Monitoring steelhead trout along Steven's Creek

Photo credit: stevenscreektrail.org

On my bike ride today I came across a team from Fishbio.com installing an RFID counter on Steven's Creek and it piqued my interest.

A super helpful engineer explained that they were replacing the RFID on behalf of Santa Clara Valley Water Authority to count the migrating steelhead trouts. 

I decided to do my own research and here's what I found ...

Credit: stevenscreektrail.org

Central California Coast steelhead trout (Oncorhynchus mykiss), larger and more silvery in colour, are a type of rainbow trout native to the South Bay that spawns in fresh water and at age two swim to the Ocean. To complete their life cycle they journey up the creek to spawn once again - that's if there is water in the creek. The lifespan can be 10 years under favorable conditions meaning the adults can potentially make many trips in their lifetime.

Until 1935, steelhead trout from San Francisco Bay journeyed for miles up Stevens Creek each year to Steven's Creek Lake to spawn in the watershed of the Santa Cruz mountains, fed mostly by rain rather than melting snow. 

This natural cycle was rudely interrupted by the construction of the Stevens Creek Reservoir and Dam. Predictably the new dam drastically reduced the volume and duration of the overflow. Not surprisingly in 2005, by one estimate 2005, only 10 and 100 steelheads made the journey up the creek. This is despite, the Department of Fish and Game working with Santa Clara Valley Water District and Stevens Creek and Permanente Watershed Council to construct four fish ladders and adopting a policy of retaining fallen trees in the creek to create a more hospital habitat for the fish. The steelheads were added to the endangered species list making it illegal to catch.

Life History (as stated in [2])

Credit: stevenscreektrail.org

• Egg: Steelheads lay eggs in gravel nests called redds.
• Parr: A juvenile steelhead trout in freshwater.
• Smolt: A juvenile steelhead migrating to the ocean.
• Adult: A mature ocean-going steelhead.

As members of the salmon family, steelhead are anadromous, meaning they are born in freshwater, spend most of their life in the sea and return to freshwater to spawn. Unlike salmon, steelhead can spawn more than one time. The life history of the steelhead trout varies more than that of any other anadromous fish regarding the lengths of time spent at sea and in freshwater habitats.

Steelhead trout are able to adapt to varying environmental conditions. They spawn in fast-flowing, well-oxygenated, gravel-bed rivers and streams. Those remaining in the freshwater their entire lives are called rainbow trout. The fish that migrate to the open ocean are called steelhead. Adult steelhead return to their place of hatching (natal stream) to spawn.

Recent studies have shown conclusively that steelhead females have displayed a flexible reproductive strategy that can produce ‘resident’ or 'anadromous' (a fancy word for migratory fish) depending on the environmental conditions - this might be the saving grace for the trout [3]. How cool is that?

Steelhead can live to be ten years old. Males mature at two years and females at three. They typically spend up to two years in freshwater before migrating as smolts to the open ocean through San Francisco Bay. They remain at sea for one to three years before returning to spawn in the fall.

Using RFID to tag steelhead trouts

Science and technology have progressed to a point where it is feasible to deploy 23 mm RFID chips called a “PIT Tag", available as small bioglass encapsulated tags. 

And yes, individual fish are tagged, and their movements can be traced using readers and antennas mounted over streams, rivers, inside culverts, etc. [4] 

RFID reader at Steven's Creek

The Fishbio team, I met was replacig the damaged RFID sensors that can record the RDIF tag as fish pass downstream or upstream and record the data on a solar-powered computer. 

Solar powered RFID setup at Steven's Creek

Although the technology exists to automatically transfer the data to the cloud, this setup requires a technician to come to collect the data periodically.

Steven's Creek after the January 2023 rains

It was heartening to know that the steelhead trout might be making a comeback in Steven's Creek. 

References:

1. Weiner, J. (2005) Tracking steelhead in Stevens Creek. Available at: https://www.mv-voice.com/morgue/2005/2005_10_21.dsteel.shtml (Accessed: February 10, 2023). 
2. Friends of Stevens Creek Trail (no date) FoSCT - Deep Cliff Fish Passage. Available at: https://www.stevenscreektrail.org/Projects/FishPassage_DeepCliff/ (Accessed: February 10, 2023).
3. Rainbow trout or steelhead? - FISHBIO: Fisheries consultants (2022) FISHBIO. Available at: https://fishbio.com/rainbow-trout-or-steelhead/ (Accessed: February 10, 2023). 
4. Group, A.M. (2018) The fishy side of RFID technology, Mobile Computing, RFID & Voice Solutions - Advanced Mobile Group. Available at: https://www.advancedmobilegroup.com/blog/the-fishy-side-of-rfid-technology (Accessed: February 10, 2023).