Before. After. BACI-design example: The Blue Reef Project at Læsø Trindel, Kattegat. Restaurering i marin miljø 3 4 februar Sverige

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1 BACI-design eample: The Blue Reef Project at Læsø Trindel, Kattegat Josianne G. Støttrup, Claus Stenberg, Karsten Dahl Before After Restaurering i marin miljø 3 4 februar Sverige DCE, Århus University Danish Center for Environment and Energy

2 BACI B Before A After Impact C Control Y I Impact Control Before After Time Step change between Before and After Impact 2 DTU Aqua, Technical University of Denmark

3 Four standard BACI designs: 1 Single impact site single control site One year Before one year after 2 Single/multiple impact site multiple control sites One year Before one year after 3 Single impact site single control site Multiple years Before multiple years after 4 Single impact site multiple control sites Multiple years Before multiple years after 3 DTU Aqua, Technical University of Denmark From Carl James Schwarz, Simon Fraser Univ. Canada

4 BACI BACI designs are good for: Large potential changes after impact Montoring for changes in the MEAN (not changes in variability) From: Carl James Schwarz, Simon Fraser Univ. Canada BLUE REEF = only BA possible due to limited funding. 4 DTU Aqua, Technical University of Denmark

5 Baggrund for BLUE REEF Oversigtskort fra én stenfisker 5 DTU Aqua, Technical University of Denmark

6 Hvad sker det når stenene fjernes helt eller delvist fra stenrev 6 DTU Aqua, Technical University of Denmark

7 Project aims: To restore/improve the nature quality status for Læsø Tindel reef. Document the effect on biological communities General flora and fauna (AAU) Fish communities (DTU Aqua) Blue Reef: DTU Aqua, Technical Photo: University Karsten of Dahl Denmark

8 Stop further erosion Document 8 DTU Aqua, Technical Photo: University Karsten of Dahl Denmark

9 Document Re-establish original depth of ~1.2 m (now at ~4 m) 9 DTU Aqua, Technical Photo: University Karsten of Dahl Denmark

10 Document Restore perennial vegetation and bottom fauna Ensure good habitat for fish and shellfish 10 DTU Aqua, Technical Photo: University Karsten of Dahl Denmark

11 Nyt rev New stone areas at depth intervals: 1½-4½m m 2 4½-7½m m 2 7½-10m m 2 11 DTU Aqua, Technical University of Denmark

12 (før) 12 DTU Aqua, Technical University of Denmark

13 Hvad er samlet set den biologiske gevinst? Hvad er tabt i askefri tørvægt? (den gamle bund) Fauna 220 kg Algal vegetation kg Total kg (< 3% infauna) Hvad er opnået indtil videre? Fauna kg Algevegetation kg Total kg Estimeret overskud på cirka: 6100 kg askefri tørvægt alge biomasse 2850 kg fauna biomasse 13 DTU Aqua, Technical University of Denmark

14 Relativ forekomst af læbefisk, torskefisk og andet i oversigtsgarn Blue Reef projekt 14 DTU Aqua, Technical University of Denmark

15 Abundansen af torskefisk, læbefisk, fladfisk og andet i oversigtsgarn, før og efter. Blue Reef projekt CPUE (est. catch in numbers station -1 ) a. Gadidae Before After b. Labridae Before After West 6-10 m Central 2-6 m East 6-10 m 0 West 6-10 m Central 2-6 m East 6-10 m CPUE (est. catch in numbers station -1 ) c. Pleuronectiformes Before After d. Other Before After 0 West 6-10 m Central 2-6 m East 6-10 m 0 West 6-10 m Central 2-6 m East 6-10 m Area 15 DTU Aqua, Technical University of Denmark Area Støttrup et al. 2014

16 Lack of control CPUE from research trawl surveys within 50 km distance. Cod data: no increase in abundance Before ( ) to After ( ). 16 DTU Aqua, Technical University of Denmark

17 Change in overall size distribution of fish Before Frequency Fish>14 cm 16% After Frequency Fish >14 cm 30% DTU Aqua, Technical University of Denmark Fish length (cm)

18 80000 < 20 cm P>0.55 On Blue Reef: Cod < 20 cm; p< CPUE (number per ½ hour haul) cm P<0.02 Cod cm; p= > 30 cm P<0.001 Cod >30 cm; p= Before Period After CPUE from research trawl surveys Before = After = DTU Aqua, Technical University of Denmark

19 Regitrations of cod throughout the day/night in July Sunrise Sunset 6 Registrations % Time of day 19 DTU Aqua, Technical University of Denmark

20 Gennemsnitlig antal timer pr mærket torsk pr måned på Læsø Trindel for og efter reetableringen. 2.5 Cod (G. morhua) 2.0 Before After llog10 (hours) Jun Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr May Month 20 DTU Aqua, Technical University of Denmark

21 Stomach content of cod > 20 cm Relative occurrence in stomach (in numbers) Cod >20 cm Small crustecean Big crustacean Cnidaria Bivalvia Fish Polychaeta Mollusca Gastropoda Oct-2007 Oct-2012 Bryzoa Other Numbers m Potential prey availability in environment Big crustacean Small crustecean Bivalvia Cnidaria Gastropoda Mollusca Polychaeta Other Groups Groups 21 DTU Aqua, Technical University of Denmark

22 Blue Reef - Naturgenopretning af stenrev tiltrækker marsvin F Mikkelsen et al

23 Resultater 18 Læsø Trindel Reference PPM per day Year PPM (Porpoise Positive Minute) = et minut med klik detektion Mikkelsen et al

24 Conclusions Reef stabilised and shallow part restored Significant increase in benthic macrophyte and bottom fauna biomasses Fish fauna Before / After was dominated of species belonging to the wrasse family (Labridae). Cod and saithe (Gadidae) were Before infrequent but increased significantly After (factor 3-4). A full BACI may have given more conclusive results as to whether the increase in cod was due to the restored reef. 24 DTU Aqua, Technical University of Denmark

25 Conclusions Size distribution patterns in fish changed and to include larger individuals (relative occurrence of fish >14 cm increased by a factor 2) Higher frequency of larger cod in restored reef area relative to surrounding area Activity of cod on the reef showed a clear daily rhythm (active on shallow parts during the night and passive in deeper parts during the day). Activity on reef increased After. Purpoises spent more time on Blue Reef After restoration 25 DTU Aqua, Technical University of Denmark

26 Acknowledgements We would like to epress our gratitude to all the participants in the field programme and lab. work: Local fishermen: Poul Olsen and Jørgen Rulle DTU Aqua: Jesper Knudsen, Per Dolmer, Thomas Møller, Stine Kjærulf Andersen, Per Ladewig, Hans-Jørn Aggerholm Christensen, Lars Thomsen, Søren Post, Ole Henriksen, Marie Plambech, Nidia Graff Aarhus University: Jan Damgaard Nielsen and Jens Larsen Copenhagen University: Peter Rask Møller, Tammes Menne and Stine V. Christensen