downstream migration of salmon smolts in the river rhine ... · tabel 3.1 information on detection...

Report: VA2007_57

Assigned by:

LANUV NRW

October, 2008

I.L.Y. Spierts, R. Caldenhoven, F.T. Vriese (VisAdvies) & A.W. Breukelaar (RWS

Waterdienst)

Downstream migration of salmon smolts in the river Rhine in 2008

Statuspage

© VisAdvies BV

Statuspage

Title: Downstream migration of salmon smolts in the river Rhine in 2008

Produced by: VisAdvies BV Address: Vondellaan 14 3521 GD Utrecht KvKnr. 30207643 0000 Telephone: +31 (0)30 285 1066 E-mail [email protected] Homepage: http://www.VisAdvies.nl Assigned by: LANUV NRW Authors: I.L.Y. Spierts, R. Caldenhoven, F.T. Vriese & A.W. Breukelaar E-mail: [email protected] Number of pages: 41 Key words: Salmon smolts, NEDAP TRAIL System ® Version: Final Project number: VA2007_57 Date: October, 14th 2008 Bibliographic reference: Spierts, I.L.Y., R. Caldenhoven, F.T. Vriese (VisAdvies) & A.W. Breukelaar (RWS Waterdienst), 2008. Downstream migration of salmon smolts in the river Rhine in 2008. VisAdvies BV, Utrecht. VA2007_57. 41 pag. Copyright: © 2008 VisAdvies BV Behoudens wettelijke uitzonderingen mag niets uit dit document worden verveelvoudigd, opgeslagen in een geautomatiseerd gegevensbestand, of openbaargemaakt, in enige vorm of op enige wijze hetzij elektronisch, mechanisch, door fotokopieën, opnamen of enig andere manier, zonder voorafgaande schriftelijke toestemming van VisAdvies BV.

Contents

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Contents

1 Introduction ............................................................................... 4

2 Objectives of the project ........................................................... 5

3 Materials and methods.............................................................. 6 3.1 Telemetry system ...................................................................................... 6 3.2 Salmon smolts used in the project ............................................................ 8 3.3 Tagging and surgical procedures.............................................................. 9 3.4 Data and data analysis............................................................................ 11

4 Results.................................................................................... 13 4.1 Tagging.................................................................................................... 13 4.2 Smolt detection and migration activity..................................................... 17 4.3 Migration routes of smolts in the Netherlands, losses in the river system and escapement to sea ........................................................................... 19

5 Conclusions and discussion.................................................... 29

6 References ............................................................................. 32

7 Annexes.................................................................................. 33 7.1 Registrations of smolts on the NEDAP TRAIL system®......................... 33 7.2 Most important migration routes of smolts in 2008 ................................. 38

Introduction

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1 Introduction

With the purpose of reintroduction of Atlantic salmon (Salmo salar) in the river Rhine, smolts are released every year in the tributaries of this river by the ‘Landesamt für Natur, Umwelt und Verbraucherschutz NRW (LANUV)’, in the framework of the Migratory fish programme of Northrhine-Westfalia. These smolts are introduced in the rivers shortly before their seaward migration. During their stay in the rivers, the smolts are imprinted by the characteristics of these so called ‘home waters’ and will return as adult salmon after having spent 1 to 3 years at sea. The first results of these stocking operations show that the return rate of adult salmon is relatively low compared to other salmon rivers and reintroduction programmes. It is possible that the return rate eventually is too low to establish a sustainable salmon population. Several causes for the low return rate are currently discussed:

• Loss of downstream migrating smolts; • High mortality in the marine phase of salmon, due to over fishing on the

feeding grounds; • High mortality of returning adult salmon, caused by a high level of by-catches

in commercial fisheries in the coastal area, Rhine delta and rivers. There is evidence that downstream migrating smolts are caught by professional fishermen in Lake IJsselmeer (Hartgers & Van Willigen, 2000). Also post-smolts are caught in the months May and June in the coastal waters near Haringvliet (Vriese & Wiegerinck, 1991). There is, however, no real insight in the downstream migration routes of smolts, the amount of losses during this downstream migration and the number of smolts that succeed in reaching the sea. In 2006 a pilot project on the downstream migration of salmon smolts was performed using the NEDAP TRAIL System® (Vriese & Breukelaar, 2006), to test the feasibility of a large scale study in 2007. Vriese & Breukelaar (2006) concluded that the NEDAP TRAIL System® is a viable tool for studying downstream smolt migration as 50% of the tagged smolts (n=10) were detected on the system. LANUV (Germany) and RWS Waterdienst, in cooperation with Sportvisserij Nederland, started a full scale project on the tagging of salmon smolts in 2007. In this research 78 smolts were tagged and subsequently released in the Rhine system, of which 62 were detected somewhere along the Rhine by detection stations (Downstream migration of salmon smolts in the river Rhine in 2007, Ir. F.T. Vriese (contact person) & A.W. Breukelaar, RWS Waterdienst). LANUV ordered VisAdvies to continue this large scale research, with the cooperation of RWS Waterdienst and Sportvisserij Nederland. RWS Waterdienst plays an important role in this cooperation, as this organisation donates the transponders for tagging, is responsible for the operation of the NEDAP TRAIL System®, delivers the collected data and is co-author of this report, which gives the results of the project in 2008.

Objectives of the project

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2 Objectives of the project

Strategic objective To gain insight in the downstream migration of salmon smolts in the river Rhine in 2008, with the purpose of finding out whether the downstream migration of smolts is an important bottleneck in the successful reintroduction of salmon in the Rhine system. Objectives of the project:

1) To determine the relative importance of the different migration routes of salmon smolts in the lower Rhine system in 2008;

2) To quantify the losses of smolts in the different river stretches during their downstream migration in the lower Rhine system in 2008;

3) To quantify the escapement of salmon smolts to sea in 2008; 4) To investigate, if possible, (environmental) factors that possibly influence a)

the choice of migration pathways, B) smolt mortality and C) escapement to sea.

Materials and methods

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3 Materials and methods

3.1 Telemetry system

In this project the NEDAP TRAIL System® was used. This system is based on the inductive coupling between an antenna loop and a ferrite rod antenna within transponders. The system consists of a network of detection stations placed on strategically chosen locations along the river Rhine (and Meuse) and its tributaries and implantable transponders. When a tagged fish passes a detection station its unique ID-number (among other information) is logged unto a data storage system. More information on the system can be found in Breukelaar et al. (1998) and Vriese et al. (2006).The transponder type used in this experiment has a length of 3.8 cm, a diameter of 13 mm, and a weight in air of 11,5 g. In figure 3.1, is shown that the casing of the transponder is no longer surgical glass but HDPE (High Density Poly Ethylene, right transponder), which reduces its weight considerably.

figuur 3.1 The different sizes of transponders used with the NEDAP TRAIL System® Figure 3.2 shows the network of detection stations in the lower Rhine system (situation on 1 April 2007).


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figuur 3.2 Network of detection stations (situation 1 April 2007). The station names are given in table 3.1. A new detection station, installed in the river Wupper, near Bürrig makes it possible to register the start of the downstream migration, when fish are leaving the river Wupper and Dhünn and enter the river Rhine.


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tabel 3.1 Information on detection stations.

Station nr. River (branche)/lake Location Start date 2 IJssel Kampen 01-12-96 5 Spui Zuidland 01-12-96 6 Dordtsche Kil ‘s-Gravendeel 01-12-96 7 De Noord Alblasserdam 01-12-96 8 Beneden Merwede Boven Hardinxveld

Sliedrecht 01-12-96,

verplaatst feb. 08 9 Lek Nieuwegein 01-12-96 10 Waal Vuren 01-12-96 11 Bergsche Maas Capelse Veer (Dussen) 01-12-96 12 Grensmaas Stevensweert 01-12-96 13 Rijn Xanten (BRD) 22-05-97 14 Oude Maas Spijkenisse 03-11-97 15 Roer St. Odiliënberg 19-06-98 16 Sieg Menden (BRD) 01-07-98 19 IJsselmeer Den Oever 24-02-00 18 IJsselmeer Kornwerderzand 24-02-00 25 Maas Sambeek 21-09-00 23 Maas Balgoij 21-09-00 26 Maas Afferden 21-09-00 24 Maas Sambeek below weir 01-10-01 22 Haringvliet Stellendam zuid 01-11-01 23 Haringvliet Stellendam noord 03-12-01 28 Maas Borgharen 10-10-01 27 Maas Itteren 01-05-03 36 Maas Linne wkc 04-09-02 37 Maas Linne vistrap 09-09-03 33 Maas Linne dorp 27-08-02 35 Maas Alphen wkc 04-09-02 34 Maas Lith vistrap 09-09-03 32 Maas Lith dorp 27-08-02 31 Nederrijn Arnhem 24-02-05 30 Nederrijn Maurik 16-03-05 29 Nederrijn Hagestein 17-03-05 38 Berwijn Moelingen 39 Wupper Burrig 40 Lippe Wesel

3.2 Salmon smolts used in the project

The Atlantic salmon smolts used were reared at two different locations: 1) LANUV in Kirchhundem-Albaum (Rückkehrer 2+), and 2) ‘Lachscentrum Hasper Talsperre’ in Hagen-Haspe (Ätran 2+). These fish had not smoltified at age 1 and were used because of their size (minimum length of 25 cm and weight of 150 g). Current technical limitations (e.g. size of the antenna coil in the transponder) of the NEDAP system restrict a further reduction of tag size, thus making it impossible to tag age 1 smolts. Lacroix et al. (2004) state that tag length should not exceed 16% of the body length and tag weight should be less than 8%, which was respected during this study.


