Index Site Surveys Data for Olympia Oysters, Ostrea lurida, in British Columbia – 2009 to 2017

Dominique Bureau

doi:10.15468/scs2nk

Index Site Surveys Data for Olympia Oysters, Ostrea lurida, in British Columbia – 2009 to 2017

Citation

Bureau D (2022). Index Site Surveys Data for Olympia Oysters, Ostrea lurida, in British Columbia – 2009 to 2017. Version 1.4. Fisheries and Oceans Canada. Sampling event dataset https://doi.org/10.15468/scs2nk accessed via GBIF.org on 2024-12-11.

Description

The Olympia oyster (Ostrea lurida Carpenter, 1864) is one of four species of oysters established in British Columbia (BC), Canada, and the only naturally occurring oyster in BC (Bourne 1997; Gillespie 1999, 2009). O. lurida reaches the northern limit of its range in the Central Coast of British Columbia at Gale Passage, Campbell Island, approximately 52°12’N, 128°24’W (Gillespie 2009).

First Nations historically utilized Olympia oysters for food and their shells for ornamentation (Ellis and Swan 1981; Harbo 1997). European settlers harvested Olympia oysters commercially from the early 1800s until the early 1930s when stocks became depleted and the industry moved towards other larger, introduced oyster species (Bourne 1997; Quayle 1988). Since that time, Olympia oysters have likely maintained stable populations in BC, but have not recovered to abundance levels observed prior to the late 1800s (Gillespie 1999, 2009).

Olympia oysters were designated a species of Special Concern by the Committee on the Status of Endangered Wildlife in Canada (COSEWIC) in 2000 and 2010 and listed under the Species at Risk Act (SARA) in 2003 (DFO 2009; COSEWIC 2011). A management plan was developed and posted to the SARA Public Registry in 2009 (DFO 2009). One of the objectives of this plan was to ensure maintenance of the relative abundance (density) of Olympia oyster at index sites. The plan also recommended development of a survey protocol for determining relative abundance (density) estimates. In response, a Canadian Science Advisory Secretariat (CSAS) Research Document was completed recommending a survey method for Olympia oysters (Norgard et al. 2010); a CSAS Science Advisory Report (DFO 2010) for selection of index sites was also completed.

Thirteen index sites were chosen from a mixture of previously surveyed sites, and by random site selection. In 2014, a fourteenth site was added at Joes Bay in the Broken Group area in partnership with Parks Canada. The selected sites provided a representative sample of Olympia oyster populations in different geographic zones in the Pacific region and span the much of the range of Olympia oysters in BC.

Purpose

Olympia oysters were designated a species of Special Concern by the Committee on the Status of Endangered Wildlife in Canada (COSEWIC) in 2000 and 2010 and listed under the Species at Risk Act (SARA) in 2003 (DFO 2009; COSEWIC 2011). A management plan was developed and posted to the SARA Public Registry in 2009 (DFO 2009). One of the objectives of this plan was to ensure maintenance of the relative abundance (density) of Olympia oyster at index sites. The plan also recommended development of a survey protocol for determining relative abundance (density) estimates. In response, a Canadian Science Advisory Secretariat (CSAS) Research Document was completed recommending a survey method for Olympia oysters (Norgard et al. 2010); a CSAS Science Advisory Report (DFO 2010) for selection of index sites was also completed.

Sampling Description

Study Extent

Thirteen index sites were chosen from a mixture of previously surveyed sites, and by random site selection. In 2014, a fourteenth site was added at Joes Bay in the Broken Group area in partnership with Parks Canada. The selected sites provided a representative sample of Olympia oyster populations in different geographic zones in the Pacific region and span the much of the range of Olympia oysters in BC. During initial site investigations (2009-2011), oyster beds were identified from literature (e.g., Gillespie 2009; Stanton et al. 2011; Finney et al. 2012) and through reconnaissance to determine beaches that had Olympia oysters present. The rationale for index site selection followed DFO (2010). Survey strata were positioned to cover as much of the oyster bed as possible while maximizing the area to be surveyed in one tide. Survey strata were rectangular in shape to allow for ease of survey set-up. Stratification was used at 10 index sites where beds were large or discontinuous. The remaining index sites had one stratum. Refinements to stratum boundaries have been made since 2009 to exclude areas that are not able to be surveyed (e.g., subtidal portions) and slight increases to stratum area have occurred to included more habitat if time allowed. Coordinates of all Olympia oyster beds, strata and corner points were collected each survey year using Trimble GPS Pathfinder Pro. Mapping of Olympia oyster beds was focused on survey stratum when time did not permit mapping of the entire beach. The outer boundaries of the beds were defined by the absence of oysters. Strata coordinates from prior survey years were used to locate index sites. All 43 surveys followed either two-stage (TS) or stratified two-stage (StTS) survey design (fide Gillespie and Kronlund 1999; Norgard et al. 2010); the rationale and methodology for use of two-stage designs for Olympia oyster index surveys was described in Norgard et al. (2010) . Transect and quadrat positions were chosen in advance of surveys using R software code. Sampling intensity (number of quadrats) surveyed in each stratum was determined at the time of survey and was dependent on the amount of time available to complete the survey and the density of Olympia oysters at the site. A sampling intensity of 50 quadrats was targeted for high density beaches and 100 quadrats for low density beaches as per Norgard et al. (2010). Refinements to sampling intensity have been made at numerous sites to address the objectives of narrowing confidence intervals (CIs) and improving survey precision.

