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Climate change driving California native fish species to extinction
Eighty two percent of native freshwater fish species in California, including salmon, are likely to become extinct on present trends within the next century due to climate change, reports a study lead by Professor Peter Moyle from University of California Davis.
The study - Climate Change Vulnerability of Native and Alien Freshwater Fishes of California: A Systematic Assessment Approach - found that, of 121 native fish species, 82 percent are likely to be driven to extinction or very low numbers as climate change speeds the decline of already depleted populations. In contrast, the study reported that 19 percent of the 50 non-native fish species in the state face a similar risk of extinction. Many non-native fish are likely to thrive in changed aquatic conditions, mostly at the expense of native species.
"If present trends continue, much of the unique California fish fauna will disappear and be replaced by alien fishes, such as carp, largemouth bass, fathead minnows and green sunfish," said Peter Moyle, a professor of fish biology at UC Davis who has been documenting the biology and status of California fish for the past 40 years.
"Disappearing fish will include not only obscure species of minnows, suckers and pupfishes, but also coho salmon, most runs of steelhead trout and Chinook salmon, and Sacramento perch," Moyle said.
This is another example of the great loss of biodiversity we are seeing with the 6th mass species extinction event in the history of the planet - this one caused by human degradation of the environment, the atmosphere and climate change disturbance. Only a few days ago I reported on the rapid decline in amphibian numbers across the United States.
With reduced winter snow and spring ice melt, and drier conditions more likely in many catchments, fish species face increased variability of stream flows with reduced flows during summer. Higher air temperatures and reduced stream flows will increase water temperatures. Salmon and trout which prefer cold water are particularly threatened.
According to the study California is projected "to experience advancement in the timing of precipitation events and an increase in the ratio of rain to snow. This will result in more high flow events during winter, increased variability in flows, diminished spring snowmelt pulses, and protracted periods of low (base) flows. Such changes in precipitation and flow regimes will likely alter seasonal availability of spawning and rearing habitat for some native fish species (e.g., Chinook salmon, Oncorhynchus tshawytscha) and favor fishes (mostly aliens) that can persist during long periods when stream flows are low and intermittent. The more the natural flow regime is altered, the less native fishes will be favored."
The authors conclude in the abstract of the study:
"Native species had both greater baseline and greater climate change vulnerability than did alien species. Fifty percent of California's native fish fauna was assessed as having critical or high baseline vulnerability to extinction whereas all alien species were classified as being less or least vulnerable. For vulnerability to climate change, 82% of native species were classified as highly vulnerable, compared with only 19% for aliens. Predicted climate change effects on freshwater environments will dramatically change the fish fauna of California. Most native fishes will suffer population declines and become more restricted in their distributions; some will likely be driven to extinction. Fishes requiring cold water (&lessthan;22°C) are particularly likely to go extinct. In contrast, most alien fishes will thrive, with some species increasing in abundance and range. However, a few alien species will likewise be negatively affected through loss of aquatic habitats during severe droughts and physiologically stressful conditions present in most waterways during summer."
The study was lead by Professor Peter Moyle and co-authored by postdoctoral students Joseph Kiernan, Patrick Crain and Rebecca Quiñones of the Center for Watershed Sciences at UC Davis. The study methodology was designed for a rapid and repeatable application in other regions to assess freshwater fish species vulnerability to climate change. Around the world riparian and freshwater aquatic habitats are suffering degradation from human land use changes, which climate change will impact further upon. Freshwater fishes are bearing the brunt of these changes, especially in regions with arid or Mediterranean climates. The authors said "Our method has high utility for predicting vulnerability to climate change of diverse fish species. It should be useful for setting conservation priorities in many different regions."
