Missouri officials say native fish are outlasting Mississippi heat that is killing invasive carp

Wildlife officials say the carp turning up dead along the Mississippi River in counties surrounding Alton are largely succumbing to harsh summer river conditions, RiverBender reported.

What happened?

According to RiverBender, reports of dead carp have come from several Mississippi River locations. While the situation may resemble the aftermath of an oil spill, officials said the main cause is a mix of warm water and low oxygen in shallow areas.

The Missouri Department of Conservation said, as reported by RiverBender, the warm-water die-off is hitting silver and bighead carp the hardest. Summer heat raises water temperatures, and lower river levels mean less dissolved oxygen is available to fish. In shallow, slow-moving pockets, those conditions can quickly become unlivable.

Luckily, local fish are more likely to survive the summer heat compared to introduced carp species.

Why does it matter?

The outlet noted that the Missouri Department of Natural Resources said summer heat and lower river stages are concentrating fish in shallow backwaters where oxygen levels drop. Officials said introduced carp are less able to withstand those conditions than local fish populations.

According to the U.S. Fish & Wildlife Service, people introduced silver carp to private fish farms and water treatment facilities to control algae growth. Flooding events, however, caused the fish to escape into the Mississippi River.

The FWS stated that people introduced bighead carp, and that the fish subsequently escaped, for similar reasons. 

While these fish are in U.S. ecosystems creating imbalance now, it's because of human action that people consider them "invasive."

It's a happy coincidence now that weather conditions are favoring local fish populations. But this likely wouldn't have happened in the first place if there were better ecosystem management plans in place.

What's being done?

Working with partner environmental groups, the Missouri Department of Conservation said it is monitoring the seasonal die-off.

RiverBender stated that the agency said ordinary floating carp tied to this regional heat event do not need to be reported. People should, however, report unusual pollution or distinct fish kills through the MDC Fish Kills Information page.

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