Are There Any Fish in the Salton Sea?

The Salton Sea once teemed with fish and supported one of the most productive sport fisheries in southern California. Today, the answer is grimmer: rising salinity, toxic gas eruptions, and algal blooms have driven most fish species to effective extinction within the lake’s main body. Mozambique tilapia, the hardiest of the bunch, hung on longer than any other species but have been reduced to scattered, struggling populations. The story of fish in the Salton Sea is less about whether they exist and more about what wiped them out and whether anything can bring them back.

How the Salton Sea Got Its Fish

The Salton Sea itself is an accident. In 1905, irrigation diversions from the Colorado River broke through their channels and poured uncontrolled into the Salton Sink, a below-sea-level depression in California’s Imperial Valley. For nearly two years, the river flowed freely into the basin before engineers could stop it, creating what became the largest lake in California by surface area. The lake had no outlet. From the start, every gallon of agricultural runoff that flowed in brought dissolved salts with it, and since water left only by evaporation, those salts accumulated year after year.

In the 1950s and 1960s, the California Department of Fish and Game deliberately stocked the Salton Sea with marine and estuarine species from the Gulf of California, hoping to create an inland sport fishery. Orangemouth corvina, Gulf croaker (also called bairdiella), and sargo were among the species introduced. The plan worked, at least for a while. By the 1970s and 1980s, the Salton Sea was attracting tens of thousands of anglers annually, and corvina catches rivaled those of popular coastal destinations. Mozambique tilapia, an African freshwater species that had been introduced into nearby irrigation canals, also found its way into the sea and thrived.

The Species That Called It Home

At its peak, the Salton Sea’s fish community was dominated by a handful of introduced species. Orangemouth corvina, a predator that can exceed 30 pounds, was the marquee catch for anglers. Bairdiella, a smaller croaker species, was by far the most numerous fish and served as the primary food source for the lake’s enormous bird populations. Sargo, another Gulf of California native, filled out the mid-level of the food web. And Mozambique tilapia, a generalist feeder, became the workhorse species, reproducing prolifically in the warm, nutrient-rich water.

One native fish also lived in and around the Salton Sea: the desert pupfish. This tiny, endangered species had existed in desert springs and streams in the region long before the modern lake formed. Desert pupfish can tolerate extreme temperatures and high salinity, but they were largely relegated to shoreline pools, irrigation drains, and creek mouths rather than the open water of the sea itself. Their story diverges from the introduced species in important ways.

Why Tilapia Outlasted Everything Else

As the Salton Sea’s salinity climbed past the level of ocean water and kept going, most introduced species started declining. Corvina and bairdiella, though originally marine, struggled as salinity pushed into the 40-50 parts per thousand range and beyond. Tilapia, against all expectations for a freshwater species, proved remarkably resistant. Research into how they manage this has revealed that Mozambique tilapia can survive in hypersaline conditions by ramping up the activity of specific salt-handling proteins in their gut. Their posterior intestine, in particular, plays a critical role in absorbing salts and maintaining internal fluid balance when external salinity spikes far above ocean levels.¹

This physiological flexibility is why tilapia were the last species standing in the open waters of the Salton Sea while corvina and bairdiella faded. But even tilapia have their limits. Salinity alone did not finish them off. Instead, it was the one-two punch of rising salt combined with catastrophic water chemistry events that pushed fish populations toward collapse.

What Actually Kills the Fish

Massive fish die-offs have been a defining feature of the Salton Sea for decades. Visitors and news cameras periodically document miles of shoreline carpeted with dead tilapia, an image that has come to symbolize the lake’s decline. The kills are not caused by salinity alone. Two interrelated chemical processes are the primary culprits.

Hydrogen Sulfide Events

The Salton Sea is extremely nutrient-rich, fed by agricultural runoff loaded with fertilizers. This fuels enormous blooms of algae and bacteria, which consume oxygen when they decompose. In deeper layers of the lake, bacteria that thrive without oxygen produce hydrogen sulfide, a toxic gas with a rotten-egg smell. Under calm conditions, this gas stays trapped near the bottom. But when strong winds churn the lake, that sulfide-laden deep water mixes into the surface, stripping the entire water column of dissolved oxygen at once. Research documenting one such event found that hydrogen sulfide concentrations reached levels exceeding the known toxicity threshold for tilapia, and the resulting oxygen depletion left fish with nowhere to go.² These wind-driven mixing events tend to happen in late summer, when water temperatures are highest and bacterial activity is most intense.

