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PEI Oyster Monitoring Program 2013 Report Technical Report # 251 PEI Department of Fisheries, Aquaculture and Rural Development Aquaculture Division P.O. Box 1180 548 Main Street Montague, PEI C0A 1R0

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Page 1: PEI Oyster Monitoring Program 2013 Report · Oyster growers deploying collectors in Bideford River. - 2 - Monitoring for tunicates was added to the OMP in 2006 as a result of the

PEI Oyster Monitoring Program

2013 Report

Technical Report # 251

PEI Department of Fisheries, Aquaculture and Rural Development

Aquaculture Division

P.O. Box 1180

548 Main Street

Montague, PEI

C0A 1R0

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TABLE OF CONTENTS

TABLE OF CONTENTS .............................................................................................................. i

LIST OF FIGURES .................................................................................................................. ii

LIST OF TABLES ................................................................................................................... iii

INTRODUCTION......................................................................................................................... 1

METHODS .................................................................................................................................... 2

Larvae (Spat-fall Prediction) ...................................................................................................... 3 Spat-fall ....................................................................................................................................... 5 Water Quality .............................................................................................................................. 6

Tunicate Monitoring ................................................................................................................... 6

RESULTS ...................................................................................................................................... 7 Larvae (Spat-fall Prediction) ...................................................................................................... 7

Short-Term Collectors ............................................................................................................ 7

Water Temperature ..................................................................................................................... 8 Tunicate Monitoring ................................................................................................................... 8

DISCUSSION .............................................................................................................................. 22

Factors to Consider in Timing Collector Deployment ............................................................. 22 Factors Affecting Oyster Set ..................................................................................................... 23

Limitations of the OMP ............................................................................................................. 24

APPENDIX I Maps Showing Oyster and Spat Monitoring Sites ................................................ 25

APPENDIX II Historical Spat Collection Data ........................................................................... 32

APPENDIX III Maps Displaying Current Known Range of Invasive Species in PEI ............... 35

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LIST OF FIGURES

Figure 1. Bideford River seed collection area. ............................................................................... 1

Figure 3. Sample collection sites for the 2013 Oyster Monitoring Program. ................................. 3

Figure 4. Oyster larvae, with foot extended, ready to set (365 µm). .............................................. 4

Figure 5. Short-term oyster spat collector (STC)............................................................................ 5

Figure 6. Examining oyster collectors in Bideford River for tunicates. ......................................... 6

Figure 7. Oyster Monitoring Sites in Bideford River: (1) Station site, (2) Paugh’s Creek site, (3)

Old Wharf site and (4) Green Park site. ........................................................................................ 26

Figure 8. Oyster Monitoring Sites in Foxley River: Site 5 - Lot 10, Site 6 - Gibb’s Creek, and

Site 7 - Lot 6. ................................................................................................................................ 26

Figure 9. Oyster Monitoring Site 8 - Percival River and Site 9 - Enmore River. ......................... 27

Figure 10. Oyster Monitoring Site 10 - Mill River and Site 11- Dock River ............................... 27

Figure 11. Oyster Monitoring Site 12 - Bentick Cove. ................................................................. 28

Figure 12. Oyster Monitoring Site 13 - Dunk River and Site 14- Wilmot River. ........................ 28

Figure 13. Oyster Monitoring Site 15 - West River...................................................................... 29

Figure 14. Oyster Monitoring Site 16- North River. .................................................................... 29

Figure 15. Oyster Monitoring in East River: Site 17- Cranberry Wharf and Site 18- MacWilliams

Seafood. ........................................................................................................................................ 30

Figure 16. Oyster Monitoring Site 19- Vernon River and Site 20- Orwell River. ....................... 30

Figure 17. Oyster Monitoring Site 21- Pownal Bay. .................................................................... 31

Figure 18. Current known range of the clubbed tunicate, Styela clava. ....................................... 36

Figure 19. Current known range of the golden star tunicate, Botryllus schlosseri. ...................... 37

Figure 20. Current known range of the vase tunicate, Ciona intestinalis. .................................... 38

Figure 21. Current known range of the violet tunicate, Botrylloides violaceus. .......................... 39

Figure 22. Current known range of the green crab, Carcinus maenas. ........................................ 40

Figure 23. Current known range of the oyster thief, Codium fragile. .......................................... 41

Figure 24. Current known range of the oyster drill, Urosalpinx cinerea. .................................... 42

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LIST OF TABLES

Table 1. 2013 Oyster Monitoring data from Site 1: Bideford River - Station Site ......................... 9

Table 2. 2013 Oyster Monitoring data from Site 2: Bideford River - Paugh’s Creek .................. 10

Table 3. 2013 Oyster Monitoring data from Site 3: Bideford River - Old Wharf ........................ 11

Table 4. 2013 Oyster Monitoring data from Site 4: Bideford River - Green Park ....................... 12

Table 5. 2013 Oyster Monitoring data from Site 5: Foxley River – Lot 10 ................................. 13

Table 6. 2013 Oyster Monitoring data from Site 6: Gibb’s Creek and Site 7: Lot 6 .................... 14

Table 7. 2013 Oyster Monitoring data from Site 8: Percival River and Site 9: Enmore River .... 15

Table 8. 2013 Oyster Monitoring data from Site 10: Mill River and Site 11: Dock River .......... 16

Table 9. 2013 Oyster Monitoring data from Site 12: Bentick Cove ............................................. 16

Table 10. 2013 Oyster Monitoring data from Site 13: Dunk River and Site 14: Wilmot River ... 17

Table 11. 2013 Oyster Monitoring data from Site 15: West River and Site 16: North River ...... 17

Table 12. 2013 Oyster Monitoring data from East River for Site 17: Cranberry Wharf and Site

18: MacWilliams Seafood............................................................................................................. 18

