Conservation of landlocked Atlantic The thesis is based on ...kau.diva-portal.org/smash/get/diva2:1291171/FULLTEXT02.pdf · Atlantlax är beroende av att kunna vandra mellan lek-

In this thesis, I report the results from radio-telemetry studies where the behavior and success of migrating Atlantic salmon (Salmo salar) spawners has been investigated in a regulated river. I have also studied the function of using hatchery fish as supportive breeders and evaluated the upstream passage performance by Atlantic salmon and brown trout (Salmo trutta) at fishways in the River Klarälven, Sweden and Gudbrandslågen, Norway.

I identified three problems associated with management in a regulated river, namely the high incidence of fallbacks among the early migrating salmon, the negative effects of high river flow and prior experience on fishway efficacy and that the use of hatchery-reared fish as supportive breeders have little, if any, positive effect on reproduction.

Finally, I examined the competitive interactions that may occur when reintroducing Atlantic salmon to areas with native grayling (Thymallus thymallus) and brown trout.

Conservation and management of migratory salmonids requires an understanding of ecology and life-histories. The results presented in this thesis originate from concerns regarding salmonid conservation in regulated rivers, with a focus on the difficulties migratory spawners may face in these altered environments. The results of my research can be applied to other regulated systems, particularly those with trap and transport solutions.

Conservation of landlocked Atlantic salm

on in a regulated riverAnna H

agelin

Print & layout University Printing Office, Karlstad 2019

Cover photoIngemar Alenäs

ISBN 978-91-7867-002-4 (print)ISBN 978-91-7867-007-9 (pdf)

Anna Hagelin received her M.Sc. in ecology from Umeå University, which included the M.Sc. thesis “The influence of land exploitation in tropical environments on the diversity of benthic invertebrates in streams”. She started her Ph.D. project at Karlstad University in 2011. Since 2016, she has combined her Ph.D. studies with salmonid conservation work at the County administrative boards of Gävleborg and Västra Götaland.

Behaviour of migratory spawners and juveniles

Anna Hagelin

Conservation of landlocked Atlantic salmon in a regulated river


List of papers

The thesis is based on the following papers.

I Hagelin, A., Calles, O., Greenberg, L., Piccolo, J., & Bergman, E. (2016). Spawning migration of wild and supplementary stocked landlocked Atlantic salmon (Salmo salar). River Research and Applications, 32(3), 383-389.

II Hagelin, A., Calles, O., Greenberg, L., Nyqvist, D., & Bergman, E. (2016). The Migratory Behaviour and Fallback Rate of Landlocked Atlantic Salmon (Salmo salar) in a Regulated River: does Timing Matter?. River Research and Applications, 32(6), 1402-1409.

III Hagelin, A., Museth, J., Greenberg, L., Kraabøl, M., Calles, O., & Bergman, E. (2019). Upstream fishway performance by Atlantic salmon (Salmo salar) and brown trout (Salmo trutta) spawners at complex hydropower dams – is prior experience a success criterion? Manuscript.

IV Hagelin, A., & Bergman, E. (2019). Reintroducing Atlantic salmon to once native areas: Competition between Atlantic salmon (Salmo salar), brown trout (Salmo trutta) and grayling (Thymallus thymallus). Manuscript.

Conservation of landlocked Atlantic salmon in a regulated riverBehaviour of migratory spawners and juveniles

Anna Hagelin

Anna H

agelin | Conservation of landlocked A

tlantic salmon in a regulated river | 2019:7






DOCTORAL THESIS | Karlstad University Studies | 2019:7

Faculty of Health, Science and Technology

Biology


ISSN 1403-8099

ISBN 978-91-7867-007-9 (pdf)

ISBN 978-91-7867-002-4 (print)



Anna Hagelin

print: Universitetstryckeriet, Karlstad 2018

Distribution:Karlstad University Faculty of Health, Science and TechnologyDepartment of Environmental and Life Sciences (from 2013)SE-651 88 Karlstad, Sweden+46 54 700 10 00

© The author

ISSN 1403-8099

urn:nbn:se:kau:diva-71333

Karlstad University Studies | 2019:7

DOCTORAL THESIS

Anna Hagelin

Conservation of landlocked Atlantic salmon in a regulated river - Behaviour of migratory spawners and juveniles

WWW.KAU.SE

ISBN 978-91-7867-007-9 (pdf)

ISBN 978-91-7867-002-4 (print)

1

In loving memory of a special man I used to call dad

2

Abstract

Hydropower dams represent one of the major threats to river ecosystems

today. The dams block migratory routes and disrupt connectivity in many

rivers, which is problematic for migratory fish species. Different types of

fish passage solutions have often been applied to enable migration, but

with varying success. In areas with multiple hydropower stations,

fishways may be insufficient due to cumulative delays in fish migration

and low total passage efficiency. Trap-and-transport solutions may then

be an alternative to fish passage solutions at each obstacle, as a strategy

to compensate for lost river connectivity. Stocking of hatchery fish is

another mitigating measure often used to compensate for reduced yields

in fisheries, but also as supportive breeders in declining populations. In this thesis, I report the results from radio-telemetry studies where the

behavior (fall-back rate and presumed migration success) of migrating

Atlantic salmon (Salmo salar) spawners has been investigated in the

regulated river Klarälven. I also studied the function and success of using

hatchery fish as supportive breeders and if there are any effects of

migratory timing on migratory success. Further, I evaluated upstream

passage performance by Atlantic salmon and brown trout (Salmo trutta)

at fishways in the rivers Klarälven, Sweden and Gudbrandslågen, Norway.

The goal was to determine if prior fishway experience had an effect on

passage success. I identified three problems associated with the current

management of the river Klarälven stock, namely the high incidence of

fallbacks among the early migrating salmon, the negative effects of high

river flow and prior experience on fishway efficacy and that the use of

hatchery-reared fish as supportive breeders have little, if any, positive

effect on reproduction. Finally, I examined the competitive interactions

that may occur when reintroducing Atlantic salmon to areas with native

grayling (Thymallus thymallus) and brown trout. I found no evidence of

3

Atlantic salmon affecting grayling or brown trout. Instead, Atlantic

salmon were dominated by the other two species, which indicates that

reintroduction of salmon may not be successful, especially if habitat

diversity is constrained.

Conservation and management of migratory salmonids requires an

understanding of their ecology and life-histories. In the regulated river

Klarälven, with 11 hydropower dams, populations of landlocked Atlantic

salmon and migratory brown trout have declined due to river

exploitation. The results presented in this thesis originate from concerns

regarding salmonid conservation in regulated rivers, with a focus on the

difficulties migratory spawners may face in these altered environments. I

emphasize the need for holistic management to ensure viable populations

in the future. The results of my research can be applied to other regulated

systems, particularly those with trap and transport solutions.

4

Svensk sammanfattning

Vattenkraft är en viktig förnyelsebar energikälla men den har samtidigt

en starkt negativ påverkan på många av de organismer som lever i

älvarna. Vattenkraften utgör idag ett av de största hoten mot älvarnas

ekologi. Dess dammar fragmenterar vattendragen och blockerar fiskars

vandringsvägar, vilket skapar problem för vandrande fiskarter som lax.

Atlantlax är beroende av att kunna vandra mellan lek- och

uppväxtområden i älven samt mellan älv och födosöksområden i havet.

