PEI Oyster Monitoring Program Report. Technical Report # 249

Transcription

1 PEI Oyster Monitoring Program 2012 Report Technical Report # 249 By Paul Burleigh, Mark MacLeod, Chelsey Ellis & Jarrod Gunn McQuillan PEI Department of Fisheries, Aquaculture and Rural Development Aquaculture Division P.O. Box Main Street Montague, PEI C0A 1R0

2 ACKNOWLEDGMENTS The staff of the Oyster Monitoring Program, on behalf of the PEI Department of Fisheries, Aquaculture and Rural Development, would like to thank the many people who assisted in the delivery of the program. We would like to give special thanks and recognition of two employees that have provided a long-term commitment to the oyster industry and specifically the oyster monitoring program, Matt Smith and Paul Burleigh. Additionally, the Department would like to thank all the growers who provided lines to hang scallop shell collectors. We would like to extend our sincerest thanks to all of these people, as well as the countless others over the history of this program, whose contributions have helped to make this program a success. - i -

3 TABLE OF CONTENTS ACKNOWLEDGMENTS... i TABLE OF CONTENTS... ii LIST OF FIGURES... iii LIST OF TABLES... iv INTRODUCTION... 1 METHODS... 2 Larvae (Spat-fall Prediction)... 3 Spat-fall... 4 Water Quality... 4 Tunicate Monitoring... 4 RESULTS... 5 Larvae (Spat-fall Prediction)... 5 Spat-fall... 5 Short-Term Collectors... 5 Long-Term Collectors... 6 Water Temperature... 6 Tunicate Monitoring... 6 DISCUSSION Factors to Consider in Timing Collector Deployment Factors Affecting Oyster Set Limitations of the OMP APPENDIX I - Maps Showing Oyster and Spat Monitoring Sites APPENDIX II - Historical Spat Collection Data APPENDIX III - Maps Displaying Current Known Range of Invasive Species in PEI ii -

4 LIST OF FIGURES Figure 1. PEI Shellfish Association deploying collectors in the Bideford River Figure 2. PEI oyster landings and values from 1980 to Figure 3. Sample collection sites for the 2012 Oyster Monitoring Program Figure 4. Oyster larvae, with foot extended, ready to set (365 µm) Figure 5. Oyster spat collectors... 4 Figure 6. Oyster collector lines in Gibb's Creek Figure 7. Oyster Monitoring Sites in Bideford River: (1) Station, (2) Paugh s Creek, (3) Old Wharf and (4) Green Park Figure 8. Oyster Monitoring Site 5: Foxley River and Site 6: Gibb s Creek Figure 9. Oyster Monitoring Site 7: Enmore River and Site 8: Percival River Figure 10. Oyster Monitoring Site 9: Mill River Figure 11. Oyster Monitoring Site 10: Kildare River Figure 12. Oyster Monitoring Site 11: Bentick Cove Figure 13. Oyster Monitoring Site 12: Grand River Figure 14. Oyster Monitoring Site 13: Bedeque Bay and Site 14: Wilmot River Figure 15. Oyster Monitoring Site 15: West River Figure 16. Oyster Monitoring Site 16: North River Figure 17. Oyster Monitoring in East River Site 17: Cranberry Wharf and Site 18: MacWilliams Seafood Figure 18. Oyster Monitoring Site 19: Vernon River and Site 20: Orwell River Figure 19. Oyster Monitoring Site 21: Pownal Bay Figure 20. Current known range of the clubbed tunicate, Styela clava Figure 21. Current known range of the golden star tunicate, Botryllus schlosseri Figure 22. Current known range of the vase tunicate, Ciona intestinalis Figure 23. Current known range of the violet tunicate, Botrylloides violaceus Figure 24. Current known range of the green crab, Carcinus maenas Figure 25. Current known range of the oyster thief, Codium fragile Figure 26. Current known range of the oyster drill, Urosalpinx cinerea iii -