Table 13. 2013 Oyster Monitoring data from Site 19: Vernon River and Site 20: Orwell River . 19

Table 14. Oyster Monitoring data from Site 21: Pownal Bay ...................................................... 20

Table 15. Summary of occurrence of oyster larvae > 250 μm at the sites in western PEI

monitored in 2013 ......................................................................................................................... 21

Table 16. Correlation of the presence of oyster larvae > 250 μm to oyster spat set on OMP

collectors and grower collectors in the Bideford River in 2013 ................................................... 21

Table 17. PEI Shellfish Association collector deployment dates and spat set results from 1990 –

2013............................................................................................................................................... 33

Table 18. Correlation of the combined OMP larvae (> 250 μm) and spat data with grower

information from the Bideford River for 2001-2013. ................................................................... 34

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INTRODUCTION

The Prince Edward Island Oyster Monitoring Program (OMP) is a technical service provided to

oyster growers by the Department of Fisheries, Aquaculture and Rural Development (DFARD).

The OMP has operated annually since 2001, providing oyster growers with a variety of

information to assist them in the collection of oyster spat and in the management of their oyster

farming operations.

The OMP serves primarily to provide information on spat-fall prediction to oyster farmers to

assist them in determining when to deploy their spat collectors (Figure1). Information is

collected on the number and size ranges of oyster larvae present in water samples collected from

21 sites throughout the province. In addition, oyster collectors are placed in the Bideford and

Foxely River systems to monitor the timing and amount of oyster spat set. Water temperature

data is collected for the majority of monitoring sites. The emphasis of the monitoring program is

placed on the Bideford River, which is the primary oyster seed collection area on PEI.

Comparison of the numbers and size ranges of oyster larvae with the amount of spat recruitment

on OMP collectors and the water temperature data assists in predicting the timing and quantity of

oyster spat settlement. This information is collected between June and late August every year

and communicated to the growers as it is collected.

Figure 1. Oyster growers deploying collectors in Bideford River.

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Monitoring for tunicates was added to the OMP in 2006 as a result of the clubbed tunicate, Styela

clava, being identified in March Water and the potential for it to spread to the Bideford River.

The information collected from tunicate monitoring is provided to growers to make them aware

of the infestation levels, primarily in the Bideford River.

The oyster landings in PEI in 2012 were 6,143,281 lbs (aquaculture and wild fishery), with a

landed value of $7,617,000. This was an increase of 229,971 lbs from landings in 2011 (see

Figure 2). Landings have been relatively stable since 2000. Over the past several years, some

bottom leases have been converted to off-bottom leases for suspended oyster culture and it is

anticipated that cultured production may increase as a result.

Figure 2. PEI oyster landings and values from 1980 to 2012.

METHODS

Data was collected from 21 sites for the OMP in 2013 (Figure 3). Two crews were utilized to

collect the monitoring information with one crew responsible for eastern sites and the other crew

responsible for western sites. Eastern sites included East River (Cranberry Wharf and

MacWilliams Seafood), North River, West River, Pownal Bay, Orwell River and Vernon River.

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Western sites included four sites in Bideford River (Station, Paugh’s Creek, Old Wharf and

Green Park), three sites in Foxley River (Lot 10, Lot 6 and Gibbs Creek), Enmore River, Percival

River, Mill River, Dock River, Bentick Cove, Dunk River and Wilmot River. Maps displaying

the exact locations of the 21 sites are found in Appendix I.

Figure 3. Sample collection sites for the 2013 Oyster Monitoring Program.

Larvae (Spat-fall Prediction)

Collection of water samples for larvae analysis occurred from late June until mid-August.

Sampling frequency at these sites varied from 1-3 times per week with more frequent sampling

occurring during the peak setting period. Water samples were obtained by towing a 2.5 meter (5

foot) long plankton net (30 cm diameter mouth, 63 µm mesh net and bucket), from surface to

mid water column, at idle speed for approximately 5 minutes. The 63 µm net will retain all

oyster larvae greater than 90 µm (4 - 6 day old larvae). Some smaller oyster larvae were also

retained, as the net can become partially plugged during the tows. At the completion of the tow

the bucket was removed from the net and the contents transferred to a 1L bottle. In the lab, the

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sample was screened to remove any larvae, algae or debris greater than the size range of oyster

larvae, enabling oyster larvae to be observed more easily. The screened sample was transferred

to a 1L beaker, where it was swirled to concentrate the larvae to the centre of the bottom of the

beaker. A 1 mL subsample was collected from the concentrate with a pipette and placed on a

slide for microscopic examination. Each larva in the subsample was measured and its size

recorded (see Figure 4). If the sample had a very high number of larvae, a randomly chosen

subsample was collected and all the larvae were counted in the subsample. The concentration of

larvae present and their size range was made available to oyster growers via a voice mail system,

which could be accessed by calling 831-5801 locally or toll free at 1-888-831-5801. In 2013 the

monitoring results were also made available online at the following website

(http://www.gov.pe.ca/fard/oystermonitoring/). The concentration of larvae was reported using

the following scale: low (< 5), medium (6-20), high (> 20) and very high (> 100).

Figure 4. Oyster larvae, with foot extended, ready to set (365 µm).

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Spat-fall

The amount of oyster recruitment was monitored at the Station site in the Bideford River and the

―Lot 10‖ site in Foxley River using oyster spat collectors. The spat collectors consisted of a

length of galvanized wire that contains three scallop shells (scallop shells are a very good

substrate for the collection of oyster spat). The scallop shells were placed at three locations on

the wire, one at30 cm (one foot), one at 60 cm (three feet), and one at 90 cm (five feet) (Figure

5). The scallop shells had a hole drilled in the center of the shell and were slid onto the length of

wire, and supported at the correct location by a twist in the wire. Collectors were placed on a

long line every two to three days (normally Monday, Wednesday and Friday) and recovered

when the next collectors were deployed (short-term collector – STC). The oyster spat on the top

and bottom of each shell was counted using a dissecting microscope.