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3.3 Tagging and surgical procedures

In total 120 fish were tagged: on February 19th 2008 in Kirchhundem-Albaum (60 fish) and on February 20th 2008 in Hagen-Haspe (60 fish). A crew from VisAdvies, Sportvisserij Nederland and RWS Waterdienst performed the surgery. Feeding of smolts was ceased 24 hours before. The surgical procedure used, is described by Vriese (1995). This procedure was originally developed for implantation of transponders in larger salmonids. Some of the surgical equipment used (V-shaped trough, tubes etc.) had to be downsize because of the smaller size of the smolts. All smolts were individually anaesthetized, using a 40 mg/l benzocaïn solution to obtain a stage 3 level of anaesthesia (i.e., total loss of equilibrium and swimming motion, absence of reactivity and reflexes, and no opercular motion, see figure 3.3A). Induction time was 5-7 min. Total length and weight was measured first. The fish was then placed ventral side up into a V-shaped operating trough, which is part of a live support system (see figures 3.3BCD). One end of the V-shaped trough and the head of the fish were immersed in a small tank filled with a 20 mg/l aerated benzocaïn solution. A small flexible tube, within a facial mask that covers the front end of the head, is induced in the mouth of the fish and the benzocaïn solution is pumped through the gills of the smolt to ensure proper aeration during the surgical procedure.

A Anaesthetized smolt B Facility at Albaum

C Life support system D Smolt in V-shaped trough

figuur 3.3 Operation procedures.


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All surgical equipment and the transponders were cold sterilized by a minimum of 15-min. immersion in a benzalkonium chloride solution and rinsed in sterile saline. Also sterile surgical gloves and drapes were used. A small mid-ventral incision was made, starting about 1 cm anterior to the pelvic girdle with a curved-point, number 22 sterile scalpel blade, extending for 2,5 cm. The disinfected tag was positioned in the peritoneal cavity, directly under the incision. The incision was then closed with three simple, interrupted stitches that were tied with surgeons’ knots, using Vicryl® 3/0 FS-1 Ethicon. After surgery, fish were held shortly for observation in a small recovery tank. When the smolt was reacting normally, in terms of breathing, equilibrium and swimming motion, it was placed in a larger holding tank. All smolts were held in captivity for approximately 10 days to monitor the recovery and wound healing. No mortality was observed during this period and fish were released in good health. Smolts were released in three batches into the rivers Sieg, Dhünn and Wupper. One batch with 40 individuals went into the Sieg, a right-bank tributary of the river Rhine downstream of Bonn, approximately 15.3 km upstream of the mouth to the Rhine (see figure 3.4).

figuur 3.4 Location of the river Sieg, Near Bonn.

The second batch with 40 individuals went into the Wupper, a right-bank tributary of the river Rhine downstream of Cologne, approximately 22.4 km upstream of the mouth to the Rhine. The third batch of 40 individuals was transported to the river Dhünn, a small tributary of the Wupper and released about 8.9 km upstream of the Rhine (see figure 3.5). Fish operated in Hagen-Haspe and in Kirchhundem-Albaum were equally distributed over the three rivers. Fish were released in the rivers Sieg, Dhünn and Wupper on March 3rd 2008.


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figuur 3.5 Location of the rivers Wupper and Dhünn, Near Cologne.

3.4 Data and data analysis

After fish were released, RWS Waterdienst delivered spreadsheets with information on the detections of smolts on the network of detection stations (see figure 2). The spreadsheets were ‘cleaned’ of false detections, detections of other fish species, system checks and routine checks of transponder signals. Data up to May 1st 2008 were used to write this report. After this date no more smolts were detected. From the collective data each individual smolt was followed on its journey to the sea or to the detection station it was detected for the last time. In quite a few cases it became clear that smolts were not detected on one or more stations during their migration. The majority of these events were related to stations being out of order or, more important, to the particular discharge situation in the spring of 2008. During high discharge events detection station locations flooded, resulting in a possibility to pass the detection stations undetected, via the flooded areas. Transmission time of the unique transponder signal was two times 8 seconds, with a pause of 8 seconds in between, followed by a mute period of two minutes to prevent the batteries from running down in case when a tagged fish stops in the reach of an antenna. In case of a detection series at a single detection station with intervals between the detections of three minutes or less, all detections were joined together and considered to be one registration. To describe migration routes of the tagged fish, the assumption was made that in a sequence of registrations swimming direction continuously turns. Such assumption was needed because with the NEDAP TRAIL System® swimming direction cannot be detected. In an earlier study 91,5% of the animals reached the next detection station as was determined from the sequence of registrations on a particular detection station (Bij de Vaate & Breukelaar, 2001).


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Based on the detection data several aspects like smolt activity, relative importance of different routes, factors influencing the migration direction, migration speed, mortality and escapement of smolts were analysed.

Results

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4 Results

4.1 Tagging

In table 4.1 the information on the tagged salmon smolts is shown.

tabel 4.1 Data on tagged smolts from different origin.

Nr. Date Location of origin

Transponder number

Weight (g) Total length (cm)

