Photo: Jen Edgar
Tributaries
On the same token, many small creeks and streams that may not flow all year long, or may not have had flow for several years, are now open to fish passage. I’ve heard several people saying they have seen steelhead and salmon spawning in creeks they have not seen them in for many years or even in places where people have never seen them at all. Salmon and steelhead are very opportunistic in nature and will take full advantage of habitats that come available only in high water events. In fact that is one of their evolutionary life strategies. If it’s a low water year, they have the ability to spawn main stem in rivers such as the Eel, Klamath, or Smith but when water allows, they would much rather push higher up in to the headwaters where water is likely to stay cold longer, there may be more insect life for juveniles to feed off, and there will potentially be less predation by other fishes that can tolerate warmer water temps such as Sacramento pike minnow, perch, bass, and catfish.
Estuary Breach
In smaller river systems like those of Central and Southern California, often it takes a high water event to breech the sand bars that form during low water periods and cut off fish passage between the fresh water system and the ocean. Many of the small coastal rivers terminate in a lagoon. These lagoons or estuaries act as nurseries for juvenile fish. Some streams might get a few years or even longer before a good high water event flushes enough fresh water down a river to inundate the estuary and eventually push the sand out of the way and create an opening to flush to the ocean. In Southern California adult steelhead will often return to the stream of their birth only to find they can’t access it due to no flow connecting it to the ocean. They then have the option
to try and find another stream in the area that does have flow or even simply wait a year or two for that river to open back up. Likewise, juvenile fish won’t be able to push out of fresh water and into the ocean to become steelhead until such an event takes place. This has been a great year for many coastal streams allowing a healthy exchange of both adult and juvenile fish.
Flushing
Later in the season, high water events provide the perfect cover for smolt to aid their journey to the ocean. If the timing is right, a high water event can be a perfect mechanism to flush large quantities of smolt out of the river and down to the estuary or ocean. Smolt can ride that push of big water further through the delta or larger estuaries getting them closer to the ocean faster. That in turn ensures more fish will make it to the ocean and have a chance to become adult salmon or turn into steelhead. Sometimes such events are associated with a big spring storm, but rapid heat waves can create the same effect by melting snow and creating high run-off events.
Temperature
Temperature is also a factor. Most fish that predate heavily on salmon and steelhead smolt, especially invasive fish, are warm water species. High water events are typically associated with rain, snow, or snow melt and therefore are fairly cold water. That cold water can make the predator fish more lethargic as is the case with Sacramento pike minnow and black bass. This also gives the young salmonids an advantage and better survival rates.