Figure 5. Short-term oyster spat collector (STC)

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Water Quality

Water temperature was measured at each site on the day of sampling. Salinity measurements

were taken on a periodic basis and have not been included in this report.

Tunicate Monitoring

Tunicate monitoring was initiated in 2006 in the Bideford River system because of the risk of the

clubbed tunicate, S. clava, spreading into the system from the March Water area of Malpeque

Bay. Since that time, the clubbed tunicate has been identified in the Bideford River (2007) and

has become a significant fouling organism on crop and gear (especially on the submerged rack

and bag systems). Since the majority of the oyster seed collected in the Bideford River system is

transferred to leases in other areas or to public beds for enhancement purposes, there is a

possibility that the tunicates could set on the oyster collectors and then be spread to other areas

with the transfer of oyster spat from the collectors. As a result, it was decided in 2008 to make

periodic observations of the oyster collector lines, oyster grow-out lines and mussel lines as a

method to survey and provide information on tunicate densities.

Figure 6. Examining oyster collectors in Bideford River for tunicates.

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RESULTS

Larvae (Spat-fall Prediction)

Tables 1 – 13 show the concentration, size ranges and total number (> 250 μm only) of larvae

from water samples collected on sampling dates at each of the sites monitored. The first

observation of oyster larvae was in late June. Larvae > 250 μm were first observed at the

Bideford sites between July 8th

and 10th

and between July 8th

and 16th

at the other western sites

(Table 15). The first high numbers of larvae > 250 μm were observed between July 8th

and 12th

at

the Bideford sites and between July 8th

and 28th

at the other western sites (Table 15).

Spat-fall

Table 1 displays the spat set and short-term collector results from the Station site in the Bideford

River. While the number of spat on each of the 3 shells from each collector was recorded, only

the total number of spat per collector is included in these tables. As spat set can be quite variable

within areas, and on different surfaces, it must be noted that the results on the department

collectors may not be the same as those obtained on grower collectors from the same areas.

Table 16 compares observations of larvae > 250 μm and spat set on STCs from the OMP and

observations from grower collectors at the Station site.

Short-Term Collectors

The first observation of spat on STC at the Station site in the Bideford River was on July 12th

.

The first appearance of high numbers of spat on STC was on July 15th

, four days after the first

observation of larvae greater than 250 μm. The peak number of spat on STC was July 18th

, nine

days following the initial observation of larvae greater than 250 μm.

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Water Temperature

Temperature data that was collected at the monitoring sites is displayed in the Tables 1-13.

Water temperatures were within normal ranges and should have had no adverse effects on oyster

larvae or spat.

Tunicate Monitoring

Increasing numbers of clubbed tunicates (S. clava) continue to be observed on oyster grow-out

lines and mussel lines located down river from the Shipyard Point in Bideford River. The

tunicate infestation in the Bideford River continues to increase with more clubbed tunicates

being observed on gear and product in the area this year as compared with previous years (Figure

7). As well the colonial tunicates continue to be observed in increasing abundance in Cascumpec

Bay and in the Bideford River (Figure 7). In 2013, the clubbed tunicate was identified for the

first time in Egmont Bay. The tunicate was found on oyster gear in mid November. An

Introduction and Transfer License, issued by DFO, is now required to move shellfish from these

areas, to areas where those species of tunicates are not currently present. The current distribution

(updated annually) of invasive tunicates (clubbed, vase, golden star and violet tunicate) on PEI

can be found on the department’s webpage at www.gov.pe.ca/fard and in Appendix III of this

report. The known ranges of the green crab, oyster thief and oyster drill are also included in

Appendix III.

Figure 7. Clubbed tunicate (Styela clava) on oyster spat collectors (left). Colonial tunicates on spat collectors

(middle). Close-up image of clubbed tunicate (right).

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Table 1. 2013 Oyster Monitoring data from Site 1: Bideford River - Station Site

Date Station Site Larvae Data Water Temp.

(°C)

# Spat on Collectors

**

Total #* Size Range (μm) # > 250 μm STC

June 24 0 --- 0 21.0 ---

June 28 L-1 100 0 17.8 ---

July 02 0 --- 0 20.5 ---

July 03 L-3 90-150 0 21.1 ---

July 04 M-9 100-120 0 20.5 ---

July 05 M-6 120-140 0 20.9 ---

July 08 V-135 90-290 27 --- ---

July 09 V-112 90-340 30 --- ---

July 10 H-52 90-350 20 23.5 ---

July 12 V-226 120-360 139 --- 8

July 15 V-1050 120-370 913 25.3 110

July 17 V-528 100-360 481 25.2 1247

July 19 V-194 160-350 155 23.1 537

July 22 V-734 120-360 561 23.9 419

July 24 H-42 200-330 38 22.7 ---

July 26 V-296 150-340 232 22.3 ---

July 29 H-74 80-330 62 20.9 ---

August 01 M-11 90-320 5 24.5 ---

August 05 L-1 140 0 23.9 ---

August 14 M-6 120-270 1 22.9 ---

August 22 0 --- 0 23.5 ---

August 27 0 --- 0 21.7 ---

250 micron (μm) oyster larvae take 1 to 3 days to reach a setting size of 365 μm

--- No information available.

* Larvae numbers were reported as: 1 - 5 larvae as low, 6 - 19 as medium, 20 - 99 as high and ≥ 100 as very high.

** Scallop shell collectors were deployed on the previous dates shown.

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Table 2. 2013 Oyster Monitoring data from Site 2: Bideford River - Paugh’s Creek

Date Paugh’s Creek Site Larvae Data Water Temp.

