Department of Physics, Chemistry and Biology

Master Thesis

Stream channelization effects on fish abundance and

species composition

Ulf Johansson

LiTH-IFM- Ex--13/2762--SE

Supervisor: Arne Fjälling, Swedish University of Agriculture

Examiner: Anders Hargeby, Linköping University

Department of Physics, Chemistry and Biology

Linköpings universitet

SE-581 83 Linköping, Sweden

Rapporttyp Report category Examensarbete D-uppsats

Språk/Language

Engelska/English

Titel/Title:

Stream channelization effects on fish abundance and species composition Författare/Author:

Ulf Johansson

Sammanfattning/Abstract: Streams are important habitats, providing shelter and feeding opportunities for a wide range of organisms.

The species depending on running waters includes a wide array of fish species, using these waters for their

whole or parts of their lifecycle. Streams are also the subject of different anthropogenic impact, e.g. hydropower development. Hydropower development usually means lost connectivity, altered flow regimes

and channelization. Channelization is one of the major factors causing stream habitat loss and degradation

and thereby a threat to biodiversity of running waters. In the present study, the ecological impact of

channelization on the fish fauna along a gradient of channelization severeness was examined. Besides channelization, stream velocity and depth were taken in to account. The study was carried out in two

adjacent nemoboreal streams, Gavleån and Testeboån. The study was conducted between the 6th of June

and the 10th of October 2012 at 15 sites. Sites were selected using historical maps and field observations and graded 0-3 depending on the degree of channelization. Fish community were sampled with, Nordic

multi-mesh Stream Survey Net (NSSN). In all, 1.465 fish were captured, representing 15 species and seven

families. The sites differed in species richness, abundance and proportion of individuals. Based on the results from rarefaction curves and ANOVA, channelization was found to be the main factor affecting the

fish biota, both in abundance as well as species richness and composition. In general the rheophilic species

declined along the gradient of increasing channelization severeness, while limnophilic species increased

along the gradient.

ISBN LITH-IFM-A-EX—13/2762 SE ______________________________________________ ISRN __________________________________________________ Serietitel och serienummer ISSN Title of series, numbering Handledare/Supervisor Arne Fjälling Ort/Location: Linköping

Nyckelord/Keyword: Channelization, Rheophilic species, nemoboreal streams, Nordic multi-mesh Stream Survey Net, lotic,

relative abundance, fish community, limnophilic

Datum/Date 2013-05-31

URL för elektronisk version

Institutionen för fysik, kemi och biologi

Department of Physics, Chemistry and Biology

Avdelningen för biologi

Contents

1 Abstract ........................................................................................................... 1

2 Introduction ..................................................................................................... 1

3 Materials and methods..................................................................................... 3

3.1 Study area ................................................................................................. 3

3.2 Channelization .......................................................................................... 4

3.3 Sample method .......................................................................................... 4

3.4 Stream velocity and depth ......................................................................... 5

3.5 Guilds ........................................................................................................ 5

3.6 Statistical analysis ..................................................................................... 5

4 Results............................................................................................................. 6

4.1 Determinants of abundance ....................................................................... 8

4.2 Species richness and composition ............................................................ 10

4.3 Effect on guilds ....................................................................................... 11

5 Discussion ..................................................................................................... 13

6 Conclusions ................................................................................................... 15

7 Acknowledgement ......................................................................................... 15

8 References ..................................................................................................... 16

1

1 Abstract Streams are important habitats, providing shelter and feeding opportunities for a

wide range of organisms. The species depending on running waters includes a

wide array of fish species, using these waters for their whole or parts of their

lifecycle. Streams are also the subject of different anthropogenic impact, e.g.

hydropower development. Hydropower development usually means lost

connectivity, altered flow regimes and channelization. Channelization is one of

the major factors causing stream habitat loss and degradation and thereby a

threat to biodiversity of running waters. In the present study, the ecological

impact of channelization on the fish fauna along a gradient of channelization

severeness was examined. Besides channelization, stream velocity and depth

were taken in to account. The study was carried out in two adjacent nemoboreal

streams, Gavleån and Testeboån. The study was conducted between the 6th of

June and the 10th of October 2012 at 15 sites. Sites were selected using

historical maps and field observations and graded 0-3 depending on the degree

of channelization. Fish community were sampled with, Nordic multi-mesh

Stream Survey Net (NSSN). In all, 1.465 fish were captured, representing 15

species and seven families. The sites differed in species richness, abundance and

proportion of individuals. Based on the results from rarefaction curves and

ANOVA, channelization was found to be the main factor affecting the fish biota,

both in abundance as well as species richness and composition. In general the

rheophilic species declined along the gradient of increasing channelization

severeness, while limnophilic species increased along the gradient.