Sampling

Sites were surveyed at the lowest spring and summer tide cycles. Surveys utilized quadrats of area 0.25 m2 (50 cm x 50 cm) as recommended in Norgard et al. (2010) with 3 the exception of 2011, when four beaches were surveyed with quadrats covering 0.0625 m2 (25 cm x 25 cm) in area. The number of live Olympia oysters located on the surface layer of the quadrat including on rocks, shells and other substrate was counted and recorded in field notebooks. Prior to 2011, Olympia oysters were not separated into size categories and the densities for those years included all sizes of oysters. A small size category (shell length < 15 mm) was created to allow densities of small oysters to be presented separately. For beaches with both Olympia and Pacific oysters, the small size category acknowledges the level of uncertainty inherent in distinguishing small oysters of the two species. This category has the potential of documenting recruitment events like those evident at Port Eliza Beach 3 and Hillier Island where hundreds of small oysters were counted.

Method steps

In this design the first stage units were established by placing a tape measure on the beach substrate to form a baseline along the length of the stratum. First stage units or transects were then randomly selected at positions along the baseline. The transect length was then divided by the number of desired quadrats and the first quadrat on these perpendicular transects randomly selected in the first portion of the transect. The remaining quadrats were then systematically positioned along the length of transect. Corner points of each stratum and quadrat were marked with flags.
Olympia oyster shell lengths were measured and collated to understand potential trends in growth and recruitment. Quadrats were randomly selected to conduct shell measurement. All oysters within the quadrats were measured until a minimum sample size of 50 oysters was attained. Shell length was measured by bisecting the shell vertically from the umbo to the posterior shell margin (Quayle 1988). The number of oysters measured varied considerably between years and sites. Sample size was dependent on the amount of time available to complete all survey elements; if time permitted, more were measured.
To prepare this dataset for OBIS Canada publication, data was structured into an OBIS-compatible format using R and laid out in four tables: an Event Core, Occurrence Core and two Extended Measurement of Fact extensions. Defined vocabularies listed on the Natural Environment Research Council (NERC) Vocabulary Server (NVS) were used whenever possible. Oysters 15 mm and under were changed from Olympia Oysters (Ostrea lurida) in the original data to Ostreidae (oyster family) because species identification could not be verified at that size.

Additional info

T.C. Norgard, M.I. Bigg, S.E.M. MacConnachie, J.L. Finney and G.E.Gillespie. 2018. Index site surveys for Olympia oysters (Ostrea lurida Carpenter, 1864) in British Columbia – 2009 to 2017. Can. Tech. Rep. Fish. Aquat. Sci. 3153: viii + 88 p. Available online: https://pacgis01.dfo-mpo.gc.ca/FGPPublic/Olympia_Oysters/Olympia_Index_Report.pdf.

Taxonomic Coverages

Ostrea lurida
common name: Olympic Oyster rank: species
Crassostrea gigas
common name: Pacific Oyster rank: species
Ostreidae
common name: true oysters rank: family