(°C) Total #* Size Range (μm) # >250 μm

June 27 L-1 75 0 18.4

July 02 0 --- 0 20.4

July 05 H-90 --- --- 21.2

July 08 H-66 120-290 11 22.7

July 10 V-111 110-350 46 23.6

July 12 H-77 130-360 58 22.8

July 15 V-314 120-350 209 26.4

July 17 V-522 160-360 477 26.1

July 22 V-2435 110-360 2005 24.0

July 24 V-128 130-360 101 23.0

July 26 V-160 100-330 87 22.7

July 29 H-21 160-330 14 21.4

August 01 0 0 0 25.5

August 05 0 0 0 25.6

250 micron (μm) oyster larvae take 1 to 3 days to reach a setting size of 365 μm

--- No information available

* Larvae numbers were reported as: 1 - 5 larvae as low, 6 - 19 as medium, 20 - 99 as high and ≥ 100 as very high.

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Table 3. 2013 Oyster Monitoring data from Site 3: Bideford River - Old Wharf

Date Old Wharf Site Larvae Data Water Temp.

(°C) Total #* Size Range (μm) # >250 μm

June 27 0 --- 0 19.0

June 28 0 --- 0 17.9

July 05 M-13 80-200 0 21.8

July 08 H-41 90-310 2 22.3

July 10 H-54 100-350 29 23.0

July 12 V-145 120-370 84 22.6

July 15 H-58 170-360 47 25.2

July 19 V-555 110-360 451 22.9

July 22 H-52 110-350 35 24.0

July 29 M-19 100-320 12 20.7

August 01 M-16 110-310 4 23.1

August 05 L-2 300-340 2 23.3

250 micron (μm) oyster larvae take 1 to 3 days to reach a setting size of 365 μm

--- No information available.

* Larvae numbers were reported as: 1 - 5 larvae as low, 6 - 19 as medium, 20 - 99 as high and ≥ 100 as very high.

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Table 4. 2013 Oyster Monitoring data from Site 4: Bideford River - Green Park

Date Green Park Site Larvae Data Water Temp.

(°C) Total #* Size Range (μm) # >250 μm

June 24 0 --- 0 20.5

July 05 M-6 130-160 0 22.1

July 08 H-34 100-240 0 22.3

July 10 M-11 190-330 8 22.8

July 12 H-45 90-350 24 22.5

July 15 M-10 110-330 2 24.6

July 22 V-136 120-350 94 23.9

July 29 M-18 150-340 16 20.7

August 01 H-34 150-350 26 22.2

August 05 L-3 110-130 0 22.5

250 micron (μm) oyster larvae take 1 to 3 days to reach a setting size of 365 μm

— No information available.

* Larvae numbers were reported as: 1 - 5 larvae as low, 6 - 19 as medium, 20 - 99 as high and ≥ 100 as very high.

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Table 5. 2013 Oyster Monitoring data from Site 5: Foxley River – Lot 10

Date Lot 10 Site Larvae Data Water Temp.

(°C)

# Spat on Collectors

**

Total #* Size Range (μm) # > 250 μm STC

June 26 L-4 70-80 0 20.6 ---

June 28 0 --- 0 16.2 ---

July 02 H-31 80-130 0 21.6 ---

July 04 H-68 70-170 0 22.8 ---

July 08 V-356 90-280 14 24.2 ---

July 10 V-115 90-320 24 23.2 ---

July 12 V-190 90-350 68 22.9 28

July 15 V-240 100-350 230 24.9 451

July 17 V-130 160-350 118 24.5 674

July 19 V-458 100-350 421 22.9 395

July 22 V-273 100-370 233 22.3 689

July 24 V-174 110-370 130 21.5 132

July 26 H-90 80-350 58 21.5 39

July 29 H-20 110-320 14 20.7 ---

August 01 V-236 90-340 180 22.3 ---

August 05 H-62 120-320 38 22.3 ---

250 micron (μm) oyster larvae take 1 to 3 days to reach a setting size of 365 μm

--- No information available.

* Larvae numbers were reported as: 1 - 5 larvae as low, 6 - 19 as medium, 20 - 99 as high and ≥ 100 as very high.

** Scallop shell collectors were deployed on the previous dates shown.

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Table 6. 2013 Oyster Monitoring data from Site 6: Gibb’s Creek and Site 7: Lot 6

Date

Gibb’s Creek Site Larvae Data

Date

Lot 6 Site Larvae Data

Total

#*

Size

Range

(μm)

# >

250

μm

Water

Temp.

(°C)

Total

#*

Size

Range

(μm)

# >

250

μm

Water

Temp

(°C)

June 26 M-9 70-95 0 19.4 --- --- --- --- ---

July 02 M-7 80-100 0 21.2 --- --- --- --- ---

July 04 H-80 --- 0 22.8 July 04 H-93 70-190 0 21.7

July 08 V-849 100-260 36 24.4 July 08 V-776 90-260 63 23.5

July 10 V-579 110-330 108 25.2 July 10 V-482 100-340 79 23.1

July 12 V-542 110-320 377 22.9 July 12 V-456 110-350 254 22.6

July 15 V-164 140-370 152 27 July 15 V-896 170-360 859 24.8

July 17 V-227 190-350 204 25 July 17 V-960 220-360 908 23.9

July 19 V-131 110-350 96 22.5 July 19 V-1312 100-360 1137 22.7

July 22 V-136 120-350 94 23.9 July 22 V-372 90-360 307 21.8

July 24 V-182 110-350 156 21.9 July 24 V-328 120-360 296 21.2

July 29 M-8 80-90 0 21.2 July 29 V-274 110-350 234 20.2

August 01 H-69 90-330 17 22.8 August 01 V-148 90-330 50 22.1

August 05 M-18 90-280 1 24.6 August 05 M-18 90-330 2 22.1

--- --- --- --- --- August 14 V-160 90-330 10 21.8

--- --- --- --- --- August 22 M-7 150-300 2 22.4

--- --- --- --- --- August 27 L-0 0 0 20.9

250 micron (μm) oyster larvae take 1 to 3 days to reach a setting size of 365 μm.