Keywords

Channelization, Rheophilic species, nemoboreal streams, Nordic multi-mesh

Stream Survey Net, lotic, relative abundance, fish community, limnophilic

2 Introduction Rivers and streams are essential for the exchange of energy, organic matter and

nutrients between inland and coastal areas. They drive local as well as global

biochemical cycles. Minor streams are dominant interfaces between any aquatic

habitat and associated land (Dodds 2002). Streams are also important habitats,

providing shelter and feeding opportunities for a wide range of organisms like

fish, insects, plants, mollusks, birds and mammals. There is a range of migratory

fish species that use running water for foraging or as nursery areas for young

stages. Among the fish species that use running waters for such purposes are

salmon (Salmo salar) and trout (Salmo trutta). The list goes on with less well

known species such as river lamprey (Lampetra fluviatilis), sea lamprey

(Petromyzon marinus), shad (Alosa fallax), Allis Shad (Alosa alosa), whitefish

2

(Coregonus spp), grayling (Thymallus thymallus), ide (Leuciscus idus), vimba

(Vimba vimba), sabre carp (Pelecus cultratus) and burbot (Lota lota). The

biodiversity of the coast is therefore strongly dependent on intact rivers and

streams discharging into coastal waters, both for nursery habitats, migration

route and food resources (Degerman et al, 2005).

In addition, non-migrating species like stream-resident brown trout, grayling,

perch (Perca fluviatilis), roach (Rutilus rutilus) and Northern pike (Esox lucius)

form populations in rivers and streams. These populations are primarily affected

by abiotic factors like flow velocity, depth, bottom quality, light conditions and

temperature for their choice of habitat (Zalewski & Naiman 1985). The

stationary populations in rivers and streams play an important role in the lotic

habitat food webs and are largely dependent on variations in a natural

watercourse to hold feeding, resting and spawning areas.

Globally habitat loss—due to destruction, fragmentation or degradation of

habitats is the primary threat to biodiversity (Wilcox and Murphy 1985). Streams

worldwide are subject to human impacts that degrade habitat conditions

(Malmqvist & Rundle 2002) and Sweden is no exception. More than 70% of the

Swedish streams are regulated and more than 33,000 km channelized (Jansson et

al. 2000; Törnlund & Östlund 2002). Channelization results in loss of structural

complexity, simplified flow patterns, and decreased availability of microhabitats

for a wide array of lotic organisms (Karr, J. R. and Chu, E. W. 1999, Petersen et

al., 1987). Therefore channelization of running waters is one of the major factors

behind stream habitat loss and degradation and is a serious threat to biodiversity

(Allan &Flecker 1993). Channelization has been performed for diverse

purposes, in Sweden mainly for the purpose of timber floating and land drainage

which took place in the 19th century, and more recently hydropower

development.

In order to evaluate the state of aquatic organisms in running waters a range of

monitoring techniques has been developed, for fish sampling, e.g. electro

fishing, traps, hook and line and none-capture methods are some of the methods

used today (Sutherland 2006).

Studies on the effect of channelization on the fish fauna using electro fishing

showed a significant effect on species richness and abundance (Javier et al 2005,

Engman & Ramirez 2012). However no study has been found so far that

investigates the fish fauna along a gradient of increasing channelization

severeness. A contributing factor for this is probably the lack of suitable

sampling methods. The present study was made possible by and conducted with

a new sampling method, Nordic Multi-mesh Stream Survey Net

(NSSN;[Fjälling el al 2013]). NSSN is a small version of the standardized

3

Nordic Survey Net used in lakes (Kinnerbäck 2001) designed to operate in

running waters.

The main aim of this study was to investigate the effects of channelization on

fish biota in lotic habitats over a gradient of channelization severeness. The

secondary aim was to evaluate the Nordic Multi-mesh Stream Survey Net as a

tool for these kinds of investigations.

3 Materials and methods

3.1 Study area The study was performed between the 6th of June and the 10th of October 2012

in Gävleborg County. The investigation sites were located in the two adjacent

streams Gavleån (N 60° 40′ 652″, E 17° 09′700″) and Testeboån (N 60° 42′

25.74″, E 17° 09′ 14.15″) (Fig 1) which both empty into the Bay of Gävle. The

Bay of Gävle is located in the southern Bothnian Sea. At the head of the bay is

the town Gävle where both of the streams have their mouths. In total 15 sites

were investigated and 222 efforts were made. This gave an average of fifteen

efforts per site. The distance between the investigated sites range from 50 meters

to five kilometers with an average distance of 2.6 kilometers.

