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Rays are a group of creatures that natural selection has awarded many

variations. These seemingly infinite differences determine how they interact

with their environments and how they are interconnected with humans.

Pelagic lifestyles among rays might increase the threat of unsavory human

interaction., be it poaching them or accidentally reeling them in. It is vitally

necessary that this be addressed, or an important species of ray might go

extinct. Different adaptions also dictate behaviors such as feeding or

migrating, and by extension, their physical appearance, which explains the

diversity in appearance among rays that we see today. Biodiversity as rich and

strange as that of the ray family is something worth preserving.

Abstract

Migration Patterns

While the basic characteristics of rays, namely their flat bodies, complete with

an impressive wingspan, are consistent throughout the species, rays have

adapted to have different shapes, sizes and colorations. Even some of the most

basic adaptions that some would expect to universal among rays are defied by

these creatures. Despite their distinctly demersal demeanor, rays such as the

Giant Manta Ray and the Pelagic Stingray live their lives in the open water for

the most part. (Alllen & McCormick, 1996) We were able to see such a ray

during our visit to the Birch Aquarium. Rays are also able to live within

freshwater. One example of this is the Atlantic Stingray which is know to

reside within St. Johns River as well as in lakes further inland. (Bester, 2017)

That being said a majority of rays will be benthic, marine animals.

Biodiversity of the Ray Family

Due to the staggering diversity of rays, it would be inaccurate to claim that

they, collectively, are endangered. There are rays in every category of

endangerment, from least threatened to critically endangered. The cause for

endangerment when it is present is, unsurprisingly, humans. At times, human

collection of certain species has no significant effect on the population. The

Pacific Electric Ray, for example, is captured in small numbers by biomedical

firms in order to study their electricity-producing organs for medicinal

purposes. They remain a “Least Concern” species. ( Neer et al., 2015) On the

other hand, in many ways similar to the Pacific Electric Ray but with very

different implications, Manta Rays are poached in the waters of southeast Asia

for a variety of reasons. They are sold as oddities, and their gill plates are

often removed made into a tonic which is sold in China as an alternative

medicine. (Allen & McCormick, 1996) Because the Manta Ray is considered

a protected animal in most of these areas and hunting them is an illegal act

with punishments of high fines and jail time, the Reef Manta Ray remains

“Vulnerable” (Manta Trust, 2017).

Endangerment Status Feeding Habits

Though most attribute rays with typical benthic, bottom-feeding activity

similar to that of a Roomba, the way different species choose to feed is

dependent on the species’ lifestyle. Even typical demersal varies; perhaps like

the Electric Ray, it stuns its prey for an easier catch. Even large pelagic rays

like Eagle Rays will swoop down feed on crustaceans and bivalves. However,

perhaps one of the most unique feeding habits among rays is the feeding

cyclones performed by Reef Manta Rays. During dense planktonic blooms at

Hanifaru Bay in the Maldives, the Mantas will engage in chain feeding,

following each other in circles as they capture as many plankton as they

possibly can in their large, gaping mouths. Reef Manta Rays have an

individual adaption of this event to, in which they appear to continuously

perform backwards summersaults in order to capture a concentrated area of

plankton, similar to cyclone feeding; this is referred to as “barrel rolling”. This

method of simply opening their gargantuan mouths to vacuum up plankton

differs from that of the more carnivorous Eagle Ray, and is instead much more

akin to the feeding habits of their near cousins, the Whale Shark. Both species

take advantage of the planktonic blooms in the Maldives.

ReferencesAllen, T. B., & McCormick, H. W. (1996). Shadows in the sea: the sharks,

skates, and rays. New York, NY: Lyons & Burford.

Bester, C. (n.d.). Ray & Skate Biology. Retrieved November 27, 2017, from

https://www.floridamuseum.ufl.edu/fish/discover/rays-skates/biology/

Manta Trust. (n.d.). Conservation through Research, Awareness and

Education. Retrieved November 27, 2017, from

http://www.mantatrust.org/about-mantas/monsoons-and-migrations/

Neer, J.A., Freedman, R.M., Lowe, C.G & Jang, J.J. (2015). Tetronarce

californica. The IUCN Red List of Threatened Species 2015:

e.T39396A80672988. http://dx.doi.org/10.2305/IUCN.UK.2015-

4.RLTS.T39396A80672988.en

Notarbartolo di Sciara, G., Serena, F. & Mancusi, C. (2015). Mobula mobular.