--- No information available.

* Larvae numbers were reported as: 1 - 5 larvae as low, 6 - 19 as medium, 20 - 99 as high and ≥ 100 as very high.

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Table 7. 2013 Oyster Monitoring data from Site 8: Percival River and Site 9: Enmore River

Date

Percival River Site Larvae Data

Date

Enmore River Site Larvae Data

Total

#*

Size

Range

(μm)

# >

250

μm

Water

Temp.

(°C)

Total

#*

Size

Range

(μm)

# >

250

μm

Water

Temp

(°C)

--- --- --- --- --- June 27 L-2 70-80 0 18

July 03 H-21 80-130 0 20.6 July 03 M-14 80-150 0 21

July 09 M-16 80-150 0 23.0 July 09 V-1520 80-300 62 23.1

July 16 V-754 80-340 612 25.9 July 16 V-362 80-340 225 26.3

July 18 H-77 80-340 18 23.1 July 18 V-427 90-330 390 23.2

July 23 V-208 80-320 24 22.8 July 23 V-192 70-320 46 23.3

July 25 V-122 70-320 51 22.6 July 25 H-58 80-310 2 23.5

July 30 H-74 90-330 48 21.0 July 30 L-3 80-270 1 21.3

August 06 V-186 90-270 8 22.3 August 06 V-572 80-130 0 22.3

250 micron (μm) oyster larvae take 1 to 3 days to reach a setting size of 365 μm.

--- No information available.

* Larvae numbers were reported as: 1 - 5 larvae as low, 6 - 19 as medium, 20 - 99 as high and ≥ 100 as very high.

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Table 8. 2013 Oyster Monitoring data from Site 10: Mill River and Site 11: Dock River

Date

Mill River Site Larvae Data

Date

Dock River Site Larvae Data

Total

#*

Size

Range

(μm)

# >

250

μm

Water

Temp.

(°C)

Total

#*

Size

Range

(μm)

# >

250

μm

Water

Temp

(°C)

July 04 H-25 70-130 0 20.8 --- --- --- --- ---

--- --- --- --- --- July 16 V-1576 150-350 1321 23.3

July 23 H-72 80-340 10 21.3 --- --- --- --- ---

--- --- --- --- --- July 30 L-4 200-290 1 20.9

250 micron (μm) oyster larvae take 1 to 3 days to reach a setting size of 365 μm.

--- No information available.

* Larvae numbers were reported as: 1 - 5 larvae as low, 6 - 19 as medium, 20 - 99 as high and ≥ 100 as very high.

Table 9. 2013 Oyster Monitoring data from Site 12: Bentick Cove

Date Bentick Cove Site Larvae Data Water Temp.

(°C) Total #* Size Range (μm) # >250 μm

July 03 M-14 85-110 0 20.5

July 09 V-100 85-180 0 23.4

July 16 H-24 130-350 2 24.5

July 18 V-116 80-340 62 25.6

July 23 H-80 110-350 64 22.7

July 30 H-22 140-340 12 21.9

August 06 H-24 100-350 4 22.2

July 03 M-14 85-110 0 20.5

July 09 V-100 85-180 0 23.4

250 micron (μm) oyster larvae take 1 to 3 days to reach a setting size of 365 μm

— No information available.

* Larvae numbers were reported as: 1 - 5 larvae as low, 6 - 19 as medium, 20 - 99 as high and ≥ 100 as very high.

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Table 10. 2013 Oyster Monitoring data from Site 13: Dunk River and Site 14: Wilmot River

Date

Dunk River Site Larvae Data

Date

Wilmot River Site Larvae Data

Total

#*

Size

Range

(μm)

# >

250

μm

Water

Temp.

(°C)

Total

#*

Size

Range

(μm)

# >

250

μm

Water

Temp

(°C)

July 03 H-24 75-90 0 20.5 July 03 M-19 78-95 0 20.4

July 09 V-100 70-160 0 22.7 July 09 V-100 70-140 0 22.2

July 16 H-35 80-320 1 24.6 July 16 H-73 70-240 0 25.2

July 23 H-98 90-350 58 22.0 July 23 H-80 100-340 48 ---

July 30 M-17 80-360 8 21.6 July 30 H-35 70-350 15 21.5

August 06 H-21 80-360 1 21.5 August 06 H-21 110-340 1 21.5

250 micron (μm) oyster larvae take 1 to 3 days to reach a setting size of 365 μm

--- No information available.

* Larvae numbers were reported as: 1 - 5 larvae as low, 6 - 19 as medium, 20 - 99 as high and ≥ 100 as very high.

Table 11. 2013 Oyster Monitoring data from Site 15: West River and Site 16: North River

Date

West River Site Larvae Data

Date

North River Site Larvae Data

Total

#*

Size

Range

(μm)

# >

250

μm

Water

Temp.

(°C)

Total

#*

Size

Range

(μm)

# >

250

μm

Water

Temp

(°C)

--- --- --- --- --- July 02 H-48 75-150 0 21

July 12 M-13 70-85 0 19 July 10 M-7 90-320 3 21.3

July 24 V-100 80-125 0 21.3 July 29 H-48 110-330 3 22.5

August 06 M-16 115-340 14 21.4 --- --- --- --- ---

250 micron (μm) oyster larvae take 1 to 3 days to reach a setting size of 365 μm

--- No information available.

* Larvae numbers were reported as: 1 - 5 larvae as low, 6 - 19 as medium, 20 - 99 as high and ≥ 100 as very high.

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Table 12. 2013 Oyster Monitoring data from East River for Site 17: Cranberry Wharf and

Site 18: MacWilliams Seafood

Date

Cranberry Wharf Site Larvae Data

Date

MacWilliams Site Seafood Larvae

Data

Total

#*

Size

Range

(μm)

# >

250

μm

Water

Temp.