Gavleån has a length of 29 kilometers, 129 km when including the tributaries.

Gavleån empties a drainage area of about 2,500 square kilometers. Within the

drainage area 77.4% is woodland and 6.5% is farmland. The mean annual

discharge is 21 m³/s and the mean of total phosphorus is 25.8 µg/l (the mean was

calculated using measurements made between 2000 and 2012, extracted from

the database VISS (Water Information System Sweden)). Along the stretch there

are seven hydropower plants and the channelization is in general high.

Testeboån has a length of 60 kilometers, when including the tributaries 110 km.

Testeboån empties a drainage area of 1,123 square kilometers. Within the

drainage area 81.5% is woodland and 4.0% is farmland. The mean annual

discharge is 11.7 m³/s and the mean of total phosphorus is 16.4 µg/l (the mean

was calculated using measurements made between 1990 and 2005, extracted

from the database VISS (Water Information System Sweden)). Along the stretch

there are valuable wetlands, riparian forests and flowing water in a mosaic

blending. The channelization is in general low to moderate.

4

Figure 1. The location of Gävleborg County and the two streams Gavleån and Testeboån with

the investigation sites marked with a star.

3.2 Channelization

The channelized areas were chosen and categorized using historical maps,

existing habitat mapping and field observations. The areas were categorized on a

scale from 0 - 3 were “0”, is a watercourse with a natural furrow, bottom and

shorelines. “1”, is a watercourse with a natural but straightened furrow and

natural bottom and shorelines. “2”, is a watercourse with a straightened furrow

and modified bottom, the shorelines are not all-natural. “3”, is a watercourse

with a straightened furrow, flat bottom and steep smooth paved / poled

shorelines.

3.3 Sample method Fish biota was caught with Nordic multi-mesh Stream Survey Net (NSSN). The

NSSN uses the same multi-mesh principle as the Nordic net; both the mesh size

of the panels (12 panels with mesh size from 5 to 55 mm mesh side [ICES

2004]) and their sequential order are identical. The fishing height of the net is

700 mm (stretched height is 900 mm), the length of the 12 sections is 1.500 mm

each, resulting in an efficient length of 18 m, and an efficient surface of 12.6 m².

The nets were set between 6 and 8 pm and lifted between 6 and 8 am the day

after. Thereby the sampling has followed the same timeframe as the

standardized method of sampling in lakes. The nets were put in to the water

parallel with the water stream. For each sample site all captured fish were

5

identified to species level and measured for total length (mm) and weight

together (g) for total biomass.

3.4 Stream velocity and depth

The stream velocity was divided into four categories. Calm / still (from 0.0 to

0.1 m / s), low stream (0.1-0.2 m / s), streaming (0.2 to 0.7 m / s) and rushing

(0.7 m / s - 2 m / s). The stream velocity was measured with a Flow meter 1

from Geopacks (Geopacks 2010) 0.3 meters below the surface in cross sections

of the watercourse. The cross section consists of a measuring point in the middle

of the stream and one on each side, centered between the center and land. The

measurements were made in the upper, middle and lower part of the investigated

site from which the average stream velocity was calculated. The depth was

measured upstream and downstream each net with an echo sounder. The

measured depths were used to calculate the average depth of the sampled areas.

3.5 Guilds To further examine the effects of channelization the species were grouped into

guilds (a group of species that exploits the same kind of resources). The

classification followed the system developed within the EU project FAME

(FAME CONSORTIUM, 2004). The guilds are represented by rheophilic

(preferring high flow conditions, and clear water), eurytopic (having a wide

tolerance of flow conditions but not considered to be rheophilic) and limnophilic

species (preferring slow flowing to stagnant conditions). The categories are

based upon distribution and preferences in rivers and streams rather than

considering the presence of the species in lakes. Floodplain species are classified

as Limnophilic unless they exhibit tolerance of relatively high flows, in which

case they are considered as Eurytopic (FAME CONSORTIUM, 2004).

3.6 Statistical analysis A two way and a three way analysis of variance (ANOVA) was used to test for

differences in fish abundance between the two streams investigated as well as

areas of different channelization, stream velocity and depth. The abundance was

log transformed to satisfy parametric assumptions of a normal distribution. The

guilds, rheophilic, eurytopic and limnophilic species were treated with a

Kruskall Wallis test. Both ANOVA and Kruskal Wallis were carried out in IBM

SPSS statistics 2.0. To compare the species richness within the different degrees

of channelization, rarefaction curves with confidence interval (95%) and the

expected richness were calculated, using the internet-accessible Species

Richness Estimators Eco-Tool (Colwell 2013). The calculation of the expected

richness was performed since there was a difference in the number of efforts and

sample sites.

