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SPAWN leads smolt outmigration monitoring on San Geronimo, Arroyo and Larsen Creeks each spring. We also lead spawning surveys on 10 tributaries to San Geronimo Creek during the winter.
Coho salmon and steelhead trout (Oncorhynchus mykiss) are found in the Lagunitas Creek Watershed, Marin County (LCW). Coho are listed as "endangered" in this region (Central California CoastEvolutionary Significant Unit) at both the State and Federal level. Steelhead are listed as "threatened." The approximate 500 coho that return to this watershed annually are considered to be one of the more robust populations in the state. However, their abundance in this watershed are estimated to be a fraction of historical numbers. Chinook salmon (Oncorhynchus tshawytscha) and chum salmon (Oncorhynchus keta) have also been documented in the LCW in recent years. However neither of these species have been documented in the tributaries to San Geronimo Creek.