1 17-feb-08 Albaum 6142 288 32

2 17-feb-08 Albaum 6134 244 30

3 17-feb-08 Albaum 6128 273 32

4 17-feb-08 Albaum 6132 268 32

5 17-feb-08 Albaum 6141 340 34

6 17-feb-08 Albaum 6140 273 32

7 17-feb-08 Albaum 6136 259 31

8 17-feb-08 Albaum 6129 264 30

9 17-feb-08 Albaum 6138 175 26

10 17-feb-08 Albaum 6135 260 31

11 17-feb-08 Albaum 6139 246 31

12 17-feb-08 Albaum 6131 267 31

13 17-feb-08 Albaum 6143 248 31

14 17-feb-08 Albaum 6125 383 31

15 17-feb-08 Albaum 6133 244 31

16 17-feb-08 Albaum 6127 296 34

17 17-feb-08 Albaum 6144 247 31

18 17-feb-08 Albaum 6145 279 32

19 17-feb-08 Albaum 6137 256 31

20 17-feb-08 Albaum 6146 269 31

21 17-feb-08 Albaum 6175 312,7 33

22 17-feb-08 Albaum 6181 239,4 30

23 17-feb-08 Albaum 6179 313 32

24 17-feb-08 Albaum 6168 295,5 32

25 17-feb-08 Albaum 6189 238,5 31

26 17-feb-08 Albaum 6183 257,3 31

27 17-feb-08 Albaum 6172 218,1 30

28 17-feb-08 Albaum 6185 243,8 31

29 17-feb-08 Albaum 6186 242,2 30

30 17-feb-08 Albaum 6188 243 31

31 17-feb-08 Albaum 6173 228,6 31

32 17-feb-08 Albaum 6170 269,5 32

33 17-feb-08 Albaum 6171 216,5 29

34 17-feb-08 Albaum 6176 188,2 27

35 17-feb-08 Albaum 6178 222,9 30

36 17-feb-08 Albaum 6177 223,5 30

37 17-feb-08 Albaum 6187 260,7 32

Results

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Transponder number


38 17-feb-08 Albaum 6184 187,5 29

39 17-feb-08 Albaum 6180 181,6 28

40 17-feb-08 Albaum 6169 251,4 31

41 19-feb-08 Albaum 6231 241,2 31

42 19-feb-08 Albaum 6222 177,4 26

43 19-feb-08 Albaum 6213 270 32

44 19-feb-08 Albaum 6219 281,8 31

45 19-feb-08 Albaum 6235 197 28

46 19-feb-08 Albaum 6228 198,8 29

47 19-feb-08 Albaum 6233 199,3 28

48 19-feb-08 Albaum 6236 184,7 29

49 19-feb-08 Albaum 6218 176,1 27

50 19-feb-08 Albaum 6216 261,3 32

51 19-feb-08 Albaum 6220 316,2 34

52 19-feb-08 Albaum 6230 277,6 33

53 19-feb-08 Albaum 6224 205,8 29

54 19-feb-08 Albaum 6225 171,5 28

55 19-feb-08 Albaum 6223 307,2 34

56 19-feb-08 Albaum 6227 284,8 32

57 19-feb-08 Albaum 6215 263,1 31

58 19-feb-08 Albaum 6237 271,2 31

59 19-feb-08 Albaum 6214 309,6 33

60 19-feb-08 Albaum 6229 275,1 33

61 20-feb-08 Hagen-Haspe 6152 217 29

62 20-feb-08 Hagen-Haspe 6163 175 26

63 20-feb-08 Hagen-Haspe 6159 250 29

64 20-feb-08 Hagen-Haspe 6167 226 28

65 20-feb-08 Hagen-Haspe 6149 309 33

66 20-feb-08 Hagen-Haspe 6162 297 32

67 20-feb-08 Hagen-Haspe 6150 317 33

68 20-feb-08 Hagen-Haspe 6166 248 29

69 20-feb-08 Hagen-Haspe 6185 267 31

70 20-feb-08 Hagen-Haspe 6148 281 30

71 20-feb-08 Hagen-Haspe 6154 294 31

72 20-feb-08 Hagen-Haspe 6161 245 29

73 20-feb-08 Hagen-Haspe 6155 209 27

74 20-feb-08 Hagen-Haspe 6164 241 30

75 20-feb-08 Hagen-Haspe 6151 175 26

76 20-feb-08 Hagen-Haspe 6147 240 29

77 20-feb-08 Hagen-Haspe 6165 304 31

78 20-feb-08 Hagen-Haspe 6157 240 29

79 20-feb-08 Hagen-Haspe 6153 314 33

80 20-feb-08 Hagen-Haspe 6156 232 29

81 20-feb-08 Hagen-Haspe 6193 214 31

82 20-feb-08 Hagen-Haspe 6198 203 26

83 20-feb-08 Hagen-Haspe 6200 306 32

Results

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Transponder number


84 20-feb-08 Hagen-Haspe 6205 304 32

85 20-feb-08 Hagen-Haspe 6204 264 29

86 20-feb-08 Hagen-Haspe 6195 298 30

87 20-feb-08 Hagen-Haspe 6202 314 31

88 20-feb-08 Hagen-Haspe 6207 218 29

89 20-feb-08 Hagen-Haspe 6199 191 27

90 20-feb-08 Hagen-Haspe 6211 187 27

91 20-feb-08 Hagen-Haspe 6197 215 28

92 20-feb-08 Hagen-Haspe 6210 267 31

93 20-feb-08 Hagen-Haspe 6209 366 34

94 20-feb-08 Hagen-Haspe 6201 295 31

95 20-feb-08 Hagen-Haspe 6212 204 29

96 20-feb-08 Hagen-Haspe 6196 273 31

97 20-feb-08 Hagen-Haspe 6203 297 31

98 20-feb-08 Hagen-Haspe 6206 300 31

99 20-feb-08 Hagen-Haspe 6191 225 27

100 20-feb-08 Hagen-Haspe 9194 243 28

101 20-feb-08 Hagen-Haspe 6253 207 28

102 20-feb-08 Hagen-Haspe 6247 175 26

103 20-feb-08 Hagen-Haspe 6240 230 28

104 20-feb-08 Hagen-Haspe 6258 179 27

105 20-feb-08 Hagen-Haspe 6239 315 30

106 20-feb-08 Hagen-Haspe 6243 263 29

107 20-feb-08 Hagen-Haspe 6241 243 28

108 20-feb-08 Hagen-Haspe 6244 247 30

109 20-feb-08 Hagen-Haspe 6245 307 32

110 20-feb-08 Hagen-Haspe 6251 311 32

111 20-feb-08 Hagen-Haspe 6238 321 32

112 20-feb-08 Hagen-Haspe 6248 279 30

113 20-feb-08 Hagen-Haspe 6260 227 29

114 20-feb-08 Hagen-Haspe 6254 183 26

115 20-feb-08 Hagen-Haspe 6242 248 29

116 20-feb-08 Hagen-Haspe 6259 213 28

117 20-feb-08 Hagen-Haspe 6257 198 27

118 20-feb-08 Hagen-Haspe 6255 175 26

119 20-feb-08 Hagen-Haspe 6246 195 28

120 20-feb-08 Hagen-Haspe 6256 265 31 As can been seen in table 4.1, the tagged salmon smolts vary in total length from 26 to 34 cm (30 ± 2 cm) and in weight from 172 to 383 g (251 ± 45 g). Figure 4.1 shows the length frequency distribution of the smolts at the moment of tagging.

Results

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Length of smolts at tagging

0

5

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35

20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 50

Length (cm)

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er

figuur 4.1 Length frequency distribution of smolts at tagging. The total length of all tagged smolts is more or less normally distributed. Smolts from Albaum are significantly longer (31 ± 2 cm) than the smolts from Hagen-Haspe (29 ± 2 cm, Wilcoxin, P = 0,0004).

Length-weight relation smolts

0

50

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150

200

250

300

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450

0 5 10 15 20 25 30 35 40

Length (cm)

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gh

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Albaum Hagen-Haspe

figuur 4.2 Length frequency distribution of smolts at tagging. The smolts from Hagen-Haspe (251 ± 44 g) and Albaum (251 ± 48 g) do not significantly differ in average weight, as can be seen in figure 4.2 (Wilcoxin, P = 0,785). Also the length-weight distribution is very similar between the two groups of

Results

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fish. Interestingly however is the observation that the smolts from Hagen-Haspe are heavier at a certain total length, compared with the smolts from Albaum. For example: a smolt from Hagen-Haspe of 300 g has a total length of 30 cm, whereas a smolt from Albaum of the same weight has a total length of 34 cm. These differences can very likely be explained by differences in rearing conditions in Hagen-Haspe and Albaum or parental differences.

4.2 Smolt detection and migration activity

In total 120 fish were implanted with a transponder (60 in Kirchhundem-Albaum and 60 in Hagen-Haspe), of which in total 80 individuals were detected on the NEDAP TRAIL System® (67%), with in total 210 different registrations. The percentage of detections is substantially higher compared to the percentage detected individuals in downstream silver eel migration (around 50%, see Vriese et al., 2006; 2007). There is however a large difference in the percentage of detections between the six different batches of released smolts, as can be seen in table 4.2.

tabel 4.2 Detected number of smolts from different origin.

Origin of smolts River of release

N N not detected % not detected

Albaum Sieg 20 7 35%

Albaum Dhünn 20 4 20%

Albaum Wupper 20 5 25%

Hagen-Haspe Sieg 20 14 70%

Hagen-Haspe Dhünn 20 2 10%

Hagen-Haspe Wupper 20 8 40%

Total 120 40 33% In total 47.5% of the smolts released in the Sieg were detected on the NEDAP TRAIL System®. Of all fish released in the Wupper 67.5% were detected, and 85% (!) of all fish released in the Dhünn were detected. From the 60 smolts marked in Albaum 44 were detected (73%), whereas 36 smolts were detected out of the 60 that were marked in Hagen-Haspe (60%). During tagging it was observed that quite a few smolts from Hagen-Haspe were ripe males, oozing sperm. This might account for a lower willingness to migrate downstream. When looking at the detection times of smolts on the different stations, which is indicative for migration activity, there seems to be a small preference for migration during daytime as can be seen in the figures 4.3 en 4.4. The results from the study on smolts migration in 2007 also showed a similar trend in migrational preference (Vriese & Breukelaar, 2007).

Results

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Time of detection

0:00

6:00

12:00

18:00

0:00

0 30 60 90 120 150 180 210

Number of detections

Tim

e (h

ou

rs)

figuur 4.3 Time of detection of smolts

Number of detections per hour

0

5

10

15

20

25

0:00 2:00 4:00 6:00 8:00 10:00 12:00 14:00 16:00 18:00 20:00 22:00

Time (hours)

Nu

mb

er

figuur 4.4 Number of detection per hour during 24 hours The number of detections is highest between approximately 10.30 AM and 23.00 PM, although there is a lot of variation. In the early spring of 2008 (March 5th) there was a clear peak in discharge of the river Rhine (at Lobith). Several days after this peak the number of detections increased slightly (March 12th and 17th). Between March 18th and March 25th the discharge of the river Rhine at Lobith also increased. Interestingly, a few days after this increase

Results

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smolt migration seems to intensify, when looking at the number of registrations of smolts on the NEDAP TRAIL System® (April 1st, 18th and 14th, see figure 4.5).