För att ändå möjliggöra denna vandring i utbyggda älvar har ofta olika

typer av fiskpassagelösningar implementerats vid kraftverken, men med

varierande resultat. I älvar med många kraftverk är ofta

passagelösningar, även de funktionsdugliga, otillräckligt då inte alla

fiskar lyckas passera och de som gör det ofta blir fördröjda. I dessa fall

kan fångst och transport vara ett alternativ. Fisken fångas då i en

fällanordning för att sedan transporteras förbi kraftverken och släppas ut

längre uppströms. Ett annat sätt att kompensera för minskad

fiskproduktion är att sätta ut odlad fisk för att underhålla ett fiskeuttag

samt stärka den vilda populationen. I denna avhandling redovisas studier på lekvandrande lax där jag

analyserat rörelsemönster och beteenden under lekvandringen. Jag har

tittat på hur tidpunkten för vandringen påverkat antalet laxar som ”faller

tillbaka” dvs återvänder nedströms innan lek. Jag har också studerat hur

odlade fiskar som transporterats till lekområden, för att stärka den vilda

populationen, förflyttat sig och om de antas ha påverkat den vilda

populationen på ett positivt sätt. Vidare har jag också undersökt hur

lekfisk, både lax och öring, beter sig nedanför ett kraftverk, t.ex. hur flödet

påverkar deras rörelsemönster och hur fångsteffektiviteten varierar över

tid. Jag har också tittat på hur erfarenhet påverkar lax och örings vilja att

försöka passera en fiskväg en andra gång.

5

Jag har identifierat tre områden där hantering av lax och öring påverkar

den vilda populationen av laxfisk I Klarälven. Det första är den relativt

stora mängd av tidigt vandrande individer som faller tillbaka efter

utsättning. Jag har också pekat på bristerna i fiskvägens funktion, där

flödesförändringar och högt spill ger betydligt lägre effektivitet. Jag fann

också att både lax och öring verkar undvika fiskvägen om de har

erfarenhet av den sen tidigare, en kunskap som är ytterst viktig då många

studier på fiskvägars effektivitet använder just erfarna fiskar på grund av

att det är det enklaste sättet att fånga försöksdjur.

Jag har även undersökt interaktioner mellan lax, öring och harr när dessa

förekommer tillsammans med artfränder och i kombination med de

andra två arterna. Detta för att förutsäga vad effekterna kan tänkas bli om

man återintroducerar lax till områden där de tidigare funnits men som nu

endast hyser stationär öring och harr. Resultaten visar att lax troligen inte

kommer att ha en negativ påverkan på harr och öring i områden där de

samexisterar, men att lax kan komma att påverkas negativt av de andra

två, ett scenario som kan bli särskilt betydande i habitat som saknar

komplexitet och möjlighet till uppdelning mellan arterna.

Bevarande och förvaltning av vandrande laxfiskar kräver kunskap om

deras ekologi och livshistorier. I Klarälven/Trysilelva/Femundselva finns

elva kraftverk vilka tillsammans med flottledsrensning och tidigare

nyttjande av älven gjort att de unika, sjövandrande stammarna av lax och

öring i Vänern idag är hotade. Arbetet i denna avhandling bottnar i ett

intresse av bevarande av laxfiskar i reglerade vattendrag med fokus på

lekvandrande fisk. Jag vill lyfta fram behovet av ett helhetsperspektiv

inom förvaltning och bevarande av dessa arter, så att vi kan säkra

populationerna för framtiden. Resultaten i denna avhandling kan

appliceras på andra reglerade vattendrag.

6

Contents

Abstract .................................................................................................................................. 2 Svensk sammanfattning ............................................................................................... 4 List of papers ...................................................................................................................... 7 Contributions ...................................................................................................................... 8 Introduction ........................................................................................................................ 9

Hydropower and migration ....................................................................................... 9 Migration: behaviour and life history ................................................................. 10

Conservation: population restoration in regulated rivers ........................ 13 Restoring connectivity ......................................................................................... 14

Supportive breeding and stocking ................................................................. 15 Reintroductions in general ................................................................................ 15 Reintroductions: competition among juveniles ....................................... 17 Objectives .......................................................................................................................... 19 Material and Methods ................................................................................................. 20 Study areas ...................................................................................................................... 20 Telemetry techniques ................................................................................................. 22 Tracking data .................................................................................................................. 22 Results ................................................................................................................................. 25

Paper I ............................................................................................................................... 26 Paper II ............................................................................................................................. 27 Paper III ............................................................................................................................ 29 Paper IV ............................................................................................................................ 31

Discussion .......................................................................................................................... 33 Acknowledgements ...................................................................................................... 41 References ......................................................................................................................... 41 Appended papers ....................................................................................................... I-IV

7

List of papers

The thesis is based on the following papers, which are referred to by

their Roman numerals. Papers I and II are reprinted with the permission

from John Wiley and Sons.

I Hagelin, A., Calles, O., Greenberg, L., Piccolo, J., & Bergman, E.

(2016). Spawning migration of wild and supplementary

stocked landlocked Atlantic salmon (Salmo salar). River

Research and Applications, 32(3), 383-389.

II Hagelin, A., Calles, O., Greenberg, L., Nyqvist, D., & Bergman,

E. (2016). The Migratory Behaviour and Fallback Rate of

Landlocked Atlantic Salmon (Salmo salar) in a Regulated

River: does Timing Matter?. River Research and

Applications, 32(6), 1402-1409.

III Hagelin, A., Museth, J., Greenberg, L., Kraabøl, M., Calles, O., &

Bergman, E. (2019). Upstream fishway performance by

Atlantic salmon (Salmo salar) and brown trout (Salmo

trutta) spawners at complex hydropower dams – is prior

experience a success criterion? Manuscript.

IV Hagelin, A., & Bergman, E. (2019). Reintroducing Atlantic

salmon to once native areas: Competition between Atlantic

salmon, brown trout and grayling. Manuscript.

8

Contribution

Paper I-II

AH contributed to study design, data collection, data analysis,

conclusions and writing of both papers. The basic idea was given by EB,

JP, LG and OC. OC helped plan the telemetry layout. EB, JP, LG and OC all

contributed with input on study design conclusions and manuscript. EB

and LG helped with the statistical analysis. DN helped with data

collection and input on manuscript in paper II.

Paper III

AH and MK designed the study with input from EB and JM. AH

contributed to data collection, data analysis, conclusions and writing of

the paper. The basic idea was given by EB and LG. OC contributed to the

telemetry layout. JM contributed to the statistical and data analysis. All

coauthors contributed to the manuscript.

Paper IV

AH contributed to the experimental study design, data collection, data

analysis, conclusions and writing of the paper. JA provided input on

thestatistical analyses. EB contributed with input on statistical analyses,

conclusions and manuscript. LG gave input on manuscript. The basic

idea was given by EB and LG.