Geographic Coverages

Range of BC index site surveys for Olympia Oysters

Bibliographic Citations

Bourne, N. 1997. Molluscan fisheries of British Columbia. NOAA Tech. Rep. NMFS 128: 115-130 - Available online: http://spo.nmfs.noaa.gov/Technical%20Report/tr128.pdf
COSEWIC. 2011. COSEWIC assessment and status report on the Olympia oyster Ostrea conchaphila in Canada. Committee on the Status of Endangered Wildlife in Canada. Ottawa. xi + 56 pp. - Available online: http://www.registrelepsararegistry.gc.ca/virtual_sara/files/cosewic/sr_olympia_oyster_0911_eng.pdf
DFO. 2009. Management plan for the Olympia oyster (Ostrea conchaphila) in Canada. Species at Risk Act Management Plan Series. Fisheries and Oceans Canada, Ottawa. v + 31 p. - Available online: https://www.registrelepsararegistry.gc.ca/virtual_sara/files/plans/mp_olympia_oyster_0509_e.pdf
DFO. 2010. Rationale for index site selection for Olympia Oysters (Ostrea lurida Carpenter, 1864) in British Columbia. DFO Can. Sci. Advis. Sec. Sci. Advis. Rep. 2010/053. 10 p. - Available online: http://www.dfo-mpo.gc.ca/csassccs/Publications/SAR-AS/2010/2010_053-eng.html
Ellis, D.W. and L. Swan. 1981. Teachings of the tides: uses of marine invertebrates by the Manhousat people. Theytus Books, Nanaimo BC. 118 p. -
Finney, J.L., T.C. Norgard, P.D.G. Boutillier, S.E.M. MacConnachie and G.E. Gillespie. 2012. Field verification of historic records of Olympia oysters (Ostrea lurida Carpenter, 1864) in British Columbia – 2010 and 2011. Can. Tech. Rep. Fish. Aquat. Sci. 3011: vii + 91 p. - Available online: http://waves-vagues.dfompo.gc.ca/Library/347603.pdf.
Gillespie, G.E. 1999. Status of the Olympia oyster, Ostrea conchaphila, in Canada. Can. Stock Assess. Secretar. Res. Doc. 99/150. 33 p. - Available online: http://www.dfo-mpo.gc.ca/csas-sccs/Publications/ResDocsDocRech/1999/pdf/99_150e.pdf
Gillespie, G.E. 2009. Status of the Olympia oyster, Ostrea lurida Carpenter 1864, in British Columbia, Canada. J. Shellfish Res. 28(1): 59-68. -
Gillespie, G.E. and A.R. Kronlund. 1999. A manual for intertidal clam surveys. Can. Tech. Rep. Fish. Aquat. Sci. 2270. x + 144 p. - Available online: http://waves-vagues.dfo-mpo.gc.ca/Library/234406.pdf.
Harbo, R.M. 1997. Shells and shellfish of the Pacific Northwest. Harbour Publishing, Madiera Park BC. 270 p. -
Norgard, T., S. Davies, L. Stanton and G.E. Gillespie. 2010. Evaluation of survey methodologies for monitoring Olympia Oyster (Ostrea lurida Carpenter, 1864) populations in British Columbia. Can. Sci. Advis. Sec. Res. Doc. 2010/006. iv +56 p. - Available online: http://waves-vagues.dfo-mpo.gc.ca/Library/340695.pdf
Quayle, D.B. 1988. Pacific oyster culture in British Columbia. Can. Bull. Fish. Aquat. Sci. 218. 241 p. - Available online: http://waves-vagues.dfompo.gc.ca/Library/109165.pdf.
Stanton, L.M., T.C. Norgard, S.E.M. MacConnachie and G.E. Gillespie. 2011. Field verification of historic records of Olympia oysters (Ostrea lurida Carpenter, 1864) in British Columbia - 2009. Can. Tech. Rep. Fish. Aquat. Sci. 2940: vi + 115 p. - Available online: http://waves-vagues.dfo-mpo.gc.ca/Library/344226.pdf.
T.C. Norgard, M.I. Bigg, S.E.M. MacConnachie, J.L. Finney and G.E.Gillespie. 2018. Index site surveys for Olympia oysters (Ostrea lurida Carpenter, 1864) in British Columbia – 2009 to 2017. Can. Tech. Rep. Fish. Aquat. Sci. 3153: viii + 88 p. - https://pacgis01.dfo-mpo.gc.ca/FGPPublic/Olympia_Oysters/Olympia_Index_Report.pdf.

Contacts

Dominique Bureau
originator
position: Biologist
DFO
CA
email: Dominique.Bureau@dfo-mpo.gc.ca

Dominique Bureau
metadata author
position: Biologist
DFO
CA
email: Dominique.Bureau@dfo-mpo.gc.ca

Dominique Bureau
administrative point of contact
position: Biologist
DFO
CA
email: Dominique.Bureau@dfo-mpo.gc.ca

Erin Herder
administrative point of contact
position: Biologist
Fisheries and Oceans Canada
email: erin.herder@dfo-mpo.gc.ca