0

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figuur 4.5 Discharge of the river Rhine at Lobith (m3/s) and number of registrations per day.

4.3 Migration routes of smolts in the Netherlands, losses in the

river system and escapement to sea

In tables 4.3-4.8 the individual migration routes are given, sorted by origin and release site. Some remarks regarding the information in the tables. When a transponder number is highlighted in yellow it is believed that the particular smolt succeeded in reaching the sea. When a detection station is in italics, there is no actual detection on the station but it is deduced from other detections that the smolt must have passed the station.

Results

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tabel 4.3 Smolts from Albaum, released in the river Sieg 03-03-08

Transponder nr.

Migration route Time (# days)

6125 Sieg-Menden 1

6127 Sieg-Menden � Rijn-Xanten (33 days) 33

6128 Sieg-Menden 1

6133 Sieg-Menden 1

6134 Sieg-Menden 1

6136 Sieg-Menden → Rijn-Xanten (3 days) 3

6138 Sieg-Menden 1


6140 Sieg-Menden 1

6141 Sieg-Menden 1

6142 Sieg-Menden 1

6143 Sieg-Menden → Rijn-Xanten → Waal-Vuren → HV-Stellendam-noord (48 days) → HV-Stellendam-zuid (2 days)

50


tabel 4.4 Smolts from Albaum, released in the river Dhünn 03-03-08

Transponder nr

Migration route Time (#days)

6169 Wupper-Burrig 5

6170 Wupper-Burrig → Rijn-Xanten (35 days) → Waal-Vuren → HV-Stellendam-noord (7 days) → HV-Stellendam-zuid → HV-Stellendam-noord → HV-Stellendam-zuid (1 day)

43


6173 Wupper-Burrig (4 days) → Rijn-Xanten) → Waal-Vuren → Beneden Merwede-Sliedrecht → De Noord-Kinderdijk (27 days)

32

6175 Wupper-Burrig (1 day) → Rijn-Xanten (6 days) 7

6176 Wupper-Burrig → Waal-Vuren → Rijn-Xanten → Beneden Merwede-Sliedrecht (9 days)

9




6181 Wupper-Burrig → Rijn-Xanten (4 days) 4


Results

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6187 Wupper-Burrig → Rijn-Xanten (37 days) → Waal-Vuren → HV-Stellendam-zuid (6 days) → HV-Stellendam-noord → HV-Stellendam-noord

43



tabel 4.5 Smolts from Albaum, released in the river Wupper 03-03-08

Transponder nr.



6214 Wupper-Burrig → Rijn-Xanten (6 days) → Waal-Vuren → Beneden Merwede-Sliedrecht (2 days)

8

6215 Wupper-Burrig → Rijn-Xanten → Nederrijn-Arnhem (23 days) → Lek-Nieuwegein (1 day)

24

6218 Wupper-Burrig → Rijn-Xanten (8 days) → Waal-Vuren (1 day) 9

6219 Wupper-Burrig → Wupper-Burrig → Rijn-Xanten → Waal-Vuren → HV-Stellendam-zuid (40 days)

40



6223 Wupper-Burrig → Rijn-Xanten (41 days) → Waal-Vuren → Beneden Merwede-Sliedrecht (2 days) → DeNoord-Kinderdijk

43




6230 Wupper-Burrig → Rijn-Xanten → Waal-Vuren (2 days) → HV-Stellendam-noord (2 days)

4


6233 Wupper-Burrig → Rijn-Xanten (5 days) → Waal-Vuren → HV-Stellendam-noord (1 day)

6


Results

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tabel 4.6 Smolts from Hagen-Haspe, released in the river Sieg 03-03-08

Transponder nr.


6150 Sieg-Menden 3

6153 Sieg-Menden 3

6156 Sieg-Menden → Rijn-Xanten → Waal-Vuren → HV-Stellendam-noord (37 days)

37

6164 Sieg-Menden 11

6166 Sieg-Menden → Rijn-Xanten (36 days) → Waal-Vuren (1 day) → HV-Stellendam-zuid (3 days)

40


tabel 4.7 Smolts from Hagen-Haspe, released in the river Dhünn 03-03-08

Transponder nr.


6191 Wupper-Burrig → Rijn-Xanten (15 days) → Waal-Vuren → HV-Stellendam-noord (7 days)

24


6194 Wupper-Burrig → Wupper-Burrig (7 days) → Rijn-Xanten (9 days) → Waal-Vuren → HV-Stellendam-noord (5 days) → HV-Stellendam-zuid → HV-Stellendam-noord

21

6195 Wupper-Burrig → Rijn-Xanten (29 days) → Waal-Vuren → HV-Stellendam-noord (4 days) → HV-Stellendam-noord (1 day)

34

6196 Wupper-Burrig → Rijn-Xanten (36 days) → Waal-Vuren → HV-Stellendam-zuid (3 days)

39

6197 Wupper-Burrig → Rijn-Xanten (3 days) → Waal-Vuren → HV-Stellendam-noord ( 13 days)

16





6203 Wupper-Burrig → Rijn-Xanten (1 day) → Waal-Vuren → HV-Stellendam-zuid (4 days)

5



6207 Wupper-Burrig → Rijn-Xanten → IJssel-Kampen (3 days) 3

6209 Wupper-Burrig → Rijn-Xanten → Waal-Vuren → HV- 20

Results

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Stellendam-noord (20 days)


6211 Wupper-Burrig → Rijn-Xanten → IJssel-Kampen (3 days) 3


tabel 4.8 Smolts from Hagen-Haspe, released in the river Wupper 03-03-08

Transponder nr.


6238 Wupper-Burrig → Rijn-Xanten → Waal-Vuren (3 days) → Beneden Merwede-Sliedrecht

3

6239 Wupper-Burrig → Rijn-Xanten (3 days) → Nederrijn-Arnhem (1 day) → Lek-Nieuwegein

14


6243 Wupper-Burrig → Rijn-Xanten (1 day) → Waal-Vuren → HV-Stellendam-noord (5 days)

6

6244 Wupper-Burrig → Rijn-Xanten (1 day) 1

6246 Wupper-Burrig → Rijn-Xanten → Waal-Vuren (3 days) → Beneden Merwede-Sliedrecht → Oude Maas-Spijkenisse (1 day)

4

6248 Wupper-Burrig → Rijn-Xanten (1 day) 1


6253 Wupper-Burrig → Rijn-Xanten (9 days) → Nederrijn-Arnhem (1 day) → Lek-Nieuwegein (1 day)

11



6260 Wupper-Burrig → Rijn-Xanten (1 day) 1 When looking at the tables, it can be concluded that from 24 fish, at least a part of, the migration route is unclear and that the passing of several stations (31 times in total) had to be deduced from detections on other stations. The stations were fish passed without being detected were: Waal-Vuren: 18 times (58% of all ‘non-detections’); Rijn-Xanten: 12 times (39% of all ‘non-detections) and 1 time at Beneden-Merwede Sliedrecht (3% of all ‘non-detections’). All these stations were also on the list of ‘non-detections’ in 2007. In all these cases fish are detected on other stations, so the overall picture of the migration routes is still valid. Nevertheless, it shows that the NEDAP TRAIL System® is to some extend vulnerable to high water situations and that there is a possibility, however small, that some fish are not detected at all.

Results

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24

Out of the 44 detected smolts from Albaum 9 fish have reached the sea (this is 15 % of all smolts marked in Albaum, see table 4.9). It is important to notice that in some cases the escapement to sea is actually observed, i.e. when fish pass the Haringvlietdam; and in some cases the escapement is assumed, when fish have passed the most downstream detection stations. The downstream migration of the fish from Hagen-Haspe was clearly more successful, 13 out of 36 detected fish reached the sea (22% of all released smolts in Hagen-Haspe). When looking at the location where smolts were released (3 rivers), the numbers of fish that successfully reach the sea are different. From the 19 detected smolts released in the Sieg, only 3 reached the sea (7,5% of all released smolts there). From the 27 detected smolts released in the Wupper, 9 reached the sea (22,5% of all released smolts there). Finally, 34 smolts released in the Dhünn were detected, of which 10 reached the sea (25% of all released smolts there). These findings are reflected in the different durations of the downstream migration of the smolts. When looking at the time it takes to reach the sea (see tables 4.3-4.8) the average duration of the seaward migration is not significant different between the smolts from Albaum (32 ± 17 days) and the smolts from Hagen-Haspe (21 ± 13 days, (Wilcoxin, P = 0,3). More interestingly are however the differences in migration time to the sea between the different release locations. Smolts released in the Sieg reached the sea slower (42 ± 7 days) than those released in Dhünn (28 ± 12 days) and those released in the Wupper (17 ± 15 days), but in both cases not significantly: Wilcoxin, P = 0,5 and P = 1, respectively). The difference in migration time between smolts released in Dhünn and those released in Wupper was significant (Wilcoxin, P = 0,03). It is however important to realise that the specific discharge situation at the time of release is of influence on the speed of the downstream migration. On the date of release of the different batches (Sieg, Dhünn and Wupper) on march 3rd 2008 the discharge at Lobith is 2322 m3/s.

