Nutria- Another danger to California’s water

Nutria are back in California

Image courtesy of U.S. Fish and Wildlife Service

Nutria, an introduced rodent once thought eliminated from California, is the latest of a string of dangerous invasive species wreaking havoc in California’s critically-important Sacramento-San Joaquin Delta.

The nutria, like many other destructive non-native species (large-mouth and striped bass, Asian clam, Chinese Mitten crab, Quagga mussels and Nerodia water snakes, among others) not only threaten the critical infrastructure that provides water, protects our communities, and creates jobs, but they also carry disease, and disrupt natural ecosystems that  threatened and endangered native species rely on.

Acting quickly can help prevent these invasive pests from gaining a foothold.

Why are nutria such an urgent challenge for California?

Infrastructure damage – Nutria excavate burrows in California’s aging levee system, degrading the integrity of the levees and putting farms, communities, and cities in danger.

Ecosystem Destruction/Competition – Nutria consume approximately 25% of their weight daily, burrowing through and destroying the vegetation of wetlands and estuaries as they seek roots, plant stems, and rhizomes to eat. They compete with native species for ecosystem resources, while spreading parasites and pathogens that affect native life.

Water Quality Degradation – In addition to excavating burrows, and eating plant stems and roots, nutria often disturb the ground cover that protects waterways from silt and debris during the winter.

Public Health Threat – Nutria are known to carry pathogens and parasites that can infect not only local Delta wildlife, livestock, and pets- but also humans.  Nutria can carry bacteria that cause tuberculosis and septicemia, as well as blood flukes, tapeworms, liver flukes

 

What is a nutria?

Image courtesy of U.S. Fish and Wildlife Service

The nutria, called a coypu outside of North America, is a semi-aquatic rodent of unusual size- particularly large for a rodent, they are typically about 12 pounds, but can grow to be between 15 and 20 pounds. They are native to South America.

The nutria reproduces year-round, and reach maturity quickly. While each mature female can carry up to three litters per year, each litter has on average 5 young, with as many as 13 not being uncommon.

Originally introduced to California in the late 19th century as a non-native species to support the fur industry, nutria were reintroduced periodically up until the collapse of the fur industry in the 1940s.

Nutria, like other non-native species, are a critical threat to the riparian ecosystems needed to promote recovery of endangered and threatened species in California.

 

If you see a nutria, report it to the State of California online at: https://www.wildlife.ca.gov/Conservation/Invasives/Report

 

 

For more information on Nutria:

https://www.wildlife.ca.gov/Conservation/Invasives/Species/Nutria

 

For more information on other non-native species in California:

Fish: http://calfish.ucdavis.edu/Non-Native_Fish_Species/

Plants: https://www.nrcs.usda.gov/wps/portal/nrcs/detail/ca/home/?cid=stelprdb1041704

Mammals: http://www.dfg.ca.gov/wildlife/nongame/t_e_spp/mammals.html

 

Many Delta Stressors Impacting Delta Smelt and Delta Health

Delta bass predation

There are far bigger issues affecting the Delta than water exports and Delta bass predationreturning to a time prior to Western development is unrealistic.

To describe the Delta as altered is to say that New York City is populous or California water politics contentious. Since the 19th century when locals began to reclaim the marshlands, dike the rivers, and develop settlements on the rivers- the history of the Delta has long been one of change. California’s largest river delta, the Sacramento – San Joaquin Delta has been forever altered by human habitation. Little remains of the complex estuary network of tidal wetlands, freshwater rivers and recurring saline incursions.

Long gone are the nuanced networks of sloughs and wetlands that once dominated the historic delta. Today’s Delta is a scene dominated by numerous dried islands often sitting 20-30 feet below the water level just beyond the 1100 miles of earthen dikes. Plans exist to restore more than 30,000 acres of riparian and wetland habitat, but to date these plans continue to undergo environmental review.

Beyond the edges of these islands ongoing dredging of channels for deepwater shipping to the inland port cities of Stockton and Sacramento applies greater pressure to the species looking for shallow water habitat.

The Delta today is one of artificially fresh water- held far to the west of pre-project development, flows originating in the state’s network of reservoirs now support in-delta diversions for use by in-delta agriculture, cities as near as Stockton and as far away as San Diego. It is used to grow avocados on small farms near San Diego and organic cantaloupee near Firebaugh, among more than 300 other types of food and fiber that rely on water flowing through the Delta. as well as providing water to more than 25 million Californians.

There are numerous stressors impacting the health of the Delta and the threatened and endangered species living there, including the Delta Smelt. The region’s biosphere has changed dramatically and is now dominated by invasive species that have decimated native fish populations.

The National Marine Fisheries Service has stated that predation by non-native bass on winter-run salmon is a “major stressor,” while widespread invasive Asian clams and other species continue to alter the delta’s complex food network. Industrial chemicals being found in species at the mouth of the bay are also tied to what has been called Pelagic organism decline by researchers studying the health of the Delta.

Regarding the decline of the Delta Smelt, the federal agency responsible for studying and restoring threatened species, the Fish and Wildlife Service, acknowledges that “we are unable to determine with certainty which threats or combinations of threats are directly responsible.” Since 1994, Fishery and wildlife regulators have limited their focus to delta exports, though the agency acknowledges that its “existing regulatory mechanisms have not proven adequate” to stop the fish’s decline since its listing nearly 20 years ago.

Yet sensational news stories continue, declaring water exports culpable- “With Just Six Delta Smelt Left, Controversial California Fish Species Faces Impending Extinction” and “Threatened Smelt Touches Off Battles in California’s Endless Water Wars” but scientists who study the complex Delta ecosystem suggest that this claim is likely overly simplistic. Researchers discussing the issue with the Wall Street Journal noted that “Other studies have noted that the biggest driver of species abundance in the delta is precipitation, which may explain why the smelt population has plummeted over the past four years of drought after rebounding in 2011—a wet year.”

ExportsInflowandSmelt

Suggested changes to the Delta export facilities, intended to reduce possible impacts to threatened and endangered species while restoring reliability to water supplies remain under review, and could allow the Delta to return to a more natural condition, while restoring water supply reliability to more than 25 million Californians and millions of acres of the most productive farmland on the planet.