Monday, March 30, 2015

Interesting Pinnipeds information.....

“Sea lions-eye view” of the Columbia River at the Lewis and Clark Bridge between Rainier Oregon and Longview Washington. Photo: ODFW via National Geographic Critter Cams.

ODFW presentation on the California Sea Lion, Stellar Sea Lion and Harbor seals occupying areas of the lower Columbia River and major tributaries. It provides factual overview data on many of their studies including historical presence, populations, habits and diet including salmonids and sturgeon from the rivers. Provided with supporting information from:
  • NOAA Fisheries
  • National Marine Mammal Laboratory
  • Washington Department of Fish and Wildlife
  • Pacific States Marine Fisheries Commission
  • U.S. Army Corps of Engineers
  • Columbia River Inter-Tribal Fish Commission
  • Northwest Power and Conservation Council
  • Bonneville Power Administration 
Read more and find link.........

A few elaborations on slide text:
Slide 7 - note that numbers found at the various locations can vary widely from day to day, week to week, and month to month. And that over the course of a season there are more individual animals that cycle through than are represented by any single day count. 
Based on the USACE Fish Field Unit observation program data collected from 2005 to 2014, SSL have taken a minimum of 8K salmonids and 12K white sturgeon just within 1/2 mile of Bonneville Dam over that period.

Slide 9 - In the spring months, there may be 50-100 CSL found on the CR South Jetty, typically around 250 hauled out in the Astoria East Mooring Basin; 20+ in the area of Willamette Falls; another 25 near Bonneville Dam; 2-3 CSL that locked above Bonneville Dam years ago - 2 of which frequent the area near The Dalles Dam and regularly rest on house boat decks in The Dalles Marina to the dismay of the home owners.

Slide 12 - Prior to the early 2000s, no more than just 1 or 2 CSL were ever seen upriver at Bonneville Dam. CSLs began occurring regularly and in growing numbers in the early 2000s and USACE observations of sea lion predation on salmonids at the face of Bonneville Dam began in 2002. In 2005 and 2006 Steller sea lions also began occurring in the river just below Bonneville Dam, initially foraging almost exclusively on white sturgeon, but in more recent years have often taking more salmonids than the CSL in the area have.

Slide 16 - In February of this year, we have seen record numbers of seals and sea lions in the estuary and the lower river, with thousands of pinnipeds following the healthy eulachon return up to the Cowlitz River at Longview, WA.
This one image is from a series of photographs taken by WDFW during a survey of the Columbia River estuary early in February. Over 6,000 harbor seals were found resting on Desdemona Sands, just west of the Hwy 101 bridge at Astoria.

Slide 17 On February 11 this year, over 1,500 CA sea lions were resting on the docks in the Astoria East Mooring Basin.

Slide 21 -  On average, the total loss of chinook to CSL predation at the dam over the entire spring season may be only 1-4%, but the rate of loss of the early arriving fish can be far greater than that, sometimes to the point where the number of chinook consumed on a single day equaled the number of chinook that successfully passed the dam.

[continue reading past the introductory information for the graphic report.]