 482 482.0 38 39.5 3 1.5 !P(x)=0.791-year-srolts lCx:>4 984 986.9 10 9.0 10 8.0 1x2:1.24

SU:]andafj. release 995 981 918.1 '8 9.0 6 8.0 lP(x)=0.46

2-year-srolts 535 518 512.9 13 18.5 4 3.6 ~2=3.56

SUgarrlaIj. release 504 478 483.0 23 17.5 3 3.4 "!p(x)=0.83

82 2=9.17

18

36

79

l.OCAT10N

Kollafj.

Kollafj.

S.igandafj •

SUgarrlafj •

.1_97_8__r_el~e~a~se;s~.~~DIFFERENCEBETWEEN RELEASE LOCATIONS.

1 YEAR V=1

llafjör6ur stock

-yeax-SIlDlts

llafjörour stock

l-year srolts

18 2=8.45

36 (x)=1.00

82 2=11.21

79 (x)=l.oo

DIFFERENCE BETWEEN AGE-CLASSES OF SMOLTS.

1 YEAR 2 YEAR "=1

COMPARISON OF REPLICATES

1-year

2- ear

1- ear

2-year

SMOLT AGE

1978 releases.

1979 releases.- -

Kollafjör6ur stocknu...,.... o YEAR 1 YEAR 2 YEAR V=.2RELLASED

1-year-SIlDlts. 1076 985 980.4 69 74 7 22 2nQ 1K.2=1.02Kollafj . release pcnJ 1086 985 989.6 81 75.3 20 21.1 !Plx)=O.40l-year-sirolts. 1042 953 962.6 73 64.5 16 14.9 1x.2.::2.57Kollafj. sa1 twater FO" ~ 1057 986 976.4 57 65.5 14 15.1 lP(x)=O.72

l-year-SIlDlts. 978 953 952.8 12 10.4 13 'u.8 tx.2=0.92

SUgandafj . release fOI' ~ lCOJ 974 974.2 9 10.6 17 15.2 IP (x)=O. 37

1-year-SIlDlts 1040 1005 11002.6 20 23.5 15 14.0 1X.2:1.20

!SUgandafj , floatin;J pE r 1043 1003 Q)5.4 27 ~.5 13 14.0 'IP (x)=O. 45

1979 releases. DIFFERENCE BETWEEN RELEASE LOCATIONS.

llafjör6ur stock

l-year-SIlDltsFDIW'.

.;;.;.....;..:;....;;,.,......--. DIFFERENCE BETWEEN RELEASE METHODS.1 YEAR 2 YEAR

llafjör6ur release "'~'::'::'';::~~_--I~_~---,o.:::::.'--i~15:::2:.:.,-=-7-+--,4:.::2'--+-,,3:.::9;.;:.•.::;.3-r1- ear-SIlDlts 27.3 3D 32.7

.gandafj. release nd. 27.5 30 23.51-year-SIlDlts 47 ta.5 28 34.5