[5] Although steelhead can no longer run above Searsville Dam to spawn, stream resident coastal rainbow trout (O. m. irideus) populations live in upper Corte Madera Creek and its tributaries.

They noted that federally threatened California red-legged frogs (Rana draytonii) occur in the lotic portions of Corte Madera Creek below the dam but not above, likely due to depredation by non-native fish and American bullfrogs (Lithobates catesbeiana).

A private bridge apron adjacent to Willowbrook Drive and another downstream of the confluence with Damiani Creek were described as impassable barriers to upstream migrating steelhead.

In addition, there are also several private ponds stocked with warm water non-native species, such as Smallmouth Bass, Redear Sunfish and Bluegill that threaten the surviving native trout population fry and eggs.

The most notable pond is on Iroquois Trail and empties into Corte Madera Creek through a single outlet which floods during El Niño, or a wet winter.

[10] This unique confluence of streams and natural wetlands was submerged and buried with sediment due to the construction of Searsville Dam and the siltation of the reservoir.