Written by Kelly Davidson Chou, District Biologist
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| Otter surfaces with Duckweed covered whiskers |
The 70,000 commuters traveling daily along I-680 in Martinez, CA speed past two oil refineries, a chemical plant, and a wastewater treatment plant, but few realize that much of this stretch of the interstate bisects a critically important wetlands habitat in the San Francisco Bay Area. Known as the Peyton Slough Wetlands Complex, the marsh system is located about 2 miles east of downtown Martinez, CA, and is home to an impressive array of aquatic wildlife. [excerpt from Kelly's article in The River Otter Journal Spring 2011 - see link below to read the article in its entirety].
As of January 15, 2013, the Moorhen/McNabney Marsh otters are doing well! From the spraints
(otter scat) I find every day on the trail system, as well as the many large
carp scales we see along the levees, I am guessing that the otters have
transitioned from their favored warm weather diet of crayfish, to a winter diet
of carp and sunfish species. The carp scales are much more prevalent late
November through March and the spraints I find in the warmer months, are much
pinker in color from all of the red crayfish shell (as compared to what I see
now). But I have not been able to do any methodical analysis of the spraints at
this time, so I can’t say for sure. I am hoping to get a small grant to help me
figure it out.
I saw 11 otters traveling together around Christmas. Since then, I usually see them in much smaller groups (2 – 5) swimming and fishing in Peyton Slough or in the open water of Moorhen or McNabney Marsh. We do have some worries for the otters and other wildlife though. McNabney Marsh experienced a severe algae bloom mid August through early December 2012. We had the algae identified and preliminary toxicology performed by Dr. Raphael Kudela at the University of California - Santa Cruz [UCSC] indicated moderate levels of the hepatotoxin microcystin. Compiled literature suggests that cyanotoxins (toxins produced from cyanobacteria or blue-green algae), such as microcystins, are associated with a plethora of acute, chronic and fatal illnesses in animals and humans. To determine if wildlife were potentially affected by toxic conditions, I trapped crayfish (Procambarus sp.) and grass shrimp (Paleamonetes sp.) in McNabney Marsh in early November and sent the specimens in for analysis by Dr. Kudela’s lab. I also sent in species collected in Moorhen Marsh at the same time as a comparison (Moorhen Marsh did not experience an algae bloom). We have not yet received the results of this analysis. However, a similar bloom that occurred in Pinto Lake near Watsonville, CA was linked to the deaths of over 20 sea otters (Enhydra lutris nereis) in the Monterey area. Although we have no evidence that any wildlife was harmed because of the 2012 bloom, Mt. View Sanitary District is very concerned about potential harm to fish and wildlife in McNabney Marsh and we are contracting with researchers at UCSC to perform studies to help us avoid and/or control any potential blooms that may arise in the future.
Kelly Davidson Chou is a District Biologist for the Mt. View Sanitation District (http://www.mvsd.org) and has reported on the Moorhen/McNabney Marsh otters previously to The River Otter Alliance (see article in the The River Otter Journal, Spring 2011 edition, available at http://otternet.com/ROA/Spring2011.pdf). Otter News sends sincere appreciation to Kelly for this informative update!