5 LIST OF TABLES Table Oyster Monitoring data from Site 1: Bideford River - Station Site... 7 Table Oyster Monitoring data from Site 2: Bideford River - Paugh s Creek... 8 Table Oyster Monitoring data from Site 3: Bideford River - Old Wharf... 9 Table Oyster Monitoring data from Site 4: Bideford River - Green Park Table Oyster Monitoring data from Site 5: Foxley River and Site 6: Gibb s Creek Table Oyster Monitoring data from Site 7: Enmore River and Site 8: Percival River Table Oyster Monitoring data from Site 9: Mill River and Site 10: Kildare River Table Oyster Monitoring data from Site 11: Bentick Cove and Site 12: Grand River Table Oyster Monitoring data from Site 13: Bedeque Bay and Site 14: Wilmot River.. 14 Table Oyster Monitoring data from Site 15: West River and Site 16: North River Table Oyster Monitoring data from East River for Site 17: Cranberry Wharf and Site 18: MacWilliams Seafood Table Oyster Monitoring data from Site 19: Vernon River and Site 20: Orwell River. 17 Table Oyster Monitoring data from Site 21: Pownal Bay Table 14. Summary of occurrence of oyster larvae > 250 μm at the sites in western PEI monitored in Table 15. Correlation of the presence of oyster larvae > 250 μm to oyster spat set on OMP collectors and grower collectors in the Bideford River in Table 16. Correlation of the combined OMP larvae (> 250 μm) and spat data to grower information in the Bideford River for the period and Table 17. PEI Shellfish Association collector deployment dates and spat set results from iv -

6 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 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 (Figure 1). Information is collected through the monitoring of the number and size of oyster larvae in water samples collected from 21 sites throughout the province. Oyster collectors are also placed in the Bideford River System to monitor the timing and amount of oyster spat set. Water temperature data is collected from 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. PEI Shellfish Association deploying collectors in the Bideford River. Since 2006, with the possibility of the clubbed tunicate, Styela clava, spreading to the Bideford River from nearby March Water, tunicate monitoring was added to the OMP. The information collected from monitoring for tunicates is to provide information to growers on the infestation levels, primarily in the Bideford River

7 Dollars (000's) or MT In 2011, the Island oyster industry (including aquaculture and the wild fishery) had landings of 5,913,310 lbs, with a landed value of $6,622,000 which was an increase of 451,310 lbs as compared to 2010 (see Figure 2). Landings have been relatively stable since 2000, with some fluctuations. Over the past four years some bottom leases have been converted to off-bottom leases. Cultured production capacity is expected to continue increasing as a result of these new lease conversions Dollars (000's) MT Figure 2. PEI oyster landings and values from 1980 to METHODS Data from 21 sites in 16 river systems was collected for the OMP in 2012 (Figure 3). Staff based in Charlottetown collected and evaluated data from sites in East River (sites are named Cranberry Wharf and MacWilliams Seafood), North River, West River, Pownal Bay, Orwell River and Vernon River. Staff based in the western portion of PEI monitored four sites in Bideford River (sites are named Station, Paugh s Creek, Old Wharf and Green Park), and additional sites in Foxley River (sites are named Lot 10 and Gibbs Creek), Enmore River, Percival River, Mill River, Kildare River, Grand River, Bentick Cove, Bedeque Bay and Wilmot River. Maps displaying the locations of the 21 sites are found in Appendix I. Figure 3. Sample collection sites for the 2012 Oyster Monitoring Program

8 Larvae (Spat-fall Prediction) To ensure that the oyster spawning and the first appearance of oyster larvae would not be missed, adult oysters were frequently opened and the gonads examined to monitor for the first release of eggs and sperm. This monitoring began in early June in the Bideford River, as it is historically one of the sites where spawning occurs first. Once the release of eggs and sperm was observed, tows for oyster larvae were initiated. At all of the Oyster Monitoring Program sites, 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. The sampling period was extended from late August until late September in the Vernon and Orwell Rivers. This sampling was done to determine when oysters were finished setting, so growers could determine when to treat their adult oysters to kill and remove the oyster spat that had set on them. Water samples were obtained by towing a 2.5 metre (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 5 minutes. The 63 µm net should 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 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 larvae in the subsample was measured and its size recorded, for Western sites only (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 locally or toll free at 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)