Cyanobacteria and Their Toxins

The same nutrient overload that drives hydrogen sulfide production also feeds massive blooms of cyanobacteria. Testing of Salton Sea water found that 85 percent of samples contained detectable levels of microcystins, potent liver toxins produced by cyanobacteria. The dominant toxin-producing organisms were a tiny open-water species called Synechococcus and a bottom-dwelling filamentous species called Oscillatoria. Both were confirmed to produce microcystin-LR and microcystin-YR, among the more dangerous variants of this toxin family.³ The toxins do not just affect fish. Researchers analyzing the livers of eared grebes, diving birds that use the Salton Sea as a migratory stopover, found microcystin levels high enough to potentially explain some of the mass bird die-offs that periodically devastate the lake’s avian population.³

Together, hydrogen sulfide and cyanotoxins create a lake that is chemically hostile even to the most salt-tolerant fish. A single bad summer event can kill millions of fish in days, and with populations already stressed by chronic salinity, there are fewer fish to rebound from each successive die-off.

Contaminants in Whatever Fish Remain

Even during the years when Salton Sea fish were plentiful enough to catch, eating them carried risks. Agricultural runoff does not just bring fertilizer into the lake. It carries pesticides, heavy metals, and industrial chemicals accumulated from decades of farming in the Imperial and Coachella Valleys. Researchers examining fish from the Salton Sea found that selenium, arsenic, DDT breakdown products, and polychlorinated biphenyls (PCBs) were the contaminants most worth worrying about.

Selenium concentrations in fish muscle tissue ranged from roughly 1.9 to 2.7 micrograms per gram of wet weight across species.⁴ A more detailed risk assessment found that average selenium levels in bairdiella fillet tissue ran about 2.9 micrograms per gram, and in tilapia about 1.7 micrograms per gram. At those concentrations, an adult angler could eat up to roughly a pound of tilapia per week without exceeding safety guidelines, even accounting for selenium consumed from other foods. Corvina and bairdiella had lower safe consumption thresholds, but none of the species posed an immediate selenium hazard at moderate intake levels.⁵

Arsenic was a more nuanced story. Total arsenic in fillet tissue averaged about 1.2 to 1.3 micrograms per gram across species, but the inorganic fraction, the form that poses cancer risk, made up only about 0.3 to 0.4 percent of total arsenic. Under EPA guidelines, those levels would not cause non-cancer health effects, but long-term heavy consumption could slightly increase cancer risk. Eating roughly 13 ounces of bairdiella per week for a lifetime, for instance, would raise the upper-bound cancer risk by about one case per 100,000 people.⁵

DDT residues were also present, with 4,4′-DDE, the most persistent DDT breakdown product, accounting for about 94 percent of total DDT-related compounds in fish tissue. Total DDT concentrations varied widely, from about 17 to 239 nanograms per gram wet weight. PCBs were lower, ranging between roughly 2.5 and 19 nanograms per gram, with a handful of specific PCB congeners making up over half the total.⁴ These are legacy pollutants. DDT was banned in the United States in 1972, and PCB production ended in 1979, but both persist in soils and sediments for decades and continue washing into the lake through agricultural drainage. For wildlife that depends on Salton Sea fish as a food source, chronic exposure to these cocktails of contaminants adds yet another stress on top of salinity and toxic blooms.

The Desert Pupfish Exception

The desert pupfish deserves separate attention because it occupies a completely different ecological niche than the introduced species. Cyprinodon macularius is a tiny fish, rarely exceeding two or three inches, that evolved in the harsh desert waterways of the lower Colorado River basin. It can tolerate water temperatures above 110°F, salinities well above seawater, and dissolved oxygen levels that would kill most other fish almost instantly. It is one of the toughest vertebrates on the planet in terms of environmental extremes.

Desert pupfish were never open-water residents of the Salton Sea in the way tilapia and corvina were. They lived, and to some extent still live, in the peripheral habitats: shoreline pools, irrigation drain outlets, creek mouths feeding into the sea, and shallow marshy areas. These microhabitats offered somewhat different conditions from the main lake, including fresher water where drains entered and warmer shallow pools where larger predators could not follow. As the introduced species declined, one of the few silver linings was reduced predation pressure on pupfish. Tilapia, in particular, had been a significant competitor and occasional predator in the habitats where pupfish sheltered.

The desert pupfish is listed as an endangered species under both federal and California state law. Conservation efforts have focused on maintaining and restoring the peripheral habitats where pupfish persist, including constructed refugia and managed drain channels. The pupfish is unlikely to repopulate the open Salton Sea regardless of what happens to salinity, but its survival in adjacent habitats gives it a chance of persisting even as the main lake continues to shrink.

Why the Sea Keeps Getting Saltier

Understanding why fish populations cannot simply bounce back requires understanding the Salton Sea’s basic plumbing. The lake has no outlet. Water enters from the New, Alamo, and Whitewater Rivers, all of which carry agricultural drainage, and from direct rainfall. Water leaves only by evaporating under the desert sun, where summer air temperatures routinely exceed 110°F. Every drop that evaporates leaves its dissolved minerals behind. The result is a salt trap that has been concentrating since 1905.

