A few days ago, I prepared a blog post about a very interesting experiment we had started. It had everything to be cool (at least in my mind): interesting, sciency and a nerdy acronym to go with it! Luke and I were deploying SMURFs (Standard Monitoring Unit for Recruitment of Fish) to look at the habitat preference of baby fishes. The reason it did not get published, is the ocean. The night after successfully deploying the first 15 units, the waves picked up and destroyed all of our work… Marine biology fieldwork can be pretty amazing and it can be rather challenging as well. But that’s the beauty of the ocean: it’s unpredictable. Which can be frustrating at times, but can mean fantastic surprises as well.
Which was proven once again when we found this very cute little baby Frogfish after assessing the damage to our equipment. We don’t know which species it is, since it was still tiny (less than 5mm). It was bright red, which would lead one to falsely believe they are easy to see on black sand. Think again! Next time you dive (or snorkel, or walk) over volcanic black sand, take a close look at the sand and you’ll notice there is a surprising amount of red grains in there. An unexpectedly efficient form of camouflage…
So how do you find a Frogfish? Or other cryptic critters for that matter? They have been evolving for millions of years to be invisible and most of them are very small, so spotting them is something that takes a while to learn. Here are a few tips to make it easier:
- Movement: Your average Scorpionfish or Frogfish does not move very much, but every now and then they do. Whether it’s a small shifting of the fins, an eyeball that rolls to follow potential prey, or a full swim, our eyes are fantastic at spotting movement. So if you see an unexpected twitch or you think you might have imagined seeing something shift in the corner of your eye, investigate it!
- Habitat: The critters I am investigating here are usually found on sand, but there are A LOT of different types of sand. Not just the type of sand, but also what’s on it, whether it’s algae, sponges, featherstars, logs, mooring blocks or anything else that offers a minor difference in structure. Certain species of frogfish (eg. Giant Frogfish) are nearly exclusively found on sponges, while other (eg. juvenile Hairy Frogfish) like to hang out in areas with a lot of shell fragments. Sand Divers (Trichonotus sp.) love very loose sand, while Thorny Seahorses seem to prefer coarse sand with plant debris. In this post I explain where to find different species of scorpionfishes.
- Shape: Even with their amazing camouflage, fish will be fish, which means they have (most of) the parts normal fish have. These shapes can help you find them. The distinctive thick pectoral fin of Stonefish are one of the best ways to recognize them. Pygmy seahorses are tiny and hide in big seafans, but they use their tails to hold on, which is one the things you can look for to try and find them.
- Position: your own position makes a massive difference when trying to spot cryptobenthic fauna. If you are high above the sand, everything blends in, these species evolved to hide from most top-down predators. Get close and get low, if there is a slope, look up the slope instead of down, silhouettes often stand out this way.
- Luck: In the end, good portion of luck can play a big role in finding that elusive critter you’re looking for. If anyone knows how to get better at this particular method of finding critters, please tell me!