The Coffin Ray (aka the Australian numbfish), is a species of electric ray endemic to Australia, where it is common in inshore waters shallower than 260 ft. It is the sole member of its genus Hypnos. The genus name is derived from the ancient Greek word 'húpnos' which means 'sleep'. As for its common names, it is named for the ray's ability to induce numbness, and "coffin ray" comes from the coffin-like shape of beached specimens, which become bloated after death.
Numbfishes, the Lesser Electric Rays of the Family Narcinidae
The Numbfishes, despite not being common in fish stores, are intriguing animals for use in the home aquarium. Their small-to-moderate size (with one species only reaching 10 inches in length) and their ability to shock prey make them desirable in their own way, but also make it near impossible to keep them with other fishes. The potential danger they pose to their owner coupled with their picky eating habits mean that they should not be added to any system without proper research.
Species
Narcinidae is part of the Order Torpediniformes, along with Narkidae (Sleeper Rays), Hypinidae (Coffin Ray), and Torpedinidae (Electric Rays), all of which are capable of delivering an electric shock. Narcinidae currently contains about 30 recognized species over 4 genera. 5 of these species are found in North American waters:
Benthobatis marcida (Blind Torpedo)
Diplobatis ommata (Ocellated Electric Ray) [pictured]
Narcine brasiliensis (Brazilian Electric Ray)
Narcine entemedor (Giant Electric Ray)
Narcine vermiculatus (Vermiculate Electric Ray)
Few of the Rays in this Family are sold with any real frequency. The Ocellated Electric Ray shows up from time to time, and the Brazilian Electric Ray is reportedly sold, albeit uncommonly, in its namesake Brazil.
Conservation Status
The Blind Torpedo populations are considered Stable and the species as a whole is of Least Concern by the IUCN. The Vermiculate Electric Ray is Near Threatened, the Ocellated Ray is Vulnerable, and the other two species are currently considered Data Deficient.
Distribution
The Giant, Ocellated, and Vermiculate Electric Rays are all denizens of the Pacific Ocean, found in the Gulf of California and south down to Central America. The Blind Torpedo and Brazilian Electric Ray are both found in the Atlantic Ocean, from the Carolinas to the Caribbean and Gulf of Mexico. As its name implies, the Brazilian Electric Ray's range extends southward to the southern border of Brazil.
Description
The Numbfishes are small-to-medium sized Rays. The smallest, the Ocellated Electric Ray, seldom reaches 10 inches in length while the largest, the Giant Electric Ray, gets to be about 30 inches. All of the other Native species have a maximum length around 20-22 inches.
Perhaps the most notable trait of the Numbfish is their ability to produce electric shocks. Unlike Torpedos of the Family Torpedinidae (which have been rated up to 220 volts), Numbfish shocks are relatively weak, around 8-37 volts depending on species. Indeed, the Lesser Electric Ray seems to have problems catching live prey like shrimps even with this ability.
Numbfish are benthic fish which spend the majority of their time either hovering over the substrate (using their Electric senses to look for prey) or digging into the substrate. A deep layer of substrate (about the length of the animal's head) allows for sufficient room for digging as well as aiding in Nitrification. Reportedly, they are also social fish and groups can be kept in larger tanks. Due to their delicate nature and electric abilities, it's probably best to keep them in Species-only tanks. That said, smaller Gobies and Clown Fishes typically do fine in Ray tanks.
Substrate should consist of rounded, calcerous materials like coral (avoid pure silica sand or sharp crushed coral). Jagged substrates will result in scrapes and high likely will lead to bacterial infections and death. Likewise, any live rock in the tank should be kept in the middle in a mound to keep Rays from swimming over it.
Rays are sensitive to many sorts of common medications, and copper specifically is deadly and should be avoided. As these fish are wild caught, they may have parasites when purchased. Numbfish do apparently tolerate Praziquantel quite well, and these Rays should be given treatments and Quarantined for 30 days prior to release into the main system.
Many Elasmobranches, particularly Sharks, are highly sensitive to metals in their aquarium (such as those for heaters, filters, etc) and the presences of metal items can cause them to stop feeding or frantically thrash about. Even metal items coated in plastic or glass, or metal reinforcements outside the tank, can prove hazardous to their health. Though no specific mentions were found for Numbfish, I would still advise against putting metal objects in their tanks.
Feeding
Feeding can be extremely difficult with these fish. Numbfish eat live invertebrates in the wild and do not seem to easily accept thawed foods. The Ocellated Electric Ray is known for starving in captivity as it refuses most "easy" foods. They eat polychaete worms primarily, but will also accept certain bait foods like clam worms and lug worms. Ghost shrimp work as well, but should be injured beforehand to make them unable to escape the Numbfish. It typically takes a few weeks of feeding injured prey right under the Ray's mouth for them to start "understanding" feeding time, at which point they will be more enthusiastic about eating.
Starvation is extremely common with these fish. It may take several weeks for them to acclimate to feeding time, and most specimens that don't adapt within 3 weeks never do and wither away. Likewise, force feeding has a very low chance for successfully adapting Numbfish to eating in captivity (only 1 in 12 individuals noted success).
Consider adding vitamins and supplements like Amino Acids and Iodide within food items given to Rays. As their diet is invariably less diverse than in the wild, this practice can help keep them healthy.