6

4 Results In all, 1,465 fish were captured, representing 15 species (Fig 2) and seven

families. Overall, 222 efforts were made giving an average CPUE (catch per unit

of effort, i.e. catch per net and night) of 6.6 individuals. Perch was the most

common species in the catch followed by ruffe (Gymnocephalus cernuus) and

roach. More species were caught in Gavleån than in Testeboån. When separating

the two streams it can be seen that all 15 species sampled were found in Gavleån

and eight species were found in Testeboån. In Gavleån the dominant species in

the catches were perch, ruffe and roach. In Testeboån the dominant species were

roach followed by perch and ruffe (Table 1). Burbot and vimba were caught in

small numbers in both streams, both species are listed in the Swedish Red List

as Near Threatened (NT) (Gärdenfors 2010).

Smelt

Bullh

ead

Burbo1

Trou

t

Rudd

Brea

m

S.br

eam

Blea

k

VimbaId

e

Roac

hPike

Zand

er

Ruffe

Perch

3,0

2,5

2,0

1,5

1,0

0,5

0,0

CP

UE

95% CI for the Mean

Interval Plot of species captured during the study

Figure 2. The average catch per unit effort for the caught species during the project.

7

Table 1. CPUE and the standard deviation both to individuals and biomass for all species

caught in the studied streams. The proportional catch of the total effort given in percent is

also shown.

Testeboån

Gavleån

Species

Mean ± SD

Percentage Mean ± SD

Percentage

Perch Ind/net 0.29 ± 0.64

21% 2.64 ± 4.3

64%

g/net 42.0 ± 119

213 ± 409

Zander Ind/net

0.036 ±0.22

3%

g/net

13.5 ± 120

Roach Ind/net 0.64 ± 1.10

39% 1.7 ± 3.71

48%

g/net 39.1 ± 78.9

100 ± 225

Bleak Ind/net 0.04 ± 0.19

3.90% 0.04 ± 0.22

3%

g/net 0.33 ± 1.66

0.48 ± 2.75

Burbot Ind/net 0.06 ± 0.24

5.80% 0.02 ± 0.13

1.80%

g/net 7.98 ± 38.9

9.87 ± 89.7

Bullhead Ind/net 0.07 ± 0.32

5.80% 0.11 ± 0.35

9.70%

g/net 2.37 ± 11.6

0.57 ± 1.94

Rudd Ind/net

0.006 ±0.08

0.60%

g/net

0.80 ± 10.3

Vimba Ind/net

0.02 ± 0.17

1.20%

g/net

7.42 ± 67.9

Trout Ind/net 0.08 ± 0.34

5.80% 0.03 ± 0.19

1.80%

g/net 2.84 ± 13.1

1.57 ± 11.6

Bream Ind/net

0.04 ± 0.18

3.60%

g/net

10.5 ± 69.5

Silver bream Ind/net

0.39 ± 0.99

21%

g/net

36.5 ± 129

Pike Ind/net 0.02 ± 0.14

1.90% 0.04 ± 0.2

4.20%

g/net 5.56 ± 39.7

59.6 ± 332

Smelt Ind/net

0.63 ± 4.40

8.50%

g/net

24.2 ± 159

Ruffe Ind/net 0.25 ± 0.63

18% 2.46 ± 7.45

40%

g/net 3.00 ± 8.40

64.0 ± 210

Ide Ind/net

0.01 ± 0.11

1.20%

g/net

10.7 ± 97.1

8

4.1 Determinants of abundance To evaluate the effects of channelization on fish abundance three more factors

were taken into account, the stream ID, stream depth and stream velocity (Table

2). To evaluate if there was a difference in fish abundance between the two

investigated streams a Two -way ANOVA was carried out (Table 3) with stream

ID and channelization as given factors showing no significant difference

between the two streams. However there was a significant difference between

the grades of channelization.

Table 2 Stream ID and sample areas with the measurements of stream velocity, and depths as

well as the grades of channelization.

