COMPARING OFF-BOTTOM OYSTER CULTURE AND EELGRASS (Z. MARINA) BEDS USING A HABITAT SUITABILITY INDEX

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1 COMPARING OFF-BOTTOM OYSTER CULTURE AND EELGRASS (Z. MARINA) BEDS USING A HABITAT SUITABILITY INDEX P R O J E C T T E A M L E A D S : B O B B I H U D S O N, P A C I F I C S H E L L F I S H I N S T I T U T E B R E T T D U M B A U L D, U S D A A R S, N E W P O R T, O R J E F F E R Y R. C O R D E L L, U N I V E R S I T Y O F W A S H I N G T O N F I O N A T O M A S N A S H, O R E G O N S T A T E U N I V E R S I T Y S H A R O N K R A M E R, H. T. H A R V E Y & A S S O C I A T E S PACIFIC SHELLFISH INSTITUTE By: Katie Houle & Dan Cheney katie@pacshell.org PCSGA/NSA-PCS Annual Meeting Blaine, WA September 18 th, 2018 F U N D E D B Y : N O A A S A L T O N S T A L L - K E N N E D Y G R A N T N O. N A 1 5 N M F P R O J E C T W O R K G R O U P : M A R Y M I D D L E T O N, A N D Y S U H R B I E R ( P S I ), D A C E Y M E R C E R, ( U S D A A R S ), J A S O N T O F T, J A M E S K R A L J, ( U W ), L A R I S S A C L A R K E, K E L LY M U E T H I N G, C O R Y M A C K, J O N AT H A N M I N C H ( O S U )

2 US West Coast Study Sites Samish Bay, WA Taylor Shellfish Willapa Bay, WA Taylor, Pacific (Coast), Ekone Tillamook Bay, OR Pacific Seafoods Humboldt Bay, CA Pacific Seafoods Pacific Shellfish Institute (PSI) Fostering sustainable shellfish resources and a health marine environment through research and education

3 WHY DOES THIS WORK MATTER?

4 HABITAT COMPLEXITY

5 How do these habitats support other managed fish and invertebrates? Juvenile salmonids Juvenile Dungeness Juvenile English sole

6 Habitat Suitability Index: A simplified model to quantify & compare ecosystem services 1. 3D STRUCTURE/REFUGE Juvenile fish and crab seek refuge from predation in eelgrass blades, oyster clusters and aquaculture gear in these systems 2. ENHANCED PREY AVAILABILITY Epibenthic invertebrates live near the sediment surface These organisms are preferentially preyed upon by juvenile salmonids and other fish and crab species of interest

7 Habitat Suitability Index: [((NBT + DHS + DPS) x Relative Value Indices)/Max Condition]*100 Benthic Rating = NBT - Number of benthic taxa DHS - Density of total Harpacticoids (#/m 2 ) DPS - Density of total Peracarids(#/m 2 ) Each Ranked 1-3

8 Epibenthic Sampling 1 of 3 sites per bay: 7-10 reps/strata EG ED AQ

9 Habitat Suitability Index: Relative Value Indices [((NBT + DHS + DPS) x Relative Value Indices)/Max Condition]*100 Structural Complexity = mean shoot density (m 2 ) x mean leaf surface area (m 2 ). Epiphyte Loads = dry weight of epiphytes/dry weight of eelgrass (Z. marina) Macroalgae = % cover in m 2 quad

10 Eelgrass & Macroalgae Sampling

11 Habitat Suitability Index Fish Observations/1 hr Video Samish Bay, WA Data Collected Aug Eelgrass Edge AQ -20

12 Habitat Suitability Index Fish Observations/1 hr Video Tillamook Bay, OR Data Collected July Eelgrass Edge AQ 0

13 Farm-Scale Assessment: Sample multiple locations to get mean HSI value for farm Consider spring & summer sampling Assess from year to year, values may change +/- thru time Above, Samish Bay site: 48 acres/2,000,000 ft 2 of longlines!

14 Variability in Space & Time Difficult to extrapolate across broad spatial scale: Water quality Elevation Sediment composition Detrital foodweb Local predation pressure Season Year to year More brackish species! Oyster Creek Jerry s Bar

15 Limitations of our study: Should be viewed as model, not absolute values One snapshot in time Epibenthic sampling limited to one site/bay Only two ecosystem services, many more to quantify and include

16 Conclusions: Sample at multiple sites/time periods to get a mean farm-scale value Methods are replicable, simple calculations Index allows for additional parameters of interest to be included Off-bottom oyster aquaculture in mixed eelgrass systems has ecological value that should be considered by regulators