Habitat use, movements and site fidelity of the gray smooth-hound shark (Mustelus californicus Gill 1863) in a newly restored southern California estuary

a r t i c l e i n f o It is thought that some elasmobranchs use shallow temperate estuaries during warmer months because these habitats may provide thermal physiological advantages. However, extensive loss and degradation of southern California bays and estuaries has reduced coastal species access to estuarine habitats. While restoration of southern California estuaries has increased over the last two decades, little is known about the recovery of ecological function. Top predators are thought to be important indicators of restoration of ecological function in many ecosystems, including estuarine habitats. In this study, abundance surveys and acoustic telemetry were employed to examine how gray smooth-hound sharks (GSH) use the newly restored Full Tidal Basin (FTB) of Bolsa Chica. GSH were most abundant inside the FTB during the spring and summer, and numbers decreased during the winter. Over 83% of all individuals (n = 336) caught were immature juveniles and were most abundant when water temperatures were between 20 and 22 °C. Sharks fitted with acoustic transmitters (n = 22) were continuously detected for 6–153 days (August 2008–December 2009). Forays into coastal waters were uncommon until individuals left for the season. GSH selected warmer habitats within the middle FTB; however, they also exhibited diel movements along the basin. GSH were most often found associated with mud and eelgrass at night, presumably for feeding. Since its restoration, population and behavioral data suggest that the FTB may provide juvenile GSH with a suitable seasonal environment for feeding and growth. The extensive habitat loss and degradation of southern California wetlands has reduced coastal species access to estuarine environments (Gillanders et al., 2003). As a result, restoration has become a popular approach to offset loss of estuarine habitats (Zedler, 2005). While restoration of southern California estuaries has increased over the last two decades, studies measuring the recovery of ecological function have been limited (Roberts, 1993). Due to the lack of baseline information on ecologically mature restored habitats (10 years or more since restoration), restoration should presently be viewed with caution, and the ability to assess ecological function remains critical for conservation. Top predators such as sharks and rays are thought to be important indicators of restoration of ecological function in many ecosystems, including bays and estuaries (Berger and Smith, 2005; Sergio et al., 2008). Patterns of abundance and behaviors of predatory fish inside restored habitats may provide critical information needed to assess their …