Stream ID Sample area Velocity (m/s) Channelization Depth (m)

Gavleån Islandsbron 0,79 3 2,9

Gavleån Idrottsplatsen 0,49 2 2

Gavleån Kvarnbron 0,21 3 1,6

Gavleån Gråströmmarna 0,48 2 2,4

Gavleån Gustavs bro 0,30 1 3

Gavleån Boulognerskogen 0,42 2 3,1

Gavleån Mackmyra bruk 0,44 3 1,7

Gavleån Bruksallen 0,35 0 0,75

Gavleån Kvarnåkersvägen 0,55 2 1,7

Gavleån Lundvägen 0,27 2 4,7

Gavleån Hälleh 0,30 1 3,2

Testeboån Deltat 0,15 1 2,3

Testeboån Brännssågen 0,35 0 0,65

Testeboån Åbyggeby 0,47 2 1,7

Testeboån Torsved 0,36 1 2

Table 3 Results from the two-way ANOVA were the channelization shows a significant result

but the streams (Testeboån, Gavleån) do not.

Dependent Variable: Total abundance

Source ss df Ms F P

Channelization 0.727 3 0.242 4.938 0.023

Stream 0.06 1 0.06 1.215 0.296

9

A three-way analysis of variance (ANOVA) was used to determine whether

channelization, stream velocity or depth influenced the number of fish (Table 4).

The results showed a highly significant result of channelization while the other

factors tested showed no significant difference in variance.

Table 4 Result from the three-way ANOVA with channelization, velocity and depth as fixed

factors.

Dependent Variable: Total abundance

Source Ss df Ms F P

Channelization 11.05 3 3.683 24.473 <0.001

Stream velocity 6.84E-05 1 6.84E-05 0 0.983

Depth 1.285 7 0.184 1.22 0.293

Although the channelization has a significant effect on the relative abundance, it

does not follow the gradient of channelization severeness (Figure 3).

Figure 3 Relative abundance of all fish species caught during the project. The abundance is

based on the CPUE.

10

4.2 Species richness and composition In order to evaluate the species richness within the different channelization rates

a rarefaction curve with the expected richness was calculated (Fig 5). The curve

showed considerable differences in species richness, especially between

channelization one and channelization three with almost twice as many species

in channelization grade three. Also the species composition differed between the

channelization rates. Trout were only caught in the 0 areas, constituting 6% of

the number of fish. Smelt, zander and vimba were exclusive for channelization

grade 3 and together with ide, bream and rudd they were only caught in

channelized sections of grade 2 two and 3, together constituting 10 % of the fish

caught. Perch, roach, ruffe, bleak and bullhead were caught in all four grades of

channelization (Table 4).

Figure 4 The species richness plotted against channelization class for sampling sites

0

2

4

6

8

10

12

1 3 5 7 9 11 13 15 17 19 21 23 25 27

Ric

hn

ess

Samples

CH_0

CH_1

CH_2

CH_3

11

Table 5 The species composition, CPUE ± SD in the different areas.

Channelization0 Channelization1 Channelization2 Channelization3

Species Mean ± SD Mean ± SD Mean ± SD Mean ± SD

Perch 1.24 ± 3.02 0.32 ± 0.73 1.57 ± 1.98 4.78 ± 6.19 Roach 2.50 ± 2.69 0.41 ± 1.10 1.22± 3.29 2.14 ± 4.44

Ruffe 0.03 ± 0.19 0.39 ± 0.71 0.67 ± 1.15 6.14 ± 11.9

Bleak 0.03 ± 0.19 0.02 ±0.15 0.03 ± 0.24 0.05 ± 0.22 Bullhead 0.41 ± 0.56 0.06 ± 0.33 0.05 ± 0.27 0.03 ± 0.18

Pike 0.03 ± 0.19 0 0.04 ± 0.21 0.05 ± 0.22

Silver bream 0 0.07 ± 0.33 0.29± 0.79 0.58 ± 1.31

Ide 0 0 0.01± 0.10 0.02 ± 0.13 Bream 0 0 0.03± 0.18 0.05 ± 0.22

Smelt 0 0 0 1.76 ± 7.28

Zander 0 0 0 0.10 ± 0.36 Vimba 0 0 0 0.05 ± 0.29

Rudd 0 0 0.01± 0.11 0

Trout 0.28 ± 0.59 0 0 0

Burbot 0.03± 0.19 0.04 ± 0.20 0.03± 0.18 0

4.3 Effect on guilds The results from the Kruskall Wallis test showed a significant channelization

effect in all guilds, rheophilic, limnophilic as well as eurytopic species (Table

6).

Table 6 The table gives the mean catch ± SD and the P value for the guilds limnophilic,

intermediate and rheophilic species.

