The Secrets of Sargassum

By Jayne Jenkins

Traveling half way around the world to Bermuda with XT Catlin Seaview Survey provides no guarantee of finding the elusive Sargassum frogfish (Histrio histrio). Fast-forward to Aniloa in the Philippines and I was lucky enough to finally photograph this amazing little fish. This experience would not have been a possible without the eagle eyes of my two great boat operators.

Always in search of this particular frogfish, I was hopeful the rafts of sargassum algae I saw floating past on trips to the dive sites would be housing this animal. Inquiring if the boat crew had ever seen the little frogfish in the algae, I got a disappointing “no”.
During one my dives, the brilliant eyes of Cpt. Jack and Manny had spotted sargassum and, and on closer inspection, they spotted the frogfish moving amongst the surface fronds. After my excitement settled, a huge team effort with my dive guide Webster allowed me to finally photograph the frogfish that had been on my bucket list for so long. The Philippines has incredible diving but this was just the icing on the cake for me. Camera lenses are seldom the perfect choice when one makes random (opportunistic?) finds on a dive, but luckily I had a 105mm lens on my camera - this frogfish was not much bigger than my thumbnail.

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Sargassum is a seaweed and numerous species are distributed throughout the temperate and tropical oceans around the world. Sargassum generally inhabits coral reefs and shallow water and is a free floating species. Usually most divers ignore floating seaweed but sargassum provides a habitat for many species of fish, crabs, shrimps and other invertebrates. H. histrio, with its weed like appendages, has adapted itself to blend into the floating raft to live out its life amongst the algae. The rafts of sargassum drifting on the ocean surface provide a unique habitat and refuge for the frogfish that hitches a ride on this floating home. This frogfish’s unique colouration blends so well with the sargassum algae you can hardly see him unless he moves. For food they can ambush shrimp and other small fishes that use this marine raft as a shelter. They also have an illium  (slender tentacle with the tip bearing a bulbous swelling resembling a fishing rod with bait) that they use to lure other prey. If threatened by a predator, a Sargassum frogfish can jump out of the water onto the top of his algae raft and may stay out of the water for some time.

The sargassum frogfish spends all of its life floating on/in the rafts of algae, as they usually don’t swim too far. They can often be found after storms have blown beds of algae towards the shores of the tropical and subtropical seas. The world of the H. histrio may sound quite relaxing, drifting around the oceans on a comfortable bed of algae, but as you can see by the images there are huge amounts of marine debris concealed in the rafts of sargassum. Sadly, fishing twine and bits of plastic now hold the rafts together. During storms the algae can be washed ashore, leaving the frogfish high and dry. Although they can survive out of the water for a period of time, it is highly likely that the protective floating home of the frogfish could also be their demise. Small groups of conservationists search the shores after storms a few times a year to hopefully rescue and save any stranded frogfish.

This was one of the best experiences with one of the coolest little fish.

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Ocean Geographic Explorer (OGX) is a diving adventure resource with a special focus on marine photography and ocean conservation. Our content is divided up into six primary categories: Travel, Sea Science,  Equipment, Photography &Video, Conservation, and Lifestyle. We endeavor be a portal for people with all levels of interest in the marine environment  to learn about and become part of a community of like-minded ocean lovers who enjoy sharing their knowledge of and experiences in our fascinating ocean world.

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