Anna Hagelin (AH), Daniel Nyqvist (DN), Eva Bergman (EB), Jari Appelgren (JA), John

Piccolo (JP), Jon Museth (JM), Larry Greenberg (LG), Morten Kraabøl (MK), Olle Calles

(OC)

9

Introduction

Hydropower and migration

Hydropower is an important renewable energy source, which has been

established in many rivers worldwide and stands for 40% of Sweden’s

energy production (Rudberg et al., 2014, SCB, 2017). Our limited ability

to store energy increases our demand of energy production that can be

regulated, and will continue to do so as societies energy consumption

continues to increase. Due to the regulation ability, hydropower are

therefore highly requested in today’s society. Despite hydropower’s

obvious benefit for society as a carbon-free energy source, the dams

constructed for hydropower have a very strong negative impact on river

connectivity, which is especially crucial to salmonids and other migrating

fishes. Anadromous species like Atlantic salmon (Salmo salar) and brown

trout (Salmo trutta) depend on river connectivity since they need to be

able to migrate downstream to their feeding grounds as well as upstream

to their spawning grounds (Calles & Greenberg, 2009). Thus, there is a

major conflict between the society’s strive to develop sustainable fossil

free energy sources and the need to create a sustainable environment for

our wild-life. The effects of hydropower plants are manifold and affect the survival,

growth, migration and reproduction of salmonids and other fishes (Aas et

al., 2011). Even when fish passage solutions have been implemented,

dams may still reduce passage, and moreover, delay migrating salmon

(Thorstad et al., 2008 and references within). If the delay is extensive or

if there are multiple obstacles present that the fish need to pass, there is

a possibility that they will deplete most of their energy reserves before

spawning has even started (Gowans 2003; Brown et al., 2006; Mesa &

10

Magie, 2006). Salmon may also arrive too late to the spawning grounds

and miss spawning, which is synchronized to both the environment and

to other spawners (Nordeng, 1977; Heggberget, 1988). Increased energy

consumption during upstream migration may also reduce the survival of

post-spawners, thus affecting lifetime reproductive fitness (Stevens &

Black, 1966; Peake, 2004, Nyqvist et al., 2016). Today, hydropower dams

affect more than half of the world’s large river systems (Nilsson, 2005;

Zarfl et al., 2015). Not surprisingly, dams, through their effects on the

migration of fish to spawning or feeding grounds, are considered one of

the greatest threats to freshwater fish diversity worldwide (Liermann et

al., 2012).

Migration: behaviour and life history

Migration is a behavioural strategy by which many animals increase their

opportunities to gain resources and it is defined as; movements of a large

part of the population at specific, predictable times in the animal’s

lifecycle (Lucas & Baras, 2001). The migrations are often cyclic

movements between feeding and reproductive areas that allow the

individuals to increase their fitness by moving between areas at a specific

life stage. Migrations in water may also be vertical or between areas with

different temperatures, water chemistry and velocities (Lucas & Baras,

2001). Seasonal migrations make fish species such as Atlantic salmon

sensitive to exploitation, as they, apart from being hindered or delayed

during their migration, became an easy target for commercial and

recreational fishing (Thorstad et al., 2008 and references within).

Most Atlantic salmon are anadromous, i.e., they migrate from freshwater

to the sea for increased growth (Fig. 1). After 1-4 years at sea they reach

maturity and return to their natal river to spawn (Jonsson & Jonsson,

11

2011a). The migrations between the different habitats are linked to both

high energy costs and high mortality rates, and they are often dependent

on certain environmental conditions such as river flow, temperature and

turbidity to be successful (Fleming, 1996; Quinn et al., 1997; Verspoor et

al., 2005).

Figure 1. Atlantic salmon life cycle. Illustration courtesy of the Atlantic Salmon Trust and

Robin Ade.

Most Atlantic salmon home to their natal river with high precision but a

small number of fish may stray to other rivers (Stabell, 1984; Heggberget

et al., 1993; Jonsson et al., 2003). If the river is altered or blocked in some

way the salmon may give up on reaching the natal spawning areas and

spawn in the lower reaches instead or leave the river to search for an

alternative spawning site in another river (Solomon et al. 1999). Homing

behaviour results in local adaptations through natural selection, and

12

salmon populations in different rivers and within rivers may differ both

ecologically and genetically (Klemetsen et al., 2003; Verspoor et al., 2005;

Primmer et al., 2006). The strong imprinting mechanism to the natal site

and sequential memorization of their downstream migration makes this

high precision homing possible (Hansen et al., 1993; Keefer & Caudill,

2014). Recent research has demonstrated the ecological importance of

fine-scale local adaptation of migration timing (Aykanat et al., 2015) and

such adaptions may be particularly susceptible to disruption through

river regulation. By altering temporal and spatial aspects of salmon

migration, such as causing delays or blocking access to spawning sites,

river regulation may influence the structure of locally-adapted

populations negatively (Garcia De Leaniz et al., 2007).

Migration occurs at a time that maximizes the fish´s fitness, and spawning

migrations may begin several months before the fish actually spawn

(Jonsson & Jonsson, 2011b). This variation in migration time between

populations is thought to be a response to local environmental conditions

that the returning adults must meet (Taylor, 1991; Quinn & Adams, 1996;

Quinn et al., 2000). Long distance migrations or migrations into

tributaries or past demanding passages may require an early migration

(Burger et al., 1985; Klemetsen et al., 2003; Östergren et al., 2011), but

there are also early migrations where no such relationships have been

found (Thorstad et al., 1998). Variation in migration timing may also vary

between years and within populations. Why some individuals from the

same population migrate months before spawning, whereas others move

upstream just in time for spawning is debated (see Thorstad et al., 2008)

but no general conclusion has been reached. To migrate early in the

season is expected to be costly to the individual since the fish stop eating

during migration, which could lead to reduced growth and reduced

reproductive success (Fleming, 1996). On the other hand, an early arrival

13

at the breeding ground could give an advantage due to the prior residency

effect, which may allow the fish to acquire a prime spawning position and

by that increased breeding success. Differences in run timing may play a

fundamental role in the evolutionary trajectory of a population and

knowledge about migrations patterns can be a significant tool in salmon

conservation.

Conservation: population restoration in regulated rivers

Like many migratory salmonid species, the Atlantic salmon has been

eliminated from much of their historic range, and populations of the

species are in decline worldwide (Parrish et al., 1998; Limburg &

Waldman, 2009). In addition to hydropower development, human

activities such as habitat degradation, pollution, changes in water quality,

exploitation, fish farming and climate change are all anthropogenic

factors that affect salmon populations negatively (Jonsson & Jonsson,

2011c). Although research and management of commercially-important

salmonids have moved from a focus on stock enhancements and

maximizing yields towards a more conservation- and biodiversity-

oriented approach, there is still a need for developing mitigating

measures and solutions due to human impacts (Aas, 2011). The complex

life cycle and local adaption of migratory salmonids demands a life-

history based approach to research and management if conservation and

restoration measures are to succeed (Piccolo et al., 2012). Mitigation

measures for Atlantic salmon in regulated rivers include habitat

restoration, restoring connectivity through fishways or transporting fish,

supportive breeding, and reintroductions.

14

Restoring connectivity

The construction of dams without fish passage facilities has eliminated

many salmon populations and is listed as the main cause of salmon

extirpations (MacCrimmon & Gots, 1979). Different types of fishways

have been used to minimize the negative effects of habitat fragmentation

caused by hydropower dams many (Larinier, 2001). Fishways placed at

hydropower plants may be limited in their ability to attract fish because

the flow from the fishways is relatively small compared to the water

released from turbines and/or spill gates, i.e., low attraction flow. It is

therefore of absolute importance that fishway entrances are designed

and positioned so that fish are able to enter and pass without too much

delay and use of energy (Clay & Eng, 2017; Calles & Greenberg, 2009;

Larinier 1998). Even properly designed fishways will vary in their

effectiveness, depending on individual differences in swimming

behaviour, size and physiological condition of the fish (Saltveit, 1993;

Hasler et al., 2009; Pon et al., 2009). Many fishways do not function well

and some may hinder or delay migration of target species (Boggs et al.,

2004; Keefer et al., 2004). In some of these cases, and in particular in

rivers with multiple dams, trap and trucking methods are used as an

alternative to solve passage problems (Roscoe & Hinch 2010). Trap and

trucking involve operating a trap system, followed by transportation of

fish in tanks upstream past the dams. The fish are then released back into

the river to spawn (Clay & Eng, 2017). The total handling and

transportation of the fish is a very stressful procedure, and some will fail

to spawn after release (Keefer et al., 2010; Murauskas et al., 2014; Hagelin

et al., 2016).