Chann 0 Chann 1 Chann2 Chann 3

Guilds mean ± SD mean ± SD mean ± SD mean ± SD

Limnophilic 0,03± 0,19 0,46± 0,81 1,01± 1,58 7,00± 12,02 P < 0,001

Eurytopic 3,90± 5,14 0,80± 1,65 2,92± 4,30 5,63± 8,62 P < 0,001

Rheophilic 0,69 ± 0,81 0,07± 0,33 0,05± 0,21 0,03± 0,18 P = 0,002

The relative proportions of the guilds (Fig 5) varied with regard to

channelization severeness. Proportionally the rheophilic species showed a rapid

decline from channelization 0 to channelization 3. An opposite trend can be seen

among the limnophilic fish species where catches increased with channelization

severeness. The proportion of euryotopic species followed the same pattern as

the total abundance of fish with the lowest abundance at channelization rate 1.

The proportions are based on the CPUE.

12

Figure 5 Proportions based on the CPUE for Rheophilic, Limnophilic and Eurytopic species

caught along the gradient of channelization severeness. Channelized areas are categorized

from 0-3.

13

5 Discussion Fish abundance was strongly influenced by channelization but not significantly

influenced by the other test variables. This points to anthropogenic impact as

one of the primary factors controlling the fish abundance in the studied streams.

These results are confirmed by other studies regarding channelization

(Scarnecchia 1988, Engman 2012, Knight et al 2012) showing a significant

effect on fish abundance and composition in channelized parts of streams and

rivers.

When adverse conditions prevail, fish communities in streams are regulated by

habitat complexity and availability of shelter (Cunjak 1996), over time causing

greater variability in fish community structure at disturbed sites with simplified

habitats ( Paller 2002). Channelization results in loss of structural complexity

and simplified flow patterns. A channelized stream is typically a stream with a

high but non-turbulent velocity, deeper than a riffle (Rankin 1989).

The channelized part of a stream becomes dominated by tolerant species and

lacks a high abundance of sensitive species. Tolerant species have the ability to

thrive in environments altered by anthropogenic disturbances, whereas sensitive

species have a reduced range of environmental tolerance and are generally not

present in degraded habitats (Smoger and Angermeier 1999). These findings

may explain the results of the present study that examined the fish fauna over a

gradient of channelization severeness. The results show increased species

richness as well as higher abundance in the most channelized areas of the

investigated streams. There is also a shift in species composition along the

channelization gradient.

This shift in species composition with an increased channelization was best seen

when species were grouped into guilds. Stream parts with low channelization

severeness contain rheophilic and eurytopic species, while a high channelization

severeness leads to a higher occurrence of eurytopic and limnophilic species.

Rheophilic fish species depend on flowing water for food, shelter, spawning and

movement between different habitats. Limnophilic and eurytopic species

however do not in the same extent dependent on such conditions and thereby

taking advantage of the tranquil nature following channelization

(Naturvårdsverket 2006).

It has been shown that many species that are normally found in lakes or slow

flowing, lower parts of the rivers are favored by water regulation where

channelization is a common element (Calles 2005). In the present case there is

no significant difference between the highly regulated Gavleån and the mostly

natural but partly channelized Testeboån. This indicates that it is the

14

channelization itself acting as the determining factor, forming the fish

community structure in the investigated streams.

An unexpected outcome of the study was the low abundance as well as the low

species richness in channelization category 1, in relation to channelization

category 0. The areas with channelization degree 1 have high naturalness but is

deeper than the null areas. This suggests that the bottom may be more distorted

than been observed in the field. However the depth did not have a significant

impact on the relative abundance, but channelization did. This indicates that

even a low impact on the watercourse can have a large impact on the fish

community. A possible reason for the low abundance of fish and also the low

species richness, may be that areas with channelization degree 1 are sufficiently

affected to put rheopholic species to disadvantage. However, they are not so

affected that limnophilic or eurytopic species are significantly favored, thus

leaving a gap with low abundance areas.

Studies on the effects of channelization on fish communities have reported a

wide range of often conflicting results (Gidley 2012). Results from some studies

indicate that channelization results in a lower relative abundance as well as a

low species richness (Sullivan et al., 2004, Rhoads et al 2003), while other

studies describe the opposite (Lyons et al 1996, Mundahl and Simom 1999).

Reasons for the differing results among these studies are likely to be different

sampling scales, different sampling methods and sampling in different aquatic

environments.

The outcome of this study, rests on and is influenced by the characteristics of the

new sampling method. The new method made it possible to sample also difficult

areas not normally investigated. These areas differ from those sampled with

conventional methods in respect to depth, bottom substrate and stream velocity.

