Ecosystem goods and services of geoduck farming in South Puget Sound: A modelling analysis

Transcription

1 Ecosystem goods and services of geoduck farming in South Puget Sound: A modelling analysis Alhambra M. Cubillo, Joao G. Ferreira, Robert Marshall, Chris M. Pearce, Daniel Cheney, Bobbi Hudson, Andrew D. Suhrbier, William F. Dewey, Peter Becker, Shina Wysocki The authors dedicate this talk to John Lentz, in memoriam PESCA project, funded by NOAA Sea Grant Rotterdam, The Netherlands, October 2015

2 Outline of the talk Introducing geoducks Geoduck farming in Puget Sound Environmental effects of geoducks Case study & two-step modelling approach Individual growth model Farm-scale population model Model results: production, environmental effects and economics of geoduck farming Scaling geoduck services for the whole Puget Sound Conclusions

3 Overview of Pacific geoducks (Panopea generosa) "gooey-duck" is of Native American origin and means burrow deep Largest (up to 3 kg) and longest-lived (up to 160 years) clam Intertidal and subtidal zones of the Pacific coast of North America, in deep sandy sediments Highly priced in Asiatic markets: landed value $15-20/lb ( 35/kg) Asian culinary delicacy (crisp texture, aphrodisiac) Most are exported live to China & Hong Kong

4 Farming geoducks Seed production on-land hatcheries Harvest pressurized water jets Nursery stage (2-4 months) kg 5-6 years 10 mm seed Intertidal culture Planting intertidal beds in PVC tubes Netting & PVC pipes removal (1-2 years)

5 Geoduck harvesting in Puget Sound

6 Ecosystem interactions of geoducks Air Water Rejection and resuspension Phytoplankton and other organic matter Filter feeding Ecosystem service Removed through harvest Rejection and burial in sediments Sediment Quantify these processes to assess the environmental effects of geoduck farming

7 Geoducks can filter a huge amount of water Exhalent siphon causes a seawater bubble (video courtesy Bill Dewey).

8 Study site Simulate ecosystem goods and services of geoduck farming in Eld Inlet farm-chelsea Farms. The individual and population models were calibrated and validated for the Eld Inlet farm

9 Key processes and relationships The model simulates the physiology and growth of geoducks How the different physiological rates are affected by the environmental variables and animal size? CR (L ind -1 h -1 ) Kobayashi et al (calibrated for geoduck) y = x Tissue dry weight (g) Total Wet Weight (g) Bureau et al y = x Shell Length (mm) Most data were taken or adapted from the literature and parameterised for the study site.

10 Development of the individual model Free on-line modelling platform This model uses a net energy balance approach

11 AquaShell individual model More sophisticated model, based on the generic AquaShell framework for bivalves Seed size: 2 g TFW; culture period: 1825 days; drivers from NOAA website. AquaShell provides outputs on individual growth, metabolism and environmental effects.

12 Simulation of individual growth with Eld Inlet environmental drivers 600 Growing season Wet weight (g) Total wet weight Shell Length (mm) 100 Tissue wet weight 20 0 Shell Length Time (days) 0 The predicted growth is in good agreement with field & literature data (25 mm shell length y -1, and 600 g TFW in 5-6 years).

13 Geoduck individual growth model (AquaShell) Mass balance over a 5-year cycle Simulation of geoduck growth using Eld Inlet drivers provides outputs on production and environmental effects. These effects are scaled to the culture area in FARM.

14 Scaling to FARM population model FARM includes transport, biogeochemistry, and population dynamics Model setup: Area of 122 X 22 m; geoduck stocking density for standard model: 21 ind. m -2 ; culture period: 1825 days; drivers from NOAA website. FARM simulates production, environmental effects and economics at the farm scale.

15 Production and environmental effects of geoduck farming in Eld Inlet Farm (per 5-year cycle) VARIABLE FARM MODEL RESULTS CHELSEA FARMS Model inputs Seeding per production cycle (kg TFW) Model outputs Production Total production (TPP; kg TFW) Average Physical Product (APP; output/input) Environmental externalities Change in percentile 90 th ammonia conc. (µmol L -1 ) Change in percentile 90 th chlorophyll (mg chl m -3 ) Change in percentile 10 th O 2 concentration (mg L -1 ) ASSETS eutrophication model score Economics Geoduck sales revenue ($ per cycle) Seeding costs ($ per cycle) Farm profit ($ per cycle) 14, No change 624,629 27, ,850 Reported annual harvest is 3.5 t and annualized output from FARM is 2.9 t, considering 560 g live weight as minimum weight for harvest. Annualized gross profit determined with FARM is about US $120, , ,759 27, ,909

16 FARM model mass balance Eld Inlet farm Nutrient removal to assess eutrophication status & quantify ecosystem services At a cultivation density of 21 ind. m 2 geoducks provide an annual ecosystem service of 45 PEQ in the area of Eld Inlet Farm additional potential revenue

17 Scaling FARM results to Puget Sound For a 587 tonne annual production of farmed geoducks Phytoplankton filtered 67.6 ton C y -1 Net nitrogen removal 6.1 ton N y -1 Detritus filtered 36.3 ton C y -1 Population equivalents 1,840 PEQ y -1 Geoducks provide Puget Sound with an annual ecosystem service of 1,840 PEQ, or about USD 74,000, in removing primary symptoms of eutrophication.

18 Conclusions Local-scale models such as FARM are a good tool to assess the environmental services of cultivated animals, and are easily applied, without requiring large volumes of data Results from the FARM model indicate that geoduck and Manila clam aquaculture in Puget Sound provide a combined ecosystem service corresponding to 90,000 populationequivalents (3.6 million USD) in reducing eutrophication To the economic and social value of shellfish we have to add the ecosystem services they provide Filter-feeders such as geoducks are not only a valuable product, but can be used as nutrient bioextractors, in a bioremediation role

19 Thank you for your attention! This work was part of the PESCA (Production, Ecological, and Social Carrying Capacity Assessment) project, funded through NOAA Sea Grant. Alhambra M. Cubillo PhD Biology & Aquaculture