Join us identifying species aboard the Nansen
- Antennarius striatus, commonly known as Frogfish, has an unusual method for finding dinner – it tricks smaller fishes to swimming directly into its mouth
- This Rhinobatos albomaculatus is part of the group of flattened dorsoventrally sharks, collectively known as “batoids”
- This Raja miraletus is a type of skate, one of the known 630 species of “batoids”
- The green stingray Dasyatis cf. hastata is a relatively common but unnamed stingray found over coastal soft bottoms in the eastern Atlantic from Mauritania to Congo
We thought you’d like to see some of the taxonomical work we have underway. Here are some of the species we are identifying during our Ghana survey trip… and some new facts and curiosities for all you budding marine biologists out there.
Curiosities from the deck: Frogfishes
Antennarius striatus is a small benthic fish characterized by its elongated first dorsal fin (illicium) bearing at its top a fleshy appendage (esca).
Despite its sedentary nature, A. striatus is actually a voracious carnivore that sits quietly and patiently waiting for its dinner – generally smaller fishes - to pass by. This is when we see A. striatus at its most active, wriggling its bait to attract the potential prey directly into its cavernous mouth.
A. striatus’ body is globose and unstreamlined to further conceal its motionless presence on the sea bottom.
Let’s talk about batoids
Many people speak about shark and rays as if they were different creatures. Yet there are no reasons for doing so. These flattened dorsoventrally sharks, collectively known as “batoids”, are a successful variation of the basic shark body plan, represented today by more than 630 species.
These include sawfishes, guitarfishes, torpedo rays, skates, stingrays, eagle rays and mantas rays. The characteristic flattened shape and wing-like pectoral fins of batoids are adaptations to their bottom-associated lifestyle. Nevertheless, some more recently evolved forms such as manta and devil rays have abandoned a benthic life style for a full pelagic existence.
The green stingray Dasyatis cf. hastata is a relatively common but unnamed stingray found over coastal soft bottoms in the eastern Atlantic from Mauritania to Congo. As with other members of its family, the green stingray possess a strong serrated sting on the base of its tail which is used as defensive weapon against sharks and other predators. The sting is covered with a mildly venomous sheath of skin and can cause painful injuries but like most fish toxins, stingray venom is a large protein that can be broken up by immersing the wound in hot water for at least 30 minutes.
(Man the) torpedo rays…
Torpedo rays form a relatively diverse assemblage of electrogenic rays occurring in tropical to temperate latitudes around the globe, usually to depths of about 100 m, and most commonly occurring in shallow water coastal regions.
The electrogenic organs of torpedinoid rays are situated on either side of the forward part of the body and are used both as anti-predator device and to immobilize or disorient prey.
The diversity of torpedo rays is not yet complete and as many as four new Torpedo species are presently being described from the Eastern Atlantic.
- Torpedo rays live in tropical to temperate latitudes around the globe
- Torpedo rays like this example are usually found in depths of up to 100 meters, most commonly in shallow water in coastal regions
Plastic garbage: A global issue
Up to 2 full baskets of plastic garbage was recovered from one single trawl haul (Fig. 1). Plastic floating bags and containers, plastic and metallic debris on the bottom are increasingly polluting seas and oceans worldwide. Populated areas, ships, factories are the main sources of these wastes. Currents along the coast and oceanographic conditions can then disperse them in areas hundreds of miles away from the source points. The end results is visible to everyone, either walking on a beach or trawling in the open sea. They also impact on important marine habitats such as nursery areas and feeding grounds. It is not only an “esthetic” problem.
Microplastics, not visible to eyes, were found in fish tissue and thought to be part of their metabolic process thus entering in the food chain and in the food we eat. It is an alarming global issue, and its impact can be devastating with negative consequences on fish populations and the fishing industry. On board of the Nansen, all waste materials from the trawls are collected and put aside to be delivered to a proper waste facility when ashore. From water sampling, small fragments of plastics are sorted and counted using the microscope to estimate their abundance in the water column.
Thanks for joining us on for our taxonomy lesson today. Any questions? Just jot them down and submit them in the comments segment below – we’ll do our best to answer them. Until next time!