15

Supportive breeding and stocking

Supportive breeding is a common way to restore and enhance declining

populations in regulated rivers where dams isolate fish from upstream

spawning grounds. Stocking has often been used as a management tool

when yields, for some reason, decline but can also be used to rehabilitate

and enhance existing populations. Reared fish are mainly released for two

reasons: 1) To support and restore wild populations for conservation

purposes 2) to compensate for lost fishing opportunities and reduced

yields. Supportive stocking may be functional in rivers that have no

natural reproduction, where reproduction is below carrying capacity or

in areas without spawning grounds but that have intact rearing

environments (Jonsson & Jonsson, 2011c). It is worth mentioning that the

effects of using hatchery-reared individuals to support wild populations

are not fully understood, and there is a lack of evidence showing that

increasing populations with reared salmon has a long-term positive effect

on wild population productivity (Fraser, 2008; Araki et al., 2009).

Introduction of diseases, competition for resources, and genetic changes

in the populations are all risks associated with the release of hatchery-

reared individuals into wild populations. Straying is yet another factor

that can cause negative effects from stocking as hatchery-reared

salmonids stray more that wild conspecifics (Schroeder et al., 2001;

Keefer & Caudill, 2014), which may affect populations in other rivers as

well.

Reintroductions in general

Nearly all salmonid species have endemic populations that have recently

gone extinct or are endangered (Jonsson et al., 1999; Powles et al., 2000;

Behnke & McGuane, 2014). As the number of local extinctions in

16

salmonids increases, reintroduction of salmon becomes an increasingly

important tool in conservation. Reintroductions may be used to

reestablish populations into historical ranges but also to support

populations that are below carrying capacity (Harig & Fausch, 2002;

Jonsson & Jonsson, 2011c; Anderson et al., 2014). The reintroductions

might involve the release of either captive-bred or wild-caught

individuals or eggs. One of the major challenges confronting restoration

efforts is that introduced individuals often have evolved in a different

environment than their wild born conspecifics. Local adaptation is strong

in salmon and individuals introduced to the new location may initially be

maladapted (Taylor, 1991). Populations are also often reintroduced at

relatively low densities and therefore more vulnerable to common,

generalist predators (Gascoigne & Lipcius, 2004; Sinclair et al., 2008).

This vulnerability to predation may be exacerbated by the reintroduced

population’s lack of experience or adaptation to local predators (Griffin

et al., 2000). There have been many unsuccessful attempts to establish

Atlantic salmon outside its native range (Waknitz et al., 2003), and so

have attempts to reestablish Atlantic salmon populations in native

habitats as well (Emery, 1985). In the early 1900s, the failure of many

introductions of Atlantic salmon to produce self-sustaining populations

might have been partly due to the rather primitive hatchery methods

used. However, the same primitive methods have often proved to be

successful in establishing brown trout, brook trout, and rainbow trout to

both native and non-native areas, perhaps indicating that Atlantic salmon

are especially difficult to introduce? Successful reintroductions are

dependent upon a variety of factors, such as the number and frequency of

releases, removal of the original problem responsible for the population

loss and the absence of ecologically competing exotic species (Fischer &

Lindenmayer; Kleiman et al., 1994).

17

Reintroductions: competition among juveniles

The early life stages are the most sensitive periods of the Atlantic salmon

life-cycle and the dominant mechanisms regulating the survival and

cohort strengths of these juvenile salmon are competition, predation and

parasitism (Scott et al., 2005; Nislow et al., 2010), where competition

have received most attention within research. Competition is defined as

“the negative effect which one organism has upon another by consuming,

or controlling access to, a resource that is limited in availability” (Tilman,

1982). Therefore, fitness will decrease because competitors will reduce

available resources needed for survival, growth and reproduction

(Blanchet et al., 2006). Competition may act directly between interfering

individuals or by exploitation of available resources (Wootton, 1998;

Begon et al., 2006). Juvenile Atlantic salmon compete both amongst

themselves, intraspecific competition, and with other species,

interspecific competition, for resources as food, shelter and space. The

intensity of these competitive interactions usually increase with

competitor density, i.e. density dependent competition (Cole & Noakes,

1980; Blanchet et al., 2006; Kaspersson et al., 2010; Wipf & Barnes, 2011).

Habitat complexity may however reduce these competitive interactions

by creating shelter, increase food abundance and preventing fish from

seeing each other (Sundbaum & Näslund, 1998; Imre et al., 2002;

Gustafsson et al., 2012; Enefalk & Bergman, 2016). Juvenile salmon are

sit-and-wait foragers and feed mainly on drifting invertebrates, and since

the amount of drifting food increases with current velocity, certain

locations will be more desirable, and thereby worth defending.

In Scandinavia, Atlantic salmon commonly co-occur with two other

salmonids, brown trout and grayling (Degerman & Sers, 1992). As

juveniles, these three species depend largely on invertebrates, both

terrestrial and aquatic, as prey, which creates conditions for resource

18

competition. Atlantic salmon are often associated with riffle habitats and

fast moving water in the main stem, whereas brown trout and grayling

use more slow flowing areas and tributaries (Northcote, 1995; Heggenes

et al., 1999). This habitat segregation may be a response to the occurrence

of the other competing species, i.e. interactive segregation, or it may be

an adaptation to local conditions, i.e. selective segregation. Studies have

shown that Atlantic salmon prefer slower pools as fry and parr but may

move when subjected to competition (Blanchet et al., 2006). Size and

aggressiveness affect dominance in juvenile stream-dwelling salmonids

(Adams et al. 1998, Cutts et al. 2001) and as trout often dominate other

salmonids they can restrict habitat use of the less aggressive salmon

(Gibson 1993, Heggenes et al. 1999). Habitat selection and river

movement is less known for grayling (Nykänen 2004), which differ some

from salmon and trout in life history and behaviour as they are spring-

spawning. Although grayling are also drift feeders, they are however

more opportunistic in their feeding and rely more on benthos than

salmon and trout (Northcode 1995, Jonsson and Jonsson 2011a).

