Marine Field Studies 2021: Spot-fin Porcupinefish

Looe Key Spot-fin Porcupinefish

When I saw this big guy while snorkeling at Looe Key I was very excited because in my high school marine science class we took care of a striped burrfish. At the time we thought it was a porcupinefish so we named it porky, but later we found out it was in fact a burrfish. So as soon as we saw this one at Looe Key I knew I wanted to write about it for this post as I absolutely love getting to see these guys up close.

I initially thought this was just a puffer fish that had gotten really big, but after doing some research I've discovered it's a spot-fin porcupinefish. It can also go by giant porcupinefish, which suites it the best, or its scientific name Diodon Hystrix. I believe the one I saw (pictured above) was close to 18 inches long and just very large for a group of fish that is normally as big as your hand. As an adult this species can be 15-35 inches long and weigh around 6 pounds. They are found in tropical and temperate areas from California to Chile, most of the eastern coast of the U.S., the Caribbean, and Brazil. They like to live inshore in reefs, caves, and other structured places. These big guys are typically found at depths up to 50 meters but like to stay a little shallower than that as I saw this one around 8 meters down.

Most people commonly mistake porcupinefish for pufferfish. They are very similar however the main difference is that porcupine fish are covered in spines and puffers are more smooth with no spines. Spot-fin porcupines have lots of spines that lay very flat and can be hard to see unless they're puffed up. They are normally a sandy brown color on top and white on bottom with darker spots all over. They're easy to identify by their large round eyes, tapered body, and small fins, and are even easier to identify when they're defensive.

Instead of having many smaller teeth in rows, porcupinefish have a hard plate that crushes up small crustaceans like crabs and urchins. They mainly eat hard shelled animals as their mouths are specially adapted for them. There are not many predators of these fish as they have a great defense mechanism in place that consists of inflating themselves with water. Which then makes their spines poke out. As they make themselves a large pointy balloon shape it becomes difficult for predators to get them. They can also emit poisons in defense.

To reproduce a few males will corral a single female towards the surface where they all release their eggs and sperm. The eggs are then fertilized and freely float until ready to hatch. This typically happens once a year. Spot-fins also live alone mostly and are fairly docile. They can be slower fish that like to hide during the day, which was exhibited with one I found as it hid in the rocks every time I swam closer.

I love these fish and all of their close relatives, like puffers and the burrfishes. I think they have one of the most unique and distinctive looks so it's never boring looking at them. I also thought this fish was really special as I had no clue a species that large existed and thought I had just struck gold finding this guy. It will definitely be one of my favorite and most memorable parts of this whole trip!