Geoduck Aquaculture: An Examination of Predator Protection Methodology and Potential Environmental Impacts C.M. Pearce, Y.X. An, J.M. Blackburn, L.J. Keddy, D.L. Paltzat, S.W. Williams Fisheries and Oceans Canada Pacific Biological Station

Project Objectives Intertidal and subtidal projects with objectives: (1) To assess the effect of different forms of predator protection on survivorship and growth of juvenile clams (2) To assess the potential effects of geoduck culture on the benthic environment (3) To assess the potential effects of harvesting the clams with a high-powered water jet on the benthic environment

Intertidal Study Site Location: Head of Nanoose Bay, BC Intertidal plot: ~0.5 m chart datum Plot size: 20 m x 3 m

Experimental Treatments Predator Protection PVC tube protection methodology as used in WA Examining 3 factors: (1) PVC tube diameter (10.2 vs cm) (2) PVC tube length (25.4 vs cm) (3) Size of mesh screen on the PVC tubes (6 vs. 12 mm) 8 treatments with 30 reps per treatment (240 tubes total)

Intertidal Research Plot

Experimental Protocols Growth and Survivorship Seed (SL: mm) out-planted in July 2005 after having measured shell length and wet weights Density of two seed per tube (hand planted) Planted at 0.5-m tidal height Growth (SL and WW) and survivorship assessed after 12 months, upon removal of clams

Experimental Protocols Assessing Impacts on Benthic Environment Benthic sediment samples taken before outplanting and immediately after for determination of: (1) Sediment grain size(4) TOC and TN (2) Percent organics(5) Infaunal diversity (3) Sulphide/ORP Samples also collected at 4, 6, 10, and 12 months of experiment (post-seed) Clams then extracted with stinger and sediment samples taken immediately after and at 4 and 6 months (post- harvest)

Experimental Protocols Assessing Impacts on Benthic Environment Benthic sediment samples collected at each sample period within culture plot (0 m) and at 5, 10, 25, and 50 m distance from plot along 3 transects (3 replicates) (1) Parallel to shore line at same tidal height as plot (2) Perpendicular to shore line towards ocean (3) Perpendicular to shore line towards beach

Collection of Sediment Samples

Results Growth (length and wet weight) (1) Significantly better in the larger diameter (15 cm) than in the smaller diameter (10 cm) pipes (2) Significantly better in the shorter (25 cm) than in the longer (30 cm) pipes (3) Significantly better in the larger mesh (12 mm) than in the smaller mesh (6 mm) pipes Survivorship (1) Not significantly affected by pipe diameter, pipe length, or mesh size (average survivorship: 47.7 ± 2.5 %)

Results Pre-seed vs Post-seedPre-harvest vs Post-harvest Seeded PlotResearch PlotSeeded PlotResearch Plot (0 m)(0-50 m)(0 m)(0-50 m) Variable Percent OrganicsNS S, reductionNS [Sulphide] at 2 cmS, reduction NS [Sulphide] at 4 cmS, reduction NS ORP at 2 cmNS S, reduction ORP at 4 cmNS S, reduction Total Organic CarbonNS Total NitrogenNS

Results Pre-seed vs Post-seedPre-harvest vs Post-harvest Seeded PlotResearch PlotSeeded PlotResearch Plot Variable (0 m)(0-50 m)(0 m)(0-50 m) Grain Size >2 mmNS S, reductionNS 1-2 mmNS 500 μm-1 mmNS μmNS μmNS S, increaseNS μmNS S, increaseNS μmNS S, increaseNS <45 μmNS

Results

Conclusions (1) Growth better in the larger diameter pipes than in the smaller diameter pipes (2) Growth better in the shorter pipes than in the longer pipes (3) Growth better with the larger mesh than with smaller mesh (4) Planting and harvest have some impacts on the benthic environment, but relatively minimal

Future Research Impacts on nearby “sensitive habitat” (e.g. eelgrass and kelp beds) Monitoring potential impact of commercial-scale aquaculture development –Benthic impacts –Water column impacts

Acknowledgements Funding: DFO ACRDP, BC MAL, Manatee Holdings Ltd. TOC/TN Analyses: Maureen Soon, UBC Technical Assistance: Chanelle Mathieu, Laura Skinner, Damien Barnes (Katimavik volunteers) March Klaver, Ryan Sherman, Caroline Fox (DFO)

Results (Shell Length) Source of VariationSignificance Pipe Diameter (D)P < 0.05 Pipe Length (L)P < 0.05 Mesh Size (M)P < D x LNS D x MP < 0.05 L x MNS D x L x MNS

Results (Shell Length)

Results (Wet Weight) Source of VariationSignificance Pipe Diameter (D)P < 0.05 Pipe Length (L)P = 0.06 Mesh Size (M)P < D x LNS D x MNS L x MNS D x L x MNS

Results (Wet Weight)

Results (Survivorship) Source of VariationSignificance Pipe Diameter (D)NS Pipe Length (L)NS Mesh Size (M)NS D x LNS D x MNS L x MNS D x L x MNS

Pipe Diameter (cm) Pipe Length (cm) Mesh Size (mm) Survivorship % (mean ± SE) ± ± 7.1 (min) ± ± ± 6.5 (max) ± ± ± 7.8 Overall47.7 ± 2.5 Results (Survivorship)

Environmental Data Caveats Infaunal species data not yet ready Results somewhat complicated due to 3-way analysis (date, transect, distance) Talk will focus on the effect of date –post-seeding versus pre-seeding comparison –post-harvesting versus pre-harvesting comparison Talk will focus on specific results within the seeded plot (0 m data) and on general results within the experimental area (0-50 m)

Results (Percent Organics)

Results (Sulphide, 2 cm)

Results (Sulphide, 4 cm)

Results (ORP, 2 cm)

Results (ORP, 4 cm)

Results (TOC %)

Results (TN %)

Results (Grain Size, 0 m)

Results (Grain Size, 0-50 m)