Snorkel Surveys: What Stream Explorations Can Reveal

Snorkel Survey Team (Left to Right): Steve Williams, Resource Conservation District of the Santa Monica Mountains (RCDSMM); Luke Benson, RCDSMM; Bernard Yin, Rebecca Ramirez, and RJ Van Sant; California State Parks Project Manager for the MCERP, who provided insight on creek monitoring surveys. (Photos by RCDSMM Stream Team)

The Resource Conservation District of the Santa Monica Mountains (RCDSMM), a project partner of the Malibu Creek Ecosystem Restoration Project (MCERP), has been conducting southern California steelhead (Oncorhynchus mykiss) snorkel surveys in Malibu Creek for nearly 20 years. The surveys help track the endangered species’ populations and distribution. They are a key restoration component of the MCERP, said Project Manager and Senior Environmental Scientist R.J. Van Sant. He recently joined a survey to help document baseline conditions for the MCERP.

Stream explorations not only track the presence of southern California steelhead but also other native species and the non-native species which tend to be more aggressive than natives. Other important data collected includes stream pool depth, shelter value, visibility, and instream cover. In addition, small data loggers placed throughout the creek track stream temperature, pH, and dissolved oxygen. “These data help monitor and track the quality of the overall habitat. All these conditions impact the survival of southern California steelhead and other native species” explained Van Sant.

Invasive species, such as this school of carp, are throughout the watershed. Programs to remove them will help in the recovery of southern California steelhead to the watershed.

If water levels are safe to perform them, stream surveys are usually conducted monthly between March and November. Malibu Creek’s water level can vary dramatically based on the year’s rainfall. Heavy rainfalls for the past two years have kept the creek flowing with many pools.

In June, the snorkeling crew spent two days conducting surveys in strategic locations along the creek. They spent the first day upstream of Malibu Lagoon (restored by the California State Parks and partners in 2012) and the second day surveying up to the base of Rindge Dam and upstream above it. They snorkel approximately 2 miles of creek over the two days.

View of Rindge Dam from Malibu Creek. (Photos by RCDSMM Stream Team.)

To accurately conduct the survey, teams of two to three snorkelers start downstream and proceed upstream in unison. This method helps to observe as much creek as possible and to avoid double counting any species. Depending on the year and season, underwater visibility can range from ten feet or more to just one foot or less.

The crew found that Malibu Creek was still diverse in depth—ranging from a few inches in some locations to 5-10 feet in others! In deeper areas, they dive down to the bottom to check under rocks, tree roots, and undercut banks. They use flashlights to check in crevices and spot animals at lower depths.

The water level in the creek can dramatically vary from year to year based on how much rain falls. The last two years have kept the creek flowing through summer. During droughts, the creek can dry up in most places except the deep pool areas. (Photos by RCDSMM Stream Team.)

While the team primarily focused on searching for southern California steelhead, they documented any animals spotted, including eggs and juveniles. They recorded what they observed.

“The native species that we documented included southwestern pond turtle, California tree frog, pacific tree frog, lots of tree frog and California toad tadpoles, two-striped garter snake, and arroyo chub,” reported Van Sant. “Non-natives documented included lots of carp and crayfish, a Texas spiny softshell turtle, a bluegill, and largemouth bass.”

Rebecca Ramirez holding a southwestern pond turtle. (Photos by RCDSMM Stream Team.)

Disappointingly, the RCDSMM Stream Team hasn’t seen any southern California steelhead or rainbow trout so far this year in Malibu Creek. The last salmonid believed to be seen by the team was in 2018. It couldn’t be determined if it was anadromous or not. Southern California steelhead were once abundant in Malibu Creek but have suffered due to development, invasive species, and human made barriers. This dynamic species travels throughout watersheds from San Luis Obispo to the Mexican border. With the removal of the 100-foot-tall Rindge Dam on Malibu Creek and remediation of 7-8 barriers upstream of the dam, 15 miles of stream habitat will open for the first time in 100 years for the endangered southern steelhead as well as other species to finally access. In the meantime, the Stream Team will keep on the hunt!