Table 4.10 gives an overview of the order of importance of the different migration routes that smolts have taken in the Rhine system and where smolts have been lost in the various branches of the river system.

tabel 4.10 Migration routes in order of importance (cap behind transponder number is origin of

fish, H = Hagen-Haspe, A = Kirchhundem-Albaum).

Route nr.

Migration route Transponder nr.

Time (#days)

1a Wupper-Burrig → Rijn-Xanten → Waal-Vuren → HV-Stellendam-noord

6191H 6197H

24 16

tabel 4.9 Number and percentage of smolts detected and escaped to sea.

Origin Released Detected Sea (% of released; % of detected)

Albaum 60 44 (73%) 9 (15; 20)

Hagen-Haspe 60 36 (60%) 13 (22; 36)

Results

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6209H 6243H 6230A 6233A

20 6 4 6

1b Wupper-Burrig → Rijn-Xanten → Waal-Vuren → HV-Stellendam-zuid

6196H 6203H 6219A

39 5 40

1c Wupper-Burrig → Wupper-Burrig → Rijn-Xanten → Waal-Vuren → HV-Stellendam-noord → HV-Stellendam-zuid → HV-Stellendam-noord

6194H 21

1d Wupper-Burrig → Wupper-Burrig → Rijn-Xanten → Waal-Vuren → HV-Stellendam-noord → HV-Stellendam-zuid → HV-Stellendam-noord → HV-Stellendam-zuid

6170A 43

1e Wupper-Burrig → Rijn-Xanten → Waal-Vuren → HV-Stellendam-noord → HV-Stellendam-noord

6195H 32

1f Wupper-Burrig → Rijn-Xanten → Waal-Vuren → HV-Stellendam-zuid → HV-Stellendam-noord → HV-Stellendam-noord

6187A 43

2 Wupper-Burrig 6169A 6172A 6177A 6178A 6180A 6184A 6185A 6188A 6189A 6213A 6220A 6222A 6224A 6225A 6229A 6193H 6199H 6200H 6206H 6210H 6212H 6251H 6255H

5 1 1 9 1 9 6 8 8 8 8 1 3 9 1 8 14 9 17 19 18 11 30

3 Wupper-Burrig → Rijn-Xanten → Waal-Vuren → Beneden Merwede-Sliedrecht → Oude Maas-Spijkenisse

6246H 4

4 Wupper-Burrig → Rijn-Xanten → Waal-Vuren → Beneden Merwede-Sliedrecht → De Noord-Kinderdijk

6173A 6223A

32 43

5 Wupper-Burrig → Rijn-Xanten 6181A 6186A 6231A 6237A

4 17 34 36

Results

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6175A 6198H 6202H 6204H 6242H 6244H 6248H 6256H 6260H

7 2 11 9 2 1 1 4 1

6 Wupper-Burrig → Rijn-Xanten → Waal-Vuren 6218A 8

7 Wupper-Burrig → Rijn-Xanten → Waal-Vuren → Beneden Merwede-Sliedrecht

6214A 6176A 6238H

8 9 3

8 Wupper-Burrig → Rijn-Xanten → Nederrijn-Arnhem → Lek-Nieuwegein

6215A 6239H 6253H

24 14 11

9a Wupper-Burrig → Rijn-Xanten → IJssel-Kampen 6207H 6211H

3 3

9b Sieg-Menden → Rijn-Xanten → Waal-Vuren → HV-Stellendam-noord

6156H 37

9c Sieg-Menden → Rijn-Xanten → Waal-Vuren → HV-Stellendam-zuid

6166H 40

10 Sieg-Menden → Rijn-Xanten → Waal-Vuren →HV-Stellendam-noord → HV-Stellendam-zuid

6143A 50

11 Sieg-Menden 6125A 6128A 6133A 6134A 6138A 6140A 6141A 6142A 6150H 6153H 6164H

1 1 1 1 1 1 1 1 3 3 11

12 Sieg-Menden → Rijn-Xanten 6127A 6136A 6139A 6144A 6167H

33 3 40 3 11

In total 80 fish were detected (67%: last year 80% was detected!), 23 fish that were released in the Dhünn/Wupper and another 11 fish that were released in the Sieg were probably lost in the Rhine during migration. In other words, 43 % of the detected fish did not really migrate (34 individuals, although they very likely entered the river Rhine) and 57,5 % of the detected fish did for sure enter the river Rhine (46 fish). 15 Fish released in the Dünn and 8 fish released in the Wupper were last detected in Burrig. From the fish released in the Sieg 11 were last detected in Menden.

Results

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As can be seen in table 4.10, 22 fish are believed to have reached the sea. This means that 48% of the fish that actually entered the river Rhine (detected) for their downstream migration escaped to the sea (last year this escapement was 60%). Based on the detected amount of fish the escapement is 28%, which is much lower than the 46% escapement to sea last year. The most important migration route to sea is: 1a and 9b). Wupper-Burrig (or Sieg-Menden)→ Rijn-Xanten → Waal-Vuren → HV-Stellendam-noord. A total of 7 fish took this route (9% of the detected amount of fish, n=80). Routes 1b – 1f, 9c and 10 are, more or less, variations on a theme as all smolts migrated via the Waal and entered the sea by way of Haringvliet (Stellendam-noord; Stellendam-zuid). When including the 9 fish traveling alternatively to Stellendam, a total of 16 fish took this route (20 % of the detected amount of fish). The fish taking this route, expressed as a percentage of fish reaching the sea (n=22) is 73 % (in 2007 this was 64%). Other important routes leading to sea are 3 and 4, via the river Waal and several branches in the ‘Benedenrivierengebied’, leading to the Nieuwe Waterweg into the sea. In total 3 fish that reached the sea used these routes, being 4 % of the detected amount of fish and 14 % of the fish that reach the sea. Finally, the last 3 fish reached the sea via the Nederrijn-Lek and the Nieuwe Waterweg, also being 4 % of the detected amount of fish and 14 % of the fish that reach the sea. When dividing the released smolts in a group that reaches the sea and a group that does not, it can be concluded that smolts that do escape are slightly heavier (258 ± 43 g) than those who do not escape (251 ± 46 g), although not significantly (Wilcoxin, P = 0,18). Fish that escape are not significantly longer (30 ± 2 cm) than those who do not escape (30 ± 2 cm, Wilcoxin, P = 0.11). So, with regard to the success of downstream migration (in this experiment) it might be a plus to be heavier, as in general larger smolts are likely to be less susceptible to predation or other risks like impingement/entrainment. It could, however, also be that larger and heavier smolts are better equipped to deal with implanted transponders and are not as affected by these implants as the smaller, lighter, smolts (it has to be kept in mind that the natural smolt size is much smaller, between 13 and 22 cm). In table 4.11 downstream smolt migration and losses in the different river stretches are summarized.

tabel 4.11 Downstream smolt migration and losses in numbers and percentages of total number

of released smolts

Release site 120 smolts 100%

Losses in Dhünn 6 smolts 5%

Losses in Wupper 13 11%

Losses in Sieg 21 18%

Entering the Rhine 80 smolts 67%

Losses between Wupper-Burrig and Rijn-Xanten Losses between Sieg-Menden and Rijn-Xanten

23 smolts 11 smolts

19% 9 %

Entering the Netherlands 46 smolts 38%

Results

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Losses between Rijn-Xanten and downstream detection stations

18 smolts 15%

Entering the river IJssel 2 smolt 2%

Losses in the IJssel/IJsselmeer 2 smolt 2%

Entering the river Nederrijn-Lek 3 smolts 3%

Losses in the river Nederrijn-Lek 0 smolt 0%

Entering the river Waal 23 smolts 19%

Losses in the river Waal 4 smolts 3%

Entering the sea 22 smolts 18% The losses in the release area amount to 33% (40 of the 120 released smolts were not detected at all). A total of 67 % of the smolts probably enter the river Rhine. In the river stretch between detection stations Sieg-Menden / Wupper-Burrig and the station Rijn-Xanten another 28% of the smolts are lost (34 ind.). A total of 38% probably enter the Netherlands. In the river system between Rijn-Xanten and the detection stations directly downstream 15% of the smolts are lost. Two smolt enter the river IJssel and are lost (2%). Three smolts enter the Nederrijn-Lek (3%), of which all reach the sea. The remaining 23 smolts enter the river Waal. Of this number, 19 smolts reach the sea (16%) and 4 smolts are lost (3%). Summarizing, 62 % of the smolts are lost in the German part of the river Rhine, 20 % are lost in the Dutch part of the river Rhine and 18% of the released smolts reach the sea. Annex 7.1 shows the registrations of smolts on the NEDAP TRAIL System®. In the annex 7.2 the most important downstream migration routes are given, as the numbers of smolts that migrated via these routes. The average duration of the downstream migration to sea is approximately 13 days (from release to entering the sea at Haringvlietdam or to the most downstream detection station on the other routes, 80 detections in total). The shortest duration of downstream migration is 1 days (15 smolts) and the longest duration is 50 days (1 smolt).

