Water quality strongly shapes which fish live in Yucatán’s coastal wetlands. A 2026 study of 4,863 fish from 20 species found that higher salt, dissolved solids, and ammonium were linked to less diverse fish communities, while higher oxygen levels were linked to more. According to research reviewed by Gram, protecting water quality is essential for these wetlands’ fish.
According to research reviewed by Gram, the chemistry of the water plays a major role in which fish live in two coastal wetlands near Progreso and Chicxulub in Yucatán, Mexico. Scientists sampled the wetlands every two months from September 2017 to July 2018 and recorded 4,863 fish from 20 species. Fish communities were more varied in Progreso, where water had more oxygen and lower levels of salt and ammonium. In Chicxulub, very salty and low-oxygen water was common, and only a few hardy species, such as Cyprinodon artifrons, did well there during the dry season. The authors conclude that water quality affects both which fish live in these wetlands and what they eat, and they call for conservation to protect rare local species from pollution and climate stress.
Key Statistics
A 2026 study published in the Journal of Environmental Quality recorded 4,863 fish from 20 species across two Yucatán coastal wetlands between September 2017 and July 2018.
In the same study, fish community measures were negatively correlated with salinity, total dissolved solids, and ammonium, and positively correlated with dissolved oxygen.
The Progreso wetland showed higher fish species richness and diversity than the Chicxulub wetland, where hypersalinity and low oxygen were especially notable.
The Quick Take
- What they studied: How the water conditions in two coastal wetlands affect which fish live there, how many kinds of fish there are, and what the fish eat.
- Who participated: Researchers did not study people. They collected 4,863 wild fish from 20 species in the Progreso and Chicxulub wetlands in Yucatán, Mexico, sampling every two months over about one year.
- Key finding: Fish variety tracked closely with water conditions. Fish communities were less diverse where water was saltier, had more dissolved solids, or had more ammonium, and more diverse where oxygen levels were higher. The Progreso wetland had more fish species and variety than Chicxulub.
- What it means for you: This is a field study of wetland ecosystems, so it does not give personal health advice. It does suggest that clean, well-oxygenated water supports healthier fish populations, which matters for anyone who cares about local wildlife, fishing, or coastal conservation.
The Research Details
The researchers studied two coastal wetlands in Yucatán, Mexico, called Progreso and Chicxulub. Between September 2017 and July 2018, they visited each site every two months. At each visit, they measured water conditions such as oxygen, salt level, temperature, total dissolved solids, and nutrients like ammonium. These measurements show what the water was like at the exact moment of sampling.
The team also caught fish at each site. They identified each fish by species and examined what was in their stomachs. By looking at the food inside, the scientists could group fish by feeding style, such as fish that eat other fish, fish that eat small invertebrates like insects and crustaceans, and fish that eat plants or algae.
By comparing the water measurements with the fish counts and diet groups, the researchers looked for patterns over time and between the two locations. This approach shows how environmental conditions and fish communities move together across seasons.
Because the researchers tracked both water and fish across many months and two sites, they could see how changes in conditions lined up with changes in fish life. This is more informative than a single snapshot. It helps show that the water chemistry, not just random chance, is connected to which fish are present and what they eat.
The study followed a regular schedule of sampling and used standard methods to measure water and identify fish, which are strengths. It captured thousands of fish, giving the results a solid base. However, this was observational fieldwork at only two sites over about one year, so it cannot prove that one water factor directly caused a change in fish populations. Other factors, such as weather, habitat, or human activity, may also play a role. Readers should treat the findings as strong evidence of association rather than proof of cause and effect.
What the Results Show
The water in these wetlands changed a great deal from place to place and season to season. Chicxulub often showed hypersalinity, meaning the water was saltier than normal for these ecosystems, and hypoxia, meaning oxygen levels were low. These extremes were especially noticeable there compared with Progreso.
In total, the researchers recorded 4,863 fish representing 20 species. Progreso had higher species richness, which means more different kinds of fish, and higher diversity, which means a more balanced mix of species. This suggests that Progreso’s water conditions supported a broader range of fish.
The fish community was linked to water chemistry in clear ways. Measures of fish community health were negatively associated with salinity, total dissolved solids, and ammonium, meaning fish variety tended to drop as those levels rose. They were positively associated with dissolved oxygen, meaning more oxygen went along with more fish variety.
