Confusion Surrounds Dead Fish Washed Up in Pennsylvania

Mystery surrounds the huge number of fish that have washed up dead at a Pennsylvania park.

Dozens of fish—some already dead, some dying—have been washing up from a lake in Codorus State Park.

This phenomenon has been observed in the past, but this but this year, there are much more than usual.

"What happened to the fish?! We are seeing a lot of dead or dying fish along the shores of the lake right now. While every spring we see a die back due to the stress of the upcoming breeding season, this year is particularly intense," the Codorus State Park said in a Facebook post.

However, there may be a simple explanation for the large amount of fish washing ashore.

Fish wash ashore every year in the park during breeding season. Some become stressed and die as a result.

But this year, summer-like temperatures arrived in the state quite suddenly.

This caused the lake temperature to rise 15 degrees in just over a week.

"[This] is incredibly fast! Rising water temperatures cause extreme stress to the fish – one effect being their respiration, on average, doubles for every 10 degrees increase," Codorus State Park said.

The rising temperatures mean that fish need twice as much oxygen as normal.

"When this happens too rapidly, the fish becomes extremely stressed and will most likely perish," the park said.

Warm water temperatures do not just affect the oxygen levels. High temperatures can alter the hormonal levels, digestion, osmoregulation and nervous systems of fish.

Codorus State Park said these are all additional stressors that can cause more fish to wash ashore dead and dying.

This then creates a cycle of additional stressors for the fish. As more fish wash ashore dead, predators start using it as an opportunity for an easy meal. Eagles, for example, will be attracted to the area looking for food.

This then creates additional stress.

"The fish simply cannot survive the rapid changes," the park said.

Officials at Codorus State Park will continue to monitor the situation closely.

Right now, the main cause for this appears to be the breeding season and the high temperatures.

Fish strandings can occur in all bodies of water. It can usually be linked to high temperatures.

As climate change worsens, high temperatures can cause threats to all sorts of wildlife living in bodies of water.

Hot summer temperatures can also cause lower water levels, increasing the chance of fish washing ashore.

In July 2022, piles of dead fish washed up on a beach in Staten Island. This caused a bad odor that swept across the nearby area.

Do you have an animal or nature story to share with Newsweek? Do you have a question about fish? Let us know via nature@newsweek.com.