Thus, the new approach contributes to a greater knowledge of fish communities

in running water.

The new sampling method proved to be easy to use and gives just as ordinary

multi-mesh survey nets a picture of the fish community, in terms of length,

distribution, relative density and species diversity. The nets do not require a

specific depth and can be set from about 0.5 meters and deeper, making studies

of whole streams possible. No comparisons with other sampling methods were

made in this study, however earlier studies has shown that there is no difference

in fishing capacity between the NSSN and fyke nets (Johansson 2011). There

has also been limited comparisons between NSSN and electrofishing boat

showing a dominant catch of perch and roach in the survey nets while more

pelagic species such as bleak dominated when electro fishing (Johansson et al

2012).

15

6 Conclusions Channelization is one of the primary factors affecting the abundance and species

richness in the studied streams

Increased channelization severeness results in a shift in species composition,

causing changes in the stream ecosystem.

A limited impact on the watercourse can have a large impact on the fish

community in terms of both relative abundance and species richness.

Nordic multi-mesh Stream Survey Nets proved to be relatively easy to operate

and were found well suitable for these kinds of investigations.

They will make possible studies that will yield new knowledge of fish

communities in running waters

7 Acknowledgement First I would like to thank my supervisor Arne Fjälling at the Swedish

University of Agriculture for his valuable support and contribution. Further I

would like to thank Erik Degerman at the Swedish University of agriculture. I

would also like to send a special thanks to Lars Westerberg at IFM Biology for

great help at the closing stages of the project. Big thanks go to the Fisheries

Director Karl Gullberg at the County Administrative Board Gävleborg for

coordination of state, material, shelter etc. Thanks also to field staff Peter

Olsson, Marcus Lindgren, Daniel Källman and Elin Svensson who made the

fieldwork with The Nordic Multi-mesh Stream Survey Net possible.

16

8 References Allan J D., Flecker A S (1993) Biodiversity conservation in running waters.

BioScience 43, 32–43.

Calles O (2005) Fiskars migration och reproduktion i reglerade vatten -

Restaureringsåtgärder och dess effekter. Introduktionsuppsats nr 2.

Colwell R K (2013) EstimateS: Statistical estimation of species richness and

shared species from samples. Version 9. User's Guide and application published

at: http://purl.oclc.org/estimates.

Cunjak R A (1996) Winter habitat of selected stream fishes and potential

impacts from land-use activity. Canadian Journal of Fisheries and Aquatic

Sciences 53 (Suppl. 1): 267–282.

Degerman E, Beijer U, Bergquist B (2005) Bedömning av miljötillstånd i

kustvattendrag med hjälp av fisk. Fiskeriverket informerar 2005: 1, 67 sidor

Dodds W.K (2002) freshwater ecology. academic press, California USA.

Engman A C, Ramı´rez A (2012) Fish assemblage structure in urban streams of

Puerto Rico: the importance of reach and catchment scale abiotic factors.

Hydrobiologia 693,141–155

FAME CONSORTIUM (2004) Manual for the application of the European fish

index EFI.http://fame.boku.ac.at, 81 s.

Fjälling A, Degerman E , Johansson U (2013) Nordic multi-mesh gillnet for fish

sampling in lotic environments. Short Comm. Submitted. 9pp.

Gärdenfors U. (ed.) (2010) Rödlistade arter i Sverige 2010. ArtDatabanken,

SLU, Uppsala

Hortle K, Lake G (1983) Fish of channelized and unchannelized sections of the

Bunyip River, Victoria. Australian Journal. of Marine and limnology research

4.441-450.

ICES. (2004). Mesh Size Measurement Revisited. ICES Cooperative Research

Report, No. 266. 56 pp.

Jansson R, Nilsson C, Dynesius M, Andersson E (2000) Effects of river

regulation on river-margin vegetation: a comparison of eight boreal rivers.

Ecological Applications 10, 203–224.

17

Javier O, Pedro M, Leunda R, Miranda C, Garcı´a F, Francisco C , Ma Carmen

E (2005) River channelization effects on fish population structure in the Larraun

river (Northern Spain). Hydrobiologia 543,191–198

Johansson U (2011) Migration of spring-spawning fish, and comparison in

capture between fyke nets and strömöversiktsnät in the stream Hammerstaån in

the Stockholm area. Department of physics, chemistry and biology Linköping

University ,LiTH-IFM- Ex-11/2509-SE

Johansson U, Gow R, Fjälling A, Degerman E, Hedenskog M (2012)

Kartläggning av fisksamhället i Klarälven med strömöversiktsnät hösten 2011.

http://projektwebbar.lansstyrelsen.se/vanerlaxensfriagang/SiteCollectionDocum

ents/Dokumentation/Rapporter/stromoversiktsnat-i-klaralven-2011.pdf (assessed

March 2013)

Karr J R, Chu E W (1999) Restoring life in running waters: better biological

monitoring. Island Press.

