Liam Gwynn, EcoNews Intern
Since 1991, the City of Arcata has implemented a series of restoration projects and legal protections for the urban waterways within the city limits. Before the logging industry and urban development took hold, these streams teemed with Coho Salmon and Cutthroat Trout. After decades of erosion these populations were forced entirely out of urban creeks and there have been no documented sightings of either Coho Salmon or Cutthroat Trout in over thirty years. That is, until earlier this year when a group of researchers hired by the City to assess the effectiveness of Arcata’s decades of restoration projects found both Coho Salmon and Cutthroat Trout in Jolly Giant and Janes Creek.
Colton Dixon is a postgraduate student at Cal Poly Humboldt and was hired by the City to test the effectiveness of Arcata’s restoration projects.
“So I’m looking at dissolved oxygen, temperature, pH, turbidity, specific conductivity, salinity, just a bunch of different things, just to kind of get an idea of how well the water’s doing,” said Dixon. On top of the water testing, they also were recording the populations of wildlife, specifically fish and amphibian species.
“So I start out by setting up minnow traps, and it’s just basically this little metal cage that fish can get inside. I usually let that soak overnight and then the next day, I come back with the seine net, which is basically this fine mesh net that’s between two poles. It’s about anywhere from like, eight to 10 feet long and then we just walk through the creek and on the bottom of the net, there’s these lead lines that keep it on the bottom, and then floats on top. And we just kind of drag it through and then scoop up and we see what we can catch from each little sampling effort,” said Dixon.
While the data regarding the historical salmon populations in Jolly Giant Creek are lacking, there are records of Coho Salmon spawning in Janes Creek before logging activity became prevalent. Now it has been at least thirty years since salmon have spawned in the stream, so why are they coming back now?
Researchers believe these Coho Salmon are demonstrating an example of non-natal rearing. This is a life history strategy that is rare in salmon species as a whole where instead of staying in the stream they are spawned in and traveling to the ocean when they are grown enough, these juveniles are leaving their home waterway and finding smaller and less populated streams before making their journey out to sea.
“What we think is happening is that during high winter flows these juveniles that were born that previous year, then get washed out into the bay, they hang out on the lens of fresh water, because fresh water is less dense than saltwater. So it sits right on the top. So the fish get through there and then they find their way into Jolly Giant Creek,” said Dixon.
Jolly Giant Creek doesn’t have the right sediment and size to sustain salmon spawning, however it and similar streams make for an excellent habitat for juvenile salmon to grow and thrive.
“What it (Jolly Giant Creek) does have is its slow moving water, which Coho juveniles love. There’s lots of invertebrates. These fish then don’t have a lot of competition from other salmon. So then they come here, and they just get really big and they grow really fast,” said Dixon.
Researchers have been able to make these findings by tagging fish with integrated responder tags which allows them to identify salmon they had caught previously and see how much they had grown in the time passed, and then compare that to the salmon in more densely populated rivers and creeks. They found that the juveniles in Janes and Jolly Giant Creeks were growing significantly faster and longer than the other salmon that were not demonstrating non-natal rearing.
One of the largest contributing factors to this growth is the implementation of habitat enhancement developed by the City and cooperative property owners. This includes the addition of large boulders and woody debris to urban, open-air portions of the stream. These structures give a place for species to rest and feed as they swim upstream. While the research has shown promising population growth, there is still room for improvement. Both Jolly Giant and Janes Creek still have large portions of the stream that run through pipes. The longer sections of these pipes can make it near impossible for fish to swim upstream because there is nowhere for them to rest and they can only swim upstream continuously for so long. This problem could be solved by replacing these pipes with larger ground-level culverts that would drastically expand salmon and trout access to connecting waterways.
Protecting smaller coastal streams is more important than ever because these streams act as a vital backup in the case of environmental catastrophes like droughts, wildfires or even chemical spills which are becoming increasingly prevalent as each year passes.