9 Spat-fall The amount of oyster recruitment was monitored at the Station site in the Bideford River using oyster spat collectors. The spat collectors consisted of a length of galvanized wire with one scallop shell (scallop shells are a very good substrate for the collection of oyster spat) placed at 30 cm (one foot), one at 60 cm (three feet), and one at 90 cm (five feet) along the wire. 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. Two collectors were placed on a long line every two to three days (normally Monday, Wednesday and Friday). One of these collectors was recovered when the next two collectors were deployed (short-term collector STC) and the second collector remained in the water for approximately three weeks (long-term collector LTC). The oyster spat on the top and bottom of each shell was counted using a dissecting microscope. Long-term collectors were not left out for the entire summer, as spat would have grown over each other or been covered and killed by fouling, making it impossible to get an accurate count of the oyster spat. No treatment was performed on any of the department scallop shell collectors to control fouling. Water Quality Figure 5. Oyster spat collectors Water Temperature was measured at all the sites 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 the rack and bag system). As much of the oyster seed collected in the Bideford River system is moved to leases in other areas or public beds for enhancement purposes, there is a possibility that the tunicates could set on the oyster collectors and then spread to other areas with the transfer of oyster spat from the - 4 -

10 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 for tunicate densities. RESULTS Larvae (Spat-fall Prediction) Tables 1 13 display data describing the concentration and size ranges of larvae from water samples collected on different sampling dates at each of the sites monitored. To help clarify the timing of the spat set the tables showing data from the western PEI sites contain the actual number of larvae present and the number of larvae > 250 μm; however, because of high sedimentation in the water column in the eastern sites only a range (low, medium, high, and very high) has been reported. Oyster larvae that are 250 μm are almost ready to set and will reach a setting size of μm in approximately 1-3 days. The first observation of oyster larvae was in late June. Larvae > 250 μm were first observed at all four of the Bideford sites between y 2 nd and y 9 th and between y 5 th and y 20 th at other sites. The first high larvae numbers were observed between y 9 th and y 11 th at the Bideford Sites and between y 15 th and 28 th at the other sites. This data is summarized in Table 14. Spat-fall The spat set results from the OMP oyster spat collectors allows for correlation between larvae numbers observed in the water samples and the amount of spat set for any particular time. Table 1 displays the spat set results from the Station site in the Bideford River. The table containing the data from the Station site displays information for both short-term collectors (STC) and long-term collectors (LTC). While the number of spat on the top and bottom of 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 an area 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 15 contains data comparing the sample collection date, the number of larvae > 250 μm present, the number of spat set on STC, the number of spat set on LTC and grower results at the Station site. Short-Term Collectors The first observation of spat on STC at the Station site in the Bideford River was on y 6 th. The first appearance of high numbers of spat on STC was on y 13 th, or nine days after the first observation of larvae greater than 250 μm. The peak number of spat on STC was y 18 th, or fourteen days following the initial observation of larvae greater than 250 μm

11 Long-Term Collectors The long-term collectors (LTC) were deployed weekly between y 6 th and August 10 th. The collectors were deployed approximately every 2-3 days and remained in the water until they were brought in approximately three weeks later. In an attempt to get a good indication of the number of spat that set over a period of time, the collectors were retrieved before the spat started to get so large that they would cover each other and before fouling organisms, such as sea squirts, started to cover the spat. As a result, the collectors were not susceptible to the same crowding and fouling that grower collectors were and this may have resulted in higher numbers of spat on the LTC as compared to the grower collectors. The data displayed in Table 1 indicates that there were good oyster sets on the LTC deployed at the Station site in the Bideford River between y 6 th and y 20 th (LTC that were deployed early had a chance to collect spat over a long period of time if they remained clean). Water Temperature Temperature data that was collected at the monitoring sites is displayed in the Tables 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. The colonial tunicates continue to be found in increasing abundance in Cascumpec and have also been detected in the Bideford River (2011) In 2012, clubbed tunicate was also newly identified in Grand River and Souris River and colonial tunicates (golden star and violet) were newly identified in North Rustico, South Rustico and Southwest River. 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 and in Appendix III of this report. Known range of the green crab, oyster thief and oyster drill is also included in Appendix III. Figure 6. Oyster collector lines in Gibb's Creek

