Geoduck Aquaculture: An Examination of Predator Protection Methodology and Potential Environmental...

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. 15.2 cm)

(2) PVC tube length (25.4 vs. 30.5 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

Intertidal Research Plot

Experimental Protocols

Growth and Survivorship

• Seed (SL: 20-60 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-seed Pre-harvest vs Post-harvest

  Seeded Plot Research Plot Seeded Plot Research Plot

  (0 m) (0-50 m) (0 m) (0-50 m)

Variable        

Percent Organics NS NS S, reduction NS

[Sulphide] at 2 cm S, reduction S, reduction NS NS

[Sulphide] at 4 cm S, reduction S, reduction NS NS

ORP at 2 cm NS NS NS S, reduction

ORP at 4 cm NS NS NS S, reduction

Total Organic Carbon NS NS NS NS

Total Nitrogen NS NS NS NS

Results

Pre-seed vs Post-seed Pre-harvest vs Post-harvest

  Seeded Plot Research Plot Seeded Plot Research Plot

Variable (0 m) (0-50 m) (0 m) (0-50 m)

Grain Size        

>2 mm NS NS S, reduction NS

1-2 mm NS NS NS NS

500 μm-1 mm NS NS NS NS

250-500 μm NS NS NS NS

125-250 μm NS NS S, increase NS

63-125 μm NS NS S, increase NS

45-63 μm NS NS S, increase NS

<45 μm NS NS NS NS

Results

0

4

8

12

16

Jun 05

Aug 05

Jan 06

Jul 06

Jul 06

Jan 07

0

10

20

30

40

50

60

70

80

90

Jun 05

Aug 05

Jan 06

Jul 06

Jul 06Jan 07

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 Variation Significance

Pipe Diameter (D) P < 0.05

Pipe Length (L) P < 0.05

Mesh Size (M) P < 0.0001

D x L NS

D x M P < 0.05

L x M NS

D x L x M NS

Results (Shell Length)

P<0.05P<0.0001

10 15Pipe Diameter (cm)

0

50

100

150

Cha

nge

inS

hell

Leng

th(%

)

12 mm6 mm

Mesh Size

P<0.005NS

6 12Mesh Size (mm)

0

50

100

150

Cha

nge

inS

hell

Leng

th(%

)

15 cm10 cm

Pipe Diameter

Results (Shell Length)

25 30Pipe Length (cm)

0

50

100

150

Cha

nge

inS

hell

Leng

th(%

)

P<0.05

Results (Wet Weight)

Source of Variation Significance

Pipe Diameter (D) P < 0.05

Pipe Length (L) P = 0.06

Mesh Size (M) P < 0.0001

D x L NS

D x M NS

L x M NS

D x L x M NS

Results (Wet Weight)

10 15Pipe Diameter (cm)

0

200

400

600

800

1000

1200

Cha

nge

inW

etW

eigh

t (%

)

P<0.05 P=0.06

25 30Pipe Length (cm)

0

200

400

600

800

1000

1200

Cha

nge

inW

etW

eigh

t (%

)

Results (Wet Weight)

Mesh Size (mm)

0

200

400

600

800

1000

1200

Cha

nge

inW

etW

eigh

t (%

)

126

P<0.0001

Results (Survivorship)

Source of Variation Significance

Pipe Diameter (D) NS

Pipe Length (L) NS

Mesh Size (M) NS

D x L NS

D x M NS

L x M NS

D x L x M NS

Pipe Diameter(cm)

Pipe Length(cm)

Mesh Size(mm)

Survivorship %(mean ± SE)

10 25 6 45.0 ± 6.5

10 25 12 38.3 ± 7.1 (min)

10 30 6 45.0 ± 7.7

10 30 12 51.7 ± 7.8

15 25 6 55.0 ± 6.5 (max)

15 25 12 50.0 ± 6.3

15 30 6 48.3 ± 7.4

15 30 12 48.3 ± 7.8

Overall 47.7 ± 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)

ABC ABBCD

BCDBC

A

DCD

Range of means: 1.16 - 1.86%

Date

0

1

2

30 m

ABC ABCBC

ABABC

AABC

C

Date

0

1

2

3

4

5

6Range of means: 1.46 - 1.83%

0-50 m

Results (Sulphide, 2 cm)

Date

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9Range of means: 0.019 - 0.162 ppm

0-50 m0 m

Date

0.0

0.1

0.2

0.3

0.4

0.5Range of means: 0.005 - 0.327 ppm

Results (Sulphide, 4 cm)

Range of means: 0.018 - 0.540 ppm

0 m

Date

0.0

0.2

0.4

0.6

0.8

1.0

1.2Range of means: 0.031 - 0.332 ppm

0-50 m

Date

0.0

0.2

0.4

0.6

0.8

1.0

1.2

Results (ORP, 2 cm)

Date

0

100

200

300

400

5000-50 m

Range of means: 249.4 - 318.0 mV

0 mRange of means: 230.3 - 342.3 mV

Date

0

100

200

300

400

500

Results (ORP, 4 cm)

Date

0

100

200

300

400

5000-50 m

Range of means: 250.1 - 315.3 mV

0 mRange of means: 240.0 - 324.0 mV

Date

0

100

200

300

400

Results (TOC %)

Date

0.0

0.2

0.4

0.6

0.8

1.0

1.20 m

Range of means: 0.164 - 0.500 %

0-50 mRange of means: 0.246 - 0.384 %

Date

0.0

0.5

1.0

1.5

Results (TN %)

Date

0.00

0.02

0.04

0.06

0.08

0.10

0.120-50 m

Range of means: 0.033 - 0.051 %

0 mRange of means: 0.027 - 0.046 %

Date

0.00

0.01

0.02

0.03

0.04

0.05

0.06

0.07

Results (Grain Size, 0 m)

Date

0

1

2

3

4

5

6

7

8

9

1-2

mm

Gra

inS

ize

(%)

Date

0

10

20

30

500

um-1

mm

Gra

inS

ize

(%)

Date

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1.0

<45

umG

rain

Siz

e(%

)

Date

0

10

20

30

>2

mm

Gra

inS

ize

(%)

Date

0

10

20

30

40

50

60

250-

500

umG

rain

Siz

e(%

)

Date

0

10

20

30

125-

250

umG

rain

Siz

e(%

)

Date

0

5

10

15

20

63-1

25um

Gra

inS

ize

(%)

Date

0.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

45-6

3um

Gra

inS

ize

(%)

Results (Grain Size, 0-50 m)

Date

0

10

20

30

40

50

>2

mm

Gra

inS

ize

(%)

Date

0

10

20

30

40

500

um-1

mm

Gra

inS

ize

(%)

Date

0

10

20

30

40

50

60

70

250-

500

umG

rain

Siz

e(%

)

Date

0

10

20

30

40

125-

250

umG

rain

Siz

e(%

)

Date

0

5

10

15

1-2

mm

Gra

inS

ize

(%)

Date

0

10

20

30

63-1

25um

Gra

inS

ize

(%)

Date

0.0

0.5

1.0

1.5

2.0

2.5

45-6

3um

Gra

inS

ize

(%)

Date

0.0

0.5

1.0

1.5

<45

umG

rain

Siz

e(%

)