Characterization of the Habitat of Ammodytes hexapterus (Pacific Sand Lance) in the San Juan Channel Sand Wave

Abstract

Ammodytes hexapterus or Pacific sand lance (PSL) are forage fish that spend most of their time buried in benthic substrate (Robards 1999). PSL exhibit a peculiar behavior of actively swimming into sandy substrates as a refuge to avoid predation (Gidmark et al. 2010, Robards 1999, Blaine 2006). A sand wave field was identified in the San Juan Channel, WA in 2004 and discovered to be a suitable habitat for PSL. The San Juan Channel sand wave field is non-uniform and is composed of different substrate types. While physical attributes of the sand wave field have been explored (Greene et al. 2011), there is little known about how PSL use various substrate types as habitat. I am asking the question: How does benthic substrate composition influence the abundance and distribution of Pacific sand lance in the San Juan Channel sand wave? Samples were collected from the San Juan Chanel sand wave with the use of a Van Veen grab. The abundance and size of PSL were examined in each grab as well as the substrate composition. There were apparent trends of PSL abundance decreasing as the amount of gravel increased, and increasing as the amount of sand increased in the sample (Fig 1). Substrate composition seems to not have an influence on PSL size (Fig 3, Fig 4). A map showing the different substrate compositions in different areas of the sand wave in 2013 shows the non-uniform composition of the sand wave (Fig 6).