Snorkeling above the sandy bottoms of CIMI’s shores, you might spot a cute little ray shuffling along… or is it a skate? No wait, it is a ray! But it might be a skate. Maybe. These closely related cartilaginous fish can certainly be difficult to tell apart, but each has certain qualities that make it unique and distinguishable.
Though both rays and skates have flattened bodies with which they can hide on the ocean floor, skates typically have fleshier tails with enlarged, thorny scales running along their backs for protection. Meanwhile, most rays have thinner tails barbed with one or two stinging spines that ward off potential predators. If you happen to see these guys moving about, you might observe that they swim differently too. Skates move by undulating their tails left and right, whereas rays flutter and flap their pectoral fins to get where they need to go.
Beyond the differences that you might notice at a glance, rays and skates have unique life cycles with disparate modes of reproduction. Skates are oviparous, which means that they reproduce by laying eggs. These eggs (or “mermaid purses” as they’re often called) are dark and flat with small projections that keep them anchored to marine substrate. Each egg is equipped with nutrients to keep the developing skates healthy for up to 12 weeks, at which point the pup will hatch and take on the big bad ocean. Rays, on the other hand, are viviparous, meaning that they give live birth to their pups. The gestational period (a.k.a. pregnancy) of some ray species can last over a year and once born, the juvenile rays usually separate from their mothers.
The next time you find yourself face to face (or fin to fin) with a flat cartilaginous fish, remember these differences so that you can distinguish the tail-stinging, fin-flapping, birth-giving rays from those back-spiking, tail-swinging, egg-laying skates.
When most people think about cartilaginous fish, they think about sharks! There are two other species of fish that belong in the class chondrichthyes (cartilaginous fish) as well, and they are our stingrays and skates! Most of you have probably never even heard of a skate before, while rays seem to take most of the spotlight. In this article I’m going to give you some similarities and differences of stingrays and skates, so by the time you are done reading this, you can become an expert at identifying them too!
Skates and stingrays can be hard to differentiate. They can look very similar in appearance, but there are three main differences that set them apart from each other. The first difference between a skate and a stingray is their stinging barb. Most stingrays will have a stinging barb that is found midway along their tail, while a skate lacks a stinging barb in general. Most skates have enlarged thorn-like scales along the midline of their back or tail, which helps to act as their defense mechanism.
The second difference that sets skates and stingrays apart involves their pelvic fin. On a stingray, each one of their pelvic fins is one lobe. While on a skate, their pelvic fins are each divided into two lobes. [You can see in the photos below, the differences between the pelvic fins.]
The last difference between stingrays and skates is how they produce their young. Stingrays are viviparous, which means they give live birth to their young, which are called pups. All skates on the other hand are oviparous. This means that skates lay eggs otherwise known as “mermaid’s purses.” This developing embryo can live up to 12 weeks inside of its egg case.
While these are several differences between stingrays and skates, they also have some similarities as well! Both of these species are flat and bottom dwelling, with their mouths on the underside of their bodies. They are also both excellent at camouflaging and hiding from their predators. They do this by covering themselves with sand and burying themselves into the ocean floor. Knowing these differences and similarities of skates and stingrays can help you distinguish them, and hopefully now you will never mistake these two cartilaginous species of fish ever again!
References: Love, Milton. Probably more than you want to know about the Fishes of the Pacific Coast. 1996.
We would like to thank you for visiting our blog. Catalina Island Marine Institute is a hands-on marine science program with an emphasis on ocean exploration. Our classes and activities are designed to inspire students toward future success in their academic and personal pursuits. This blog is intended to provide you with up-to-date news and information about our camp programs, as well as current science and ocean happenings. This blog has been created by our staff who have at least a Bachelors Degree usually in marine science or related subjects. We encourage you to also follow us on Facebook, Instagram, Google+, Twitter, and Vine to see even more of our interesting science and ocean information. Feel free to leave comments, questions, or share our blog with others. Please visit www.cimi.org for additional information. Happy Reading!