Salt marsh is a threatened but critical coastal habitat that provides important ecosystem services including flood protection from storm surges, water purification, wildlife habitat and opportunities for recreation. Elkhorn Slough, a small 11km tidal estuary located in the Monterey Bay, California, has the most salt marsh south of San Francisco Bay and is the only estuary with a resident, threatened, sea otter population (Enhydra lutris nereis). In 2013, we initiated an intensive study of sea otters in Elkhorn Slough, which included monitoring of 25 radio-tagged animals and bi-monthly distribution surveys to quantify habitat use and abundance. Both tagged and untagged sea otters used salt marsh extensively; however, the degree of use of different creek watershed networks was highly variable. We now seek to identify features of salt marsh tidal creeks that predict sea otter abundance and distribution to aid in salt marsh restoration plans and the conservation of the southern sea otter.
Using survey locations of sea otters as our response variable, we are employing Maximum Entropy and generalized additive models to define the relative importance of each environmental predictor variable (tidal creek network geometric efficiency, depth, width, bank slope, distance to main channel). One general model and four specific models based on sea otter behavior (foraging vs. resting) and status (female with pups vs. males and females without pups) were created to determine differences in salt marsh habitat use.
Results/Conclusions
Overall results suggest that sea otters prefer salt marsh tidal creeks that are deep, have shallowly sloped banks with high water flow close to the main channel. Sea otter behavior plays an important role in tidal creek selection, while sea otter status determines salt marsh watershed selection. Results from our study will be used by resource managers to guide the design of new tidal creeks as part of an extensive salt marsh restoration project, that aims to provide sea otters with protected habitat and the coastal community with added flood protection from rising seas.