By Miranda Tilcock
Salmon in the Stream
10 little salmon eggs, resting in a redd
1 was covered in silt, now the egg is dead
9 little alevin, with their yolks attached,
1 was washed away, and never made it back
8 little salmon fry, looking for something to munch
1 wandered too far, now it’s a striper’s lunch
7 little salmon parr, in need of food to eat
1 swam near the surface, into an egret’s beak
6 little salmon parr, swimming close to land
1 was trapped by falling waters, temperatures too hot to stand
5 little salmon smolts, almost at the ocean
1 smolt got lost, never to feed on grunion
4 little salmon smolts, so silvery and fine
1 got tangled up, stuck in a fisherman’s old line
3 large salmon adults, chasing some anchovy
1 salmon bit a baited hook, now it’s being served as sushi
2 large salmon adults, trying to come back home
1 couldn’t scale a ladder, all its energy was gone
1 last salmon adult, made its way at last
To dig its redd in pebbles, before its final gasp
It’s tough being a California salmon. There are many manmade and natural perils and predators, including humans, which want to eat you. Their life is like a horror movie! The story above is optimistic. The real world is far scarier, with each salmon egg having a 1 in 1,000 chance of returning to spawn. Numerous additional dangers, beyond those above, affect salmon at every life stage.
Salmon are particularly vulnerable during the fry/parr life stage due to their small size, an abundance of predators, and lack of food. The Nigiri Project study, jointly run California Trout, UC Davis, and the California Department of Water Resources, is quantifying the effects of floodplain habitat on salmon growth, to increase the likelihood that salmon will survive past the vulnerable fry/parr life stage. Slowing and spreading water across the landscape leads to far more productive food webs and provides salmon additional time to grow, compared with channelized rivers. Chlorophyll production increases in shallow, slow moving water and plant materials decompose in standing water, in turn fueling food webs. Chlorophyll and bacteria are key foods for zooplankton communities; their abundance allows zooplankton to reproduce at astronomical rates.
In 2016, the Nigiri Project compared food web communities in the Sacramento River, Tule Canal, and nearby managed floodplains. The three pictured samples were taken on March 25, 13 days after natural floodplain inundation. It’s pretty clear where the food is! Reconnecting floodplains to rivers provides salmon access to water rich with food resources and lacking in predators. As such, young salmon benefit by gain fat quickly, allowing them to essentially “pack their lunch” for the long voyage to sea. Like bears in winter, salmon live off these fats when food is scarce during outmigration or in the ocean.
The Center for Watershed Sciences is active in research and various educational outreach programs. Schools visiting Knaggs ranch use visual aids, like the Wheel of Misfortune, to demonstrate how difficult life is for salmon. The wheel, originally developed by the Department of Fish and Wildlife, is numbered from 1-24. Each number corresponds to a deadly fate on the matching Board of Misfortune, designed and built by Mollie Ogaz and Miranda Tilcock from the UC Davis Center of Watershed Sciences.
Each color on the wheel represents a different salmon life stage. The wheel is proportioned to show how vulnerable salmon are at each life stage. For example, most of the wheel is bright yellow indicating the fry stage, a periods when salmon are most vulnerable to predation and other perils due to their small size and lack of food. Some examples of salmon mortality include eggs being washed away in a flood, fry being eaten by other fish, birds, or humans, smolts getting lost in the Delta, and adults being caught by anglers. The best salmon fort
une is the one “spawner” spot on the wheel (and in real life). After Chinook salmon spawn, they die. (There is no easy retirement.) This seems unfortunate, but for a salmon, this completes their life cycle. People of all ages enjoy spinning the wheel and seeing their fate on the board, while learning about Chinook salmon and conservation.
This iconic species is important to California’s economy and environment. The commercial and recreational fishing industries provide many jobs and revenues to the state. Salmon runs are also integral in bringing marine nutrients into less productive rivers, providing food for bears, birds, other fish, and the broader ecosystem. Salmon are also important to the human diet, being a healthy alternative to other meats. When people think of salmon conservation, dam removal and access to spawning grounds usually come to mind, but salmon require help at every life stage. Improving salmon growth and life history diversity through the restoration of historical habitat will aid in recovery.
Miranda Tilcock, a graduate from UC Davis, is a fish biologist with the Center for Watershed Sciences. Her work focuses on salmonid restoration, food web interactions, and educational outreach to local schools.
Grosholz, E., and E. Gallo. 2006. The influence of flood cycle and fish predation on invertebrate production on a restored California floodplain. Hydrobiologia 568:91-109.
Schemel, L. E., T. R. Sommer, A. B. Müller-Solger, and W. C. Harrell. 2004. Hydrologic variability, water chemistry, and phytoplankton biomass in a large floodplain of the Sacramento River, CA, USA. Hydrobiologia 513:129-139.
Center, USGS Western Fisheries Research. “Questions and Answers About Salmon.” USGS Western Fisheries Research Center. USGS, 13 Jan. 2013. Web. 27 Oct. 2016
“Innovations in floodplain modeling: A test drive on the Yolo Bypass.” California Water Blog. October 18, 2013
“Reconciling fish and fowl with flood and farming” California Water Blog. December 2, 2014.
“Salmon experiment gets new twist in Yolo Bypass.” Sacramento Bee. February 19, 2016