The Forward-Thinking Fish
On the sustainability mindset of the Steephead parrotfish
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Farmer, Mentor, Fish
After another night spent comfortably protected from parasites in a see-through sleeping bag he had formed from his own mucus, Burt awoke excited for the day. With two big beats of his wide pectoral fins, he broke out of the filmy cocoon and emerged from his nook in the coral reef. Back when he was a young black-and-white stripey thing, Burt mostly swam with an undulation of his body and tail. But at six years old he was now a solid block of bright blue-green parrotfish who had lost much of his waggle and instead flew through the water on the lift generated from his powerful, flapping fins.
As he pulled up into the expansive blue waters of the Pacific, Burt saw that some of the other steepheads from his school were already out on their patch of reef, scraping off a breakfast of delicious algae. He glanced at his own most recent patch and confirmed his decision from the day before—it was time to rest this field if he wanted to keep it alive. He'd nipped and nibbled at this area, carefully cutting off meals that kept portions of the algae intact. Now he needed to give it time to regrow so he could have a future that was as filling as the present.
Burt pushed himself over the crest of the reef, his mind on another nearby patch he had left fallow a few weeks before. But first he swam out to the slightly deeper area his school used as a latrine. Often the best way to get at the algae was to use your powerful beak to break off a chunk of dead coral and let the teeth in your throat grind the algae out from between the inedible bits. Overnight his body has processed more of the leftover calcium-carbonate into a fine grain, so Burt unleashed a fresh cloud of white sand from his back end before heading off for breakfast.
But what was this? As his patch came into sight, Burt was dismayed to see another steephead scraping away at it. It was a young male, starting to show some blue-green in his colouring but with almost no facial bump to speak of. His sloping forehead contrasted sharply with the front of Burt's face, which at this age looked like a sheer cliff. Burt usually wasn't territorial— there was plenty of reef to go around, after all—but the young male should have seen from the old bite patterns that this patch was claimed. Feeding here wasn't only an insult to Burt himself, it was an affront to the steephead philosophy of conserving your resources for the future.
His sharp beak gaping, Burt barreled through the water toward the offender. He had no intention of actually biting the other fish, but a headbutt certainly wasn't out of the question. The young male looked up from the reef in time, and frantically paddled up and away, towards the sunny surface. Burt didn't continue the chase; instead he stuck out his stiff fins to brake, then started moving methodically back and forth over the field, inspecting the damage. The young male watched from above and off to the side as Burt twisted and flipped his body, peering at the details of the patch with one eye and then the other.
For the most part the damage wasn't too bad. The young male had probably only been feeding here since the day before, based on the amount he'd harvested. And most of the feeding was spaced out, just as Burt would have done. But there was one large bare spot where the young male had gotten carried away and gouged out a wide swath of reef. It would be a long time before the live coral and algae would properly fill this back in. Hovering over the spot, Burt angled upward to face the young male. Burt held his beak open and gave a few small swishes of his impressive tail. The young male turned slightly sideways in supplication, then slowly swam away and down into another area of the reef.
Burt looked back at his damaged patch and hoped the young male had learned his lesson. He knew it was hard to restrain yourself when the eating was good, but a smart fish always needed to plan for the future.
~ Marilyn Anne Campbell
About Steephead Parrotfish
There are over 80 different species of parrotfish, a charming type of saltwater fish whose super-strong, fused front teeth look and work like a beak. Even better, when they hold their beak open and you catch them at the right angle, they look as though they have a goofy smile. Parrotfish really do crunch on coral and poop out the white sand mentioned in all of those tropical beach resort ads. Many parrotfish species also sleep in bubbles of their own mucus, and change colour as they age (some also change sex, with all members of the species born female and some later changing to become males, but I couldn't confirm if that was the case for steepheads).
But the steephead, or blunt-head, parrotfish (Chlorurus microrhinos) is the only one who has been found to "rotationally harvest" algae in a way that sustains the feeding grounds (Read the 2017 article "Farming Fish" on the UC Santa Barbara news site to learn more about the research done by marine biologists Peter Carlson, Katie Davis, and Jenn Caselle that inspired this short story).
Considering all of the talk out there about goldfish having short memory spans (which is entirely false) and the failure of many humans to grasp the basic concepts of sustainability, it seems noteworthy that at least one fish actively conserves resources for the future.
As it turns out, parrotfish are closely related to wrasse, who were also featured in a previous issue of Mouse and Minnow for their own intelligence. So don’t underestimate the brain power of fish. (Especially ones with a massive head who already happen to be named after some very smart birds.) It seems we may still have a lot to learn from and about our underwater friends.
Most of the links this week are pretty science-y!
Read about the chainmail-like structure that gives steephead parrotfish teeth their strength.
Watch 18 seconds of a parrotfish sleeping in his mucus bubble on YouTube.
And watch a male Steephead parrotfish swimming and nibbling in this short YouTube video from Lucy In The Sea:
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Thanks for reading,
Marilyn & Steve
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