Cooperative Extension San Joaquin County
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Cooperative Extension San Joaquin County

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Frolicking fat floodplain fish feed furiously

A very wet spring brought a good deal of water to the floodplains this year—good news for juvenile salmon that thrive in this habitat. Floodplains — such as the Yolo and Sutter Bypass areas and the Cosumnes River floodplains — provide a link for juvenile salmon between the gravel bedded rivers where they hatched and the ocean where they will spend the next one to five years.

Although salmon may only use the floodplain for a month or two, this could mean the difference between success and failure in their long journey to the ocean and back again. When juvenile salmon spend time on the floodplain, they grow faster than those that use only the river channel during their migration to the ocean (Sommer et al. 2001, Jeffres et al. 2006).  Because of the increased growth, the juveniles are larger when they head out to sea; they can survive better by swimming faster and being more able to avoid predators.

What makes a floodplain a good place for rearing salmon?  First of all, it needs to be connected to the river.   This sounds obvious, but most of the floodplain habitat in California is isolated behind levees and only gets flooded during extreme high water events when the levees are overtopped or breached. The reason that the levees are there is to protect housing and agricultural land (orchards, vineyards, etc.), which doesn’t allow for regular inundation of floodwaters.

Juvenile Chinook salmon reared on a restored floodplain on the Cosumnes River (right) and in the main channel. Photo: Jeff Opperman
Despite these challenges, some floodplains are still active in California and studies of these active floodplains are changing our minds about their value.  Multi-purpose floodplains such as the Yolo Bypass and Cosumnes River Preserve, for example, provide flood protection, seasonal agricultural land for annual crops, and restored habitat for many species, not just salmon.

Why are these multi-purpose floodplains better than the river channel for rearing salmon?  As cold floodwater enters a floodplain from the river, it spreads out, slows down and deposits sediment. Throughout this process, the water also warms slightly.  This is essentially the priming of the productivity pump that will ultimately feed the juvenile salmon for the next couple of months.  As the water slows, clears and warms, phytoplankton and algae begin to grow.  Populations of animals that feed on the fast-growing plant life, such as zooplankton and other aquatic invertebrates boom.  These animals comprise the main food of juvenile salmon on the floodplains.

Because salmon are cold blooded, water temperature it is an important component to floodplain suitability.  If water is too cold, juvenile salmon are lethargic and growth is slow.  If the water is too warm it causes increased metabolic demands and reduced dissolved oxygen, inhibiting growth and increasing mortality.  Fortunately for California salmonids, out-migration is in the spring when temperatures are generally moderate.  The timing of spring high flows onto floodplains allows for ideal temperatures for juvenile salmonids compared to the relatively cold water in the main river channel.  When temperatures are good and food is abundant, juvenile salmon can grow at impressively fast rates, especially when compared to fish using the main river channel.

The combination of complex physical processes and ecological function is what separates the floodplain from the river corridor in the eyes of juvenile salmon.  Leveed river channels provide little complexity and less than ideal growing conditions during the annual spring out-migration.  When juvenile salmon have access to complex floodplain habitats where temperatures are good and food resources are abundant, they will grow to larger sizes and thus be able to survive better than fish that remained in the main river channel.

So, next time you catch a big healthy salmon, thank your local floodplain.

Further Reading:

Jeffres, C., J. Opperman and P. Moyle (2008), “Ephemeral floodplain habitats provide best growth conditions for juvenile Chinook salmon in a California river,” Environmental Biology of Fishes 83 (4): 449-458.

Sommer, T., B. Harrell, M. Nobriga, R. Brown, P. Moyle, W. Kimmerer and L. Schemel (2001), “California’s Yolo Bypass: Evidence that flood control can be compatible with fisheries, wetlands, wildlife and agriculture,” Fisheries 26 (8): 6-16.

Posted on Friday, July 1, 2011 at 2:42 PM
  • Posted By: Trina Wood
  • Written by: Carson Jeffres, fish ecologist, UC Davis Center for Watershed Sciences

Residential runoff still contains banned chemicals

Pesticides that have not been sold at the retail level for years are still regularly found in residential runoff water, according to research in Sacramento and Orange counties by UC scientists. So called “legacy pesticides” are probably old products that homeowners still have on their garage shelves and are still using to control pests.

