Why do so many dead fish end up in Newark?


Hundreds of dead carp were found in a Newark lake.

Visitors to Lakeshore Park took photos of the fish floating on the surface of the man-made lake.

Cassandra Trejo documented the deaths and expressed concern as she watched the “all out of breath” fish.

Preliminary results from the City of Newark show fish are dying from low oxygen levels in the water, exacerbated by the recent heat wave.

The Noble Research Institute points out that hot water physically cannot contain as much dissolved oxygen as cold water. Thus, the maximum dissolved oxygen potential is lower during the summer than at other times of the year.

Second, there are plants that grow in the summer that are less abundant the rest of the year and a byproduct of photosynthesis is oxygen, according to the institute. So when the sun is shining, plants put oxygen into the water. But at night, plants use oxygen along with everything else in the water, including fish, which creates a high demand for oxygen at night.

If plants and animals use more oxygen at night than is available, a fish is killed.

Dissolved oxygen levels are highest in the afternoon and lowest just before dawn. A common sight in a pond with low levels of dissolved oxygen is the piping of the fish, which (looks like a sip) on the water surface in the early morning. After photosynthesis restarts, the oxygen levels increase and the fish stop whistling.

Trejo filmed this “hissing fish” just before taking pictures of the dead fish.

The public works department said it was adding fresh, oxygenated water to the lake.


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