Figure 1. Preliminary impressions from these 100 surveys suggest that leather sea stars (shown here at Hick’s Bay Wall on 9/20/16) continue to be abundant after the sea star wasting disease outbreak.
For three years, SeaDoc has been working with REEF Environmental Education Foundation to use trained recreational SCUBA divers to monitor the undersea life of the San Juan Islands. Annually, ten invited divers stay at Friday Harbor Laboratories for a week and conduct 10 sub-tidal surveys each (2/day) over the course of 5 days. Divers use a scientifically approved technique called the Roving Dive Survey methodology and record all fish sightings and a subset of marine invertebrates on a long-scale. Survey results are entered into a national database and are freely available to researchers working on a variety of topics from abalone to rockfish recovery. Most recently we used these data to document and understand the impacts of the 2013 outbreak of sea star wasting disease (SSWD) on 3 different subtidal sea stars and associated prey like urchins. Out study has shown dramatic impacts of SSWD on sunflower and spiny pink stars with a possible increase in leather stars and is being prepared for publication. We propose to repeat these advanced assessment team REEF surveys in the San Juan Islands in September 2016 to compare to prior studies pre-outbreak (2013) and post-outbreak (2014 and 2015), to see which sea stars are recovering and if urchin populations continue to grow.
From September 19 through September 23, 2016, 16 REEF Advanced Assessment Team divers (all at the REEF level of Expert for the region) completed 100 survey dives in the San Juans (Table 1). In addition to conducting the usual REEF Roving Dive Survey, which collects data on a log scale, divers recorded the exact number of sunflower sea stars they saw.
Table 1: Dive sites surveyed in September 2016
We expected that sunflower sea stars would remain at an abundance of 0 in 2016. Surprisingly, on 6 of 100 dives, divers saw sunflower sea stars. Each time, they only saw 1 star. This means that The sighting frequency was 6% with an average density of 1, which converts to 1 animal on the log scale (single =1, few = 2-10, many =11-100 and abundant 101 or >). While this was higher than we expected, this was still dramatically lower than pre-sea star wasting disease outbreak. For example, for 2012 and 2013 in the San Juan Islands (pre-outbreak data), there was a sighting frequency for sunflower stars of 89% with a density of 2.4. This means that historically divers would see sunflower stars on almost 90% of their dives and would see over to 10 animals per dive when seen. This year they were almost as rare as giant pacific octopuses with sunflower stars being sighted on only 6% of dives and only a single animal sighted each time. As planned, these data will be share with NOAA Fisheries as part of our recommendation to list the sunflower sea star as a US Federal Species of Concern. Data on other invertebrate species, including other stars (Fig 1) and urchins, as well as on fish, will soon be uploaded to the REEF database where they will be freely available. ($12,300)