An earlier study by the California Department of Pesticide Regulation and the UC Integrated Pest Management Program found that 60 percent of pesticides sold to consumers are for ant control. For that reason, UC Cooperative Extension specialist in landscape horticulture Loren Oki of UC Davis and UC Cooperative Extension water resources/water quality advisor Darren Haver focused on ant control pesticides in their residential runoff research project. The scientists collected 830 water samples from the storm drains in four Sacramento County neighborhoods and four Orange County neighborhoods between 2006 and 2010.

“In Sacramento County, we trained a team of about 25 volunteer UC Master Gardeners to collect the samples,” Oki said. Orange County samples were collected by Haver and his staff. All the samples were sent to UC Riverside for analysis.

“Pesticides that have been off the market since 2004 are still found in the water,” Oki said. “We found organophosphates – diazinon and chlorpyrifos – in differing amounts, typically more in Orange County than Sacramento County. We also found a fairly new pesticide, fipronil, in most of our water samples.”

The scientists also noted random spikes in the amount pesticides in runoff water, unconnected with storms or other conditions, which suggested that they were directly associated with particular pesticide applications in the neighborhoods.

There are several ways homeowners can help prevent contamination of the California water supply. For one, dispose of old pesticides properly. Most cities and counties have programs for disposal of household hazardous waste.

When using pesticides, Oki suggests residents carefully read the label and use common sense.

“Don’t put pesticides on impervious surfaces, like concrete walkways and driveways,” he said. “Don’t put pesticides in garden areas where runoff might be generated. That runoff will carry the pesticides with it.”

Residents can also minimize the amount of water runoff from the property. Oki suggests reducing irrigation and targeting the water application properly. In addition, promote soil infiltration by promoting soil health.

“If you don’t generate runoff, you won’t have pesticides running off too,” Oki said.

Residential runoff can convey pesticides into water supplies.
Residential runoff can convey pesticides into water supplies.

Posted on Wednesday, June 29, 2011 at 9:22 AM
Tags: Darren Haver (2), Loren Oki (2), pesticides (4)

Rangelands conservation helps farmers

As it turns out, the farmer and the cowman should be friends, as the classic “Oklahoma!” song suggests. According to a just-published UC Berkeley study, wild bee species pollinate California crops to the tune of $937 million to $2.4 billion per year. That amounts to more than one-third of all pollination “services” to the state’s crops.

Many of those crop-pollinating wild bees live in rangelands – chiefly ranches that graze cattle.

“This means that preserving rangelands has significant economic value, not only to the ranchers who graze their cattle there, but also to farmers who need the pollinators,” said Claire Kremen, UC Berkeley associate professor of environmental science, policy and management, and senior author of the study.

The assumption that wild pollinators were not a significant source of crop pollination is more than just conventional wisdom – it’s business: a majority of farmers rent European honeybees to ensure crop pollination.

But beekeepers have suffered high rates of colony losses due to diseases, pesticides and management factors, increasing the uncertainty of both supply and rental prices.

The California native bee species Bombus vosnesenskii, the yellow-faced bumble bee, forages on almond flowers that are located right next to rangelands habitat. (Alexandra Maria-Klein photo)










And wild pollinator species have also shown declines in abundance and diversity on farmlands, most likely due to habitat loss from the intensive monoculture, or single crop, production system that typifies much of California’s agricultural lands.

The result? They are most scarce precisely where they are needed the most.

“Currently, wild pollinators are least abundant in intensive monoculture production areas such as sunflowers, almonds and melons, where demand for pollination services is largest,” said Kremen.

Kremen equated depending mainly on one species – the European honeybee – with putting all our retirement savings in one stock.

“The wisdom of diversification holds true for agriculture as well and yet, many Calfornia farmers rely solely on European honeybees for crop pollination,” Kremen said, adding that the unpredictability associated with climate change amplifies the importance of diversification.

“Some insect species will thrive in changed climate conditions, and other won’t. Maintaining a biodiverse stock of pollinators is like the insurance that a diversified stock portfolio brings: some will be up, some will be down, but having a portfolio of many different species ensures viability into the future,” Kremen said.

While it’s common sense that healthy crops result in a healthy food supply, a separate study led by Kremen, also just published, put a number on the human health benefit of ensuring the viability of pollinators. The researchers estimated that up to 40 percent of some essential nutrients provided by fruits and vegetables could be lost if there were no pollinators around to do the job.