Conclusions and discussion

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5 Conclusions and discussion

1. The tagged salmon smolts vary in total length from 26 to 34 cm (mean ± STD: 30 ± 2 cm) and in weight from 172 to 383 g (mean ± STD: 251 ± 45 g). The total length of all tagged smolts is normally distributed. Smolts from Albaum are significantly longer (31 ± 2 cm) than the smolts from Hagen-Haspe (29 ± 2 cm). The smolts from Hagen-Haspe (251 ± 44 g) and Albaum (251 ± 48 g) do not significantly differ in average weight.

2. Survival rate after tagging 120 (Rückkehrer 2+ and Ätran 2+) smolts with the

newest generation of NEDAP transponders was 100% until the day of release. After tagging the smolts were held for 10 days in captivity to monitor the healing process.

3. In total 120 smolts were implanted with a transponder (60 in Kirchhundem-

Albaum and 60 in Hagen-Haspe). Of these 120 smolts 80 individuals were detected on the NEDAP TRAIL System®, with in total 210 different registrations. The detected amount of smolts is almost 67%, which is substantially higher compared to the percentage detected individuals in downstream silver eel migration (around 50%). Compared to the total detection percentage in 2007 however (80%), this result is clearly lower. Below the relation with the discharge of the Rhine is dicussed.

4. There is a large difference in the percentage of detections between the six

different batches of released smolts. In total 47.5% of the smolts released in the Sieg were detected on the NEDAP TRAIL system®. Of all fish released in the Wupper 67.5% were detected, and 85% (!) of all fish released in the Dhünn were detected.

5. From the 60 smolts marked in Albaum 44 were detected (73%), whereas 36

smolts were detected out of the 60 that were marked in Hagen-Haspe (60%). During tagging it was observed that quite a few smolts from Hagen-Haspe were ripe males. This could account for a lower willingness to migrate downstream.

6. Smolts started their downstream migration very shortly after being released.

Several fish started their migration on the day of release. Smolts released in the Sieg reached the sea slower (42 ± 7 days) than those released in Dhünn (28 ± 12 days,) and those released in the Wupper (17 ± 15 days), but in both cases not significantly). The difference in migration time between smolts released in Dhünn and those released in Wupper was significant.

7. From the 40 smolts released in the Sieg 21 were not detected (53%). From

the 40 smolts released in the Dhünn 6 were not detected (15%). Finally, from the 40 smolts released in the Wupper 13 were not detected (33%).


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8. When looking at the detection times of smolts on the different stations, which is indicative for migration activity, there seems to be a small preference for migration during daytime. The results from the study on smolts migration in 2007 also showed a similar trend in migrational preference. The number of detections is highest between approximately 10.30 AM and 23.00 PM, although there is a lot of variation.

9. In the early spring of 2008 (March 5th) there was a clear peak in discharge of

the river Rhine (at Lobith). Several days after this peak the number of detections increased slightly (March 12th and 17th). Between March 18th and March 25th the discharge of the river Rhine also increased. A few days after this increase smolt migration seems to intensify (April 1st, 18th and 14th).

10. From 24 fish, at least a part of, the migration route is unclear and the passing

of several stations (31 times in total) had to be deduced from detections on other stations. The stations were fish passed without being detected were: Waal-Vuren: 18 times (58% of all ‘non-detections’); Rijn-Xanten: 12 times (39% of all ‘non-detections) and 1 time at Beneden-Merwede Sliedrecht (3% of all ‘non-detections’). All these stations were also on the list of ‘non-detections’ in 2007. In all these cases fish are detected on other stations, so the overall picture of the migration routes is still valid. Nevertheless, it shows that the NEDAP TRAIL System® is to some extend vulnerable to high water situations and that there is a possibility, however small, that some fish are not detected at all.

11. Out of 44 detected smolts from Albaum 9 fish have reached the sea. The

downstream migration of fish from Hagen-Haspe was more successful, 13 out of 36 detected fish reached the sea.

12. When looking at the location where smolts were released (3 rivers), the

numbers of smolts that successfully reach the sea are different. From the 19 detected smolts released in the Sieg, only 3 reached the sea. From the 27 detected smolts released in the Wupper, 9 reached the sea. Finally, 34 smolts released in the Dhünn were detected, of which 10 reached the sea.

13. The most important migration route to sea is: Wupper-Burrig (or Sieg-

Menden)→ Rijn-Xanten → Waal-Vuren → HV-Stellendam-noord. A total of 7 fish took this route. A group of 9 other smolts took more or less the same route and entered the sea by way of Haringvliet (Stellendam-zuid and Stellendam-noord).

14. Other important routes leading to sea are via the river Waal and several

branches in the delta area of the river Rhine, leading to the Nieuwe Waterweg into the sea. In total 3 fish that reached the sea used these routes. Three fish reached the sea via the Nederrijn-Lek and the Nieuwe Waterweg.

15. When looking at the time it takes to reach the sea. The average duration of

the seaward migration is not significant different between the smolts from Albaum (32 ± 17 days) and Hagen-Haspe (21 ± 13 days).


© VisAdvies BV

31

16. The average duration of the downstream migration to sea for the whole group of smolts is approximately 13 days (from release to entering the sea at Haringvlietdam or to the most downstream detection station on the other routes). The shortest duration of downstream migration is 1 days (3 smolts) and the longest duration is 50 days (1 smolt).

17. When dividing the released smolts in a group that reaches the sea and a

group that does not, it can be concluded that both groups do not significantly differ in weight (258 ± 43 g and 251 ± 46 g, respectively).

18. The losses in the release area amount to 33% (40 of the 120 released

smolts were not detected at all). A total of 67 % of the smolts probably enter the river Rhine. In the river stretch between detection stations Sieg-Menden / Wupper-Burrig and the station Rijn-Xanten another 28% of the smolts are lost (34 ind.). A total of 38% probably enter the Netherlands. In the river system between Rijn-Xanten and the detection stations directly downstream 15% of the smolts are lost. Two smolts enter the river IJssel and are lost (2%). Three smolts enter the Nederrijn-Lek (3%), of which all reach the sea. The remaining 23 smolts enter the river Waal. Of this number, 19 smolts reach the sea (16%) and 4 smolts are lost (3%). Summarizing, 62 % of the smolts are lost in the German part of the river Rhine, 20 % are lost in the Dutch part of the river Rhine and 18% of the released smolts reach the sea.

Important factors in the downstream migration of smolts in this experiment are weight and length of the smolts, the location of release of the tagged smolts and the discharge in the river Rhine. Although smolts that succeed in reaching the sea are heavier than those who do not reach the sea, this difference is not significantly. The smolts from Hagen-Haspe and Albaum do not significantly differ in average weight. Although the smolts from Albaum are significantly longer than the smolts from Hagen-Haspe, more individuals of this latter group do reach the sea (13 from Hagen-Haspe versus 9 from Albaum). On the date of release of the different batches (Sieg, Dhünn and Wupper) on March 3rd 2008 the discharge at Lobith is 2322 m3/s. This discharge is low compared to the discharges during release last year (5424 and 3400 m3/s, Vriese & Breukelaar, 2007). In 2007 it seemed that the larger peaks in discharge probably resulted in a faster outmigration of smolts from the river. This relation does not seem to occur when looking at the results from this year. The discharge shows less pronounced peaks and is more continuous. As a result of this the triggering effect for migration might be lower. The average duration of the seaward migration is 42, 28 and 17 days for smolts released in the Sieg, the Dhünn and the Wupper, respectively. The losses of smolts in the German part of the river Rhine (or within the tributaries where the fish are released) are high, 62%, compared to the losses in the Dutch part of the river Rhine, 20%. Finally, 18% of the released smolts do actually reach the sea.

