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Invasive American razor clam Ensis directus in Belgian waters: a true opportunity for shell-fisheries? Kris Hostens1, Wouter Courtens2, Johan Craeymeersch3, Kees Goudswaard3, Jean-Sé Houziaux5†, Bea Merckx4, Gert Van Hoey1, Francis Kerckhof5, Jack Perdon3, Eric Stienen2, Vera Van Lancker5, Laurence Vigin5, Magda Vincx4 & Steven Degraer5 NIS symposium, Oostende, 22 November 2013 EnSIS: Ecosystem sensitivity to invasive species (Houziaux et al. 2011) 1 2 3 4 5 Introduction Ensis directus Labrador Ballast water North Carolina North Atlantic Ocean 2 Transportation Ensis arcuatus early development (Da Costa et al. 2008) Trochophora larvae Labrador Ballast water Veliger larvae North Carolina North Atlantic Ocean 3 Invasion pattern in Europe Ensis directus 1979: first sightings in German Bight 1987: first sightings in Belgian waters VLIZ & Severijns 2002 4 Motivation Massive strandings on (Belgian) beaches Current exploitation in the Netherlands 3000 Dutch coast Voordelta 2500 tonnes 2000 1500 1000 500 0 2006 2007 2008 2009 2010 2011 Hervás et al. 2012 What is exploitation potential of razor clams in Belgian waters ? Population structure (size classes) Abundance / Spatial distribution of Ensis directus Potential threats to the ecosystem 5 Datasets ILVO and Ghent University Macrobenthos databases 1977–ongoing – Van Veen grab samples Dave Cowles www.wallawalla.edu Van Veen = Not efficient for adults mostly only broken tips of Ensis not measurable nor identifiable OK for juveniles 6 Long-term data : Van Veen grab samples Sampling locations Ensis sp. limited to 12 nM zone Presence of Ensis directus 7 Datasets Schelp survey – ILVO July 2008 – Trawled dredge (IMARES, NL) Random stratified sampling 8 Datasets EnSIS survey – ODNature, Ugent February 2010 – – Box-Core sampler Target: higher density areas 9 Datasets ILVO epibenthos database 1989-2013 – 8m shrimp beam trawl samples Less efficient mainly ‘moving’ animals ? 10 E. directus: an introduced invasive species Houziaux et al, 2008 Gilson data 1899-1914: E. arcuatus most abundant E. directus not present yet ILVO VV data 1993-2012: E. directus most abundant Probably displaced other Ensis species nearshore E. arcuatus (E. magnus) disappeared, but present again (offshore) in low numbers since 2000 11 Relative densities of E. directus on BPNS - 2008 and 2010 Ensis directus population structure 60 Contribution to total - % (2008) Contribution to total - % (2010) Contribution to total - % (2010) - >= 6cm 50 % abundance Winter 2010 40 Summer 2008 30 20 10 0 -18 17 -17 16 -16 15 -15 14 -14 13 -13 12 -12 11 -11 10 cm cm cm cm cm cm cm cm m cm cm cm cm cm cm cm cm 0c 9-1 8-9 7-8 6-7 5-6 4-5 3-4 2-3 1-2 Shell length (cm) Ensis Spat density (VV) Strong recruitment in spring 2009 Also observed in Dutch waters 12 Relative densities of E. directus on BPNS - 2008 and 2010 Ensis directus population structure 60 Contribution to total - % (2008) Contribution to total - % (2010) Contribution to total - % (2010) - >= 6cm 50 % abundance 40 30 20 Proportional biomass same pattern in 2008 & 2010 10 Relative contributions to total weight - % 0 -18 17 -17 16 -16 15 -15 14 cm cm cm cm % Biomass Contribution to total - % (2008) Contribution to total - % (2010) Contribution to total - % (2010) - >= 6cm cm cm cm cm 30 -14 13 -13 12 -12 11 -11 10 m cm cm cm cm cm cm cm cm 0c 9-1 8-9 7-8 6-7 5-6 4-5 3-4 2-3 1-2 35 Max. 17 cm length NL min EU min 11-12 cm most common length class 25 minimum landing size EU = 10 cm ; NL = 12 cm 20 15 6-9 cm class (~ 2 years) under-represented 10 5 Predation effect? 0 cm -18 17 cm -17 16 cm -16 15 cm -15 14 cm -14 13 cm -13 12 cm -12 11 cm -11 10 cm cm cm cm cm cm cm cm cm 0 9-1 8-9 7-8 6-7 5-6 4-5 3-4 2-3 1-2 13 Ensis directus abundance Summer 2008 Juveniles (#/m²) Adults (#/m²) 14 Ensis directus adult biomass ‘Gap’ off Wenduinebank coarser sands? Summer 2008 Small yearly shifts Adult biomass max 5kg/m² Stable subtidal populations around: Nieuwpoortbank Oostendebank Vlakte van de Raan (Northern slope) Winter 2010 Extending to shallow subtidal in front of coasts Nieuwpoort and Oostende (western part of BPNS) 15 E. directus response curves Depth 5-25m Low current velocities Low mud% Low mud% in water Fine/medium sands Soft slope High Chla% Medium POC 16 Habitat Suitability models Be-Nl Based on environmental parameters Hydrodynamics (currents) Water quality (Chla, POC, %mud) Geomorphology (depth, %sand, %mud) Broad tolerance to env. parameters High reproductive and dispersal capabilities Difficult to predict abundances 17 An opportunity for commercial exploitation in Belgian waters ? 