Payment for services rendered

Placing a value on ecosystem services is an established part of conservation science, and this new finding comes at a time when there is growing interest within the ranching community in providing ecosystem services. For example, as part of conservation efforts, California ranchers have been asked to maintain flowers for endangered butterflies and to keep small spring wetlands known as vernal pools healthy – using grazing as a tool to manipulate the grassland.

Darrel Sweet, a fifth generation cattle rancher from Livermore and a former president of the California Cattlemen's Association, said that placing a dollar value on rangelands pollination services lends powerful support to these efforts.

“The value of grazing and other land stewardship practices of California’s ranchers is being increasingly acknowledged as not only a preferred land use, but also as an essential resource management tool,” said Sweet. “I hope this study is just the beginning of comparable findings that show how ranching is a critical – and multifaceted – element of California agriculture.”

The state’s rangelands have been decreasing steadily, as the foothills and oak-dotted grasslands can be highly desirable for residential development. California lost 105,000 acres of grazing lands to urbanization between 1990 and 2004, according to the state Department of Conservation. The California Oak Foundation projects that the state could lose another 750,000 acres by 2040.

Kremen said the findings suggest that if farmers paid ranchers to stay on the land and maintain the habitat, the farmers would be increasing their sources of pollination and developing critical diversification to support their agricultural practices.

Posted on Wednesday, June 22, 2011 at 1:01 PM
  • Author: Ann Brody Guy

Scientists complete eventful fisher monitoring season

The UC Berkeley Sierra Nevada Adaptive Management Project (SNAMP) Fisher Team has just finished closely monitoring reproductive-age female Pacific fishers living in the Sierra National Forest near Bass Lake for the spring 2011 denning season.  Each year the denning season for fishers starts around late March and ends in mid June.

Female fisher F01 about to squeeze into the opening for a den cavity inside a black oak tree. The cavity opening is about 25 feet up the tree.


The fact that one of the study's radio-collared female fishers moved her kit from a natal den tree (where the kits were born) in the Sierra National Forest to a maternal den tree in the Mariposa Grove area of Yosemite National Park was a highlight. The event was significant for the park service because it represents the first known fisher den tree location in Yosemite National Park. The National Park Service produced a news release detailing the story.

The Fisher Team also hosted a visit to the project area by a reporter and photographer from the Fresno Bee, which resulted in positive coverage in that newspaper and in the Sacramento Bee.

Below are images captured by den tree cameras this spring. The images illustrate the types of photographic evidence the SNAMP Fisher Science Team uses to document natal and maternal den trees being used by fishers.

Fisher leaving a den tree (the oak in the background) to forage.

Fisher climbing down her maternal den tree.


One of the projects key goals during the denning season is to estimate the typical number of kits that adult females produce each year. One way to do this is by climbing the den tree while the mother fisher is out foraging, and then lowering a specialized camera down into the den cavity. Below is an edited portion of the video footage recorded from inside the den cavity of female fisher F07. The one-minute clip shows two fully furred fisher kits snuggled up together inside the F07 den tree cavity.


Unfortunately, the 2011 denning season was not without life/death drama for the population. Last year two denning females were killed, leaving five orphan kits  behind. The Fisher Team rescued and later released the orphan kits into the wild. This year it was looking like there would not be any denning females killed during den season, up until Saturday, June 4, just two weeks before the typical end of den tree use.

On that day the researchers found the predator-killed carcass of adult female F28 about 150 yards from her den tree. After last year's orphan rescue, the California Department of Fish and Game (DFG) worked with a group of wildlife researchers (including the SNAMP Fisher Team) and agency stakeholders to develop an official policy to help guide researchers on how to deal with orphan kit situations.

In keeping with this new policy, the SNAMP Fisher Team carefully considered the characteristics of the den tree structure (a rotting white fir snag), consulted with DFG, and reached the difficult decision not to attempt to rescue the one or two orphan fishers in the den tree. Attempting to climb the tree would have been dangerous and overly risky for the SNAMP Fisher Team crew. Therefore, in this specific case, nature was left to take its course; F28’s fisher kits perished in a den cavity somewhere near the top of the white fir snag.

The SNAMP Fisher Team is currently preparing information on a wide variety of preliminary results and findings from the ongoing research, which will be reviewed during the SNAMP Fisher IT Meeting in Fresno on July 19. More analytical details from the spring 2011 denning season will be presented at that venue.

