Lesser Electric Ray
You’ve done the Stingray Shuffle, but what about the Electric Slide?
~Padre Island National Seashore Facebook
Every regular beachgoer in Texas knows the need to shuffle your feet to avoid being stung by a stingray, in a move dubbed the ‘stingray shuffle.’ The shuffle might also help protect against the lesser electric ray - a species of numbfish that lives in the Gulf. Electric rays are part of the superorder Batoidea, which includes skates, stingrays, sawfish, and guitarfish. This species of ray, Nacine bancroftii, has a flat, near-circular body, short tail, broad pelvic fins, two small dorsal fins, and a big triangular tail. It generally reaches 18 inches long and 8 inches wide (slightly smaller than other electric rays), though it can reach up to 33 inches long. Colouration ranges from dark brown to reddish orange with irregular rings on top, and white to greenish on bottom. It has 17-34 teeth in each jaw, depending on the age and size of the ray. The skin is soft and loose, and lacking any dermal denticles. Juvenile lesser electric rays usually have a number of dark rings and blotches along with dark oval loops. Two long electric organs run from the front of the eyes down to the rear end of the disc. These organs can generate up to 37 volts, which they use to stun prey and to defend themselves. Although these numbfish have a low-intensity shock compared to other electric rays, the effect can still be quite startling.
Lesser electric rays are a demersal, or benthic, fish inhabiting tropical and subtropical coastal waters, on sand or mud bottoms. They are commonly found partially buried along sandy shorelines, seagrass beds, and sometimes near coral reefs, from the surf zone up to 200 feet. They range from North Carolina to at least the north coast of South America, and it is locally common in Gulf of Mexico and Caribbean Sea. Records from further south in South America probably refer to the closely related Brazilian electric ray, Narcine brasiliensis.
This generally sluggish swimmer is nocturnal, remaining motionless during the day and foraging for food in the substrate at night. Polychaete annelids are their primary diet. However, they also eat short-length snake eels, small bony fish, different species of crustaceans, and sea anemones. The ray uses its pectoral fins to guide the food to its mouth, which is located under its body. Many larger fishes, including sharks, prey on the lesser electric ray.
Lesser electric rays, like all rays, have an ovoviviparous mode of reproduction. Ovoviviparity is distinct from oviparity (egg-laying). In oviparity, the eggs are laid and rely on the yolk sac for nourishment until they hatch. Ovoviviparous animals produce eggs, but instead of laying them, the eggs develop and hatch inside the mother's body. The embryos are first nourished with yolk and then with histotroph, a protein-rich liquid secreted from the mother’s uterine lining, and while ovoviviparous animals do not have umbilical cords or a placenta with which to provide nutrients and waste exchange, some species – such as sharks and rays – do provide gas exchange for developing eggs inside the womb. In such cases, the egg sac is extremely thin or is simply a membrane. When their development is complete, the young are born live. By delaying birth after hatching, the offspring enter the environment in a more advanced stage of development than oviparous young.
After a gestation period of 3 months, anywhere between 4 and 15 young are born. However, there is a possibility of diapause – a pause in development after fertilization until environmental conditions are optimal. This would result in a longer gestation, up to a year. Pups are independent from birth, at a length of about 3.5 inches. They are also born with the ability to give off electrical charges. Females mature around 2 years old, between 20 and 26 inches in length.
Lesser electric rays are not aggressive and pose little danger to humans – though stepping on one can certainly be a shocking experience. An updated analysis of the species examining a number of data sources determined that there has been no decrease in abundance in the northern Gulf of Mexico since 1972 and that the trend in abundance is relatively stable. Levels of bycatch from shrimp trawl fishery are small primarily because the shrimp fishery operates in areas where lesser electric rays aren’t found. Additionally, based on interactions with commercial fishing gear and the ray’s small size and fast growth rate, impacts from bycatch are likely to be low. Electric rays also have limited to no commercial value and are generally discarded.
Where I learned about lesser electric rays, and you can too!
Texas Marine Species
Florida Fish & Wildlife Conservation Commission
The Shark Forum
IUCN Red List