Water Quality
As marine fish, especially those which are found in reef settings, Numbfishes are best kept in large, stable systems. High carbonate hardness and high pH (around 7.8-8.2) are musts. They are best kept around a Specific Gravity of 1.025-1.026. These are large fish and produce a lot of waste. Multiple working protein skimmers, rated for one and a half times the volume of the tank, is highly recommended. Numbfishes absolutely require near perfect water conditions (Ammonia/Nitrites at 0, Nitrates below 10 mg/l).
The Giant, Ocellated, and Vermiculate Electric Rays are Tropical species and should be kept at around 75 F. The best way to accomplish this is to have the Heater in a sump which feeds into the main tank, avoiding putting metal objects in the Rays enclosure. The Blind Torpedo is a deep-water species and should be kept in water around the mid 50's F (requiring the use of a chiller). The Brazilian Electric Ray is a subtropical species that can be kept around room temperature (60-68 F).
Brackish Suitability
In general, no Numbfish should be kept in Brackish conditions (or indeed, in any specific gravity under Near Sea Water levels) for an extended period of time. Though some Marine fish can be kept in Hyposaline levels, around 1.017-1.020 full time or in quaratine conditions to fight Marine parasites, Elasmobranches seem to react to this treatment very poorly. Studies with the Lesser Electric Ray showed that this practice can lead to a quick decline in health.
Tank Size
For Marine Rays, a tank that houses them should really be upwards of 500 gallons. Even for the smaller Ocellated Electric Rays, I would not suggest anything smaller than 400. Why such a large tank for these medium-sized fish? There are a few reasons worth noting. Rays need a lot of space for maneuvering and surface area is extremely important, especially for tanks with live rock. All rocks should all be confined to the center of the tank and allow the Rays plenty of room to swim around it. Second, it provides a lot of room for the Rays to dig for Polychaete worms that live in the substrate and will keep them healthier with lots of access to these foods. And the benefits for having more volume for waste dilution should never be overlooked.
Breeding
Depending on the species, Numbfishes are either ovoviviparous (young are produced in eggs, which hatch inside the mother) or viviparous (no eggs, placental feeding). These fish do not seem to breed in captivity.
Final Thoughts
Numbfishes are interesting fish, there's no denying that. But their sensitivity and the fact that they are prone to stress and starvation means that they do not make good pets at the best of times. Coupled with the need for huge tanks, Numbfishes should not be kept except by extremely advanced aquarists. Really, these should just be left in the ocean or to public aquariums.
Sources
Fish Identification, Fishbase (Mexico)
Fish Identification, Fishbase (US)
Lesser Electric Ray, Florida Museum of Natural History
Sharks and Rays in the Home Aquarium, Scott W. Michael, Fishchannel.com
Saltwater Ray Husbandry, Adam Blundell M.S.
FAQs about Rays, Skates, Guitarfishes Stocking/Selection, Wetwebmedia
FAQs about Rays, Skates, Guitarfishes Systems, Wetwebmedia
Husbandry Notes on the Lesser Electric Ray, Mason N. Dean, Theresa E. Nietfeld, Daniel S. Conklin
Come To Australia - You Might Accidentally Get Killed (Part 10)
And while we're discussing sea life, how about some actual fish.
Such as the Stonefish, which has thirteen venomous spines along it's back, and camouflage so good you won't notice it until you step on it.
Or the Southern Eagle Ray, with is also deadly. Just ask Steve Irwin. He got the sting in the heart, when the ray panicked. Coreynn made the audience squirm by pointing out that the sting is serrated, and other people who step on a ray bled to death when they got their femoral artery slashed open.
Of course not.
This is an electric ray, aka torpedo or numbfish. They get up to 90 kilograms (200 lb) in weight and can deliver a 220-volt electric shock
But at least you can eat the fish, can't you?
Ha ha, says I. Ciguatera poisoning can be caused by eating any of 400 reef fish whose flesh is contaminated with toxins originally produced by dinoflagellates Ciguatoxin is odourless, tasteless and very heat-resistant, so ciguatoxin-laden fish cannot be detoxified by conventional cooking.
Hallmark symptoms of ciguatera in humans include gastrointestinal and neurological effects such as nausea, vomiting, and diarrhea, usually followed by neurological symptoms such as headaches, muscle aches, paresthesia, numbness, ataxia, vertigo, and hallucinations. Severe cases of ciguatera can also result in cold allodynia, which is a burning sensation on contact with cold.
It's occasionally misdiagnosed as multiple sclerosis.
And here's the bit that cause the entire audience to groan and squirm, most gratifyingly - the toxin may be sexually transmitted.
Or through breast milk.
And the symptoms can last up to 20 years.
After all this, it's obvious that you can't go within 50 feet of the ocean. But you'll be safe from the sea life in the rivers, won't you?
This a bull shark. This species is infamous from swimming up rivers. During the recent Brisbane floods, these sharks were swimming up and down the streets and across the golf courses. Some stayed behind in the water hazards.
also referred to as a Bullseye Electric Ray is a Numbfish (a family of electric rays) of the family Narcinidae. the ray can be found in waters of the Pacific ocean from Baja California down to Ecuador. they are a medium size fish only growing up to 10in in length. they can be identified by their Bullseye on their back. and as their name states they have an electric shock that is used primarily in defense. due to heavy trawling they have been listed as Vulnerable by the IUCN.
