Monitoring Steelhead life history in Scott’s Creek
By Sean A. Hayes
Progress Report for CA Dept of Fish & Game Award P0030648 Title:
Coho & Steelhead Recovery in a Coastal California Stream.
Below is a bulleted list of activities performed during the first quarter of 2002 on this award Data collection: Water quality and flow measurements commenced on 2/13/02 and are being conducted on a monthly basis at 4 locations (Fig.1) in the Scott’s Creek watershed. The National Marine Fisheries Service (NMFS) has completed the first phase of conducting a study funded by the California Department of Fish & Game (DFG) to evaluate the contribution of hatchery raised steelhead to the natural run population in the Scott’s Creek watershed. This was a complex study, (actually designed by MBSTP board member Jamie Alonzo) which looked at the interaction between fish released from the MBSTP Kingfisher Flat Fish Facility and natural run fish at all life history stages from fry to smolt and then adults that happen in the Scott’s Creek watershed.
The first phase of the project looked at genetic, age, and size distribution of the spawning adult steelhead population. To do this we used divers and netters to capture returning adults in the stream. While the fish are in hand we measure them (length and weight), sex them, determine their origin, (hatchery or natural) and collect scale samples for aging captured adult steelhead to collect tissue samples for genetics and scale samples for fish aging.
There was a great steelhead run this year and with the assistance of MBSTP volunteers we were able to capture and release over 100 adult steelhead. We also helped to collect several Scott’s Creek steelhead that were spawned at the hatchery for the STEP program. Based on scale data and stream surveys we observed that hatchery fish went to sea soon after spring planting at age one, while natural steelhead often spent 1.5-2 years in the stream before going to sea. Natural fish on average spent slightly less time at sea and both hatchery and natural fish were typically between 3 and 4 years old as returning adults. The average size fish was 26″, 6.5 lbs. The largest was 33″ and 11.4 lbs. We observed no difference in size between hatchery and natural fish. Also because the hatchery fish leave for the ocean sooner after planting, it means there is very little competition for food and space between hatchery and natural fish in the stream. Fish collected received a color coated floy tag and were then released. Due to the very low abundance of coho salmon in Scott’s Creek, only the steelhead component of this study is being pursued. 54 adult steelhead (37 natural fish, 17 hatchery fish).have been captured and released for the purposes of tagging, collecting DNA biopsies, scales and size information. We were also able to attach data logging tags to 10 of these fish. These tags will record temperature and depth of where these fish travel in the ocean this year. If anyone catches or sees a fish carrying one of these tags, please remove the tag, release the fish and give me a call (831-420-3937) We’d love to get the tags back and learn what these fish are doing at sea! Gill filament samples were collected from 25 juvenile hatchery steelhead (from 2001 year class) prior to their planting in Scott’s Creek in 3/2002. We are currently conducting concluding our surveys for Steelhead spawning behavior. While we haven’t analyzed the data yet, we have already learned several things. Steelhead are very promiscuous, with both males and females spawning with several different males and females over a period of several days to weeks. In addition we saw lots of spawning between natural and hatchery fish, indicating that hatchery fish are doing well when they return and are making healthy contributions to the population. (we haven’t collected the genetic data on offspring yet to determine just how well they did yet- so the final results are still out). We observed a lot of spawning over the past two winters. One of the objectives was to observe interactions between hatchery and natural fish. What we learned was hatchery fish and natural fish spawn together on a regular basis. In general they chose to spawn in the same places. In addition, when deciding which male gets to spawn with a female that is digging a redd, size matters. The largest male almost always wins a competition with another male. We observed no problems between hatchery and natural fish during our spawning surveys. Finally we observed a lot of “sneaker” spawning by small males that haven’t gone to sea and may possibly be resident trout.
We have begun genetic analysis of the DNA samples collected from all the fish we have handled. While the results are preliminary and more work needs to be done, it appears that the Scott Creek Steelhead population has a healthy amount of genetic variation. As expected this year was a poor year for Coho. We were only able to collect a few males (and 1 hermaphrodite). These were spawned with some 4-yr old females that were residing at the hatchery. Unfortunately spawning efforts at the hatchery were unsuccessful. However a few coho fry have been observed in the creek so apparently some coho made it in and spawned successfully. We have received permission from the NMFS and DFG permitting agencies to collect a few of the coho fry and transport them to the hatchery where their chances of surviving to adulthood will be much better.
DNA samples and gill filament samples were collected from 63 hatchery steelhead prior to their release in Scott’s Creek. In addition we have set up an out-migrant trap in lower Scott’s Creek to start monitoring the movements of hatchery and natural smolts as they head to sea. To date we have caught and released 51 steelhead smolts (24 hatchery, 27 natural) and 1 coho smolt. We will be analyzing samples soon to measure physiological changes that are occurring in the fish as they prepare to go to see.
At this point we are planning to put a temporary weir in the watershed next fall. This will help to provide valuable data on the total number of returning adults each year. It will also make the collection of adults for spawning at the hatchery much easier. We are continuing to broaden our studies in Scott Creek and work very closely with members of the MBSTP. The last year has been not only very informative, but also a lot of fun. We look forward to seeing all of you out in the creek!We are also conducting measurements of water quality and flow to evaluate habitat quality. Measurements commenced on 2/13/02 and are being conducted on a biweekly basis at 4 locations in the Scott’s Creek watershed. We plan to put out temperature loggers at several locations along the watershed to get hourly temperature measurements throughout the year. We didn’t receive much rain in March or April and flows levels are really starting to go down. We will continue to monitor this throughout the year. On a more positive note, we are beginning to see the results of the amazing Steelhead run this year. The creeks are just full of Steelhead fry emerging from their redds. Please check out some of the photographs of we’ve supplied to the MBSTP web page. We will continue to monitor the creeks throughout the summer for distribution and growth of this years coho and steelhead fry.
