Scientists left worried about mystery illness killing critically endangered smalltooth sawfish in the Florida Keys.
Can there be a more distinctive-looking fish swimming in our oceans than the sawfish? It has the body of a shark (although they are actually members of the ray family) but with a long, sword-like snout, which is used for hunting, digging and as a weapon that would make a medieval knight cower in fear.
Despite its memorable appearance, all five sawfish species are considered to be critically endangered. This makes the recent news that smalltooth sawfish living in the tropical waters of the Florida Keys have been seen exhibiting abnormal behaviours – including spinning and whirling – all the more worrying.
Alongside smalltooth sawfish around fifty other fish species have been recorded suffering from the same symptoms. These include blacktip sharks, Atlantic needlefish, goliath groupers, lionfish, sand perch, scaled sardines and Spanish mackerel.
The Florida Fish and Wildlife Conservation Commission (FWC) is currently investigating this behaviour and trying to discover what might be causing it. Water samples from areas where abnormal behaviour was observed have been taken for laboratory analysis, and tests are also being carried out on the fish.
At the moment there are no signs of a communicable pathogen and specimens have all returned negative test results for bacterial infection. The FWC also say that dissolved oxygen, salinity, pH, and temperature of the water are not suspected to be the cause of the fish behaviour or deaths. In addition, Red Tide toxins produced by harmful algal blooms have not been detected in water samples.
NOAA Fisheries has initiated an emergency response effort with partners to attempt to rescue and rehabilitate smalltooth sawfish affected by this event. However, an emergency response of this kind has never been done before in the United States and, as NOAA makes clear, the logistics are complex and success far from certain.
‘If the opportunity presents itself, this would be the first attempt ever to rescue and rehabilitate smalltooth sawfish from the wild,’ said Adam Brame, NOAA Fisheries’ sawfish recovery coordinator. ‘We’re hopeful for positive outcomes from these rescue attempts, and grateful to our partners for their support as we work to protect this endangered species.’
As of 3 April, the death of 32 smalltooth sawfish had been reported, but as Adam Brame says, ‘We suspect that total mortalities are greater, since sawfish are negatively buoyant and thus unlikely to float after death’. Given the limited population size of smalltooth sawfish, the mortality of at least 32 sawfish could have an impact on the recovery of this species.
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