Annexes

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6 References

Breukelaar, A.W., A. bij de Vaate & K.T.W. Fockens, 1998. Inland migration study of sea trout (Salmo trutta) into the rivers Rhine and Meuse (The Netherlands), based on inductive coupling radio telemetry. Hydrobiologia 371/372: 29-33. Bij de Vaate, A. & A.W. Breukelaar (eds.), 2001. De migratie van zeeforel in Nederland. Rijksinstituut voor Integraal Waterbeheer & Afvalwaterbehandeling, rapport nr. 2001.046. RIZA, Lelystad. Hartgers, E.M. & J.A. van Willigen (2000). Zeldzame vissen in het IJsselmeer in 1999. IJmuiden:RIVO. C014/00: pp. 1-52. Lacroix, G.L., D. Knox & P. McCurdy, 2004. Effects of implanted dummy acoustic transmitters on juvenile Atlantic salmon smolts. J. Trans. Am. Fish. Soc. 133: 211-220. Vriese, F.T. & H.J.A.M. Wiegerinck, 1991. Trout tagging experiments in Dutch coastal waters during the summer of 1990. ICES International Council for the Exploration of the Sea. – Kopenhagen, ICES C.M. 1991/M:22., 17 pp. Vriese, F.T., 1995. Implantering van transponders in salmoniden. Organisatie ter Verbetering van de Binnenvisserij, Nieuwegein. OVB-Onderzoeksrapport 1995-26, 59 p. Vriese, F.T , J.C.A. Merkx.(VisAdvies) & A.W. Breukelaar (RWS-RIZA), 2006. Population study of female downstream migrating silver eel Anguilla anguilla in the Rhine system in 2005. VisAdvies BV, Utrecht. Project VA2005_06, 72 pages. Vriese, F.T. & A.W. Breukelaar, 2006. Pilot study smolt tagging 2006. VisAdvies BV, Utrecht. VA2006_66. 8 pag. Vriese, F.T. & A.W. Breukelaar, 2007. Downstream migration of salmon smolts in the River Rhine in 2007. VisAdvies BV, Utrecht. VA2006_68. 35 pages. Vriese, F.T , J.C.A. Merkx.(VisAdvies) & A.W. Breukelaar (RWS-RIZA), 2007. Population study of female downstream migrating silver eel Anguilla anguilla in the Rhine system in 2006/2007. VisAdvies BV, Utrecht. Project VA2006_62, 31 pages.

Annexes

© VisAdvies BV

7 Annexes

7.1 Registrations of smolts on the NEDAP TRAIL system®

(sorted on transponder number)

Number Detection station Transponder number Time Date

1 Sieg_Menden 6125 14:59 3-3-2008 2 Sieg_Menden 6127 14:29 3-3-2008 3 Rijn_Xanten 6127 11:17 5-4-2008 4 Sieg_Menden 6128 22:42 3-3-2008 5 Sieg_Menden 6128 22:47 3-3-2008 6 Sieg_Menden 6133 14:19 3-3-2008 7 Sieg_Menden 6134 15:58 3-3-2008 8 Sieg_Menden 6136 14:46 3-3-2008 9 Rijn_Xanten 6136 7:15 6-4-2008

10 Sieg_Menden 6138 14:54 3-3-2008 11 Sieg_Menden 6139 15:51 3-3-2008 12 Rijn_Xanten 6139 11:51 12-4-2008 13 Sieg_Menden 6140 12:18 4-3-2008 14 Sieg_Menden 6141 15:31 3-3-2008 15 Sieg_Menden 6142 15:49 3-3-2008 16 Sieg_Menden 6143 14:40 3-3-2008 17 HV_Stellendam_noord 6143 21:11 20-4-2008 18 HV_Stellendam_zuid 6143 22:19 22-4-2008 19 Sieg_Menden 6144 14:55 3-3-2008 20 Rijn_Xanten 6144 14:20 6-3-2008 21 Sieg_Menden 6150 12:03 6-3-2008 22 Sieg_Menden 6153 6:53 6-3-2008 23 Sieg_Menden 6153 7:32 6-3-2008 24 Sieg_Menden 6156 21:45 3-3-2008 25 HV_Stellendam_noord 6156 14:51 9-4-2008 26 HV_Stellendam_noord 6156 14:59 9-4-2008 27 Sieg_Menden 6164 22:13 14-3-2008 28 Sieg_Menden 6166 16:09 3-3-2008 29 Rijn_Xanten 6166 13:25 8-4-2008 30 Waal_Vuren 6166 18:42 9-4-2008 31 HV_Stellendam_zuid 6166 16:51 12-4-2008 32 HV_Stellendam_zuid 6166 17:07 12-4-2008 33 Sieg_Menden 6167 23:42 12-3-2008 34 Rijn_Xanten 6167 9:08 23-3-2008 35 Wupper_Burrig 6169 1:24 8-3-2008 36 Wupper_Burrig 6170 3:56 4-3-2008 37 Rijn_Xanten 6170 8:16 7-4-2008 38 HV_Stellendam_noord 6170 20:16 14-4-2008 39 HV_Stellendam_zuid 6170 20:50 14-4-2008 40 HV_Stellendam_noord 6170 22:59 14-4-2008 41 HV_Stellendam_zuid 6170 14:06 15-4-2008

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42 Wupper_Burrig 6172 20:16 3-3-2008 43 Wupper_Burrig 6173 20:35 7-3-2008 44 DeNoord_Kinderdijk 6173 8:37 3-4-2008 45 Wupper_Burrig 6175 22:20 3-3-2008 46 Wupper_Burrig 6175 23:46 3-3-2008 47 Wupper_Burrig 6175 0:06 4-3-2008 48 Rijn_Xanten 6175 20:47 10-3-2008 49 Wupper_Burrig 6176 23:52 22-4-2008 50 BenMerwede_Sliedrecht 6176 19:25 1-5-2008 51 Wupper_Burrig 6177 20:30 3-3-2008 52 Wupper_Burrig 6178 3:24 12-3-2008 53 Wupper_Burrig 6180 20:26 3-3-2008 54 Wupper_Burrig 6181 2:13 10-3-2008 55 Rijn_Xanten 6181 12:36 14-3-2008 56 Wupper_Burrig 6184 2:03 12-3-2008 57 Wupper_Burrig 6185 22:51 9-3-2008 58 Wupper_Burrig 6186 20:28 2-4-2008 59 Rijn_Xanten 6186 11:38 19-4-2008 60 Wupper_Burrig 6187 3:07 8-3-2008 61 Rijn_Xanten 6187 17:27 14-4-2008 62 HV_Stellendam_zuid 6187 18:32 20-4-2008 63 HV_Stellendam_noord 6187 19:59 20-4-2008 64 HV_Stellendam_noord 6187 20:12 20-4-2008 65 Wupper_Burrig 6188 21:10 11-3-2008 66 Wupper_Burrig 6189 22:13 11-3-2008 67 Wupper_Burrig 6191 8:39 17-3-2008 68 Rijn_Xanten 6191 11:18 1-4-2008 69 HV_Stellendam_noord 6191 6:21 8-4-2008 70 HV_Stellendam_noord 6191 6:25 8-4-2008 71 HV_Stellendam_noord 6191 6:46 8-4-2008 72 HV_Stellendam_noord 6191 6:54 8-4-2008 73 HV_Stellendam_noord 6191 6:59 8-4-2008 74 Wupper_Burrig 6193 21:22 11-3-2008 75 Wupper_Burrig 6194 6:41 18-3-2008 76 Rijn_Xanten 6194 7:51 27-3-2008 77 HV_Stellendam_noord 6194 8:58 1-4-2008 78 HV_Stellendam_noord 6194 9:08 1-4-2008 79 HV_Stellendam_noord 6194 9:15 1-4-2008 80 HV_Stellendam_noord 6194 9:26 1-4-2008 81 HV_Stellendam_noord 6194 10:39 1-4-2008 82 HV_Stellendam_noord 6194 10:44 1-4-2008 83 HV_Stellendam_noord 6194 10:52 1-4-2008 84 HV_Stellendam_noord 6194 10:58 1-4-2008 85 HV_Stellendam_noord 6194 11:11 1-4-2008 86 HV_Stellendam_noord 6194 11:23 1-4-2008 87 HV_Stellendam_noord 6194 11:30 1-4-2008 88 HV_Stellendam_noord 6194 11:37 1-4-2008 89 HV_Stellendam_noord 6194 11:53 1-4-2008 90 HV_Stellendam_zuid 6194 12:07 1-4-2008 91 HV_Stellendam_zuid 6194 12:15 1-4-2008 92 HV_Stellendam_zuid 6194 12:19 1-4-2008

