Time series of German catch data of flounder, cod and perch in the Western Baltic See (coastline off Mecklenburg-Western ) Eel monitoring program, Reef program

Introduction

The data set contains by-catch abundance data of flounder and perch collected during an eel monitoring program (Dorow et al. 2012), which was established in 2008. The survey design was created by dividing the Mecklenburg- coastline in an external part of about 350 km and an internal part of about 1.358 km shoreline. Altogether 9 different areas were monitored (4 areas off the coast, Wismar Bight incl. Salzhaff, north of Kühlungsborn, north and east of Rügen island and east of island; and 5 areas in internal waters, Darß-Zingst Bodden chain, Strelasund, Greifswalder Bodden, river, and Stettin lagoon) This was done due to the salinity gradient from 15 PSU in the western areas to 10 PSU east off Usedom island and due to the different habitat types ranging from exposed sand-silt habitats off the coast to sheltered highly eutrophic internal waters with submerged vegetation. In the 9 areas each year 6 stations were randomly selected and monitored. Monitoring sites

 Wismar Bight and Salzhaff - Darß-Zingst Bodden chain  North of Kühlungsborn city - Strelasund  Northeast of Ruegen Island - Greifswalder Bodden  East of Usedom Peninsula - Peene river / Achterwasser - Stettin Lagoon

Gear system used: The fyke net system consist of an external leader net weir (high 1.8 m, length 100 m, mesh size 10 mm) with a fyke net chamber in each corner. The net square encloses a fished area of 1 ha. In addition, 6 chains of eel traps (4 double chamber fyke nets with an 8 m leader net) were placed inside the 100m x 100 m net square.

Mean catch per haul off coast

Perch area 1-4

10,00 8,00 6,00 4,00

2,00 Index Index value 0,00 2008 2009 2010 2011 2012 Year Flounder area 1-4 100,00

80,00

60,00

40,00 Index Index value 20,00 0,00 2008 2009 2010 2011 2012 Year Mean catch per haul inside coastline

Perch area I-V

250,00

200,00 150,00 100,00

50,00 Index Index value 0,00 2008 2009 2010 2011 2012 Year Flounder area I-V 14,00 12,00

10,00 8,00

6,00 Index Index value 4,00

2,00

0,00 2008 2009 2010 2011 2012 Year Mean catch per haul all areas

Perch area 1-V 150,00

125,00

100,00 75,00

50,00 Index Index value 25,00

0,00 2008 2009 2010 2011 2012 Year

Flounder area 1-V 50,00 40,00 30,00 20,00

Index Index value 10,00 0,00 2008 2009 2010 2011 2012 Year Species list

Species Outer part (area 1-4) Inner part (area I-V)

Eel pout x x Perch x Common bream x Cod x x Flounder x x Plaice x Turbot x European smelt x x Greater Sand eel x Lesser Sand eel x Longspined bullhead x Shorthorne sculpin x Ruffe x x Roach x Pike perch x x Three-spined stickleback x Black goby x x Round goby x X Sand goby x Lesser pipefish x Reef Nienhagen

UsedPrime gears: reason for Nienhagen reef deployment was to improve, increase,1 Gill net: mesh or at size least 60 mm;maintain length 45the m, fisherydrop 2.4 mresources in this local area 1 Gill net: mesh size 55 mm; length 45 m, drop 2.4 m 1 Trammel net: mesh size 50/350 mm; length 50 m, drop 2.0 m 2 Nordic coastal survey nets: mesh size 6.5–15–20–26–35–50–70 mm length 49 m each, drop 2.0 m 5 Eel basket chains Several Cod pots

Annually 8 to 12 surveys, launching time: 24 h

Reef Nienhagen

 Used gears:  1 Gill net: mesh size 60 mm; length 45 m, drop 2.4 m  1 Gill net: mesh size 55 mm; length 45 m, drop 2.4 m  1 Trammel net: mesh size 50/350 mm; length 50 m, drop 2.0 m  2 Nordic coastal survey nets: mesh size 6.5–15–20–26–35–50–70 mm length 49 m each, drop 2.0 m  5 Eel basket chains  Several Cod pots

 Annually 8 to 12 surveys, launching time: 24 h

Reef Nienhagen

 Mean catch per haul (number per 100 m gillnets)

 Cod Flounder

11 5,5 10 5 9 4,5

8 4

7 3,5 6 3 cod Reef Nienhagen flounder Reef 2,5 5 Nienhagen

Index Index value 2 Index Index value 4 cod Reference flounder Reference 1,5 3 Börgerende Börgerende 2 1 0,5 1 0

0

2011

2012

2010

2003

2005

2007

2004

2008

2006

2009

2011

2012

2010

2003

2005

2007

2004

2008 2006 2009 Year Year Reef Nienhagen

 Mean catch per haul (number per 100 m nordic survey nets

 Cod Flounder

40 4,5 35 4

30 3,5

25 3 2,5 20 cod Reef flounder Reef 2

15 Nienhagen Nienhagen Index Index value cod Reference Index value 1,5 10 flounder Reference Börgerende 1 Börgerende 5 0,5

0 0

2011

2012

2010

2003

2005

2007

2004

2008

2006 2009 Year Year Reef Nienhagen

 Mean catch per haul (number per 100 m gill nets and nordic survey nets cobined)

 Cod Flounder

14 5 12 4,5 10 4

3,5 8 3 cod Reef 6 2,5 flounder Reef nets) Nienhagen 2 Nienhagen

4 cod Reference Index value 1,5 Börgerende flounder Reference 2 1 Börgerende 0,5 0

Index Index value (numberper 100 m 0

2011

2012

2010

2003

2005

2007

2004

2008

2006

2009

2011

2012

2010

2003

2005

2007

2004

2008 2006 Year 2009 Year Remarks

 This surveys use different gears and seasons (once a month in the reef area and only 58 24 hours lasting hauls within the eel monitoring programme,  The indices might benot comparable to the methods (gears) used in the Fish-Pro programme,  Our reef programme will continue at least until 2015,  The eel monitoring surveys probably until 2020,  The responsible authorities in the state of Mecklenburg-Vorpommern seems to have no financial resources to announce a coastal fish monitoring project,  It might be helpful to have some support from the HELCOM WG.