18 Impact of Hydraulic dredging technique ? Addison et al. 2006 Pumping water in top sediment layers Fluidizes sediment over a depth of 30 cm Dredge width upto 2.5 m (Tuck et al. 2000) Resuspension of PM (particulate matter) (higher mud% in BPNS) Mixing the sediment deeply changed structure 19 Impact on macrobenthic fauna ? Ensis HSM 70% match with Abra alba community HSM Richest macrobenthos community Community ‘used’ to disturbance (natural and humaninduced) Low mortality rates in thick shelled bivalves and worms Most species fast turnover rates HSM – A. alba community Degraer et al (2008) Fast recovery (~ weeks) after dredging (e.g. Hall et al, 1990 - Scotland) Fragile species selectively impacted e.g. Echinocardium cordatum (green urchin) : 30 % mortality; Lutraria lutraria (deep-burying bivalve) : 10 % Trawling/Dredging = slow Low direct impact HSM Ensis macrodat Indirect impact through seafloor structure disturbance? Overall ecosystem impact ≈ exploitation intensity ! 20 Impact on seabirds & fish ? Few seabirds prey upon benthos Mainly seaducks (common scoter, velvet scoter & eider duck) 2000 - 2011 Ensis in stomachs Literature research: Seabirds mainly prey upon Ensis length class ~ 6-9 cm Juvenile flatfish (dab, plaice, sole) mainly prey upon siphons Impact of Ensis fishery on seabirds limited ? 21 Impact on / interaction with other fisheries ? Ensis area largely overlap with coastal (shrimp) fishery ‘low impact’ on ecosystem yet unknown impact of Ensis fishery on shrimp and coastal fish stocks Duality in Belgian fishing industry: Belgian Shrimp trawls 2008-2011 • Damage to beamtrawler nets (= main métier) fishermen don’t appreciate Ensis beds • Opportunity, but conservative sector will Belgian fishermen adapt to new resource or will Dutch experienced Ensis fishermen be attracted? Demand-driven fishery Shellfish fisheries (still) forbidden by Belgian law Exploitation potential but proper management ! 22 Sustainable exploitation ! Dutch Ensis fishery started in 1990s Since 2006: 8 fishing licenses (5 active) 2012: MSC label for Ensis fishery (Hervas et al. 2012) Harvest strategy complies with conservation requirements of Voordelta & Dutch coastal zone Precautionary approach to maintain the productivity of the stock at sustainable levels maximum allowed catch 8000 tons Maximum 2400 hours / year / vessel ~ 200 fishing days of 12 h 23 Exploitation vs. standing stock in NL Stock estimates 2011 (IMARES): 100 000 million specimens ~ 500 000 to 0.8 million tons !!! Proportion >12 cm ~ 12.5% total biomass = 62 500 – 100 000 tons 3000 Dutch coast Voordelta 2011: 3700 tons landed (Hervas et al. 2012) 2500 tonnes 2000 On average 5 kg/m² in total 70 ha (0.7 km²) dredged = 50% of allowed ‘surface’ 1500 1000 500 0 2006 2007 2008 2009 2010 2011 Ensis fishery ~ 4 to 6 % of adult stock biomass in NL 24 Yield vs. Sustainable exploitation 2008 Belgian Coast (1356 km²) Amount Avg ind. /ha (millions) Voordelta (1276 km²) Amount Avg. ind/ ha (millions) Dutch Coast (6438 km²) Amount Avg ind. /ha (millions) Small (<12cm) 3 890 28 630 10 120 79 310 26 430 41 050 Big (>12cm) 2 100 15 490 1 470 11 540 4 490 6 970 Siphons 6 470 47 710 14 780 115 770 34 840 54 110 12 460 91 820 26 370 206 620 65 760 102 130 Total 2008 2013 Total 2013 Big (>12cm) Amount (millions) WetWeight (tons) ! Amount (millions) WetWeight (tons) Amount (millions) WetWeight (tons) 21 280 95 300 71 000 51 160 323 700 182 200 ILVO - IMARES IMARES J. Craeymeersch ILVO – 8m Beam trawl 1989-2013 25 What about the consumer ? I tasted them: they are delicious ! Dutch Ensis mainly exported to Spanish & Italian markets 26 Are you an Ensis eater ? no; 1 Did you already eat Ensis? yes; 15 uk; 1 In which country did you eat it? Did you like it ? ok; 6 no; 26 yes; 8 fr; 2 es; 3 be; 10 mayb e; 5 Would you eat it again ? yes; 10 no; 0 nl; 1 raw; 1 How was it served/prepared? soup; 1 boiled ;8 grilled ;8 fried; 3 Would you buy it if it were available at the supermarket ? yy; 7 ny; 14 yn; 7 nn; 12 27 Conclusion Implementation of an Ensis targeted fishery in Belgian coastal waters could be profitable & probably with limited ecosystem impacts… …if properly managed ! Continuous monitoring and further research needed Change in Belgian legislation required Change in fishermen mentality might be necessary Recipe: cooking, cleaning, baking with peas & ham serving with tomato/basilicum/whipped cream Chef-kok Eric van Veluwen, recept met scheermessen 28