12 Table Oyster Monitoring data from Site 1: Bideford River - Station Site Date Station Site Larvae Data Water # Spat on Collectors * Temp. Size Range Total #** # > 250 μm ( C) STC LTC (μm) June 19 L June 22 M June 25 L June 29 M y 2 H y 3 VH y 4 H y 6 VH y 9 VH y 11 VH y 13 VH y 16 VH y 18 VH y 20 VH y 23 VH y 25 H y 27 H y 30 M August 1 M August 3 M August 6 L August 8 M August 10 L August August 16 M August 20 L August micron (μm) oyster larvae take 1 to 3 days to reach a setting size of 365 μm. --- No information available. * Scallop shell collectors were deployed on the dates shown. ** Larvae numbers were reported as: 1-5 larvae as low, 6-19 as medium, as high and 100 as very high

13 Table Oyster Monitoring data from Site 2: Bideford River - Paugh s Creek Date Paugh s Creek Larvae Data Water # Spat on Collectors * Temp. Size Range Total #** # >250 μm ( C) STC LTC (μm) June 19 L June 22 M June 25 L June 29 M y 2 H y 4 VH y 6 H y 9 H y 11 H y 13 VH y 18 VH y 20 VH y 23 VH y 25 H y 27 VH y 30 L August 1 M August 3 L August 6 L August 8 L August August 13 L August 16 L August August 23 L micron (μm) oyster larvae take 1 to 3 days to reach a setting size of 365 μm. --- No information available * Scallop shell collectors were deployed on the dates shown. ** Larvae numbers were reported as: 1-5 larvae as low, 6-19 as medium, as high and 100 as very high

14 Table Oyster Monitoring data from Site 3: Bideford River - Old Wharf Date Old Wharf Larvae Data # Spat on Collectors * Water Size Range Temp. Total #** # >250 μm (μm) ( C) STC LTC June 25 L June 29 L y 2 M y 4 M y 6 M y 9 VH y 11 VH y 13 VH y 18 VH y 20 VH y 23 VH y 25 H y 27 H y 30 H August 1 H August 3 H August 6 M August 8 M August 10 M August 13 L August 16 M August 20 L August 23 L micron (μm) oyster larvae take 1 to 3 days to reach a setting size of 365 μm. --- No information available. * Scallop shell collectors were deployed on the dates shown. ** Larvae numbers were reported as: 1-5 larvae as low, 6-19 as medium, as high and 100 as very high

15 Table Oyster Monitoring data from Site 4: Bideford River - Green Park Date Green Park Larvae Data Water Temp. # Spat on Collectors * Total #** Size # >250 μm ( C) STC LTC Range (μm) June 29 M y 2 M y 4 M y 6 H y 9 VH y 11 VH y 13 VH y 18 VH y 20 VH y 23 VH y 25 VH y 27 H y 30 H August 1 H August 3 H August 6 M August 8 M August 10 M August 13 M August 16 L August 20 M August micron (μm) oyster larvae take 1 to 3 days to reach a setting size of 365 μm. No information available. * Scallop shell collectors were deployed on the dates shown, except *** deployed y 13. ** Larvae numbers were reported as: 1-5 larvae as low, 6-19 as medium, as high and 100 as very high

