What is a Ray ?

Rays are elasmobranchs that actually belong to a super-order called Batoidea that includes the Guitarfish (Rhynchobatiformes), Sawfish (Pristiformes), Electric Rays (Torpediniformes), Skates (Rajiformes) and Stingrays (Myliobatiformes); the batoids are very close relatives of the sharks and members of the class Chondrichthyes. They share many similar characteristics with the sharks such as their electro sense and cartilaginous skeleton amongst others. However they have a very different body plan. They are also much more diverse than the sharks with over 550 described species to date.

They typically have a body that is flattened with a mouth on the bottom of the fish and eyes and spiracles on the top. The gills are located on the bottom of the fish. The pectoral fins are highly expanded and are attached to the side of the head that gives the batoids its distinctive disc like shape. (This is not to be confused with the Pacific Angel Shark (Squatina californica) that has pectoral fins that are detached from the head. The anal fin is absent and typically the caudal fin is absent instead replaced by a long whiptail sometimes with a sting on it.

They swim by undulating their enlarged pectoral fins and many have drawn comparisons to them ‘flying through the water’ by ‘flapping’ their pectoral fins. Some of the batoids such as the sawfish do rely more on the caudal fin however causing them to swim in a much more familiar shark like fashion.

The predominant orders that occur within the Southern California Bight are the Guitarfish, Skates and Stingrays.

Did I see a Shark or a Ray ?

In general sharks and rays are hard to confuse. Although there are instances when it might occur.

A few tips are firstly to look at the body form.

The Batoids have a much flatter body profile then the sharks do and as such are much more suited to a life on the ocean floor, able to bury themselves and breath using little holes by their eyes called spiracles.

Also notice use of the fins. Sharks swim by undulating their caudal fin from side to side and as such have a fin that is large enough to propel the body forward. The Batoids have narrow tails that are rarely used for propulsion instead relying on their greatly enlarged pectoral fins that they undulate in a wave like fashion to propel themselves forward.

One of the biggest giveaways on what you are looking at is the gill placement of the fish. Sharks gill openings are on the side of their head in front of the pectoral fins. Batoids are found on the underside of the body.

There are some confusing species that you may find in the Southern California Bight. The Pacific Angel Shark (Squatina californica) is a similarly flattened body plan to a Batoid, however when you look at its pectoral fins and the way it swims you will see it is distinctly a shark. Sometimes when a Bat Ray (Myliobatis californica) swims near the surface the tips of the pectoral fins stick out of the water making observers think there are two sharks swimming side by side.

Did I see a Skate or a Ray?

There are several types of elasmobranchs that live within the Southern California Bight and many will come into contact with Humans on a regular basis. So how do you distinguish between a shark, a ray or even a skate?

The Southern California Bight plays host to all three types of these elasmobranchs and many look very similar to each other. The Skates and Rays are both members of the Batoids and look very similar to each other. The batoids are a highly successful group of the elasmobranchs. they receive much less media coverage than their cousins the sharks. They did receive a lot of press late last year due to the tragic death of Steve Irwin who died as a result of a stingray spine to the heart.

Rays and skates belong to the Order Rajiformes, although there is controversial debate regarding this and some scientists believe they belong to two orders, Rajiformes (skates) and the Myliobatiformes (rays). So how do you distinguish between the two?

To eliminate the possibility that you might be looking at a shark there are a few morphological characteristics that are present with Rays and Skates by virtue of where they live. They are typically a Benthic species and their body form has evolved to reflect this. They have a dorso-ventrally (squashed from above) flattened body with eyes and their spiracles (an ancient gill slit) are often enlarged. Their mouths, nostrils and gill slits can be found underneath a Ray and a fleshy nasal flap covers the Skates mouth.

The primary form of swimming with the Skates and Rays is their greatly enlarged pectoral fins that form the main part of the body. These are attached to the head to form their ‘disc’ that makes up most of the body surface area. They achieve locomotion by undulating a wave of energy down the pectoral fins to move forward. This motion is slightly altered in the larger pelagic species such as the family Mobulidae (Manta Rays) with pectoral fins that are extended further and are oscillated up and down in a similar motion to wings flapping giving the impression of flying through the water.

However there are a few primary differences between a Stingray and a Skate. Firstly the Stingrays have their famous defence, a barbed spine that arises from modified dermal denticles. While the Skates primary defence are thorny barbs on their dorsal surface (back). The Skates are exclusively marine while the Stingrays are found in a range of salinities even into fresh water. Perhaps the largest difference is that most Stingrays give birth to live young (Viviparous) while the Skates will lay eggs (Oviparous).

This text is from the ReefQuest Centre for Shark Research.

Skates and rays can be difficult to differentiate. Both are flat and (with a few notable exceptions, such as the eagle and manta rays) bottom-dwelling elasmobranchs sharing a similar diamond or rhomboid shape. Some of the most familiar forms occur together in coastal habitats. Adding to the confusion, the term 'ray' is also used in reference to the electric and torpedo rays (order Torpediniformes); fortunately, torpedinoids are unlikely to be confused with either skates or rays (especially if one handles a live specimen!), being easily identified by the following characteristics: a rounded pectoral disc; soft, flabby body; dorsal fins nearer the pelvic fins than the tail tip; and kidney-shaped electrogenic organs at the base of the pectoral fins. Distinguishing skates from rays is rather subtle, but once one has learned their respective field marks, it is relatively easy to tell them apart.

Skates (order Rajiformes):

• Pelvic fins divided into two lobes 

• Tail relatively stocky, without a stinging spine 

• Tail usually with two small dorsal fins near its tip and a tiny caudal fin (some forms lack dorsal and caudal fins)

• Many have enlarged, thorn-like scales ('bucklers') along the midline of back and tail; enlarged scales also occur along the side of the body (near the pectoral fin base) in some species 

• Males have rows of enlarged scales near the eyes and wingtips (termed 'malar' and 'alar' spines, respectively)

Stingrays (order Myliobatiformes),

• Each Pelvic fin has one lobe 

• Tail is relatively slender to whip-like, usually with a saw-edged stinging spine midway along its length

• Tail usually without a dorsal fin (in some forms, a single dorsal fin occurs near the tail base), caudal fin reduced and continuous or absent 

• No bucklers along the midline of back or tail (although Hypolophus sephen, sometimes called the 'Pearl Ray', has three rounded scales in the midline of its back) or along the side of the body 

• Males lack malar or alar spines

• In addition, skates are typically drab, brownish or greyish deep-water inhabitants, while many rays are boldly or colourfully patterned, shallow-water inhabitants. But these are generalizations only. Some skates are attractively blotched or spotted and others occur in shallow and even estuarine water, while some rays are plain greyish above, lighter below, and some live at great depths.