To continue from yesterday's BLOG post, mosquitofish are among the most common aquatic invasive species in the Western United States.  Native east of the Rocky Mountains, mosquitofish (Gambusia affinis and Gambusia Holbrooki) have been introduced to every continent except Antartica.  Their widespread introduction has resulted from their use as biological control agents of larval mosquitos which transmit human pathogens.  Mosquitofish are successful invaders because they are livebearing, can reach sexual maturity in only 18 days and are able to survive a wide range of environmental conditions.  Our UC-HoplandREC study involves introducing mosquitofish to one-half of a barrier-divided wetland (see photo) containing native species.  Our aim is to understand how they influence native wetland communities of invertebrates and amphibians. While mosquitofish may be useful for controlling mosquitos, we suspect they have unintended effects on native aquatic species, which should be considered before they are released into water bodies in northern California (and elsewhere).  Author - Dan Preston

The Mosquitofish (Gambusia affinis) is a species of freshwater fish that is native to the watersheds of the Gulf of Mexico.   The genus name gambusia is derived from the Cuban Spanish term "gambusino", mean "useless".  However, the species is remarkably hardy, surviving waters of varying oxygen levels, varying salinities (up to 2x seawater salinity), and varying temperatures.  They feed readily on the aquatic larval and pupal stages of mosquitoes.  For all the reasons above, the mosquitofish has been used throughout the world as a biological control for mosquitoes (ie malaria control) and may now be the most widespread freshwater species in the world.

Vector control agencies in California and throughout the world have for decades promoted the introduction and release of this species into water bodies that may harbor mosquito larva.  However, invasive species such as mosquitofish, represent major drivers of ecosystem change, especially in freshwaters.  At UC-Hopland Research and Extension Center a current research project will be examining the impacts of mosquitofish on a native California pond community.  The exotic fish will be introduced to one-half of a large vernal pool for one summer season, and then the impacts on invertebrate and amphibian species will be monitored for three years.

Over the last six decades the UC Hopland Research & Extension Center has been able to keep its 5358 acres relatively "yellow star thistle free".   It is probably one of the few large acreages within Mendocino County that can make that claim.   However, that does not mean that problem spots do not occur on the Center, and many of those are in steep terrain that makes other control methodologies, like intensive and timely grazing, or ATV/backpack herbicide spraying, risky and problematic.  With special funds, HREC was able to get a certified aerial applicator to apply MILESTONE, a broad-leaf selective herbicide, onto the problem spots.  MILESTONE is relatively "easy" on woody species such as our native oaks... just in case of accidental drift of the herbicide.  The photo shows the Twin Cities Aviation helicopter out of Yuba City, CA., applying the herbicide in the early morning hours.   We were able to selectively treat 50 acres, scattered throughout the Center, in about two hours of flight time.

The UC Hopland Research & Extension Center has three very old natural "sag" ponds, geologically formed as a result of seismic activity which is common throughout California.  A sag pond is a body of water which forms as water collects in the lowest portions of a depression that forms between two strands of an active strike-slip fault.  Basically, as the land mass "stretches" because of seismic activity over time, the land between them sinks, thus forming such ponds.

The Maacama Fault runs directly underneath this region.

One of the "Lake Biological Area" ponds holds a permanent body of water (see photo), one is semi-permanent holding water throughout the summer in all but the most extreme drought years, and one is a "vernal pool" filling each winter but drying each summer.

Once home to Northern California Red-legged Frogs, as known from 1950s collected specimens, the introduction of non-native large-mouth bass, green sunfish, and bluegill along with the invasion by bullfrogs led to the extermination of this population of native frog species.   The ponds, however, are home to many unique plants, birds, animals, amphibians and invertebrates of the local area due to the long-standing, permanent wetlands habitat.