16 Table Oyster Monitoring data from Site 5: Foxley River and Site 6: Gibb s Creek Date Total #* Foxley River Larvae Data Size Range (μm) # > 250 μm Water Temp. ( C) Total #* Gibb s Creek Larvae Data Size Range (μm) # > 250 μm Water Temp ( C) June 26 L L June 28 L L y 3 H H y 5 VH H y 9 H VH y 11 H VH y 13 VH H y 16 VH VH y 18 VH VH y 20 VH VH y 23 M VH y 26 L VH y 30 M H August 2 H H August 6 H H August 10 H H August 21 H M 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, as high and 100 as very high

17 Table Oyster Monitoring data from Site 7: Enmore River and Site 8: Percival River Date Enmore River Larvae Data Percival River Larvae Data Total #* Size Range (μm) # > 250 μm Water Temp. ( C) Total #* Size Range (μm) # > 250 μm Water Temp. ( C) June M June 28 L H y 3 VH VH y 5 VH VH y 9 VH VH y 12 H VH y 16 VH VH y 19 VH VH y 23 VH VH y 26 H VH y 30 L VH 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, as high and 100 as very high

18 Table Oyster Monitoring data from Site 9: Mill River and Site 10: Kildare River Date Total #* Mill River Larvae Data Size Range (μm) # > 250 μm Water Temp. ( C) Total #* Kildare River Larvae Data Size Range (μm) # > 250μm June 26 M June 28 M y 3 VH y 5 VH Water Temp. ( C) y 9 H L y 16 H y 20 H H y 23 VH y 26 H August 2 VH August 6 H 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, as high and 100 as very high

19 Table Oyster Monitoring data from Site 11: Bentick Cove and Site 12: Grand River Date Total #* Bentick Cove Larvae Data Size Range (μm) # > 250 μm Water Temp. ( C) Total #* Grand River Larvae Data Size Range (μm) # > 250μm Water Temp. ( C) June 26 M L June 28 M H y 3 L M y 5 H H y 9 H H y 12 H H y 16 H VH y 19 H VH y 23 H H y 26 VH VH 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, as high and 100 as very high. Table Oyster Monitoring data from Site 13: Bedeque Bay and Site 14: Wilmot River Bedeque Bay Larvae Data Wilmot River Larvae Data Date Total #* Size Range (μm) # > 250μm Water Temp. ( C) Total #* Size Range (μm) # > 250μm Water Temp. ( C) June y 12 VH VH y 16 VH VH y 26 H H 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, as high and 100 as very high

20 Table Oyster Monitoring data from Site 15: West River and Site 16: North River Date Total #* West River Larvae Data Size Range (μm) Water Temp. ( C) Total #* North River Larvae Data Size Range (μm) Water Temp. ( C) June 25 M L June 27 L L June 29 H y 3 L H y 6 H y 9 M M y 11 H y 16 M H y 18 H M y 20 M M y 23 M M y 25 M L y 27 M y 30 L August 1 H August 3 M August 8 L L August 14 M 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: L = low (1-5 larvae); M = medium (6 19 larvae); H = high (20-99 larvae); and VH = very high ( 100 larvae)

21 Table Oyster Monitoring data from East River for Site 17: Cranberry Wharf and Site 18: MacWilliams Seafood East River Date Total #* Cranberry Wharf Larvae Data Size Range (μm) Water Temp. ( C) Total #* MacWilliams Seafood Larvae Data Size Range (μm) Water Temp. ( C) June 25 H H June 27 L M June 29 L M y 3 H H y 6 H H y 9 L M y H y 13 M M y 16 H H y 18 VH VH y 20 H H y 23 M H y 25 L H y 27 M M y 30 H M August 1 M H August 3 L L August 8 L M August M 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: L = low (1-5 larvae); M = medium (6 19 larvae); H = high (20-99 larvae); and VH = very high ( 100 larvae)

