You likely don't know this, but a species swimming around New Brunswick waters is the only fish that has been to space.

Granted, they didn't travel there on their own, but the tiny mummichog managed to meet NASA's tough criteria for a trip to Skylab.

Found in salty estuaries along the East Coast from the Maritimes to Georgia, researchers marvel at the mummichog's toughness and adaptability.

"They are cool," Noah Bressman, an assistant professor at Salisbury University in Maryland, said in a phone interview.

"They can move on land. They can breathe air. They are extremely tolerant of a wide range of conditions. They live in the most extreme habitats of fish."

Bressman has been studying the mummichog since his undergraduate days.

"Also they have these adorable little smiles when you look at them," Bressman said. "You can't not think, 'Oh, that's a cute little fish' when you see one."

His interest in them piqued one day working at a sea table — essentially a large, low aquarium with about 10 centimetres of water in it used for studying fish in the lab.

He noticed a mummichog on the floor, about three metres from the tank. The fish are known to jump and flop over land to get to nearby tidal pools.

Bressman thought nothing of it, just a fish that had accidentally jumped the wrong way.

"So I put it back in the tank, and the next day, a different 'mummi' within the exact same spot, 10 feet away on the shiny floor. Like, this can't be a coincidence."

Bressman decided to film the fish moving over dry land, using a high-speed camera.

That's when he noticed that mummichogs stood upright on their tails for a few tenths of a second between jumps.

"And, so, that upright behaviour, it seemed functionally unnecessary to do two consecutive jumps. So, I was like, 'What could they be doing?' Perhaps maybe it's reorienting them because they have their eyes on the side of their head."

Bressman soon discovered the fish would always jump in the direction of a reflective surface, similar to sunlight shining on water. Put them in the dark and they'd jump about randomly.

"And so that spot where I found those two mummichogs initially, 10 feet away from the tank, that's the spot where the sunlight shines … onto the shiny tile floor," Bressman said.

"And that was my first huge aha moment in science and I've been hooked on mummichogs ever since that." 

Two workers with ACAP Saint John, a non-profit community organization focused on the local environment, drag a seine net through waist-deep water near the mouth of Little River.

Dressed in chest waders and wearing latex gloves that extend almost to the shoulder, they're trying to catch fish as part of a monitoring program.

As they move through the water, dark sludge is stirred up from the bottom.

Shauna Sands, a conservation co-ordinator with ACAP, said this site just off Bayside Drive is her least favourite site to work in, describing the water as looking "like Mountain Dew," the greenish-yellow soft drink.

But, Roxanne MacKinnon, the executive director of the organization, said this is one of the places they'll most likely find mummichogs.

"We often find mummichogs here at Little River and also at Marsh Creek, in the forebay, which is one of our other fishing sites and very occasionally we've also found them at Spar Cove," she said.

"All those areas are not the most pristine sites we have here in Saint John. They are known [for] stormwater influences, different fecal contamination issues and creosote contamination issues within all those sites."

Mummichogs make their homes in places often mistreated by humans. But that means they are valuable to scientists studying the effects of pollution.

Usually 7.5 to 9 centimetres in length, they have stubby bodies and squared-off tail fins, tiny sharp teeth and a jutting lower jaw, with colours similar to their habitat.

Their name comes from an Indigenous word that roughly translates as "moves in crowds."

They have shown an incredible ability to adapt.

NASA chose them over goldfish, another remarkably hardy species, because the agency's scientists believed the fish had the best chance of surviving launch.

Not only did they survive the trip, they seemed to adapt quickly to being in a bag of water in a weightless environment.

They immediately oriented themselves to put their backs toward light, just as they do with sunlight here on Earth.

For a few weeks, they swam in tight loops, but they eventually reverted to their regular swimming patterns.

But it's their ability to adapt here on Earth that is so useful to scientists.

Richard Di Giulio began studying mummichogs in the Elizabeth River near Norfolk, Va.

Some fish were living in the vicinity of several former wood treatment plants, where creosote had been seeping into the waterway for nearly a hundred years.

The Duke University scientist said he became interested in them after researchers put mummichogs that had lived in clean water into the polluted water mummichogs had been living in for generations.

"It's just so dramatic," Di Giulio said in a phone interview. 

"I mean, the fish from the clean side put in the tanks that had the Elizabeth River mud… killed them outright, 100 per cent killed them, and had no effect on the ones from that site. And I was like, 'Wow, that's amazing'."

He's been studying them ever since, for about three decades.

"They are one of the best examples of pollution driving evolution," he said.

Di Giulio said the fact that they spend their whole lives in one area, and have the ability to endure pollution without dying, is valuable to a toxicology researcher.

"They're like the canary-in-the-coal-mine kind of fish. If you catch [a mummichog] someplace and you see something like cancer or whatever, some effect on it, you can be pretty certain that it's due to whatever happened at that site."

That's why Deborah MacLatchy has been studying them since the mid-1990s, when she was at University New Brunswick in Saint John.

"They were living in environments, some of which were very clean and pristine and others which had exposure from various effluents, whether coming from the pulp mill or from sewage treatment plants, from the oil refinery and other areas," MacLatchy said in an interview from Wilfrid Laurier University, where she is now the school's president.

MacLatchy's research on mummichogs exposed to pulp mill effluent has shown how the chemicals affected fish reproduction and has led to changes in the industry.

She still does research with them in the Wilfrid Laurier lab, and believes the fish will give scientists insight into climate change in the coming years.

"Although they are hardy, they do have limitations on, for example, the temperature ranges that they will survive in," she said.

"And so as we think about … climate change and other impacts for the mummichog and all other species, we have to understand how that interplay between … habitat change, environmental temperature change, etc., is going to play out for these species."

MacLatchy is happy that there is interest in mummichogs "because they are, especially in New Brunswick … just such a really, really, really important fish. And they are … pretty well [across] North America, this really cool, universally recognized research fish." 

"I guess they just like to hide their light under a bushel a little bit."

Steven Webb is a producer for CBC based in Saint John.

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