The SNAMP Fisher Study is funded by the USDA Forest Service. The agency also provides an airplane and full-time pilot to assist in locating radio-collared fishers living in remote parts of the forest. The image below is a logo for the SNAMP Fisher Project affixed to the tail section of the Cessna 185 airplane used to track fishers by aerial radiotelemetry.

SNAMP logo on the Cessna 185 Tail
SNAMP logo on the Cessna 185 Tail

Posted on Wednesday, June 15, 2011 at 8:11 AM
  • Author: Rick Sweitzer

These bees 'cut it'

We're in the midst of a housing crisis, so why not build a 30-unit, high-rise condo in your yard?

No, not for people--for native bees.

We just installed a bee condo for leafcutting bees (Megachile spp.), on a five-foot high pole overlooking catmint, lavender and salvia.  The "housing development" is actually a wooden board drilled with small holes to accommodate our tiny tenants. Comfy and convenient. Rooms with a view. No housing permits or EIR required. Rent-free, mortgage-free.

Leafcutting bees, aka leafcutter bees, are about the size of a honey bee but darker, with the characteristic light-banded abdomens. They are important pollinators.

Why are they called leafcutter bees? Because the females cut leaf fragments to construct their nests to raise their brood. In nature, they build their nests in soft, rotted wood or in the pithy stems of such plants as roses, raspberries, sumac and elderberry. 

Unlike honey bees, which are social, the leafcutting bee is a solitary nesting bee.  She provisions her leaf-lined nest with nectar and pollen, lays an egg, and seals the cell before leaving.

Commercially made bee condos are available at beekeeping supply stores or on the Internet. You can make or buy a board with different sized-holes so other native bees, such as blue orchard bees, aka mason bees, receive a "home, sweet home," too, and deliver pollinator services.

And enable you to tell your family and friends that you're a "bee landlord" or beekeeper.

The Xerces Society for Invertebrate Conservation offers tips on building bee condos on its website and in its publications, including Farming for Bees: Guidelines for Providing Native Bee Habitat on Farms.

If you don't want bee boards housing your tenants, you can provide straws or hollow bamboo stems.

At the UC Davis Department of Entomology, doctoral candidate Emily Bzdyk is doing research on leafcutter bees. "Basically I'm doing a revision of the subgenus Litomegachile, part of the large genus Megachile, which includes leafcutter and resin bees," she said. "They are native to North America. My goals are to find out how many and what the species are in Litomegachile, and find out as much as I can about their biology, or how they make a living."

"I also want to identify clearly what the boundaries between the species are, or how to tell them apart from one another," said Bzdyk, whose major professor is Lynn Kimsey, director of the Bohart Museum of Entomology. "Litomegachile are very common and hard-to-identify to species, and I feel they deserve attention."

Bzdyk noted that some Megachile are used in commercial alfalfa production. The alfalfa leafcutter bee, native to Europe, is used for commercial pollination of alfalfa, she said. "The Litomegachile is probably very closely related."  

The alfalfa growers erect giant bee condos in their fields to draw bees to their plants.

With home gardeners, the effect is the same.

If you build them, they will come.

Leafcutting bees, aka leafcutter bees (genus Megachile) head toward a bee condo built for these and other pollinators. (Photo by Kathy Keatley Garvey)
Leafcutting bees, aka leafcutter bees (genus Megachile) head toward a bee condo built for these and other pollinators. (Photo by Kathy Keatley Garvey)

Leafcutting bees, aka leafcutter bees (genus Megachile) head toward a bee condo built for these and other pollinators. (Photo by Kathy Keatley Garvey)

Home sweet home: Oblivious to ants, a leafcutter bee heads for home. (Photo by Kathy Keatley Garvey)
Home sweet home: Oblivious to ants, a leafcutter bee heads for home. (Photo by Kathy Keatley Garvey)

Home sweet home: Oblivious to ants, a leafcutter bee heads for home. (Photo by Kathy Keatley Garvey)

Male leafcutter bee (genus Megachile) sips nectar from a rock purslane. (Photo by Kathy Keatley Garvey)
Male leafcutter bee (genus Megachile) sips nectar from a rock purslane. (Photo by Kathy Keatley Garvey)

Male leafcutter bee (genus Megachile) sips nectar from a rock purslane. (Photo by Kathy Keatley Garvey)

Posted on Wednesday, June 8, 2011 at 9:41 AM

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