Biologists rescue sick sawfish, hoping for clues in Florida Keys fish-kill mystery
As the number of dead endangered smalltooth sawfish found in the Florida Keys since the end of January creeps up on 40, biologists made progress last week in their struggle to solve the mystery into what is killing them — and whether the culprit is linked to a larger fish kill plaguing the area since the fall.
On April 5, a scene that is becoming all too familiar played out off the Gulf side of Cudjoe Key, about 23 miles north of Key West.
A member of the public reported seeing a sawfish — a large shark-looking ray with a long serrated rostrum used for hunting fish and for defense — swimming in circles in shallow water.
The bizarre behavior has shown to be an imminent sign that the distressed fish is about to die.
Last week, however, biologists were able to rescue the 11-foot male from the Cudjoe waters. They took it to the Mote Marine Laboratory and Aquarium in Sarasota to be studied.
“This has not been attempted before, but this unusual mortality event made this necessary,” Gil McRae, director of Florida Fish and Wildlife Conservation Commission’s Fish and Wildlife Research Institute, said in a statement.
“We are hopeful this rescue and rehabilitation of an adult smalltooth sawfish will bring us one step closer to understanding the cause of this event.”
The fish was transported to Mote inside a truck operated by Ripley’s Aquarium while being monitored during the seven-hour trip by aquarium staff.
Adam Brame, sawfishrecovery coordinator for the National Oceanic and Atmospheric Administration, told the Miami Herald the fish is being kept in a large tank at
Mote and is so far responding well. It’s not eating on its own yet, but it is displaying normal behavior, such as swimming with its rostrum, where many of the animal’s sensory organs are located, elevated above its body.
“The idea is to take it out and into an environment where we can control a lot of the fish’s natural healing ability while it’s not fighting additional stressors,” Brame said.
As of Friday, the official number of dead sawfish in the Keys since Jan. 29 is
38, according to Florida’s fish and wildlife commission, known as the FWC.
These deaths have coincided with a fish kill that has been happening since November impacting hundreds of species. The other species are also demonstrating the same strange spinning behavior, and scientists are scrambling to find out what is going on and the degree to which the two events might be related.
Ruled out so far, to the relief of scientists and wildlife officials, are redtide toxins, based on water samples taken from the impacted area — from Big Pine Key down to Key West.
And necropsy data taken from dead fish samples so far has not turned up any communicable pathogens and the fish were negative for bacterial infections, according to the FWC. Dissolved oxygen levels, salinity, acidity and temperature are also not suspected to be the causes of the fish kills or spinning, according to the FWC.
And, state scientists have conducted water tests for a variety of chemicals, “which were either not detected or were below normal limits,” the FWC said on its site dedicated to the fish kill.
For the erratic, spinning behavior, scientists have speculated it might be related to a toxin called gambierdiscus, which causes a food-borne illness called ciguatera in people who eat infected fish. It’s common in the Keys because it grows as a micro algae on coral reefs. Basically, smaller fish eat the algae, and the toxin gets passed up the food chain to people who eat larger predator fish.
One of the difficulties with the focus on gambierdiscus is that, while it has been found in elevated levels in the affected area since scientists have begun investigating the fish kill, there haven’t been any more reports than usual of people getting sick with ciguatera.
“We are preparing to conduct some fish-exposure studies to home in on the mechanism of exposure and to confirm (or reject) this hypothesis,” Mike Parsons, professor of marine science at Florida Gulf Coast University and director of the Vester Field Station of the university’s Water School, told the Herald in an email on Friday.
“We are not sure if this is also the cause of the sawfish mortalities (could be coincidental), but we will use the data collected in other fish and apply these findings to the sawfish,” Parsons wrote.
Parsons said many sick fish that his team has collected recover when taken from the impacted waters, and that is a positive sign.
Among the institutions that have dispatched scientists to try to solve the fish kill/spinning case are NOAA, FWC, Florida Gulf Coast University, Florida
THIS HAS NOT BEEN ATTEMPTED BEFORE, BUT THIS UNUSUAL MORTALITY EVENT MADE THIS NECESSARY.
Gil McRae, of the Florida Fish and Wildlife Conservation Commission, about the sawfish being taken to the Mote Marine Laboratory and Aquarium in Sarasota
International University, the University of South Alabama, as well as nonprofits such as the Bonefish and Tarpon Trust.
“This type of rescue effort doesn’t happen without these types of partnerships,” Brame said.
Integral to the effort to get to the bottom of what’s happening has been the public reporting seeing distressed fish.
“It’s important to note the public plays a very important roll. They’ve been our eyes and ears on the ground,” Brame said.