For decades, a steady flow of agricultural runoff kept the lake’s volume roughly stable and diluted salt concentrations enough to keep them manageable. But water transfers, drought, and changing agricultural practices have reduced inflows. In 2003, a landmark agreement called the Quantification Settlement Agreement redirected a portion of agricultural water from the Imperial Irrigation District to the city of San Diego. Though mitigation water was supposed to cushion the blow to the Salton Sea, those mitigation provisions expired, and inflows dropped further. Less water coming in means less dilution, faster evaporation, a shrinking lake, and accelerating salinity. The sea’s salinity now exceeds 60 parts per thousand in much of its volume, roughly 70 percent saltier than the ocean. That level is beyond what even tilapia can handle long-term.

This trend is essentially irreversible without massive intervention. Proposals have ranged from building a canal from the Gulf of California to importing desalinated Pacific Ocean water, but none have advanced beyond the planning stage. Smaller-scale projects focus on creating shallow habitat ponds along the receding shoreline, which could support some aquatic life including invertebrates that birds feed on, but these would not restore the open-water fishery.

The Bird Connection

Fish in the Salton Sea mattered not just to anglers but to one of the most important bird habitats in western North America. The Salton Sea sits on the Pacific Flyway, a major migration corridor, and it serves as a critical stopover for millions of birds. Over 400 bird species have been recorded there. For fish-eating species like pelicans, cormorants, herons, and terns, the Salton Sea’s fish populations were the main attraction. The collapse of fish stocks has cascading effects on these birds, forcing them to find alternative feeding grounds in a region where natural wetlands have been almost entirely converted to agriculture.

Eared grebes, which congregate at the Salton Sea in enormous numbers during migration, feed primarily on invertebrates rather than fish, but they are still affected by the same toxic chemistry. As noted earlier, microcystins from cyanobacterial blooms were found in grebe liver tissue at levels potentially linked to mass mortality events. The loss of fish has also changed the nutrient cycling in the lake. Fish consumed algae, invertebrates, and detritus, and their absence allows organic matter to accumulate unchecked, potentially worsening the oxygen depletion and hydrogen sulfide production that drove the fish away in the first place. It is a feedback loop: fewer fish means worse water chemistry, which means conditions become even more hostile to any fish that remain.

Parasites and Disease in a Stressed Ecosystem

Even before populations collapsed, Salton Sea fish lived under heavy parasite burdens. The warm, nutrient-rich water created ideal conditions for parasitic organisms, and the high density of fish in a closed system with no escape routes allowed parasites to spread efficiently. Studies documented a range of parasitic infections in Salton Sea fish species, including trematodes, nematodes, and copepod parasites. In a healthy ecosystem with robust fish populations, parasite loads are a nuisance but rarely a population-level threat. In a stressed ecosystem where fish are already struggling with high salinity, intermittent oxygen crashes, and toxic blooms, heavy parasite infections become one more factor tipping the balance.

Disease outbreaks in Salton Sea fish were reported periodically throughout the 1990s and 2000s, sometimes coinciding with or preceding the mass die-offs that drew public attention. Distinguishing cause from effect in these events is difficult. Did disease weaken fish to the point where a moderate environmental event killed them, or did environmental stress compromise their immune systems and allow disease to take hold? Both mechanisms are plausible, and in practice they likely reinforce each other.

Recreational Fishing at the Salton Sea Today

If you are wondering whether you can go fishing at the Salton Sea, the practical answer is that it is not worth the trip for the fishing alone. The California Department of Fish and Wildlife does not actively manage the Salton Sea as a sport fishery. The boat launches that once served a thriving angling community are mostly unusable, either sitting far from the current waterline as the lake recedes or damaged beyond repair. The once-popular resorts and marinas along the shore are abandoned, their docks and buildings slowly being reclaimed by salt and sand.

Some tilapia may still be caught in drain outlets, canal mouths, and other peripheral areas where fresher water mixes with the lake. Anglers who fish these spots report occasional catches, but nothing like the abundance of decades past. Eating any fish caught from the Salton Sea or its tributaries carries the contaminant risks described earlier. There are no current fish consumption advisories specific to the Salton Sea from the state of California, but the presence of selenium, arsenic residues, and legacy pesticides in fish tissue means caution is warranted, especially for frequent consumption.

The Salton Sea’s transformation from a booming recreational fishery to an ecological crisis zone happened within a single human lifetime. People who caught trophy corvina in the 1980s can visit the same shores today and find cracked mud, salt flats, and the occasional dead tilapia washed up on a beach that used to be underwater. The fish are not entirely gone from every corner of the Salton Sea ecosystem, but as a functional fishery, the lake is effectively finished unless something dramatic changes its trajectory.