Fish diets also grouped into feeding categories: piscivores (fish-eaters), invertebrate feeders, and primary consumers (plant and algae eaters). The authors describe how these feeding groups reflect the food web in each wetland, showing that water quality may influence not only which fish are present but how the food chain works.
One species, Cyprinodon artifrons, stood out. It appeared to be resilient, meaning it tolerated harsh conditions well, and it dominated in the hypersaline (very salty) water during the dry season. This suggests that some fish can adapt to extreme conditions, but that adaptation may not extend to the wider fish community.
The researchers also highlighted that the wetlands are home to endemic species, which are found nowhere else, and threatened species, which are at risk of disappearing. This makes the protection of water quality important for preserving local biodiversity, not just for the fish themselves.
Previous research on coastal and wetland ecosystems has commonly found that salinity, low oxygen, and nutrient pollution can reduce fish diversity and change food webs. This study fits that pattern and adds detail for the Yucatán wetlands, a region that has received less scientific attention. It also supports the idea that a few tolerant species can dominate when conditions become extreme.
The study covered only two wetlands and one year of sampling, so the results may not apply to other locations or to different years with different weather. Because it observed natural conditions rather than manipulating them, it shows connections rather than proving that specific water factors directly caused changes in fish populations. The researchers also did not report a detailed sample size beyond the total number of fish, which makes it harder to judge the exact strength of each comparison. Finally, the study did not look at long-term trends beyond its sampling window.
The Bottom Line
Research shows that water quality strongly influences fish communities in these coastal wetlands, with higher oxygen linked to greater fish variety and higher salt, dissolved solids, and ammonium linked to less variety. Confidence in this link is moderate to strong for these two sites. Reducing nutrient and pollution inputs and protecting natural water flow are sensible steps that the authors urge, although this study does not test specific management actions.
Wetland managers, conservation groups, local fishers, environmental planners, and residents of the Yucatán coast should pay close attention. Students and researchers studying coastal ecology may find the methods useful. Readers outside this region can still learn from the general pattern that water chemistry shapes aquatic life, but the specific findings apply most directly to these wetlands.
Changes in water quality and fish communities can happen over seasons, but wetland recovery after pollution or salinity stress often takes years. Because this study covered one year, it cannot tell how quickly conservation efforts would show results. Long-term monitoring would be needed to measure real change.
Frequently Asked Questions
How does water quality affect fish in coastal wetlands?
Water quality appears to strongly shape fish communities. A 2026 study in Yucatán found fish variety was higher where oxygen was greater and lower where salinity, dissolved solids, and ammonium were higher. Water chemistry also appeared to influence what fish eat.
What did the Yucatán wetland fish study find?
The study recorded 4,863 fish from 20 species in the Progreso and Chicxulub wetlands. Progreso had more species and greater diversity. Chicxulub often had very salty, low-oxygen water, and only a few tolerant species, such as Cyprinodon artifrons, dominated there in the dry season.
Why are wetlands in Yucatán important to protect?
These wetlands contain endemic fish species found nowhere else and threatened species at risk of disappearing. The research reviewed by Gram indicates that human activities and climate pressures are stressing these ecosystems, so conservation actions appear urgently needed to protect local biodiversity.
What does dissolved oxygen have to do with fish diversity?
In the Yucatán wetlands study, higher dissolved oxygen was positively correlated with fish community measures, meaning more oxygen went with more fish variety. Low oxygen, called hypoxia, was especially common in Chicxulub, where fish communities were less diverse.
Want to Apply This Research?
- If you are monitoring a local waterway, record dissolved oxygen, salinity, and ammonium every two months, along with a simple count of fish species you observe. Keeping these numbers in one log lets you see whether lower oxygen or higher salt tracks with fewer species over time.
- Support local water protection by reducing fertilizer runoff from your yard, picking up pet waste, and avoiding dumping of chemicals or wastewater near waterways. You can also join or follow local wetland cleanup and monitoring groups to contribute data.
- Build a long-term record by repeating the same measurements at the same locations on a regular schedule, ideally across several seasons and years. Track trends in oxygen, salinity, nutrients, and species counts, and flag sharp changes so local managers or researchers can investigate the cause.
This article summarizes a field study of wild fish and water conditions in Yucatán, Mexico. It is not medical or health advice for people. The findings describe natural ecosystems at two sites over one year and show associations, not proof of cause and effect. Consult local environmental agencies or qualified researchers before making decisions about wetland management or fishing.
This research translation is published by Gram Research, the science division of Gram, an AI-powered nutrition tracking app.