Fall-Spring 2019/2020 Marbled Murrelet At-Sea Densities for Four Strata Associated with U.S. Navy Facilities in Washington State: Annual Research Progress Report 2020

The goal of this project is to estimate on-the-water marbled murrelet (Brachyramphus marmoratus) densities during the fall-spring non-breeding seasons (September - April) adjacent to the following U.S. Department of the Navy (Navy) facilities:

1. Naval Air Station (NAS) Whidbey Island (Crescent Harbor);
2. Manchester Fuel Depot;
3. Naval Base Kitsap (NBK) Bangor, including Zelatched Point, and Toandos;
4. NBK Keyport;
5. NBK Bremerton;
6. Naval Magazine (NAVMAG) Indian Island; and
7. Naval Station (NAVSTA) Everett.

These surveys have been conducted annually since September of 2012 and, now that 8 years of survey data have been collected, marbled murrelet density trends during the non-breeding season can be examined. Because the nearshore marine environment and marbled murrelet densities adjacent to any one of these Navy facilities is too small to derive reliable site-specific at-sea murrelet densities, Washington Department of Fish and Wildlife (WDFW) used a stratified sampling approach outlined in Pearson and Lance (2014) to derive stratum-specific density estimates. This approach uses line-transect or distance sampling methods (Buckland et al. 2015) to derive murrelet density estimates for four strata using nearshore and offshore transects placed in 32 primary sampling units (PSUs) (Figure 1). Note that Stratum 1 (coastal Pacific Ocean [Pacific Beach]) was not surveyed this year.