US Navy

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Marine Species Monitoring

Aerial Surveys of Marine Mammals Conducted in the Inland Puget Sound Waters of Washington, summer 2013 – winter 2016

Introduction & Objectives

The NWTT Study Area (Study Area) is composed of established maritime operating and warning areas in the eastern North Pacific Ocean region.  These include facilities and locations in the Strait of Juan de Fuca and Puget Sound.  In order to determine what effects Navy activities may have on marine mammals, surveys were conducted to collect baseline data. 

The primary objectives for this research were to:

1. Conduct aerial surveys during four seasonal periods within the inland Puget Sound Survey Area to assess potential differences in seasonal distribution, numbers, and behavioral state patterns of marine mammals.

2. Collect data to estimate densities of marine mammals in the inland Puget Sound waters for species with sufficient sightings.

3. Estimate abundance for each marine mammal species seen an adequate number of times, with estimates of f(0) and g(0).

4. Document the distribution and habitat use of each species observed.

5. Document and describe behaviors seen without performing focal follows.

Technical Approach

From 2013-2016, researchers conducted systematic-line transect aerial surveys in eight sub-regions of Puget Sound encompassing inland waters of Washington State.  Surveys were conducted year-round and focused on estimating seasonal in-water density and abundance of marine mammals, particularly harbor porpoises and harbor seals.

Progress & Results

A total of 35,102 km of survey effort were conducted during 61 flights on 35 days during following six survey periods.  In addition, 1,693 digital photographs and 14.5 min of video were taken.

Researchers confirmed 11 marine mammal species (including a single river or sea otter) in 5,772 groups for an estimate 10,673 individuals. Sightings identified to species included: harbor seal; harbor porpoise; California sea lion; Steller sea lion; humpback whale; gray whale; common minke whale; Risso’s dolphin; Dall’s porpoise; killer whale resident and transient pods; and otter. Totals of 98 harbor porpoise calves, 25 harbor seal pups, and 2 killer whale calves were seen.

With this data, density was determined and behavior was documented. The results confirm that harbor porpoises have recolonized all eight sub-regions of Puget Sound and are present year-round in relatively large numbers. Contrastingly, there has been a decrease in Dall’s porpoise sightings. The highest proportion of harbor porpoise calf sightings during summer and fall support the theory that calving occurs during this period in Puget Sound. With respect to pinnipeds, results also support historical and other studies indicating that the harbor seal continues to be the most common marine mammal species in Puget Sound year-round. In contrast, Steller sea lions and California sea lions inhabit the region primarily during spring and fall, when they occur throughout much of Puget Sound.

Publications:

Harbor porpoise (Phocoena phocoena) recovery in the inland waters of Washington: estimates of density and abundance from aerial surveys, 2013-2015 - Jefferson, T.A., M.A. Smultea, S.S. Courbis, and G.S. Campbell. 2016. Canadian Journal of Zoology 94:505-515.