19

Objectives

This thesis addresses the specific issues of the migratory behaviour of

upstream-migrating adult Atlantic salmon spawners in a large regulated

river, with an additional focus on inter- and intra-specific competition

among juveniles of Atlantic salmon and conspecifics in anticipation of

reestablishment of salmon populations. The research focus lies on wild

salmon migration and spawning migration behaviour in the heavily

regulated River Klarälven, Sweden, in the perspective of how well todays

and future management efforts are working. Specifically, the objectives of

this thesis are: (1) to compare the migratory behaviour, presumed

success and fallback frequency of wild and stocked hatchery salmon

spawners in the River Klarälven (Paper I), (2) to determine how the

timing of spawning migration affects the migratory behaviour and

presumed reproductive success, as inferred from holding behaviour, in

wild Atlantic salmon spawners in the River Klarälven (Paper II.), and (3)

to investigate how Atlantic salmon in the River Klarälven and brown trout

in the River Gudbrandslågen move below a hydropower plant in relation

to discharge and if prior experience of a fishway affects subsequent

fishway efficacy (Paper III). Today there are no spawners transported to

the native areas in the Norwegian portion of Klarälven, but there is an

interest to try to change that and reintroduce the salmon to these

upstream located spawning areas. Hence, my fourth study investigates

the potential competitive interactions salmon could face if reintroduced

to areas where they have been extirpated. Thus, paper IV considers

competitive interactions among juvenile Atlantic salmon, brown trout

and grayling in laboratory stream flumes.

20

Summary of material and methods

Study areas

River Klarälven (Papers I, II and III) stretches 460 km, originating in

Sweden, and then flowing into Norway and back into Sweden before

emptying into Sweden’s largest lake, Lake Vänern (Fig. 2). It has a mean

annual discharge at the outlet of 162.5 m3/s, with a mean annual high of

690 m3/s (www.smhi.se). The River Klarälven has been dammed for

hydropower purposes since the beginning of the 1900s, but has also been

affected by other human activities, as log driving and millponds, even

earlier (Ros 1981, Piccolo et. al., 2012). Prior to these activities, the river

supported a large number of landlocked, large-bodied Atlantic salmon

and brown trout. Historically, the main spawning areas are believed to

have been situated in the Norwegian part of the river, but today all salmon

spawn in Sweden, and most are believed to spawn between the eighth

and ninth hydropower station upstream of Lake Vänern (Gustafsson et al,

2015) (Fig. 2).

All power plants on the Swedish side lack functioning fishways and

constitute absolute barriers for upstream migrating fish. The upstream

migrating salmonid spawners, hatchery reared and wild, are instead

caught in a trap at the lowermost power plant in Forshaga, 25 river km

upstream of Lake Vänern, and then transported upstream. Spawners have

been transported by truck past the power plants since the 1930s, and to

compensate the lake fishery, large-scale stocking of hatchery-reared

Atlantic salmon and brown trout has been conducted in the river since

the 1970s (Piccolo et al., 2012). Caught salmon and trout are transported

past eight power plants, and released into the river 16 km above the

eighth power plant (Fig. 2). The trap in Forshaga is closed when the water

21

temperatures exceed 18o C (late July/early August) and during high

discharge events. This situation, when the trap closes for several weeks

during summer, is typical for the river and is the reason why we in paper

II looked at the behaviour of early and late running spawners. In this way,

we could make a rudimentary evaluation of the potential effect of run

time on reproductive success.

Figure 2. The study area in west-central Sweden. Hydropower stations are marked by

solid black bars over the river and logger stations by dotted lines. The circle indicates

the location of the main spawning area.

For paper III we not only studied the behaviour and passage success of

salmon in the River Klarälven, but also for brown trout in the River

Gudbrandslågen, Norway. The River Gudbrandsdalslågen is the major

spawning and nursery river for the large-bodied brown trout in Lake

Mjøsa. The River Gudbrandsdalslågen has a mean annual discharge of 248

m3/s and a mean annual high of 630 m3/s. A 78 km river section is

22

available for ascending trout, of which 62 km is situated upstream of the

intake dam at Hunderfossen power plant.

Telemetry techniques

In papers I, II and III we used external radio transmitters (ATS F2120).

The transmitters, measuring 21× 52× 11mm, were attached below the

dorsal fin, placed flat against the fish’s body. To follow the salmon, we

used both stationary loggers and manual tracking. In papers I and II we

placed automatic data loggers, model R4500S (ATS), along the river at

strategic places (Fig. 2) and in Paper III we had loggers placed around

the power plant to detect movements in the area downstream of the dam.

One data logger was placed near the turbine outlet, one at the spill gate

closest to the fish trap and one at the spill gate furthest away from the fish

trap. At the Hunderfossen dam in Gudbrandslågen we only used manual

tracking to follow the trout tagged with radio transmitters and additional

passive (only visual tagging, no signals) floy tags to examine fishway

efficacy.

Tracking data

In paper I we defined four behavioural migration patterns from the

tracking data: (a) direct migration to presumed spawning grounds; (b)

erratic swimming, wherein fish made at least one extra upstream and one

downstream movement during the tracking period; (c) fallback, wherein

fish migrated downstream past the power station after at least one

upstream migration; or (d) direct fallback, wherein fish migrated directly

downstream from the release point past the uppermost power station.

We also distinguished other specific behaviours during spawning

23

migration: overshoot, wherein fish migrated a minimum of 2 km

upstream of the presumed spawning location, then either (i) held; (ii) fell

back; or (iii) maintained erratic swimming. Holding was defined as fish

that were found in the same location for at least 6 days. Because holding

behaviour occurred during spawning season and mostly in locations

identified as the best potential spawning habitats (Gustafsson et al. 2015),

this holding behaviour was presumed to include spawning. In paper II

we used the same definition for fallbacks, holding and spawning as in

paper I.

In paper III we caught Atlantic salmon in fyke nets in Lake Vänern,

approximately 5 km from the river mouth. In 2012, the fish were tagged

on a boat and then either released at the capture site in the lake or

transported in a tank and released in the river approximately 10 km from

where they were caught, i.e. 5 km upstream of the river mouth. In 2013,

all the fish were tagged on the boat and then immediately released back

into the lake. In addition, salmon from the fish-trap in Forshaga were

tagged and then transported in an aerated tank and released 4 km

downstream of the power plant. Artificial freshets were used to attract

and capture brown trout at the spillway on the eastern side of

Hunderfossen dam. Trout were trapped in pots or stranded after spillway

closure, and thereafter netted and secured as quickly as possible in a 1 m

deep pool. All individuals were tagged with Floy anchor tags and a

subsample was radio-tagged. In addition, we caught brown trout in a trap

in the fishway, and again all individuals caught in the fishway were tagged

with Floy anchor tags and a subsample was radio-tagged. These

individuals were then released downstream of the dam in the same pool

as the trout caught at the spillway. The salmon caught in the lake and the

trout caught at the spill gate were regarded as “naïve" fish, lacking

24

experience from entering a fish trap, whereas the fish caught in the

fishway traps were termed “experienced”.

Paper IV is based on a laboratory experiment in which we used hatchery-

reared young-of-the-year Atlantic salmon, brown trout and grayling (Fig.

3).

Figure 3. Juvenile grayling in the holding aquaria.

The experimental trials were conducted in three 7-m long stream flumes.

The flumes consist of three 1.8 m long compartments of varying depth

and width plus a head-box and a filter-box. Windows for viewing the fish

underwater are present along the entire length of one side of the three

compartments. For this experiment, only the upper compartment was

used to conduct the trials. The size of the compartment in the three flumes

was 0.85, 0.88 and 0.92m2 with a mean depth of 23, 26 and 22cm. Average

flow in the compartment was 18.4 cm s-1 (SE 4.4) and each contained a

25

clay pot and a large stone to provide refuges. To compare the effect of

intraspecific versus interspecific competition for food, thirteen

treatments were randomly organized in the three stream tanks: (1) three

allopatric treatments, each consisting of 2 individuals of each species held

separately; (2) three allopatric treatments, each consisting of 4

individuals of each species held separately; (3) three allopatric

treatments, each consisting of 6 individuals of each species held

separately; (4) three sympatric treatments, each consisting of two of the

species, two individuals per species, i. e., 2 grayling + 2 trout, 2 grayling +

2 salmon, and 2 salmon + 2 trout; (5) one sympatric treatment consisting

of all three species, two individuals per species, i.e., 2 grayling + 2 salmon

+ 2 trout (Table 1).