Kinnerbäck A (2001) Standardiserad metodik för provfiske i sjöar. Fiskeriverket

informerar 2001(2): 1-33.

Knight S, Cullum R, Shields Jr, Smiley P (2012) Effects of Channelization on

Fish Biomass in River Ecosystems. Journal of Environmental Science and

Engineering A 1, 980-985

Lau J, KuerT, Weinman M (2006) Impacts of Channelization on Stream

Habitats and Associated Fish Assemblages in East Central Indiana. American

midland Naturalist.

Lyons J, Wang,L, Simonson TD (1996) Development and validation of an index

of biotic integrity for coldwater streams in Wisconsin. North American Journal

of Fisheries Management. 16, 241–256.

Malmqvist B, Rundle S (2002) Threats to the running water ecosystems of the

world. Environmental Conservation 29.

Mundahl N D, Simon T P (1999) Development and application of an index of

biotic integrity for coldwater streams of the upper Midwestern United States. In:

Simon, T.P. (Ed.), Assessing the Sustainability and Biological Integrity of Water

Resources Using Fish Communities. CRC Press, Boca Raton FL, 383–415.

18

Naturvårdsverket (2007) Återställning av älvar som använts för

flottning. Rapport 5649 ISBN 91-620-5649-2.pdf

Oberdorff T (1992) Fish assemblage structure in Brittany streams (France)

Aquatic Living Resources. Vol 5, 215-223

Petersen RC, Madsen B L, Wilzbach M A, Magadza C, Paarlberg A, Kullberg

A, Cummins K W (1987) Stream management: emerging global similarities.

Ambio 16, 166–179.

Paller, M. H. (2002) Temporal variability in fish assemblages from disturbed

and undisturbed streams. Journal of Aquatic Ecosystems Stress and Recovery 9,

149–158.

Rankin, E.T. (1989) The qualitative habitat evaluation index (QHEI): Rationale,

methods, and applications: Columbus, Ohio, State of Ohio Environmental

Protection Agency, Division of Water Quality Planning and Assessment.

Rhoads B L, Schwartz J S, Porter S (2003) Stream geomorphology, bank

vegetation, and three-dimensional habitat hydraulics for fish in Midwestern

agricultural streams. Water Resource. Research 39, 1218–1230.

Scarnecchia D (1988) The importance of streamling in influencing fish

community in channelized and unchannelized reaches of a prairie stream.

Regulated rivers; research and management, Vol 2 155-166.

Smoger R A, Angermeier P(1999) Effects of drainage basin and

anthropogenic disturbance on relations between stream size and IBI metrics in

Virginia. p. 249-273. In T. P. Simon (ed.), Assessing the Sustainability and

Biological Integrity of Water Resources Using Fish Communities. CRC Press,

Boca Raton.

Sutherland W.(2006). Ecological Census Techniques. Cambridge University

Press.

Sullivan B E, Rigsby L, Bernut A, Jones-Wuellner M L, SIMON T, Lauer T,

Piron M (2004) Habitat influence on fish community assemblage in an

agricultural landscape in four east central Indiana streams. Freshmeiter KcoL

19,141-148

Swales S (1988) Fish populations of a small lowland channelized river in

England subjected to long-term river maintenance and management works.

Regulated Rivers: Research & Management 2,493-506.

19

Törnlund E, Östlund L (2002) Floating timber in northern Sweden. The

construction of floatways and transformation of rivers. Environment and

History. 8, 85–106.

The Geography Specialists UNIT4/4a HATHERLEIGH IND. EST.

HATHERLEIGH DEVON EX20 3LP TELEPHONE 0843 2160 456.

VISS (2012)Water Information System Sweden, Länsstyrelserna,

http://www.viss.lansstyrelsen.se/ accessed December 2012

Wilcox B A, Murphy DD (1985) Conservation strategy: the effects of

fragmentation on extinction. American Naturalist 125:879-887.

Zalewski M, Naiman R J (1985) The regulation of riverine fish communities by

a continuum of abiotic-biotic factors, p. 3-9. In: J. S. Alabaster (ed.), Habitat

Modification and Freshwater Fisheries. Butterworths, London