Chesapeake sailors have undoubtedly been fooled at the sight of the cow nosed ray’s “wingtips” breaking the surface, thinking they are seeing the dorsal fin of a shark or dolphin. More likely, it is the triangular ends of the cow nosed ray’s pectoral fins. This unusual cartilaginous fish has generated much attention recently due to its diet of mollusks, oysters in particular.
A long history of contentious interactions with the commercial shellfish industry, in particular oyster restoration efforts and commercial aquaculture, has done nothing for this batoidae’s (flat fish) reputation. I have frequently seen cow nosed rays while sailing the Chesapeake, and they have certainly been caught (and released) by my fishing-crazed husband and son, but the biology of this fish was relatively unknown to me.
Cow nosed rays (Rhinoptera bonasus), a species of eagle rays, are cartilaginous fish, related to sharks, and a separate family from stingrays and skates. Their bodies are kite-shaped, with a long whip-like tail, and a square, indented snout that resembles a cow’s nose (hence the name). The color on the dorsal side ranges from brown to olive green, and their underside is white. They can weigh as much as 50 pounds (exciting anglers until they come into view) with a wingspan of up to three feet. They swim by flapping their powerful pectoral fins. Rays use their dental plates to crush shells, and then they digest the soft body parts of the mollusks. They find their prey by flapping their fins against the bottom to uncover buried shellfish while sucking in sand through their mouths and out through their gills (a vacuuming effect).
Rays have poisonous spines at the base of their tails and gained early notoriety on the Chesapeake when Captain John Smith was stung in the shoulder while spear fishing for rays at the mouth of the Rappahannock. He became so ill that his crew was planning his funeral, but apparently made a rapid recovery in time to eat the ray for dinner. This is how Stingray Point was given its name. Cow nosed rays do not lie on the bottom, so it is unlikely one would step on one and get stung.
Cow nosed rays are seasonal summer residents of the Chesapeake, migrating to the Bay in order to mate and give birth. They journey to the Atlantic Coast of Florida for the winter. The ray’s life history makes it particularly vulnerable to overfishing. Research into ray biology will be critical if a fishery is actually developed. Males mature sexually at the late age (for a fish) of five to six years old, and females at seven to eight years old. The rays mate at the end of the summer before leaving the Bay and return after a long gestation to bear a single “pup” in June of the following year. The pups measure 11-18 inches at birth.
Schools are formed based on gender and age, and schools of over 300 have been spotted at the mouth of the Bay. The ray’s main predators are coastal sharks, particularly the bull shark and sand shark. It is theorized by scientists that growth in the ray population is related to the removal of their apex predators by the coastal shark fishing industry.
The reports of destruction of shellfish beds by rays has spawned an “Eat a Ray, Save the Bay” campaign. The pectoral fins apparently have a veal- or pork-like flavor. This campaign does not seem to have led to a demand for ray on the menus of local seafood restaurants. Unfortunately it may have spurred controversial ray killing contests, where upward of 150 participants bow hunt for rays (an easy target), killing unknown numbers for sport. It is clear that a regulated fishery would be helpful in managing ray populations, especially as their life history makes them vulnerable to overfishing. An ecosystems management approach would take into account the complex web surrounding the life cycle of the cow nosed ray. The Virginia Institute of Marine Science is leading the way in studying ray biology in order to better understand and protect these unusual fish.
Next time you witness the cow nosed rays leaping into the air (a territorial display) on a summer sail, hopefully you will have a newfound appreciation for this strange-looking sea creature.
About the Author: Pamela Kellett, a gradutate student in environmental science at Johns Hopkins University, holds a 200 Ton Near Coastal Master/ 500 ton Ocean Mates license and used to be the captain of Lady Maryland.