Table 1. The thirteen different treatments used in the study.

Allopatry Sympatry

2 grayling

4 grayling

6 grayling 2 grayling

+ 2 salmon

2 graying +

2 trout

2 salmon +

2 trout

2 grayling + 2 salmon + 2 trout

2 salmon

4 salmon

6 salmon

2 trout

4 trout

6 trout

All treatments were replicated 9 times. Each trial was filmed for 30

minutes and consisted of 10 minutes prior to feeding, followed by a

feeding phase in which the fish were fed one chironomid larva/min for

10 minutes and a post-feeding phase of 10 minutes. During

observations, activities of each species were recorded as; total number

of prey consumed, the number of times a fish initiated or received an

attack, the number of times a fish initiated or received a chase, time

spent cruising (defined as 0%, 0-25%, 25-50%, 50-75%, 75-100% or

100% of the total time), and time spent holding position (defined as for

cruising).

26

Summary of results

The spawning migration studies revealed several factors that reduced the

number of fish believed to have contributed to spawning in the River

Klarälven (Paper I, II and III). Timing of the migration had very strong

effect on the number of fallbacks, which was higher early in the season

than later on (Paper II). More on, the fishway in Klarälven and

Gudbrandslågen did not provide a stable and effective fish passage, and

we also show that fishway efficacy for salmon and trout with prior

experience from the fishway was lower than for “naïve” fish (Paper III).

Our first study reveal the problems of using hatchery salmon as

supportive breeders, which in our study had very little, if any, positive

effect on the wild population as relatively few assumed holding behaviour

at the spawning grounds (Paper I). Based on our flume experiment, we

found little evidence that reintroducing Atlantic salmon to native areas in

Norway would pose any obvious negative effects on resident trout and

grayling, in terms of competition for food and energy consuming

encounters. Rather, if habitat availability is constrained salmon could

possibly be negatively affected by the other species, as they were the least

aggressive species of the three (Paper IV).

Paper I

Half (50%) of the hatchery fish, but only 11.8% of the wild fish ended up

as fallbacks, i.e. they moved (“fell back”) downstream of the first

downstream power station, and thus could not contribute to spawning. A

higher proportion (21.4%) of hatchery- reared salmon moved in an

erratic way, with several episodes of upstream and downstream

movements when compared to the wild salmon (5.9%; Fig. 4).

27

Figure 4. Classification of migratory behaviours for wild and hatchery-reared salmon (in

percentages) during their upstream migration: (a) direct upstream movement, (b)

several upstream and downstream movements before spawning, (c) upstream and

downstream movement, resulting in a fallback, and (d) direct fallback. N = 34 wild and

28 reared fish.

When analyzing the movement of the salmon we found wild individuals

to display holding behaviour more often (86.7%) than the reared ones

(50%). The wild salmon also held position (and presumably spawned) for

longer time (25.4 days) than the reared salmon (16.1 days). Reared

salmon held position, on average, 10 km further upstream than wild

salmon. The migration speed (average 17.4 km/day) did not differ

between wild and reared fish or between sexes.

Paper II

The behaviour of early and late migrating adult Atlantic salmon was

analysed, and we distinguished two phases of the spawning migration,

one phase being the migration from the place where the fish was released

to the spawning grounds. The other was a holding phase on the spawning

28

grounds with little or no movements before spawning. The late migrating

salmon spent less of their total time holding (36.2%) and more on

migration (63.8%) compared with early migrating salmon, which

distributed their time rather evenly between migration (47.5%) and

holding (52.5%; Fig. 5b). In total, early salmon spent 30% more time on

migration and 156% more time on holding than late salmon (Fig. 5a).

Figure 5. a) Mean number of days and b) proportion (%) of total time spent on migration

and holding for early (white bars) and late (grey bars) Atlantic salmon in the River

Klarälven in 2012. Error bars show +1 SE.

Some Atlantic salmon fell back over the hydropower plant after release

and were thereby excluded from spawning. The fallback rates were

higher in the early than in the late group in both years. The fallback rate

in 2012 was 42.8% for the early group and 15.1% for the late group (Fig.

6). In 2013, there were 51.7 % fallbacks in the early group and 3.4% in

the late (Fig. 6). The salmon fell back on average 9 days after being

released in 2012 and 16 days in 2013. A high mean daily discharge on the

day of release increased the probability of becoming a fallback.

29

Figure 6. Percentage (%) of early and late migrating Atlantic salmon that became

fallbacks (i.e., fish moved downstream of the hydropower dam) in 2012 and 2013.

Paper III

We investigated how Atlantic salmon and brown trout behave below a

dam when attempting to locate and ascend a fishway. We also examined

whether prior experience of the fishway affected movements and

migration success of the fish, and how handling of tagged fish may affect

their final migration success. Fishway efficacy varied greatly between

years and discharge levels and ranged from 18% to 78% (if one includes

individuals that presumed have died or lost their tag near the fishway)

and 33% to 89% (if one excludes them). Most fish (81%) entered the trap

on days without spill. For trout, the fishway efficacy was 43%. When we

compared the salmon that had prior experience of the trap to the naïve

ones we found that 70% of the naïve ones found the fishway but only 25%

of the experienced ones did (Fig. 7a). The same was seen in brown trout

where 43 % of the naïve ones and 15 % of the experienced ones

succeeded (Fig. 7b).

30

Figure 7. Percentage of naïve and experienced individuals of a) Atlantic salmon and b)

brown trout that succeeded in entering the fishtrap at Forshaga and Hunderfossen dams,

respectively. Total sample sizes are indicated above each histobar.

Positioning of the radio-tagged fish revealed that 10% of the naïve and 45

% of the experienced Atlantic salmon ceased migration after tagging and

release, corresponding figures for brown trout was 11% for the naïve and

50% for the experienced individuals. Naïve salmon that entered the trap

were delayed by a median of 15 days (3-70), whereas the experienced fish

were delayed by 7 days (7-70). For trout, the median delay for

experienced and naïve brown trout was 26 (2-47) and 25 (4-43) days,

respectively. There were no differences in attempts to enter the fishways

between the naïve and experienced salmon but we could see an effect

from handling the fish where fish that were released directly after being

tagged made more attempts to enter the fishway than fish that had also

been transported 10 km before being released. We also found that salmon

moved towards the highest water flows, i.e. high amounts of spill and

increasing spill stimulated the fish to move from the turbines to the spill

31

zone and small individuals seemed to react stronger than large fish to this

stimuli.

Paper IV

We experimentally examined feeding rate, aggression and activity of

juvenile Atlantic salmon, grayling and brown trout in allopatric and

sympatric conditions at different densities to see how they affected each

other. Atlantic salmon fed less in the presence of brown trout and

grayling, grayling and brown trout affected each other but were not

affected by Atlantic salmon (Fig. 8).

