Measuring the health of Mt. Tam
Maintaining a healthy, vibrant and diverse Mt. Tam begins with understanding how key ecological resources are faring, and how we can better care for this iconic and beloved place.
One Tam partners and Bay Area scientists have come together to try to answer the question: How healthy are Mt. Tam's natural resources?
Coho Salmon in Lagunitas Creek
Why Was This Indicator Chosen?
Endangered coho salmon (Oncorhynchus kisutch) in Lagunitas Creek are good indicators of riparian habitat and hydrological conditions as well as ocean health, and provide marine-derived nutrients for aquatic and riparian communities. Decades of monitoring data covering all life stages make it possible to assess the condition and trend of coho salmon on Mt. Tam with a fairly high level of confidence.
What is Healthy?
The desired conditions for the Lagunitas Creek coho salmon populations are described in numerical targets for each life stage, as well as the critical habitat conditions that support those life stages. The National Fish and Wildlife Service (NMFS) recovery plan for this species (NMFS, 2012) lists specific goals for the number of adult spawners and redds (nests), juveniles, and smolts (young fish migrating out to sea), and the amount of woody debris in the stream.
What Are the Biggest Threats?
- Historic hydrological changes and habitat loss that have affected anadromous fish migration, increased sedimentation, and reduced the number of pools and other critical habitats
- Current hydrological changes and habitat loss including water withdrawals, drought, channel incision, and a loss of downstream floodplain connectivity
- Ocean-related factors such as over-harvesting of salmonids as well as their prey (e.g., sardines) and changes to ocean food webs related to climate change
- Potential invasive aquatic species including exotic mollusks such as New Zealand mud snail (Potamopyrgus antipodarum) and the spread of invasive Japanese knotweed (Fallopia japonica)
- The effects of climate change such as higher water temperatures, longer droughts, more intense rainfall, and disruptions in the ocean food web
What is The Current Condition?
The overall condition of Lagunitas Creek’s coho salmon is Poor. The 20-year average for adults and redds is only approximately 20% of the NMFS recovery goal, and smolts are only at approximately 18%. Juvenile coho salmon in Lagunitas Creek are low and numbers fluctuate widely. Wood loading levels are also low.
What is the Current Trend?
Currently, we believe that coho salmon in Lagunitas Creek are experiencing No Change in habitat or population trends, except two of the three smolt year classes have shown increases over two generations. The third year class, while only increasing over one generation, reached the highest numbers seen yet.
How Sure Are We?
Overall confidence is Moderate based on the quality and the amount of data available, although there is some uncertainty about juvenile estimates and some assumptions were required to estimate wood loading and pool frequencies.
What is This Assessment Based On?
- NMFS Federal Register documents (NMFS 2012, 2015)
- National Park Service inventory and annual monitoring (Carlisle et al., 2016)
- Marin Municipal Water District annual monitoring reports (see MMWD link in References below)
What Don’t We Know?
Key information gaps include:
- The timing and magnitude of salmonid migration between streams using Passive Integrated Transponder (PIT) tag technology would provide valuable information on habitat needs during multiple life stages
Carlisle, S., Reichmuth, M., & McNeill. B. (2016). Long-term monitoring of coho salmon and steelhead trout during freshwater life stages in coastal Marin County: 2014 annual report. Natural Resource Report. NPS/SFAN/NRR—2016/1142. Fort Collins, Colorado: National Park Service. Available from https://irma.nps.gov/DataStore/DownloadFile/546839.
Ettlinger, E., Zeug, S., Doughty, P., Rogers, V., & Andrew. G. (2015a). Juvenile Salmonid Monitoring in the Lagunitas Creek Watershed – 2014. Corte Madera, CA: Marin Municipal Water District. http://www.marinwater.org/177/Lagunitas-Creek-Watershed.
Ettlinger, E., Doughty, P., Rogers, V., & Andrew. G. (2015b). Smolt Monitoring in the Lagunitas Creek Watershed – 2015. Corte Madera, CA: Marin Municipal Water District. http://www.marinwater.org/177/Lagunitas-Creek-Watershed.
Marin Municipal Water District (MMWD), Lagunitas creek management plan, and fisheries reports from 2010-2015. Available from: https://www.marinwater.org/177/Lagunitas-Creek-Watershed.
National Marine Fisheries Service (NMFS). (2012). Final CCC Coho Salmon ESU Recovery Plan. National Marine Fisheries Service, West Coast Region, Santa Rosa, California. Available from http://www.westcoast.fisheries.noaa.gov/publications/recovery_planning/salmon_steelhead/domains/north_central_california_coast/central_california_coast_coho/ccc_coho_salmon_esu_recovery_plan_vol_i_sept_2012.pdf.
National Marine Fisheries Service (NMFS). (2015). Recovery Plan for North Central California Coast Recovery Domain – California Coastal Chinook Salmon, Northern California Steelhead, Central California Coast Steelhead – DRAFT. Available from http://www.nmfs.noaa.gov/pr/recovery/plans.htm.