The IUCN Red List of Threatened Species 2015: e.T39418A48942228.

http://dx.doi.org/10.2305/IUCN.UK.2015-1.RLTS.T39418A48942228.en.

Perrine, D. (2003). Sharks and Rays of the World. Voyageur Pr.

The migratory behavior of rays varies depending on the unique lifestyle of the

species. It is common for larger, pelagic species of ray to be migrating

constantly. Giant Oceanic Manta Rays and Spotted Eagle Rays will tend to

travel the worlds oceans in search of planktonic blooms. It has yet to be seen

if these migrations have a particular pattern; it is theorized that the Giant

Oceanic Manta follows the planet’s natural polarity to migrate. Satellite

tagging has been employed to make sense of these enigmatic migrations.

(Manta Trust, 2017) As interesting as these independent migrations are, people

are far more familiar with flashy presentation, like the grand group migration

of the Golden Cownose Ray. One of the few times non-science media has

reported on rays has been this particular migration due to its sheer mass. The

current belief is that this migration is triggered by seasonal temperature

changes in the water, urging them to move to western Florida in late Spring,

and then back to the Yucatán Peninsula in late Autumn. Their migration is also

theorized to be connected to their feeding habits, migrating to the area with the

greatest abundance of food. Another piece of this migration that catches the

public’s eye is the breaching behavior of the Golden Cownose Ray. As they

migrate, it is common for the rays to leap into the air and land on their

underbelly with a distinct slapping sound. Those who study this phenomenon

do not yet have an explanation for why they do this, though some believe they

do this to attract a mate or simply enjoy the feeling of doing a belly-flop.

(Perrine, 2003)

Zane Shalauta

Rays: Champions of Diversity

Illustrations of a Demon Ray, Thornback Ray, Undulated Ray,

Electric Ray, and Long Nosed Ray from Rees’s Cyclopædia (1819)

To truly grasp the scale of diversity, it is probably easiest to look closely at a few

individual species. Above, at the top right corner of the image is the Electric

Ray. We Californians are likely more familiar with its cousin, the Pacific

Electric Ray which resides along our coasts. This nocturnal ray is an avid hunter,

seeking out its prey in rocky outcroppings and stunning them with their

electricity. Its electricity is also used defensively, since they are still a relatively

small species. (Neer et al., 2015) This contrasts greatly with, say, the Spotted

Eagle Ray, a larger ray species which lives a relatively pelagic lifestyle. They

tend to keep close to coasts and reefs, but due to their presence in many different

oceans on Earth, it is thought that they are capable of migrating over ocean

basins. These tend to be a more solitary individuals, very unlike the Golden

Cownose Ray which are well known for their grand group migrations across the

Gulf of Mexico towards Florida in search of better weather and a revitalized

food source. (Perrine, 2003) It is these differences among the ray family that

make for a diversity in lifestyle, appearance, and human interaction. Certain

species are at greater risk of extinction than others, mostly hinging on how

commonly they come into contact with humans. The benthic Electric Ray (Least

Concern) will rarely see a human, but the pelagic Giant Devil Ray (Endangered)

is often bycatch in the Mediterranean Sea. (Notarbartolo di Sciara et al., 2015)

Golden Cownose Ray Migration with an individual breaching.

Photographed by Florian Schultz (2010)

Giant Reef Manta Rays swim, mouths agape, in a cyclone feeding frenzy in

Hanifaru Bay, Maldives. Photographed by Thomas P. Peschak (2012)

Manta Ray gills confiscated by the Bali Ministry of Fisheries.

Photographed by Paul Hilton (2014)

However, hunting is rarely what causes rays to become endangered. The

negligent practices of mass fishing techniques and the subsequent bycatch of

rays caught in their path. Take the Giant Devil Ray for example. Native to the

Mediterranean Sea, constant bycatch of these rays and neglecting to release them

while still alive has rendered this species endangered. While there is one case of

a Palestinian fishery specifically targeting Giant Devil Rays using purse seines, a

majority of these unnecessary captures are by other fisheries who also happen to

have purse seines, pelagic driftnets, or trawls of any kind. Although this behavior

has been noted as dangerous to this species, the population remains in decline.

Their low reproductive rates are an additional disadvantage. European

governments have begun the process of protecting these creatures by outlawing

pelagic driftnets, but illegal activities persist. Actions that could help reduce the

unnecessary deaths of Giant Devil Rays include a mix of legal action and social

awareness. Harsher enforcement of the legal protections already in place for this

ray combined with public awareness among fishermen to release Giant Devil

Rays alive could save this species. (Notarbartolo di Sciara et al., 2015)