1) Deployment and monitoring of oysters in reciprocal transplant experiment
Adult oysters were collected from three locations in Puget Sound (Fidalgo, Dabob, and Oyster Bays) during November and December 2012 (Figure 1). Mass spawning of oysters occurred in June 2013 following several months of conditioning. Larvae were raised in flowing seawater and fed microalgae. Following setting on microcultch, juveniles were cultured in flowing seawater in Port Gamble. In August 2013, 480 oysters (5-10 mm) from each population were planted at Fidalgo, Oyster Bay, Dabob, and Manchester Bays. At each site, oysters from each population were placed into four 0.61M X 0.61M growout trays (120 each). In each tray, oysters were equally distributed in four 10x7.5cm mesh (1475 micron) bags with 24 oysters glued to ceramic tiles. Trays were anchored into substrate using using rebar stakes. In late autumn trays at Fidalgo Bay, Oyster Bay, and Manchester were transferred from substrate to a midcolumn hanging system tied to a floating docks. At each site, a HOBOlogger temperature logger (OnSet, USA) was deployed to monitor temperature every 15 minutes.
Figure 1. Map of oyster outplanting sites. Field sites include Fidalgo Bay (purple), Dabob Bay (blue), Manchester (red), and Oyster Bay (orange).
Site Monitoring and Growth
Survival and growth were assessed at all sites in December 2013, Dabob in January 2014, and Fidalgo, Manchester, and Oyster Bays in February 2014. Survival was measured by counting all live animals remaining in each tray for each population. Growth was measured via size and weight measurements taken directly from live subsamples collected in the field and measured in the lab. In the lab each of the sampled oysters was measured using calipers for hinge to bill length and weighed with shell to determine whole body weight.
Figure 2. Number of surviving oysters at each field site. Circle color reflects originating broodstock population. Temperature data is displayed to scale with 0C and 5C indicated. Grey arrows indicate when oysters were relocated from substrate to suspension. Asterisk denotes estimate as some trays were inaccessible at time of sampling.
Samples for genetic testing were collected at outplanting in August 2013 for baseline data. Samples were also taken in December 2013. These samples included approximately 32 animals per population at Fidalgo, Manchester, and Oyster Bays. At Dabob we collected 43 from the Fidalgo population, 50 from the Oyster Bay population, and 59 from the Dabob population due to the high mortality. We visited Dabob again in January to collected another 22 from the Fidalgo population, 33 from the Oyster Bay population, and 39 from the Dabob population.