Top 20 Native Californian Fish likely to become extinct
The study reported on the top 20 native fish most likely to become extinct in California within 100 years as a result of climate change. These include the following in order of vulnerability to extinction:
Many of these are not yet even listed as officially threatened. (Note: asterisks denote a species already listed as threatened or endangered)
Freshwater fish constrained by watersheds and human obstacles to migrate with climate changes
While ocean fish are able to migrate towards the poles or even dive deeper to escape warming sea surface temperatures, many freshwater species have limited mobility to adapt to climate changes, contrained by the watersheds they live in, and often by human built dams and weirs, or natural rapids and waterfalls which obstruct movement upstream.
"Given the discrete nature of watersheds, it is likely that the only place suitable habitats can be created for native fishes is upstream of present habitats, above barriers, within the same drainage network. However, many upstream habitats may be unsuitable because of their small size, low flows and/or high gradients typical of lower order streams. Where suitable physical habitats exist, they are likely to be already occupied by other native fishes or to be above barriers. " says the study.
Many native fish species have developed a high degree of habitat specialization making them particularly vulnerable to climate change.
Stocking waterways with non-native species has also impacted native fish species and amphibians. Stocked fish prey on and compete with native species for food and habitat, altering the natural ecosystem to the detriment of native species. Read more on Fish stock reform at Center for Biological Diversity.
Human Dam construction for supply of drinking water, agricultural irrigation and flood mitigation has changed stream flows for many rivers. Water diversion projects such as the Bay Delta Conservation Plan (BDCP) to build peripheral tunnels to export water from the Bay Area Delta is likely to lead to the extinction of Central Valley salmon, Delta smelt, longfin smelt and other imperiled fish species according to the Bay Institute BDCP Effects Analysis briefing paper (PDF) published February 2012. The last of the Delta tunnel plan documents were released amidst broad opposition on May 29. Opponents of the scheme alledge The peripheral tunnels will divert a large portion of the flow of the Sacramento River for use by corporate agribusiness and oil companies with a total actual cost estimated at $54.1 billion.
Increased variability of stream flow overwhelmingly increases some alien fish species at the expense of native species, as well as providing obstacles to fish migration upstream. A June 2012 paper in Bioscience - Implications of Dam Obstruction for Global Freshwater Fish Diversity (Liemann et al 2012) details that "Nearly 50% of the 397 assessed freshwater ecoregions are obstructed by large- and medium-size dams, and approximately 27% face additional downstream obstruction."
But the report by Professor Moyle and his co-authors does highlight that with careful stream flow management, cool water refuges for native species can be maintained to help in the conservation of these fish species. "Modifying the flow regime indicates that managing flow regimes in regulated streams may be a powerful tool to counter the negative effects of climate change, as demonstrated by the success of re-establishing native fishes in Putah Creek... In general, establishment of cool-water refuges for native fish is needed, even in urban streams such as those in the San Francisco Bay region."
"These fish are part of the endemic flora and fauna that makes California such a special place," said Moyle. "As we lose these fishes, we lose their environments and are much poorer for it."
The Chinook Salmon in the Upper Klamath Basin and the Clear Lake Hitch are just two of the Californian native species awaiting protection and conservation plans to be put into place:
Chinook salmon in the Upper Klamath Basin
For example, the Center for Biological Diversity and other conservation organisations petitioned (PDF) for the Chinook salmon in the Upper Klamath Basin to be listed for protection under the Endangered Species Act (ESA) in 2011.
"Chinook salmon in the Upper Klamath Basin have undergone severe declines and face many threats, including the presence of impassable dams, which have resulted in the loss of over 300 miles of spawning habitat, massive water withdrawal, logging, mining, livestock grazing, pollution, disease, predation, overfishing, hatcheries, and climate change. In combination, these threats place Upper Klamath Chinook in danger of extinction necessitating protection under the Endangered Species Act (ESA)." argued the CBD petition.
Clear Lake Hitch
In March 2013 the California Fish and Game Commission voted 2-1 to designate the Clear Lake hitch -- a large minnow found only in Northern California's Clear Lake and its tributaries -- as a candidate species for protection under California's state Endangered Species Act. The Center for Biological Diversity had petitioned for listing of this species under both state and Federal Endangered species legislation.