(°C)

Total

#*

Size

Range

(μm)

# >

250

μm

Water

Temp

(°C)

June 25 M-11 68-74 0 23.0 June 25 M-6 62 - 75 0 22.4

June 28 M-6 70-100 0 18.8 June 28 H-21 70-80 0 18.4

July 02 M-7 75-100 0 20.8 July 02 M-17 80-90 0 20.4

July 05 H-20 70-140 0 22.9 July 05 H-25 75-120 0 21.7

July 08 H-34 75-135 0 24.2 July 08 H-51 75-120 0 23.8

July 10 H-23 85-135 0 21.3 July 10 H-39 80-130 0 22.5

July 12 H-30 85-170 0 23.2 July 12 H-29 75-170 0 23.2

July 15 H-27 130-220 0 25.1 July 15 H-33 140-250 1 24.9

July 17 H-25 150-330 3 24.1 July 17 H-27 90-320 5 23.8

July 19 H-84 140-350 60 22.8 July 19 H-68 90-330 27 23.0

July 22 H-27 120-340 11 23.7 July 22 M-18 100-320 9 23.0

July 24 M-15 90-320 11 22.5 July 24 H-30 80-330 15 ---

July 26 0 --- 0 22.2 July 26 L-1 320 1 21.9

July 29 M-6 200-330 5 21.7 July 29 L-2 200-350 0 21.9

July 31 L-3 120-330 2 22.6 July 31 M-13 160-330 10 22.2

August 05 M-8 80-320 1 24.0 August 05 H-20 120-350 4 23.5

August 07 L-2 120-140 0 23.1 August 07 M-12 120-350 1 23.0

August 09 0 --- 0 23.5 August 09 M-11 180-330 4 23.1

August 20 0 --- 0 22.5 --- --- --- --- ---

August 28 0 --- 0 20.8 --- --- --- --- ---

250 micron (μm) oyster larvae take 1 to 3 days to reach a setting size of 365 μm.

--- No information available.

* Larvae numbers were reported as: 1 - 5 larvae as low, 6 - 19 as medium, 20 - 99 as high and ≥ 100 as very high.

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Table 13. 2013 Oyster Monitoring data from Site 19: Vernon River and Site 20: Orwell River

Date

Vernon River Site Larvae Data

Date

Orwell River Site Larvae Data

Total

#*

Size

Range

(μm)

# >

250

μm

Water

Temp.

(°C)

Total

#*

Size

Range

(μm)

# >

250

μm

Water

Temp

(°C)

June 25 L-3 73-80 0 21.7 June 25 M-13 65-80 0 20.9

June 28 L-4 80-90 0 17.0 June 28 M-12 75-90 0 17.2

July 02 L-4 75-90 0 20.6 July 02 L-4 80-100 0 20.2

July 05 H-27 75-115 0 21.3 July 05 H-30 70-90 0 20.6

July 08 V-100 80-110 0 24.9 July 08 V-100 75-115 0 23.7

July 10 V-100 80-140 0 22.6 July 10 V-100 80-130 0 22.0

July 12 H-52 90-190 0 22.8 July 12 H-64 80-175 0 21.6

July 15 H-39 130-215 0 23.2 July 15 H-29 110-220 0 24.0

July 17 H-59 110-320 7 23.1 July 17 H-43 130-330 4 22.9

July 19 H-62 110-330 8 22.4 July 19 H-70 130-340 12 21.9

July 22 H-82 90-350 40 22.8 July 22 H-44 180-340 24 22.5

July 24 H-23 130-340 15 22.3 July 24 H-30 90-330 15 22.1

July 26 M-17 210-330 12 21.4 July 26 H-21 130-330 11 21.8

July 29 M-9 300-340 9 21.2 July 29 H-24 200-350 20 21.3

July 31 H-28 120-340 15 23.2 July 31 M-7 130-310 1 22.7

August 05 H-47 70-320 2 24.1 August 05 H-84 80-340 4 23.7

August 07 H-42 100-240 1 23.3 August 07 H-30 120-350 2 22.6

August 09 L-4 180-280 1 22.3 August 09 M-13 150-270 1 23.3

August 14 L-1 210 0 22.5 August 14 L-3 110-320 1 22.5

August 20 L-4 310-335 4 22.2 --- --- --- --- ---

August 28 0 --- 0 21.1 --- --- --- --- ---

250 micron (μm) oyster larvae take 1 to 3 days to reach a setting size of 365 μm.

--- No information available.

* Larvae numbers were reported as: 1 - 5 larvae as low, 6 - 19 as medium, 20 - 99 as high and ≥ 100 as very high.

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Table 14. Oyster Monitoring data from Site 21: Pownal Bay

Date Pownal Bay Site Larvae Data Water Temp.

(°C) Total #* Size Range (μm) # >250 μm

July 08 V-100 85-140 0 24.0

July 15 H-34 130-250 1 24.9

July 19 H-58 80-250 0 22.2

July 22 H-32 130-320 5 22.5

July 26 M-15 310-340 15 ---

August 21 M-12 280-340 12 22.1

250 micron (μm) oyster larvae take 1 to 3 days to reach a setting size of 365 μm

— No information available.

* Larvae numbers were reported as: 1 - 5 larvae as low, 6 - 19 as medium, 20 - 99 as high and ≥ 100 as very high.

