Beginning in early June, Long Island’s northern and southern shores, as well as its narrow canals, have been overflowing with thousands of dead Menhaden fish.

Most recently, Shinnecock Bay saw three fish kills in one week in late August. An estimated 30,000 to 40,000 Menhadens were found dead.

This is not the first time massive fish kills occurred in Long Island waters. Back in 2015, the Peconic River saw its own set of fish kills when thousands were found floating atop the murky waters.

The chemical makeup of the water is to blame. Hypoxia, a condition in which warmer waters hold less dissolved oxygen than cooler waters, can kill sea creatures, according to Benning W. DeLaMater, a public information officer with the Department of Environmental Conservation (DEC). Menhaden fish are particularly sensitive to such drastic changes.

According to DeLaMater, multiple factors trigger hypoxia, such as excessive amounts of algae growth, warm temperatures and a copious amount of fish confined to one area at a time.

DeLaMater, however, said these fish kills are “natural” and “expected” during the summer months, and generally have little effect on the fish population.

Dr. Christopher Gobler, a professor in the School of Marine and Atmospheric Sciences and the endowed chair of Coastal Ecology and Conservation, disagreed with the notion that the fish kills are “natural.” He chalks up the recent die-offs to climate change.

“The climate change aspect is that our waters are warmer and therefore have less oxygen than they once did,” he said via email.

He also said the fish kills are the result of pollutants in the water.

“The anthropogenic, or human created, aspect is that high nitrogen loading from septic tanks promote algal booms that can consume that oxygen and harm fish gills, killing them,” Gobler said.

DeLaMater said that the recent fish kills don’t seem to be of any harm towards humans, although Gobler pointed out that “it’s not fun to have decaying fish in your backyard.”

On campus, students and faculty alike are tackling this issue with their own research. Gobler, along with professors Mike Frisk who teaches fish ecology, population modeling and life history theory, and Anne McElroy, who teaches Aquatic Toxicology continue to monitor more than 50 locations across Long Island, logging the levels of algae, water clarity and oxygen levels.

Junior marine biology major Sarah Jacobson believes the recent kills were from improper waste regulation in Long Island.

“After a rainstorm, sewage overflows and goes into the water,” she said. “These excess nutrients from the waste can kill fish.”

Local communities are also getting involved, most recently with the Suffolk County Executive Council, pitching for more federal assistance, such as an additional wastewater infrastructure in the Peconic River.

DeLaMater said that in cleanup attempts, as a way of “kill control,” research teams also allow fishermen to excessively harvest these fish before an anticipated fish kill. Sometimes, communities will work together to collect the dead fish and dispose of them in landfills, depending on the size of the kill.

The details of this hypoxia continues to be researched, but many of the factors causing it remain open to speculation.

“There are a lot of causes,” said Jacobson, “but I haven’t learned enough yet to give an exact answer.”