Figure 8. Average (+ SE) number of prey captured (maximum 10 prey) in the different

treatments (density 2, 4 and 6 and the different species combinations) for Atlantic

salmon, grayling and brown trout. S= Atlantic salmon, G = grayling and T= trout. The

different lowercase letters at the top of the figure indicate significant differences between

treatments (Tukey test) for each species: a and b used for salmon, c and d for grayling

and e and f for trout (P<0.05).

32

Analyses of aggression showed that grayling was the most and salmon the

least aggressive species (Fig. 9).

Figure 9. The number of attacks (+ SE) that Atlantic salmon, grayling and brown trout

initiated in different treatments Allopatric conditions with densities of 2, 4 and 6

individuals and sympatric combinations of two species at a time and with all three

species, see tab 1. Salmon = S, G = Grayling, T = Trout.

There was a significant effect of treatment on the number of initiated

attacks for all species. Salmon initiated more attacks in high-density

allopatric treatments than in the lowest allopatric density and in the

sympatric treatments (Fig. 9). Grayling initiated more attacks in sympatry

and in high-density allopatric treatments than in the lowest allopatric

density (Fig. 9). Brown trout displayed more attacks in sympatric

treatments than in the lowest allopatric density (Fig. 9). Treatment also

had a significant effect on the number of attacks each species received and

in line with the initiated aggression, grayling received most attacks and

salmon the least (Fig. 10). Salmon were attacked more in treatments with

grayling and in the two higher allopatric densities than in the lowest

allopatric density (Fig. 10). Grayling were attacked significantly less at the

33

lowest allopatric density compared to all other treatments (Fig. 10).

Trout were attacked significantly less at the lowest allopatric density

compared to all the other treatments (Fig. 10).

Figure 10. The number of attacks (+ SE) that Atlantic salmon, grayling and brown trout

received in relation to the different treatments. Allopatric conditions with densities of 2,

4 and 6 individuals and sympatric combinations of two species at a time and with all three

species, see Table 1. Salmon = S, G = Grayling, T = Trout.

There was a significant difference in activity, i.e. time spent cruising or

time spent holding, between the species with grayling being the most

active and salmon the least.

34

Discussion

Hydropower dams represent one of the major threats to river

ecosystems worldwide (Nilsson, 2005; Dudgeon et al., 2006). The dams

block migratory routes and disrupt river connectivity, affecting

migration of fish species (Fullerton et al., 2010; Fuller et al., 2015).

There is therefore a need to develop different types of remedial

measures to reestablish or improve upon river connectivity so that we

may be able to successfully conserve salmonid populations (Fullerton et

al., 2010; Fuller & Death, 2018; van Puijenbroek et al., 2018). Even

though Atlantic salmon is a well-studied species, relatively little is,

unfortunately, known about the landlocked populations (Klemetsen et

al., 2003). The Atlantic salmon found in the River Klarälven are one of

only a few remaining populations of endemic, large-bodied landlocked

Atlantic salmon populations in Europe, with Lakes Ladoga, Onega and

Vänern holding the largest populations (Kazakov, 1992; Ozerov et al.,

2010; Piccolo et al., 2012). Various stakeholders have devoted

considerable energy to conserve these valuable stocks.

In this thesis, I have identified three problems associated with the current

management of the River Klarälven stock, namely the high incidence of

fallbacks (Paper II), problems with the trap and transport system, how

flow affects fishway efficacy (Paper III) and the use of hatchery-reared

fish as supportive breeders to the wild population (Paper I).

Furthermore, I investigate possible effects of reintroducing Atlantic

salmon to native areas that resident brown trout and grayling currently

inhabit (Paper IV).

Upstream-migrating Atlantic salmon in regulated rivers face several

difficulties (Rivinoja et al., 2001; Thorstad et al., 2003; Lundqvist et al.,

2008, Thorstad et al., 2008), and the salmon studied in this thesis are no

35

exception. Trapping migrating fish below dams and transporting them to

the upper reaches is an often-used management solution in regulated

rivers with multiple dams (Larinier, 2001),but not an unproblematic one.

Our study on migratory timing (Paper II) revealed differences in

behaviour between early and late migrating Atlantic salmon. The fact that

about half of the early migrating salmon that were transported upstream

fell back before reproduction has serious management implications, since

the reproducing population is smaller than expected, with potential

effects on salmon recruitment in the River Klarälven. Worldwide, many

populations of Atlantic salmon are endangered due to hydropower

development, and it is important to evaluate and improve rehabilitation

measures. By understanding the mechanisms behind why an individual

becomes a fallback, it might be possible to develop measures to reduce

the number. Migratory timing has, in previous studies, been linked to

both environmental conditions such as temperature and flow, length of

migration as well as to the physical status of individual fish (Jonsson et

al., 1990; Fleming et al., 1996; Klemetsen et al., 2003; Crisp, 2007). We

found no relationship between mean discharge and fallback rates, nor did

we have any extreme temperatures during the migration period, although

there was a higher probability of becoming a fallback with increased

mean discharge on the day of release, which normally is more common

earlier in the season. But since the fish fell back, on average, 12.5 days

after release it is probably more likely that the late migrants were more

motivated to spawn, despite the fact that both early and late migrators

likely were disoriented and stressed after being trapped and trucked

(Johnsen et al., 1998; Thorstad et al., 2008). Even though we do not know

why they fall back, we may not need to know that to be able to improve

the situation. For example, one solution that managing authorities might

consider for the River Klarälven is to build a fishway at the eighth dam,

36

giving spawners an opportunity to continue on their spawning migration,

even if they have fallen back. Another way to maybe decrease the number

of fallbacks would be to release the fish further up the river, which would

give them a chance to move downstream, some distance, but without

falling back.

Many dams rely on a fish passage solution to enable natural reproduction

but with varying results (Noonan et al., 2012). Demanding migratory

routes, combined with challenging fish passage solutions, may cause

exhaustion and stress, and could ultimately act as bottlenecks for survival

and passage success of migrating fish (Stevens and Black, 1966; Peake,

2004). Fishways often vary in their efficacy and many are selective, which

increase the risk of losing genetic variability (Castro-Santos & Cotel,

2009; Noonan et al., 2012). The results in paper III underline the

difficulties in establishing consistently high values for fishway efficacy. As

seen in paper III, fishway efficacy varied greatly between and within

years, presumably because of different flow conditions. This emphasizes

the need to design fishways with great care so that they function over a

broad range of conditions, which is especially challenging at large dams

(Larinier 2001). The results are also important for future evaluations of

fishway efficacy since fish individuals used in efficacy-studies often are

caught in the fishway prior to using them in obtaining passage estimates.

The experienced Atlantic salmon and brown trout in paper III were

exposed to more stress factors that the naïve ones, in terms of handling

and transportation, and this could be why many of the experienced fish

did not enter the fishway when re-released into the river. Nevertheless,

we do not know why the experienced fish behaved the way they did and

in addition to stress from handling and transportation, there may have

been additional stress associated with finding, entering and passing the

37

fishway a second time. On the other hand, we did find evidence that stress

associated with transportation may be sufficient to produce the pattern

we observed, as salmon that were released directly into the lake after

tagging reached the fishway to a greater extent than salmon that were

transported 10 km by boat before released.

