The lagoon at its seasonal largest, is about 5 acres (2.0 ha) and 6 feet (1.8 m) deep, and serves as habitat for tidewater goby (Eucyclogobius newberryi)) and rearing steelhead.

[3] As part of the southern range of the Central California Coast Coho Evolutionarily Significant Unit (ESU), the creek is considered an attractive site for re-stocking.

The San Gregorio watershed has seen recently increasing residential development but remains primarily pastoral with cattle and sheep grazing, timber harvesting, and recreational trails being the main commercial uses.

[5] San Gregorio Creek is also part of the Central California Coast steelhead (Oncorhynchus mykiss irideus) ESU and historically supported a run of 1,000 fish as recently as 1971.

[9] In a 2008 survey, both coho salmon and steelhead were noted in the creek but threatened by Highway 84 related barriers to fish passage, as well as pressure from sedimentation from residential development, grazing and logging.

[10] Four special-status animal species - California red-legged frog (Rana draytonii), coho salmon, steelhead, and tidewater goby are the focus of a June 2010 Watershed Management Plan.