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Table 15. Summary of occurrence of oyster larvae > 250 μm at the sites in western PEI

monitored in 2013

Site First Observation of Larvae > 250μm

1st Observation 1

st Medium # 1

st High # Peak #’s

Station July 8 July 8 July 8 July 15

Paugh’s Creek July 8 July 8 July 15 July 22

Old Wharf July 8 July 10 July 10 July 19

Green Park July 10 July 10 July 12 July 22

Mill River/Dock River July 16 July 16 July 16 July 16

Lot 10 Foxley River July 8 July 8 July 10 July 19

Lot 6 Foxley River July 8 July 8 July 8 July 19

Gibb’s Creek July 8 July 8 July 8 July 12

Enmore River July 9 July 9 July 9 July 18

Percival River July 16 July 16 July 16 July 16

Bentick Cove July 16 July 18 July 18 July 23

Dunk River July 16 July 23 July 23 July 23

Wilmot River July 16 July 23 July 23 July 23

Table 16. Correlation of the presence of oyster larvae > 250 μm to oyster spat set on OMP

collectors and grower collectors in the Bideford River in 2013

Site Larvae > 250μm OMP Short-term Collectors Grower Collectors *

1st Observation 1

st High #’s 1

st High #’s Peak #’s Deployed Spat Set

Station July 8 July 8 July 15 July 17 July 11-12 Moderate

* PEI Shellfish Association and other grower information.

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DISCUSSION

Factors to Consider in Timing Collector Deployment

Oyster growers can utilize both historical and current information to assist them in determining

when to deploy their oyster collectors. Historical information on collector deployment from

previous years is available from various sources while current information on oyster larvae and

spat set results are available through the Oyster Monitoring Program phone and website

information systems.

Some growers use historical information to determine when to deploy their collectors and

typically put them out on dates that have given them success in previous years. A history of the

timing of collector deployment and spat set results for the PEI Shellfish Association from 1990-

2013 is contained in Table 17 in Appendix III. During these years, the period from July 9th –

15th

has been the most common period for collector deployment. However, there are years when

deployment has been as early as July 4th

(2006) and as late as July 29th

(1992). The PEI Shellfish

Association determines when to deploy their collectors based on the number and size of larvae

observed in the larval tow samples.

This variability of the timing of spawning and spat settlement from year to year suggests that the

information available from the OMP will be of assistance to determine the best deployment

dates. Growers can use the larvae size range and numbers, as reported on the OMP voice mail

system and OMP website to estimate the length of time it will take for the larvae to start setting.

While it is possible to use this method to estimate when to deploy collectors, variability in the

weather and the number of larvae present in tows often make it advisable to wait until larvae are

near set to make that determination. When larvae reach 250 μm they can set in 1 – 3 days, and it

is recommended that collectors be in the water for a couple of days prior to this time to become

conditioned to collect the optimum set. If the collector is left in the water too long the collectors

may become unsuitably fouled for spat settlement. Thus, it would appear that if collectors are

deployed when 250 μm larvae are initially seen they would be in the water in time to catch the

first spat setting. The question remains as to whether collectors should be deployed this early, as

larger numbers of setting-sized oyster larvae may appear some days after the initial appearance.

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Table 18 summarizes the spat set information for the Bideford River Station site from 2001 to

2013, in relation to the first appearance of 250 μm larvae and the 1st high number of 250 μm

larvae observed in the water samples collected for the OMP. The information presented in this

table indicates that collectors deployed at the first appearance of 250 μm larvae have achieved a

successful set. The timing of the peak set observed on short-term collectors and the set observed

on the long-term collectors suggests collectors may have achieved a successful set if deployed

when the first high numbers of larvae > 250 μm were reported.

On average, grower collectors deployed 5 – 7 days after the first 250 μm larvae were observed

were most effective in collecting spat. If aquaculturists deployed collectors when the first high

numbers of larvae > 250 μm are reported they would often miss some of the first set, but be out

in time to collect the high and peak numbers of oyster spat. The data also shows that peak oyster

spat sets on the LTCs (collectors left out for time periods similar to grower collectors, but not

treated with a lime immersion to remove fouling and predators) were observed on the collectors

that were deployed on the same day as the first observation of oyster larvae greater than 250 μm.

Factors Affecting Oyster Set

There are many factors which may affect the final quantity of spat set on a collector, even if the

collectors are set at the optimal time. Some of factors include:

Low numbers of setting size larvae present.

Low numbers of setting size larvae over an extended period of time and growers did not

remove the fouling by immersing collectors in a lime solution to ensure the collectors

would be free of fouling to allow for a collection of a later set.

Two distinct sets and the collectors were not treated for fouling to collect the second set.

No treatment of collectors resulting in predation and/or fouling.

Anecdotal reports from oyster growers indicate that there was a moderate oyster set in 2013.

There were no major problems caused by fouling organisms and predators in the Bideford River

however shellfish association personnel were forced to carry out multiple anti-fouling treatments

(lime dipping). The oyster set in East River and Vernon/Orwell Rivers was moderate as

compared to previous years.

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Limitations of the OMP

There are a number of factors that make sampling for oyster larvae a difficult process to

standardize. Larvae sampling and spat collection are typically conducted in the mid to upper

portions of the river systems. Larvae are thought to migrate up and down in the water column

with respect to the tides and tows are conducted at specific times on specific days irrespective of

tide and thus may be either rising or falling. As well, fresh water influence can cause the larvae

to descend deeper in the water column, making them less available and more difficult to collect

when sampling so heavy precipitation may impact quantities of larvae captured in tows. Current

and boat speed when conducting tows will affect the amount of water that enters the net and

potentially the numbers of larvae captured. These, and other factors, can cause variations in

sampling results, making it difficult to compare larvae numbers between river systems or even

from day to day within the same river system. Larvae sampling occurs every 2 days in some

areas, but only twice a week in most areas. The time between sampling periods could mean that

the 250 μm larvae may be present for up to four days before they are seen in the samples

collected for the OMP.

Determining the best time to deploy oyster collectors and how those collectors need to be treated

is not an exact science, but it is hoped that the information contained in this report will assist

growers in making this determination. The analysis of the success of spat collection over time

described in this report is based solely on the larvae and collector data observed through the

OMP and on grower results obtained through conversations with individual growers. If there are

questions about the data contained in this report the reader may contact the Department at (902)

838-0910, or by e-mailing Jarrod Gunn McQuillan at [email protected].