Supportive breeding is a strategy where wild fish are used as brood stock

in hatcheries to maintain the locally adapted wild population by releasing

their offspring into the wild (Blanchet et al., 2008). Even though this may

be one way of maintaining a population, which could be very useful in the

short term, there are some downsides to this approach. One negative

effect is domestication effects, which in some studies have been detected

after only one generation of rearing (Fleming & Einum, 1997; Blanchet et

al., 2008; Araki & Schmid, 2010). Therefore, there is a risk that the use of

hatchery fish could reduce local adaptation in wild populations when

used as supportive spawners (Blanchet et al., 2008, Araki and Schmid,

2010). Supportive breeders based on young born in a hatchery usually

show limited effectiveness, with low reproductive success (Fleming &

Petersson, 2001), which is what we also saw in our study (Paper I). We

found that many spawners of hatchery-reared origin showed a high

fallback frequency and an erratic migratory behaviour without signs of

spawning. Because of the large number of power plants in the river, the

fish are released as smolts downstream of the lower-most dam.

Consequently, supportive breeders were not imprinted to the upstream

river section around the spawning grounds during their downstream

migration as smolts, which might explain the erratic behaviour of the

supportive breeders; apparently, they could not identify their “natal”

spawning grounds in the River Klarälven. Had the smolts been released

at the spawning grounds it is more likely that more of them would have

38

homed correctly, but if this had been done, mortality rates of smolts

passing all eight dams would have been high (Norrgård et al. 2012). Based

on these results it is probably better to support the wild population in

other ways that through supportive breeders, and in fact managing

authorities and power companies have now discontinued the practice of

transporting spawners of hatchery origin upstream, based on genetic

awareness and the results of paper I.

As salmonid populations have continued to decline, reintroduction of

extirpated populations to areas they historically occupied has become an

increasingly important measure in conservation work, but

reintroductions of salmonids often fail to reestablish sustainable

populations, especially if there is no wild population left and brood stock

consists of hatchery fish (Fraser, 2008; Waples et al., 2007). Reintroduced

salmon populations may also have an impact on resident populations or

be vulnerable to native competitors and predators with which they used

to coexist (Mittelbach et al., 2006; Ward et al., 2007). Atlantic salmon,

brown trout, and grayling are salmonid species that have overlapping

niches with potential to interact with each other in riverine habitats

(Greenberg et al., 1996; Greenberg, 1999; Heggenes et al., 1999). Habitat

selection by brown trout is usually less affected by interspecific

competition, as brown trout often outcompete other salmonids (Gibson,

1993; Heggenes et al., 1999). Grayling is much less studied than Atlantic

salmon and brown trout and there is even less work done on how the

three species interact. We found (Paper IV) that there was no noticeable

negative impact of Atlantic salmon on the two other salmonid species,

grayling and brown trout, but that these two species had a strong

negative impact on Atlantic salmon. Habitat complexity creates different

microhabitats that can support high densities of fish and gives different

species the possibility to segregate spatially when together (Heggenes &

39

Saltveit, 1990; Greenberg, 1999; Degerman et al., 2000). In many rivers,

especially dammed ones and ones cleared for log driving, rearing habitats

are limited and the species may be forced to co-occur to a higher degree

than in a pristine river. It is therefore important to take species

composition and the need for habitat restoration into account when

planning a reintroduction.

The salmon and trout in the River Klarälven were historically among the

most productive landlocked large-bodied salmon stocks in the world, but

heavy exploitation of the river caused the populations to decline

drastically and they are now endangered (Piccolo et al., 2012).

Management efforts through hatchery stocking and trap and transport

have kept the populations alive but still at a minimum. The work

presented in my thesis all springs from an interest in salmonid

conservation in regulated rivers, and I have tried to find and underscore

the difficulties migratory spawners may face in these altered

environments. I have also tried to evaluate if there may be problems

associated with reintroducing Atlantic salmon to their historical areas in

Norway. I stress the need for a holistic management based on salmonid

life history to ensure viable populations in the future. The management

need to include functional and effective up- and downstream migration

solutions in the system, a sensible reintroduction plan and improved

handling of fish to reduce stressful situations. The results of my research

can be applied to other regulated systems, particularly those with trap

and transport solutions.

40

Acknowledgements

My time as a PhD student has been great and I will think back on it with a

warm heart!

I wish to thank my supervisors Eva Bergman, Olle Calles, Larry Greenberg

and John Piccolo for support, advice and encouragement during my PhD-

studies. Eva, for being the bravest supervisor (and fellow human) when

my world crumbled, for this I cannot thank you enough. Olle, who

introduced me to the marvelous world of telemetry and who did not

hesitate to join me rafting the wild rapids in search of salmon. Larry, you

accept nothing but the best you can get and I am very grateful for that, it

has made my thesis a lot better! Jack, you always bring encouragement

and a pat on the back, especially in times of need. Keep up the positivity!

My colleagues and fellow PhD students at the Biology department at

Karlstad University, thanks for creating a friendly and stimulating

atmosphere. To my very good friend Lars Dahlström who always support

me and even took on a job as a lab assistant to help me build aquaria.

Also, a big thank you to people whom, in one way or another, helped

during my studies, either in field or through discussions and meetings in

real life or over the internet. Thank you all!

Finally to my family, Elliot, for you unconditional love (even though I

prefer fish to Manchester United), for putting everything into perspective

and for constantly reminding me of how lucky I am.

41

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Anna Hagelin

2019:7







Faculty of Health, Science and Technology

Biology


ISSN 1403-8099

ISBN 978-91-7867-007-9 (pdf)

ISBN 978-91-7867-002-4 (print)





Conservation of landlocked Atlantic salm

on in a regulated riverAnna H

agelin

Print & layout University Printing Office, Karlstad 2019

Cover photoIngemar Alenäs

ISBN 978-91-7867-002-4 (print)ISBN 978-91-7867-007-9 (pdf)

Anna Hagelin received her M.Sc. in ecology from Umeå University, which included the M.Sc. thesis “The influence of land exploitation in tropical environments on the diversity of benthic invertebrates in streams”. She started her Ph.D. project at Karlstad University in 2011. Since 2016, she has combined her Ph.D. studies with salmonid conservation work at the County administrative boards of Gävleborg and Västra Götaland.

Behaviour of migratory spawners and juveniles

Anna Hagelin



List of papers

The thesis is based on the following papers.

I Hagelin, A., Calles, O., Greenberg, L., Piccolo, J., & Bergman, E. (2016). Spawning migration of wild and supplementary stocked landlocked Atlantic salmon (Salmo salar). River Research and Applications, 32(3), 383-389.

II Hagelin, A., Calles, O., Greenberg, L., Nyqvist, D., & Bergman, E. (2016). The Migratory Behaviour and Fallback Rate of Landlocked Atlantic Salmon (Salmo salar) in a Regulated River: does Timing Matter?. River Research and Applications, 32(6), 1402-1409.

III Hagelin, A., Museth, J., Greenberg, L., Kraabøl, M., Calles, O., & Bergman, E. (2019). Upstream fishway performance by Atlantic salmon (Salmo salar) and brown trout (Salmo trutta) spawners at complex hydropower dams – is prior experience a success criterion? Manuscript.

IV Hagelin, A., & Bergman, E. (2019). Reintroducing Atlantic salmon to once native areas: Competition between Atlantic salmon (Salmo salar), brown trout (Salmo trutta) and grayling (Thymallus thymallus). Manuscript.

Documents

Conservation of landlocked Atlantic The thesis is based on ...kau.diva-portal.org/smash/get/diva2:1291171/FULLTEXT02.pdf · Atlantlax är beroende av att kunna vandra mellan lek-