User:EvyWvy/Mohave tui chub

The Mohave tui chub, Gila bicolor mohavensis, is a type of Cyprinid fish and is the only endemic fish to the Mojave River. The Mojave River flows north easterly from the San Bernardino mountains to the basin of Soda Lake, California, about 100 miles away . There are many tui chubs distributed among Western North America, each with distinctive forms due to isolation within basins. Many of these subspecies are in decline, including the Mohave tui chub. Please note the spelling “Mojave” is the Spanish version used when referring to the Mojave National Reserve and therefore the river, and “Mohave” is used when describing the Mohave tui chub, originating from the Native American spelling .

The Mohave tui chub was listed as endangered under the Endangered Species Act in 1970, then to California’s list of endangered species in 1971. A recovery plan was created by the US Fish and Wildlife Service in 1984.

Map of the Mojave River

Life History

Mohave tui chub

Adult Mohave tui chubs' standard length ranges from 52 to 92 mm. However, some adults can reach 150 mm or longer. They have a thick body and short, rounded fins. These fish have a brown to a dark olive colored back and blue-ish white to silver belly. The species does not demonstrate sexual dimorphism. Females spawn from February to October and lay between 4,000 and 50,000 eggs that stick to aquatic vegetation. Mohave tui chubs are adapted to survive the Mojave river’s alkaline water, low oxygen levels,  and high water temperatures. Adults are solitary and inhabit deeper waters. Mohave tui chubs subsist on insect larvae, small fish, and detritus.

Threats and Causes for Population Declines

Arroyo chub

The main reason for the  Mohave tui chubs decline was the introduction of Arroyo chubs, Gila orcutti. Arroyo chubs were introduced to the river in the 1930s by trout fishermen as baitfish, and their spread was aided by significant flooding in 1938. Following their introduction, there were significant numbers of Arroyo chubs, hybridized species, and far less Mohave tui chubs. By 1967, genetically pure Mohave tui chubs no longer existed in the Mojave River. Arroyo chubs are stream adapted minnows with higher tolerances for low oxygen and higher temperatures than Mohave tui chubs, thus it is possible that competitive displacement alone could have displaced the Mohave tui chub regardless of genetics. In addition to the introduction of Arroyo chubs, other exotic species introductions such as bass, catfish, trout, bullfrog, and crayfish hurt Mohave tui chub numbers through predation and competition. Habitat alterations such as the construction of reservoirs altered the natural flow regime and created habitats more suitable for invasive species that further plummeted Mohave tui chub populations.

An additional threat to the Mohave tui chub was the discovery of Asian tapeworm within the species in 2001 in Lake Tuendae, the same time Western mosquitofish (Gambusia affinis) were found there as well. Originally from China, Asian tapeworm most often associates with Cyprinid species and is found on every continent excluding Antarctica. Native to China, this tapeworm spends a portion of its life cycle inside the intestine of freshwater fish. Its widespread introduction occurred with translocations of common carp and grass carp. The impacts of Asian tapeworm on wild fish populations need to be studied more, with various effects on differing fish species observed. Masters student Thomas Archdeacon designed an experiment to test the effects of Asian tapeworm on Mohave tui chubs in 2007. It was concluded that Asian tapeworm does not directly reduce Mohave tui chub survival and decreases growth slightly. Note that this is within a laboratory setting and Archdeacon notes that field research is necessary.

Western mosquitofish are native to the southeastern United States, but are found in almost all 50 states. Mosquitofish were intentionally spread far and wide to attempt to control mosquito populations.  Mosquitofish have negative impacts on native southwestern fishes due to competition and predation. Archdeacon studied impacts of mosquitofish on Mohave tui chub in the laboratory setting as well. While more studies are needed, he concluded that eventually, Mohave tui chub reaches a size that protects them from predation by mosquitofish. Additionally mosquitofish may even provide a food source as they were found within the stomachs of Mohave tui chubs multiple times in the field.

Lake Tuendae

Overall, the effects of Asian tapeworm and mosquitofish on the Mohave tui chub population in Lake Tuendae are unknown today.

Recovery Plan

Mohave tui chub were found in 2 isolated ponds and one spring at Soda Springs: Lake Tuendae, Three Bats Pond, and MC Spring. Mohave tui chub were thought to have gotten to Soda Springs either from introduction in 1945 or during the intense flooding of 1938. Efforts to move the chubs were largely unsuccessful, with 3 successes out of 14 attempts. The successes were at Lark Seep Lagoon, Desert Research Station Pond, and Barstow Way Station Pond. The Lark Seep Lagoon is on the China Lake Naval Weapons Center, to which tui chubs were introduced in 1971, where today the population still exists. The Desert Research Station Pond was stocked with 16 fish in 1978, but no longer exists today. 60 chubs were introduced to the Barstow Way Station Pond, but were not considered a population due to their containment in a small and artificial environment and no longer exists today.

The U.S. Fish and Wildlife Service created a Recovery Plan with the goal to delist the Mohave tui chub from the list of threatened and endangered wildlife in 1984. The authors decided that three additional habitats must be established, with minimum populations of 500, with their integrity maintained for 5 years total (the previous 3 habitats are included in this). The habitats must also be exposed to and have survived a flood before reclassification will commence. At re-evaluation in 2004, the recovery plans suggested in 1984 were not implemented. However, there is a transplanted population at Camp Cady that still persists today. As of today, the recovery plan has still not commenced.

The 1984 recovery plan was revisited in 2004 by the National Parks Service. The group consisted of academics, the old recovery team, and government agencies to discuss Mohave tui chub recovery. The group discussed the possibility of reintroducing the Mohave tui chub into the Mojave River in order to delist it.

Laboratory spawning of this fish is important to consider as a possibility to recover this species' populations. Controlled spawning can also provide individuals for experiments to help this species as well. As of now, it appears that no active breeding attempts have been made or are underway.

History of Soda Springs

Road sign for Zzyzx Mineral Springs

Zzyzx Mineral Springs and Health Resort was established in 1944 by Curtis Springer on a mining claim. For a decade, Springer built more infrastructure to run his operation and he became a millionaire by selling his special formula. In 1955, he excavated an artificial pond that is today known as Lake Tuendae. Eventually Springer was found to be a fraud due to false advertising and his role in tax evasion. The BLM regained his lands and Springer went to jail for several months.

Current Populations

As of 2013, there were 3 populations: Soda Lakes (Lake Tuendae and Mohave Chub spring), China Lake, and Camp Cady. MC is a pond with a surface area of 250 square feet and consists of a single pool with no outlet. Counts from the time predicted numbers between 257 and 618 fish in the pool. The California Department of Fish and Wildlife backs up these claims, stating that Mohave tui chubs still exist today at Soda Springs, Camp Cady, and China Lake. The population is doing well at Camp Cady in two ponds, whereas the Soda Lake population is threatened by mosquitofish and Asian tapeworm. It is thought that the most secure population exists at China Lake.

The Mohave tui chub is still listed as endangered today. There do not appear to be any recent population evaluations on this fish. Chen et al. believe that the goal to reintroduce Mohave tui chub into the Mojave River is unattainable today. The authors state that removal of Arroyo chub would be necessary, and the scale of the Mojave River is too large for such an endeavor and would cause too large an impact to sport fisheries and availability of drinking water. However, they suggest that Mohave tui chub could be introduced into upstream tributaries, ponds, and impoundments. Doing so could provide experimental management zones.