Arroyo Grande Creek
Stream Gage Modification Project
Clearing the Path for Steelhead Trout!
The gage was rated one of the top ten barriers for migrating fish in SLO County.
Built in 1939 by the United States Geological Survey (USGS), the stream gauge has been used for decades to gather water level data on Arroyo Grande Creek to manage flood risks and inform the delicate balance of releases from upstream Lopez Dam.
Over time the creek changed, and the concrete structure became a major barrier for steelhead trout migrating upstream in search of suitable breeding and rearing habitat.
Barriers like this prevent steelhead from migrating freely between the ocean and their freshwater spawning grounds, stranding them in mere fragments of their historic habitat. Listed as federally threatened in 1997, removing barriers to steelhead migration is crucial for species recovery.
The gage was rated one of the top ten barriers for migrating fish in SLO County.
Built in 1939 by the United States Geological Survey (USGS), the stream gauge has been used for decades to gather water level data on Arroyo Grande Creek to manage flood risks and inform the delicate balance of releases from upstream Lopez Dam.
Over time the creek changed, and the concrete structure became a major barrier for steelhead trout migrating upstream in search of suitable breeding and rearing habitat.
Barriers like this prevent steelhead from migrating freely between the ocean and their freshwater spawning grounds, stranding them in mere fragments of their historic habitat. Listed as federally threatened in 1997, removing barriers to steelhead migration is crucial for species recovery.
De-Fishing the Project Site
All fish needed to be relocated before dewatering of the project site and construction could begin. Block nets were installed upstream and downstream of the site to section off the portion of the creek for electrofishing.
Electrofishing works by introducing a mild electric field into the water, which temporarily stuns the fish, making them easier to catch. A netter follows closely behind to collect the fish. Once captured, each fish was measured, recorded, and released into a downstream pool, safely outside the construction zone.
2,044 fish were caught in total—including steelhead and eight other species! Not surprisingly, a greater number of fish species were found downstream of the gage, suggesting that the stream gage may have impeded not only steelhead but also other aquatic species from accessing upstream habitats.
Biodiversity in Arroyo Grande Creek
Sacramento Sucker
Catostomus occidentalis
793 fish caught
Sculpin
Cottus spp.
408 fish caught
CA Roach
Hesperoleucus symmetricus
405 fish caught
Three-Spined Stickleback
Gasterosteus aculeatus
355 fish caught
Striped Mullet
Mugil cephalus
55 fish caught
Steelhead Trout
Oncorhynchus mykiss
14 fish caught
Bullhead Catfish
Ameiurus nebulosus
13 fish caught
Plus 1 bass (Micropterus spp.) and 1 hitch (Lavinia exilicauda)!
Construction Commences
Papich Construction was contracted to implement the project in the fall of 2024. The project involved the modification of the stream gauge platform, in-channel grading and demolition, and construction of a new concrete weir to lower the jump height.
This project also upgraded the existing bubbler system, which measures water levels by detecting the pressure needed to release air bubbles underwater. The upgraded weir and bubbler system now collects vital data AND allows fish passage—a win for both nature and water management!
Construction Commences
Papich Construction was contracted to implement the project in the fall of 2024. The project involved the modification of the stream gauge platform, in-channel grading and demolition, and construction of a new concrete weir to lower the jump height.
This project also upgraded the existing bubbler system, which measures water levels by detecting the pressure needed to release air bubbles underwater. The upgraded weir and bubbler system now collects vital data AND allows fish passage—a win for both nature and water management!
Our contribution to California's year of river reclamation
Each barrier removed creates a cumulative ripple effect in the larger river reclamation movement across California, giving steelhead and salmon the freedom to once again roam the waters they historically inhabited. With four dams on the Klamath River coming down this year in the largest dam removal effort in U.S. history, California is leading the charge in river restoration. Projects big and small are gaining momentum, all working collectively to restore steelhead and salmon habitat across the state.
We feel privileged to make our small but mighty contribution to barrier removal for steelhead trout here on California’s Central Coast.
Thank you to our project sponsors!
Be Informed
Signup for the Creek Lands Conservation newsletter to hear about our ongoing efforts to improve the central coast.