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93 HV_Stellendam_noord 6194 13:44 1-4-2008 94 HV_Stellendam_noord 6194 13:50 1-4-2008 95 HV_Stellendam_noord 6194 14:01 1-4-2008 96 HV_Stellendam_noord 6194 14:14 1-4-2008 97 HV_Stellendam_noord 6194 14:34 1-4-2008 98 HV_Stellendam_noord 6194 14:38 1-4-2008 99 HV_Stellendam_noord 6194 14:43 1-4-2008

100 HV_Stellendam_noord 6194 16:42 1-4-2008 101 HV_Stellendam_noord 6194 16:47 1-4-2008 102 HV_Stellendam_noord 6194 16:58 1-4-2008 103 HV_Stellendam_noord 6194 17:25 1-4-2008 104 HV_Stellendam_noord 6194 17:33 1-4-2008 105 HV_Stellendam_noord 6194 17:47 1-4-2008 106 HV_Stellendam_noord 6194 18:33 1-4-2008 107 HV_Stellendam_noord 6194 19:11 1-4-2008 108 Wupper_Burrig 6195 1:16 12-3-2008 109 Rijn_Xanten 6195 18:38 10-4-2008 110 HV_Stellendam_noord 6195 23:49 14-4-2008 111 HV_Stellendam_noord 6195 23:55 14-4-2008 112 HV_Stellendam_noord 6195 0:07 15-4-2008 113 HV_Stellendam_noord 6195 0:46 15-4-2008 114 HV_Stellendam_noord 6195 0:58 15-4-2008 115 Wupper_Burrig 6196 22:11 4-3-2008 116 Rijn_Xanten 6196 13:38 9-4-2008 117 HV_Stellendam_zuid 6196 20:46 12-4-2008 118 HV_Stellendam_zuid 6196 22:32 12-4-2008 119 Wupper_Burrig 6197 17:49 17-3-2008 120 Rijn_Xanten 6197 16:58 20-3-2008 121 HV_Stellendam_noord 6197 7:31 2-4-2008 122 Wupper_Burrig 6198 19:12 17-3-2008 123 Rijn_Xanten 6198 16:53 19-3-2008 124 Wupper_Burrig 6199 23:26 17-3-2008 125 Wupper_Burrig 6200 0:42 12-3-2008 126 Wupper_Burrig 6202 10:19 22-3-2008 127 Rijn_Xanten 6202 6:30 2-4-2008 128 Wupper_Burrig 6203 3:00 6-4-2008 129 Rijn_Xanten 6203 14:58 7-4-2008 130 HV_Stellendam_zuid 6203 21:29 11-4-2008 131 Wupper_Burrig 6204 19:48 22-3-2008 132 Rijn_Xanten 6204 18:14 31-3-2008 133 Wupper_Burrig 6206 3:39 20-3-2008 134 Wupper_Burrig 6207 20:10 17-3-2008 135 IJssel_Kampen 6207 18:47 20-3-2008 136 Wupper_Burrig 6209 1:29 31-3-2008 137 Wupper_Burrig 6209 1:39 31-3-2008 138 Wupper_Burrig 6209 1:46 31-3-2008 139 HV_Stellendam_noord 6209 22:38 20-4-2008 140 Wupper_Burrig 6210 14:51 22-3-2008 141 Wupper_Burrig 6211 0:05 12-3-2008 142 IJssel_Kampen 6211 11:01 15-3-2008 143 Wupper_Burrig 6212 21:48 21-3-2008

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144 Wupper_Burrig 6213 20:49 11-3-2008 145 Wupper_Burrig 6214 20:19 6-3-2008 146 Rijn_Xanten 6214 17:07 12-3-2008 147 BenMerwede_Sliedrecht 6214 4:54 14-3-2008 148 Wupper_Burrig 6215 12:15 15-3-2008 149 Nederrijn_Arnhem 6215 13:21 17-4-2008 150 Lek_Nieuwegein 6215 2:16 18-4-2008 151 Wupper_Burrig 6218 21:49 5-4-2008 152 Rijn_Xanten 6218 9:17 13-4-2008 153 Waal_Vuren 6218 8:19 14-4-2008 154 Wupper_Burrig 6219 2:47 5-3-2008 155 Wupper_Burrig 6219 3:04 5-3-2008 156 HV_Stellendam_zuid 6219 19:47 14-4-2008 157 Wupper_Burrig 6220 18:37 11-3-2008 158 Wupper_Burrig 6222 19:41 4-3-2008 159 Wupper_Burrig 6222 19:58 4-3-2008 160 Wupper_Burrig 6222 20:10 4-3-2008 161 Wupper_Burrig 6223 21:31 3-3-2008 162 Rijn_Xanten 6223 18:34 13-4-2008 163 BenMerwede_Sliedrecht 6223 6:27 15-4-2008 164 DeNoord_Kinderdijk 6223 9:19 15-4-2008 165 DeNoord_Kinderdijk 6223 13:20 15-4-2008 166 DeNoord_Kinderdijk 6223 14:54 15-4-2008 167 Wupper_Burrig 6224 19:32 6-3-2008 168 Wupper_Burrig 6225 2:45 12-3-2008 169 Wupper_Burrig 6229 23:10 3-3-2008 170 Wupper_Burrig 6230 2:41 4-3-2008 171 Waal_Vuren 6230 7:11 6-3-2008 172 HV_Stellendam_noord 6230 2:03 8-3-2008 173 Wupper_Burrig 6231 22:00 11-3-2008 174 Rijn_Xanten 6231 17:18 14-4-2008 175 Wupper_Burrig 6233 2:32 28-3-2008 176 Rijn_Xanten 6233 10:22 29-3-2008 177 HV_Stellendam_noord 6233 17:57 3-4-2008 178 Wupper_Burrig 6237 22:38 8-3-2008 179 Rijn_Xanten 6237 19:45 13-4-2008 180 Wupper_Burrig 6238 14:39 16-3-2008 181 Waal_Vuren 6238 7:44 19-3-2008 182 BenMerwede_Sliedrecht 6238 12:11 19-3-2008 183 Wupper_Burrig 6239 22:32 17-3-2008 184 Rijn_Xanten 6239 19:02 20-3-2008 185 Nederrijn_Arnhem 6239 6:58 21-3-2008 186 Lek_Nieuwegein 6239 22:45 21-3-2008 187 Wupper_Burrig 6242 19:14 21-3-2008 188 Rijn_Xanten 6242 11:08 23-3-2008 189 Wupper_Burrig 6243 20:23 11-3-2008 190 Rijn_Xanten 6243 15:44 12-3-2008 191 HV_Stellendam_noord 6243 19:41 17-3-2008 192 Wupper_Burrig 6244 21:33 19-3-2008 193 Rijn_Xanten 6244 15:48 20-3-2008 194 Wupper_Burrig 6246 19:20 14-3-2008

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195 Waal_Vuren 6246 15:51 17-3-2008 196 BenMerwede_Sliedrecht 6246 20:44 17-3-2008 197 OudeMaas_Spijkenisse 6246 13:23 18-3-2008 198 OudeMaas_Spijkenisse 6246 13:27 18-3-2008 199 Wupper_Burrig 6248 21:54 1-4-2008 200 Rijn_Xanten 6248 18:01 2-4-2008 201 Wupper_Burrig 6251 20:09 14-3-2008 202 Wupper_Burrig 6253 19:10 9-3-2008 203 Rijn_Xanten 6253 13:06 18-3-2008 204 Nederrijn_Arnhem 6253 15:00 19-3-2008 205 Lek_Nieuwegein 6253 15:55 20-3-2008 206 Wupper_Burrig 6255 23:58 2-4-2008 207 Wupper_Burrig 6256 19:56 24-3-2008 208 Rijn_Xanten 6256 16:01 28-3-2008 209 Wupper_Burrig 6260 15:00 16-3-2008 210 Rijn_Xanten 6260 8:24 17-3-2008

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7.2 Most important migration routes of smolts in 2008

A). Wupper-Burrig → Rijn-Xanten → Waal-Vuren → HV-Stellendam-noord

B) Wupper-Burrig → Rijn-Xanten → Waal-Vuren → HV-Stellendam-zuid

C) Wupper-Burrig → Rijn-Xanten → Waal-Vuren → Beneden Merwede-Sliedrecht → De Noord- Kinderdijk

D). Wupper-Burrig → Rijn-Xanten

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E). Wupper-Burrig → Rijn-Xanten → Waal-Vuren → Beneden Merwede-Sliedrecht

F). Wupper-Burrig → Rijn-Xanten → Nederrijn-Arnhem → Lek-Nieuwegein

G). Wupper-Burrig → Rijn-Xanten → Nederrijn-Arnhem

H). Wupper-Burrig → Rijn-Xanten → Waal-Vuren →…… → Oude Maas-Spijkenisse

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downstream migration of salmon smolts in the river rhine ... · tabel 3.1 information on detection...

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