Fluctuating temperatures cause mass fishkill in Baltimore’s Inner Harbor

BALTIMORE — Thousands upon thousands of fish died in what officials are calling a naturally occurring, seasonal phenomenon.  
The stench is almost as bad as seeing the stretch of dead sea life near the science center at the inner harbor. 
Experts say the fish were oxygen-starved. The fluctuation in temperatures this week played a significant part.  
“Absolutely over a million fish,” Jack Cover, National Aquarium General Curator said. “I’ve been working at the aquarium for 37 years. This is the worst fishkill at the inner harbor that I’ve witnessed” 
Cover says the extreme heat during the day coupled with cool temperature dips in the evenings this week caused the phenomenon known as thermal inversion. 
“The top layer of the brackish water gets dense. It drops to the bottom like a ceiling falling down and stirs up all the inorganic material,” he explained.  
Cover says the bacteria takes oxygen out of the water and in this case, young menhaden by the thousands died, who have a lower tolerance for bad water conditions.  
“This is a primary food for our striped bass, ospreys, and cormorants down the Inner Habor, so this is really a tragedy,” Cover said. 
The fishkill was hard to miss for inner harbor visitors and not just by sight. 
“When I walked down from Federal Hill I could smell it,” Gary Coody, a Washington D.C. resident said. “I’ve never seen a kill this large” 
Not all was lost though. 
According to Cover, the aquarium’s new floating wetland exhibit acted as a refuge for some fish through aerators.  
A signal that more could be done to ease environmental pressures.  
“[I’m] very happy to see the fish in that shallow channel, including some of these menhaden, swam up into it, lived through this event,” Cover said. 
Crews with the Department of Public Works and aquarium employees helped clean up the fish Wednesday. 
The leftover fish will decompose and sink to the bottom.