Dozens of species of fish, including the endangered sawfish, have been spinning and whirling in thw waters off the Florida Keys for months, but so far, there doesn’t appear to be any threat to humans, the head of a marine laboratory and aquarium said Monday.

“No abnormal water quality parameters have been identified by any of the environmental health agencies that regularly monitor the waters there,” Michael Crosby, president and CEO of Mote Marine Laboratory, told CBS News. “This seems to be some kind of an agent that is in the water that is negatively impacting just the fish species.”  

Mote Marine Laboratory is one of several groups partnering with the National Oceanic and Atmospheric Administration to help with the agency’s emergency response to the phenomenon. 

Crosby said his group has taken tissue samples from living, but distressed, sawfish, hoping they can help scientists determine a cause of the spinning. 

While officials are largely using the terms spinning and whirling to refer to the abnormal behavior, every fish being impacted has been behaving slightly differently, Crosby said.  

Fishing in the area remains open, the Florida Fish and Wildlife Conservation Commission advises against harvesting distressed or dead animals. It also says swimming where there are dead fish is not recommended.

What’s causing the spinning and deaths?

Officials don’t yet know what’s causing the strange behavior, but Crosby said it could be a toxin or a parasite. 

“It almost seems as if it is a neurological response to some kind of agent,” he said. “Not at all sure what it is yet, [the] scientific community has not identified a smoking gun as of yet.”

There are no signs of a communicable pathogen, and specimens were negative for bacterial infection, the Fish and Wildlife Conservation Commission said. Scientists also don’t believe dissolved oxygen, salinity, pH or temperature are behind the strange behaviors and deaths. Water samples have also come up negative for Red Tide toxins.

Several aquariums and labs partnering with NOAA will house and rehabilitate sawfish, including Mote Marine Laboratory.

Rescued sawfish will be under observation in quarantine facilities, according to NOAA. The goal is to release them back into the wild once rehabilitated.

Which types of fish are being impacted?

At least 109 sawfish have been affected with 28 deaths documented, according to NOAA.

“We suspect that total mortalities are greater, since sawfish are negatively buoyant and thus unlikely to float after death,” Adam Brame, NOAA Fisheries’ sawfish recovery coordinator, said. “Given the limited population size of smalltooth sawfish, the mortality of at least two dozen sawfish could have an impact on the recovery of this species.”

Sawfish, which can be found in shallow, coastal waters, are an endangered type of ray — a fish type that has no bones, according to NOAA. Instead, sawfish skeletons are made of cartilage. 

Sawfish can grow to be 16 feet long and weigh several hundred pounds. The affected sawfish have been between 7 and 14 feet in length, according to NOAA.  

Florida officials say other types of rays and fish with bones are also being impacted by the strange spinning. Some of the affected species are: Atlantic stingray, bonnethead shark, goliath grouper, gray snapper, gray triggerfish, lemon shark, nurse shark and scaled sardine.