"This is a promising move on the part of the Fish and Game Commission. The Clear Lake Tribes have been actively engaged in studying and protecting the Clear Lake hitch since 2005," said Anthony Jack, Tribal Chairman of the Big Valley Band of Pomo Indians. "The Big Valley Band of Pomo Indians will continue to assist in protecting the few native species left in our region -- the benefits to the ecosystem will be felt by all."
Jeff Miller from the Center for Biological Diversity also commented on the listing of this species "These are culturally, biologically important fish, and state protection is one of the keys to saving them. Restoring their habitat will improve the health of Clear Lake overall. Hitch now spawn regularly in only two streams, so we're in real danger of losing these iconic Clear Lake fish. We need measures right away to improve stream flows, stop the loss and degradation of spawning habitat, and address the problems of barriers to fish migration, pollution and the impacts of invasive fish." he said in a media release.
A relative of the Clear Lake Hitch, the Clear Lake splittail, was driven to extinction in the 1970s through habitat alterations that dried out spawning streams and barriers that prevented fish migration, according to Jeff Miller. "Without restoration of stream and wetland habitats and reintroduction into former spawning tributaries, Clear Lake's hitch may go the way of the lake's former splittail population," Miller said. "We can't let that happen."
North American Freshwater fish extinction rate
Noel Burkhead, a research fish biologist with the US Geological Survey published a paper in BioScience in September 2012 on Extinction Rates in North American Freshwater Fishes, 1900-2010 (abstract) which reads in full:
"Widespread evidence shows that the modern rates of extinction in many plants and animals exceed background rates in the fossil record. In the present article, I investigate this issue with regard to North American freshwater fishes. From 1898 to 2006, 57 taxa became extinct, and three distinct populations were extirpated from the continent. Since 1989, the numbers of extinct North American fishes have increased by 25%. From the end of the nineteenth century to the present, modern extinctions varied by decade but significantly increased after 1950 (post-1950s mean = 7.5 extinct taxa per decade). In the twentieth century, freshwater fishes had the highest extinction rate worldwide among vertebrates. The modern extinction rate for North American freshwater fishes is conservatively estimated to be 877 times greater than the background extinction rate for freshwater fishes (one extinction every 3 million years). Reasonable estimates project that future increases in extinctions will range from 53 to 86 species by 2050."Fish species tend to be relatively well studied in comparison to other aquatic animals. According to Burkhead "declining fishes represent just the tip of the iceberg regarding losses of freshwater biota and their habitats. Comparatively, mussels and snails are exceptionally imperiled, with extinction rates an order of magnitude greater than that of freshwater fishes."
Global Decline in Freshwater fish species
The decline in native freshwater fish species is a global problem. Introduction of non-native fish, pollution, land use changes, alteration of stream flow, dams and climate change are driving many freshwater species rapidly to extinction, not only in California but around the world. The funny thing is, many of these species fill an ecological niche preying on insects and insect larvae which helps keep insect populations down and us humans a little more comfortable.
Burkhead says that although estimates of extinction rates are much lower on other continents, this is because of underestimates of true extinction levels. "Based on the continental extinction rate of 3.2% for North America, the worldwide loss of freshwater fishes may exceed 400 species." he says. "The loss of 3.2% of the continental fish diversity is not trivial and demonstrates that some of our resource practices are detrimental to the persistence of freshwater fishes and likely to that of other aquatic faunas."
Watch this Youtube video of Brian Zimmerman, Curator of Aquarium from the Zoological Society of London (ZSL) on Saving Freshwater Fish from Extinction. Yes, some freshwater species have been able to be preserved through aquarium programs while the species becomes extinct in the wild.
Figure 2. The native and alien fish species in California can be classified into four categories of vulnerability to extinction as the result of climate change by 2100. (Moyle et al, 2013)