22 Table Oyster Monitoring data from Site 19: Vernon River and Site 20: Orwell River Date Total # * Vernon River Larvae Data Size Range (μm) Water Temp. ( C) Total # * Orwell River Larvae Data Size Range (μm) Water Temp. ( C) June 25 M M June H June 29 M M y 3 H H y 6 H H y 9 H H y 11 L M y 13 H H y 16 H H y 18 H H y 20 H H y 23 M H y 25 L H y 27 L H y 30 M M August 1 H H August 3 H H August 8 M H August14 H H 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: L = low (1-5 larvae); M = medium (6 19 larvae); H = high (20-99 larvae); and VH = very high ( 100 larvae)

23 Table Oyster Monitoring data from Site 21: Pownal Bay. Date Pownal Bay Larvae Data Total #* Size Range (μm) Water Temp. ( C) June 29 L y 4 H y 6 H H y 16 H August 1 H 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: L = low (1-5 larvae); M = medium (6 19 larvae); H = high (20-99 larvae); and VH = very high ( 100 larvae)

24 Table 14. Summary of occurrence of oyster larvae > 250 μm at the sites in western PEI monitored in 2012 Site 1 st Observation First Observation of Larvae > 250μm 1 st Medium # 1 st High # Peak # s Station y 4 y 6 y 9 y 13 Paugh s Creek y 2 y 4 y 11 y 18 Old Wharf y 9 y 9 y 9 y 13 Green Park y 9 y 9 y 9 y 18 Mill River y 5 y 5 y 16 y 16 Kildare River y 20 y 20 y 20 y 20 Foxley River y 9 y 9 y 11 y 13 Gibb s Creek y 9 y 9 y 11 y 16 Enmore River y 9 y 9 y 9 y 19 Percival River y 12 y 12 y 12 y 19 Bentick Cove y 9 y 9 y 9 y 26 Grand River y 9 y 9 y 12 y 19 Bedeque Bay y 16 y 16 y 16 y 16 Wilmot River y 16 y 16 y 16 y 16 Table 15. Correlation of the presence of oyster larvae > 250 μm to oyster spat set on OMP collectors and grower collectors in the Bideford River in 2012 Site Larvae > 250μm 1 st Observation 1 st High # s STC OMP Collectors LTC Grower Collectors * 1 st High # s Peak # s Peak # s Deployed Spat Set Station y 4 y 9 y 13 y 18 y 11 y 13 Heavy * PEI Shellfish Association and other grower information

25 DISCUSSION Factors to Consider in Timing Collector Deployment Oyster growers have two types of information available to assist them in determining when to deploy oyster collectors - historical information and current information. Historical information is available from various sources on collector deployment dates from previous years. Current information on the number and size of oyster larvae and spat set results are available through the Oyster Monitoring Program phone information system. 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 is contained in Table 16 in Appendix III. During these years, the period from y 9th 15 th has been the most common period for collector deployment. However, there are years when deployment has been as early as y 4 th and as late as y 29 th. 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 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. Table 15 summarizes the spat set information for the Bideford River Station site in relation to the first appearance of 250 μm larvae and the 1 st high number of 250 μm larvae observed in the water samples. The information presented in this table indicates that collectors deployed at the first appearance of 250 μm larvae have achieved a good set. The timing of the peak set observed on short-term collectors (STC) and the set observed on the long-term collectors (LTC) suggests collectors may have achieved an acceptable set if deployed when the first high numbers of larvae > 250 μm were reported. On average, grower collectors deployed by 5 7 days after the first 250 μm larvae 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 sets on the LTC (collectors left out, 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 of 250 μm

