Ancient Clam Gardens and Deepwater Sand Lance Habitat

Ancient clam gardens and deepwater sand lance habitats are just two of the many varied topics that were interesting at the biennial Salish Sea Ecosystem Conference held in Vancouver British Columbia this October. 

 Researchers fromSimonFraserUniversitylooked at the effectiveness of ancient shellfish gardens created onQuadraIslandinBritish Columbia.  In these gardens, first nations’ peoples cleared rocks and small boulders down to the low ends of beaches to construct a sill.  These cleared areas filled in with smaller sized sediment particles and created areas of higher quality clam habitat. The sill wall also acted to deter some predators and was thought to increase larval retention.  When coupled with the first nations’ husbandry practices of removing predators to increase survival and removing competitors to increase growth they achieved clam aquaculture in a form that is not much different from what is practiced today.

 Another interesting presentation was of a study using acoustic multibeam ecosounder data, seafloor video, and sediment samples to identify and sample subtidal habitat in the San Juan Channel of the Pacific sand lance.  The sand lance is known to utilize near shore sandy substrates for burrowing emerging in daylight hours to forage in open water.  Sandy upper intertidal beaches are used by adults for spawning and egg deposition.  With this work, the natural history of the Pacific sand lance in its subtidal habitat has been greatly expanded.  A predictive model that uses seafloor characteristics of sediment wave fields was developed to locate potential subtidal sand lance habitats.  Densities of sand lance captured in this study were much higher than what has been reported intertidally, averaging 84 fish/m2 rather than only 5 fish/m2.  What I found the most intriguing was the collection of a single sand lance egg found in one of 59 samples.  This could indicate a low density late season subtidal spawning area that could be considered a “critical” habitat or just be an anomaly.

 Overall the conference presented a wide variety of interesting topics and studies about theSalishSea, its inhabitants, and how they interact with each other.  The Salish Sea Ecosystem Conference was an excellent opportunity to hear from and collaborate with researchers, policy makers, and natural resource managers.