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APPENDIX I

Maps Showing Oyster and Spat Monitoring Sites

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Figure 7. Oyster Monitoring Sites in Bideford River: (1) Station site, (2) Paugh’s Creek site, (3) Old Wharf

site and (4) Green Park site.

Figure 8. Oyster Monitoring Sites in Foxley River: Site 5 - Lot 10, Site 6 - Gibb’s Creek, and Site 7 - Lot 6.

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Figure 9. Oyster Monitoring Site 8 - Percival River and Site 9 - Enmore River.

Figure 10. Oyster Monitoring Site 10 - Mill River and Site 11- Dock River

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Figure 11. Oyster Monitoring Site 12 - Bentick Cove.

Figure 12. Oyster Monitoring Site 13 - Dunk River and Site 14- Wilmot River.

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Figure 13. Oyster Monitoring Site 15 - West River.

Figure 14. Oyster Monitoring Site 16- North River.

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Figure 15. Oyster Monitoring in East River: Site 17- Cranberry Wharf and Site 18- MacWilliams Seafood.

Figure 16. Oyster Monitoring Site 19- Vernon River and Site 20- Orwell River.

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Figure 17. Oyster Monitoring Site 21- Pownal Bay.

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APPENDIX II

Historical Spat Collection Data

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Table 17. PEI Shellfish Association collector deployment dates and spat set results from

1990 – 2013.

Year Collector Deployment Date Set Results

1990 July 20 Good

1991 July 15 Good

1992 July 29 Fair

1993 July 15 Fair

1994 July 11 Good

1995 July 10 Good

1996 July 15 Good

1997 July 11 Fair

1998 July 9 Good

1999 July 5 Good

2000 July 10 Poor

2001 July 9 Poor

2002 July 15 Good

2003 July 14 Good

2004 July 21 Good

2005 July 18 Good

2006 July 4 Good

2007 July 16 Good

2008 July 10 Good

2009 July 13 Poor - Good

2010 July 12 Good

2011 July 18 Poor-Good

2012 July 11 Good

2013 July 11-12 Moderate

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Table 18. Correlation of the combined OMP larvae (> 250 μm) and spat data with grower

information from the Bideford River for 2001-2013.

Year

Larvae > 250 μm Spat Set (STC) Spat Set (LTC) Grower Collectors *

1st 1st High

# Peak 1st

1st High # Peak Set

Period

Peak Deployed Spat Set

2001 Jul

6-18

Jul 9-

Aug 3

Jul 17-

Aug 3

Jul

11

Jul

13-17

Jul 13-

Aug 9

Jul 6 –

Aug 6

Jul

11-30

Jul

9-11

Nil

(most)

2002 Jul

11-17

Jul

17-22

Jul 19-

Aug 23

Jul

17-19

Jul

19

Jul

26

Jul 12-

Aug 5

Jul

12-22

Jul

15-18

Heavy

2003 Jul

8-11

Jul

9-11

Jul

14-25

Jul

11-14

Jul

11-18

Jul

14-21

Jul

11-21

Jul

11-18

Jul

15-18

Nil-heavy

2004 Jul

14-22

Jul

22

Jul 22-

Aug 9

Jul

20-22

Jul

22-28

Jul 28-

Aug 2

Jul 20-

Aug 4

Jul

20-26

Jul

19-23

Moderate

2005 --- --- --- --- --- --- --- --- --- ---

2006 Jul

4-5

Jul

4-10

Jul

12-26 Jul

7-10

Jul

7-12

Jul

12 & 21 Jun 29-

Jul 28

Jul

10-21

Jul

4-6

Light-

Heavy

2007 Jul

9-13

Jul

20-27

Jul 20-

Aug 8

Jul

9-20

Jul

18-27

Jul 27-

Aug 10

Jul 13-

Aug 10

Jul

8-23

Jul

16-19

Heavy

2008 Jul

10

Jul

14-16

Jul

14-30

Jul

11-14

Jul

14-16

Jul

18-25

Jul 8-

Aug 11

Jul

18-23

Jul

10-14

Heavy

2009 Jul

10-11

Jul

10-13

Jul 13-

Aug 5

Jul

10-13

Jul

17

Jul

17-27

Jul 10-

Aug 17

Jul

10-22

Jul

10 - ?

Nil-heavy

2010 Jul

8-12

Jul

12-14

Jul

13-26

Jul

9

Jul

9-14

Jul

12-23

Jul 9-

Aug 9

Jul

9-28

Jul

12 - ?

Heavy

2011 Jul

14

Jul

18

Jul

20

Jul

15

Jul

20

Jul

22

Aug

1

Jul

13

Jul

18

Nil-heavy

2012 Jul

4

Jul

9

Jul

13

Jul

6

Jul

13

Jul

18

Jul 6 -

Aug 10

Jul

11

Jul

11-16

Heavy

2013 Jul

8

Jul

8

Jul

15-22

Jul

12

Jul

15

Jul

17

--- --- Jul

11-12

Moderate

* PEI Shellfish Association and other grower information.

--- No information available

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APPENDIX III

Maps Displaying Current Known Range of Invasive Species in PEI

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Figure 18. Current known range of the clubbed tunicate, Styela clava.

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Figure 19. Current known range of the golden star tunicate, Botryllus schlosseri.

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Figure 20. Current known range of the vase tunicate, Ciona intestinalis.

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Figure 21. Current known range of the violet tunicate, Botrylloides violaceus.

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Figure 22. Current known range of the green crab, Carcinus maenas.

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Figure 23. Current known range of the oyster thief, Codium fragile.

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Figure 24. Current known range of the oyster drill, Urosalpinx cinerea.