Last month we watched in awe as researchers filmed a sawfish birth in the wild for the first time. The footage proved beyond a shadow of a doubt that the critically endangered rays are reproducing off North America's Atlantic coast. Now, another video brings us even more clues about the mating habits of these unique animals.

Commercial diver John Dickinson encountered what is being called the sawfish "mother lode" while exploring Florida's Jupiter Inlet, a local dive site. Spotting one wild sawfish is a rare treat – one that few of us will ever experience – but seeing so many together is almost unheard of.

"I had seen sawfish in this area before but nothing like I had experienced that day," he recalls. "We came across over ten [smalltooth] sawfish in two different locations. There were so many it was hard to train the camera on one at a time." 

What's more, nearly all of these large rays were male. 

In an interview with local news outlet TC Palmsawfish scientist Dr Gregg Poulakis notes that reports of such gatherings have surfaced in the past.

"It's unusual to hear about these sawfish in one place, but in the area of Eastern Florida there are clustered reports of sawfish encounters each year," he said. Last summer, for example, eight sawfish were reported in nearby waters over a two-month period. 

We don't know for sure what these "meet-and-greets" are about, but intel from tagging operations and topside encounters tells us that female sawfish move inland during spring, so it's possible these males are preparing for their arrival. 

"It's getting to the time of year when the adult females are getting ready to give birth, or perhaps mate," says Poulakis. "There is some seasonality to it as far as their reproductive cycle, and we've learned females are on every-other-year cycles."

You'll notice that one of the large sawfish has a fishing line wrapped around its rostrum (saw). While some commenters online have criticised Dickinson for not removing it, he tells us that he did in fact make an attempt. 

"When I grabbed the line, the sawfish allowed me to pull him in, and I noticed that the line started to slip. When he swam by again, I could see daylight between the line and his torso, so I think the line will come off on its own at this point," he notes.

Sawfish can be extremely aggressive when spooked, so backing off after the initial attempt was the right call. These animals sometimes weigh upwards of 1,000 pounds, and their formidable teeth can do damage.

Florida State University ecologist Dr Dean Grubbs, who has done extensive work on sawfish, explains that of all the species of sharks and rays he's worked up, sawfish are the most dangerous when restrained. Further attempts to remove the line could have put both the diver and the animal at risk. 

Fishing best practice dictates that anyone who accidentally hooks a sawfish must cut the line as quickly as possible, so this piece of discarded fishing gear is not necessarily evidence of illegal activity. Still, the encounter does point to a troubling reality: despite being protected under the US Endangered Species Act since 2003, these animals are still at great risk of entanglement. Tightly wrapped line and netting can prevent sawfish from feeding and breathing properly. It's also been known to break off teeth from their rostrums. 

Those "teeth" are actually modified scales, and they don't grow back if broken at the base. For the sawfish, hunting with a damaged rostrum can be difficult. 

Once abundant in the waters of 90 countries, sawfish today are found only in northern Australia and here off the coast of Florida. Trade in their namesake "noses" has declined, but it still takes a toll. Just last year, scientists tracked a green sawfish who survived for an astonishing 75 days with a severed saw.

It's estimated that the current US population of smalltooth sawfish is just five percent of historic highs, but there is some hope: the surviving group may be small, but it's considered stable, and there may even be signs of growth. 

Ensuring that recovery stays on track depends on safeguards for sawfish nursery areas – which is why videos like this one are so valuable. It's impossible to protect something when you don't know where it is, so each encounter helps scientists fill in the blanks on our still sketchy map of sawfish habitat. This allows no-fishing zones and habitat restoration efforts to be introduced in areas where they're needed most.

"This is definitely one of the highlights in my diving career," Dickinson says of his encounter. "These animals are so amazing, and realising that they are critically endangered makes you ... want to do everything possible to protect them for future generations."

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Top header image:Tony Gonzalez/Flickr