Monterey Bay Salmon & Trout Project

As the 2009-2010 steelhead season progressed on the San Lorenzo River, anecdotal reports came in from fishermen indicating that most of the fish being caught were of hatchery origin, and that there were very few wild fish in the river. Subsequently, when a fish trap was put in place on the fish ladder at the Felton Dam, we found a ratio of better than 10 hatchery fish [from wild parents] to each in-stream produced wild fish. In other words, this year there were more than ten times as many adult spawners in the San Lorenzo River than there would have been without hatchery fish.

Although not a proven fact, it appears that very low summer flows over the past several years have severely limited the in-stream rearing habitat for wild juveniles, thereby contributing to the low number of returning wild adults. It is significant, then, that this year’s returning hatchery adults will provide much more in-stream spawning than that from the wild adults alone. There will be a greatly increased number of juveniles [from our hatchery spawners] available to occupy the increased rearing habitat in the good water flows we’ll have in the San Lorenzo River this year. The presence of these hatchery steelhead in the San Lorenzo River means that spawning numbers will not be the limiting factor for in-stream production. This will greatly speed up the population recovery from the low water years. Our hatchery spawners will have raised juvenile populations to significantly higher levels this first good water year, than if only wild fish were spawning.

Of utmost importance is the fact that our hatchery fish were all from wild parents that came from the San Lorenzo River. We strive to use only wild adults as brood stock throughout our steelhead programs. Our spawning protocols are to use multiple males with each female for genetic diversity, and different size fish in a mating to provide year-class diversity as well. So our “hatchery” fish are the direct descendants of wild adults, not a domestic strain of fish.

Scientific observations of the spawning effectiveness of wild brood stock-origin hatchery fish indicate little difference from that of wild adults. In the March 2007 issue of Salmon Trout and Steelheader magazine, Dave Vedder states that Oregon State University studies have shown that hatchery steelhead raised from wild parents are as effective spawners in the wild as naturally occurring wild steelhead. In discussions I’ve had with local NMFS biologists, they’ve said that they have made similar observations. So our conclusion is that our hatchery fish are effective spawners, that will contribute diverse wild genetics to the future populations of steelhead in the San Lorenzo river.

On Saturday March 6, I had the opportunity to work the trap at the top of the fish ladder at the Felton Dam. The Project was looking for wild males to supplement the wild females we had already taken earlier. The following photos show some of the fish observed, and the activities we perform when tending the trap. All photos were taken by Sherry Whitcomb.

First the trap is raised a bit to see if fish are present.

A fish is netted and carefully taken over to a plastic tub of running water.

The fish is measured, and a small hole punched in the tail. This is so fish that go down over the dam and then back up are not double counted [this is common, usually a buck]. The material from the hole is placed in an envelope for subsequent DNA analysis. This was a nice hatchery origin hen.

Here's a fine hatchery origin female ready to go back into the river.

This nicely colored hatchery male had just a stub of an adipose fin. He's been measured and hole punched, and is ready to go back into the river. [I didn't show a photograph of another larger hatchery male we found in the trap that was very dark, and really beat up. It had obviously been in the river a while, and had been fighting over several females. He was ascending the ladder again, looking for yet another girl friend. A good strong hatchery spawner.]

This large wild male was taken to the hatchery for spawning, and a week later was brought back and released into the river. Note the large, intact adipose fin. This day we also measured a beautiful medium sized wild female and released her into the river to spawn naturally.

Here is an exquisite bright hatchery hen, just before I released her back into the river to spawn naturally. Note the leech coming out of her mouth. Several of the fish we processed this day had leeches in their gills.