26 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, such as the following: There were low numbers of setting size larvae. There were 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. There were two distinct sets and the collectors were not treated for fouling to collect the second set. There was a good set, but the collectors were not treated with lime and the spat were killed by predators (starfish) or by growth of fouling organisms (bryozoa, sea squirts, etc.). In 2012, anecdotal reports from oyster growers indicate that this was a good year for oyster set and department observations indicated good set in all collection areas. There were no major problems caused by fouling organisms and predators in the Bideford River; however, sea squirts caused enough fouling on collectors to require aquaculturalists to apply two treatments to some of the collectors. The oyster set in East River and Vernon/Orwell Rivers was good; however, the set in these areas appeared to be later in comparison to the western sites. As well, barnacle set was a challenge this year in some areas along with an abundant population of sea squirts. 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 when tides may be high or low and tidal currents ebbing or flooding. 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. Current and idling speeds will affect the amount of water that is sampled. These and other factors can cause variable 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 tows could mean that the first 250 μm larvae may be present 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. In this report the analysis of success of spat collection over time is based solely on the larvae and collector data observed through the OMP and on grower results obtained through conversations with individual growers. If you have any questions about the data contained in this report you can contact the Department at (902) , or by ing Jarrod Gunn McQuillan at jagunnmcquillan@gov.pe.ca

27 APPENDIX I Maps Showing Oyster and Spat Monitoring Sites

28 Figure 7. Oyster Monitoring Sites in Bideford River: (1) Station, (2) Paugh s Creek, (3) Old Wharf and (4) Green Park. Figure 8. Oyster Monitoring Site 5: Foxley River and Site 6: Gibb s Creek

29 Figure 9. Oyster Monitoring Site 7: Enmore River and Site 8: Percival River. Figure 10. Oyster Monitoring Site 9: Mill River

30 Figure 11. Oyster Monitoring Site 10: Kildare River. Figure 12. Oyster Monitoring Site 11: Bentick Cove

31 Figure 13. Oyster Monitoring Site 12: Grand River. Figure 14. Oyster Monitoring Site 13: Bedeque Bay and Site 14: Wilmot River

32 Figure 15. Oyster Monitoring Site 15: West River. Figure 16. Oyster Monitoring Site 16: North River

33 Figure 17. Oyster Monitoring in East River Site 17: Cranberry Wharf and Site 18: MacWilliams Seafood. Figure 18. Oyster Monitoring Site 19: Vernon River and Site 20: Orwell River

34 Figure 19. Oyster Monitoring Site 21: Pownal Bay

35 APPENDIX II Historical Spat Collection Data

36 Table 16. Correlation of the combined OMP larvae (> 250 μm) and spat data to grower information in the Bideford River for the period and Year Larvae > 250 μm Spat Set (STC) Spat Set (LTC) Grower Collectors * 1 st 1st High # Peak 1 st 1st High # Peak Set Period Peak Deployed Spat Set Aug Aug Aug 9 6 Aug Nil (most) Heavy Aug Aug Nil-heavy Moderate Aug Aug 2 12 & 21 Aug 4 Jun Light- Heavy Heavy Aug Aug 10 Aug Heavy Aug Nil-heavy Aug Aug ? Heavy Aug ? 2011 Aug Nil-heavy Aug Heavy * PEI Shellfish Association and other grower information

37 Table 17. PEI Shellfish Association collector deployment dates and spat set results from Year Collector Deployment Date Set Results 1990 y 20 Good 1991 y 15 Good 1992 y 29 Fair 1993 y 15 Fair 1994 y 11 Good 1995 y 10 Good 1996 y 15 Good 1997 y 11 Fair 1998 y 9 Good 1999 y 5 Good 2000 y 10 Poor 2001 y 9 Poor 2002 y 15 Good 2003 y 14 Good 2004 y 21 Good 2005 y 18 Good 2006 y 4 Good 2007 y 16 Good 2008 y 10 Good 2009 y 13 Poor - Good 2010 y 12 Good 2011 y 18 Poor-Good 2012 y 11 Good

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

39 Figure 20. Current known range of the clubbed tunicate, Styela clava

40 Figure 21. Current known range of the golden star tunicate, Botryllus schlosseri

41 Figure 22. Current known range of the vase tunicate, Ciona intestinalis

42 Figure 23. Current known range of the violet tunicate, Botrylloides violaceus

43 Figure 24. Current known range of the green crab, Carcinus maenas

44 Figure 25. Current known range of the oyster thief, Codium fragile

45 Figure 26. Current known range of the oyster drill, Urosalpinx cinerea