Patrick Dotsy- Delta Smelt

Smeltdown on the Horizon

By Patrick Dotsy

November 28, 2016

            Hypomesus transpacificus, more commonly known as the Delta Smelt, is one of the 12 remaining indigenous Delta species that inhabits the California Delta and their numbers are quickly dwindling. This slender body fish typically ranges from 5-7 centimeters and is semelparous, meaning that it has a life span of only a year and dies after its first spawning. The Delta Smelt is endemic to the Sacramento-San Joaquin estuary.  During spawning season (typically between January and July) the smelt seek out freshwater which usually leads them to inhabit the Sacramento River, the Mokelumne River system, the Cache Slough region, the Delta, and the Montezuma Slough area. The delta smelt has large eyes and is nearly translucent. Their primary food sources are planktonic copepods, cladocerans, amphipods and insect larvae. Delta smelt play a huge role in our waters because they are known as an indicator fish of the overall health of the Delta ecosystem.

     Geographic and Population Changes

           

Historic Range of Delta Smelt

The delta smelt was once the most abundant fish in the delta. But during the 1950s large water export facilities were built and continued to be added on to for several years. In 1967, the State Water Project was complete which started pumping even more water out of the delta. Eventually herbicides and pesticides were contaminating the water and invasive species showed up in the water from Chinese ships in San Francisco. The delta spelt population began to plummet in the 1970s and stayed on that downhill slope.

Listing Date and Type of Listing

The Delta Smelt were listed as threatened under the Endangered Species Act in 1993 at both the federal and state levels. Nobody actually knows the number of smelt remaining, but scientist do fear that the small remaining amount is nearly too small reproduce. The current listing status still remains as threatened.

Main Threats and Cause of Listing

1)    Years of extreme low or high outflows

2)    Water diversion

3)    Changes in food organisms

4)    Toxic substances

Years of extreme outflow, whether it be low or high, has a direct correlation with delta smelt populations. For example, years of high outflow from substantial amount of rain flushes the delta smelt and zooplankton out of the system. Not only are smelt affected, but also their main food source. Years of low outflow from dry years (that we seem to have a lot of recently) causes more diversion from delta leaving less water.

Water Diverted from the Delta via State Water Project

Water diversion from the Sacramento River is a pressing issue that effects delta smelt populations. Water being diverted from the delta throw the Central Valley Project and State Water Project leave little freshwater available to the smelt especially on dry years. This is on ongoing battle and pressing issue between conservationists and farmers.

            Changes in food organisms include three exotic copepods being successfully invaded the estuary which reduced native euryhaline copepods. These new exotic species are much more elusive and able to escape hungry smelt and juvenile striped bass than the declining native species.

            Toxic substances are entering the Sacramento-San Joaquin estuary from agricultural pesticides, heavy metals, and other harmful societal products. These toxic substances cause direct mortality and stress to larval striped bass and it is assumed that they have the same affect on delta smelt larval.

Delta Native Fishes Recovery Plan

            The main objective of the recovery plan approved on November 26, 1996 is to remove the delta smelt from the federal list of threatened species through a rebound in the populations throughout the delta. The two phases of this recovery plan include restoration and delisting. Through management of the estuary and Suisan Bay, where smelt population are highest, populations of the delta smelt will be restored. The aim is not to have all-time high in population of smelt in order to delist, but rather to have the same amount of smelt as the pre-declined population in the 1970s. Furthermore, they need to prove that they can withstand extreme outflow years. Once this is achieved, then the delta smelt will be delisted.

What can we Do?

            There is no question that the delta smelt are in need of our help. The first and foremost easiest thing we can do as Californians is increase public awareness of the importance of native delta species like the smelt. Furthermore, we can advocate and vote to improve enforcement on commercial/recreation harvest as well as how we regulate outflow. We could also get involved with teams that do monitor and research on fish biology and requirements. With the efforts of a majority, we can make the delta smelt a priority to conserve in California.

For more information, visit:

http://www.biologicaldiversity.org/species/fish/Delta_smelt/index.html

Works Cited

“Recovery Plan for The Sacramento-San Joaquin Delta Native Fishes.” US Department of Interior Fish and Wildlife. Approved November 26, 1996. Retrieved at: http://ecos.fws.gov/docs/recovery_plan/961126.pdf

Kay, Jane. "Delta Smelt, Icon of California Water Wars, Is Almost Extinct." National Geographic. N.p., 3 Apr. 2015. Web. Retrieved at: http://news.nationalgeographic.com/2015/04/150403-smelt-california-bay-delta-extinction-endangered-species-drought-fish/

Picture URL’s:

http://www.watereducation.org/aquapedia/state-water-project

http://news.nationalgeographic.com/2015/04/150403-smelt-california-bay-delta-extinction-endangered-species-drought-fish/     x 2

http://calfish.ucdavis.edu/files/79471display.jpg