Thornback Skate | Thornback ray

The thornback ray (Raja clavata) or thornback skate is a species of fish in the Rajidae family. It is found in coastal waters of Europe and the Atlantic coast of Africa, possibly as far south as Namibia and even South Africa. Its natural habitats are open seas and shallow seas. It is sometimes seen trapped in large estuarine pools at low tide. 

The thornback ray is probably one of the most common rays encountered by divers. Like all rays, it has a flattened body with broad, wing-like pectoral fins. The body is kite-shaped with a long, thorny tail. The back is covered in numerous thorny spines, as is the underside in older females. Adult fish can grow to 1 m (3.3 ft) in length, although most are less than 85 cm (33.67 in). This ray can weigh from 4.5 to 8.75 lb (2 to 4 kg). 

In sexually mature fish, some of the spines are thickened with button-like bases (known as bucklers). These are particularly well developed on the tails and backs of sexually mature females. Their colours vary from light brown to grey with darker blotches and numerous small darker spots and yellow patches. Sometimes the yellow patches are surrounded by small dark spots. The underside is creamy-white with a greyish margin.When threatened they can appear black. 

The thornback ray is usually found on sedimentary seabeds such as mud, sand or gravel at depths between 10 and 60 m. Juvenile fish feed on small crustaceans, particularly amphipods and bottom-living shrimps; adults feed on crabs, shrimps and small fish.

Stellate Sturgeon | Starry Sturgeon

The Stellate Sturgeon, Acipenser stellatus, also known as starry sturgeon or sevruga is a species of sturgeon. It is native to the Black, Azov, Caspian and Aegean Sea basins, but the fish has been extirpated from the last and it is predicted that the remaining natural population will follow soon due to over fishing. The starry sturgeon is an anatropous species, which migrates up rivers to spawn.

The starry sturgeon or Stellate Sturgeon reaches about 220 cm (7.2 ft) in length and weighs up to 80 kg (180 lb). It is a slim-bodied fish easily distinguished from other sturgeons by its long, thin and straight snout. A row of five small barbells lies closer to the mouth than to the tip of the snout. The scales on the lateral line number between thirty and forty and these features distinguish this fish from the Russian sturgeon (Acipenser gueldenstaedtii). The maximum reported age for this species is 27 years.

Facts and figures of Stellate Sturgeon:

• Acipenser stellatus was always rare in the Middle and Upper Danube, but also ascended several tributaries as Prut, Tisza, Drava, Sava and Morava.
• Stellate Sturgeons migrate in spring and autumn. Males remain at spawning sites for up to six weeks, females for only 10-12 days.
• Stellate Sturgeons stop eating once they start their migration. After spawning, they return to the sea quickly where they begin feeding again.
• 87% decline in global commercial catch reflects the decline in species population.
• 55,000 sturgeons found dead in the Sea of Azov in 1990 as the result of pollution.
• 72.5% is the decline of Stellate Sturgeon catch over a 4-year period according to data from Romania.

The starry sturgeon is an important commercial species of fish. It is one of the three most important species for caviar along with the Beluga sturgeon and the Persian sturgeon. Its flesh is considered an expensive delicacy in the Caspian region. It is used to make kebabs, or is consumed pan fried, broiled, or smoked.

Scalloped hammerhead | Scalloped Hammerhead Shark

Sharks have been around for over hundreds of millions of years. While many of us may be familiar with a few shark species, there are over 400 of them and Scalloped Hammerhead Sharks is most familiar among them. This shark is also known as the bronze, kidney-headed or southern hammerhead.

Scalloped Hammerhead Sharks (Sphyrna lewini) are probably the most commonly found species of hammerheads located in coastal regions, appearing in very shallow waters such as estuaries and inlets. It is a species of hammerhead shark, family Sphyrnidae. Originally Zygaena lewini, it was later moved to its current name. The Greek word sphyrna translates into "hammer" in English, referring to the shape of this shark's head.

Behavior: At certain times of the year and places, and during certain phases of their lives, scalloped hammerheads form very large schools this is most likely because it is easier for the scalloped hammerhead shark to obtain food in a group than alone. This behavior allows for them to catch larger and trickier prey, as commonly seen. The younger the sharks, the closer to the surface they tend to be, while the adults are found much deeper in the ocean. They are not considered dangerous and are normally not aggressive towards humans. Sometimes counting hundreds of individuals, but they also swim the oceans alone. Some populations remain stationary; others clearly wander, migrating in the direction of the poles in summer. Some sexually-related migrations have also been observed, e.g. females who undertake migrations during particular periods of their sexual development.

Size: Mature females can reach a length of more than 4 meters; the average length is, however, less. Males reach sexual maturity at a length of about 160 cm, females when they reach approx. 210 cm. The pups measure approx. 50 cm at birth.

Distribution: It primarily lives in warm temperate and tropical coastal waters all around the globe between latitudes 46° N and 36° S, down to a depth of 500 meters (1,600 ft).  Scalloped hammerhead sharks are found practically around the world in the coastal regions of tropical, subtropical and moderate climate zones.

Diet/ Feeding: This shark feeds primarily on fish such as sardines, mackerel and herring, and occasionally on cephalopods such as squid and octopus. Large scalloped hammerhead sharks also eat small-sized shark species such as the Atlantic sharpnose shark (Rhizoprionodon terraenovae) or the blacktip reef shark (Carcharhinus melanopterus).

Sandbar Shark

The sandbar shark, Carcharhinus plumbeus, is a species of requiem shark, family Carcharhinidae, native to the Atlantic Ocean and the Indo-Pacific. It is distinguishable by its very high first dorsal fin and inter-dorsal ridge. One of the most notable features of the Sandbar shark is its strikingly tall first dorsal fin. It can be more than one-tenth of the length of this sizable shark, which usually reaches 6.6 feet in length. They have a streamlined body with a broad flattened head, with a moderately long rounded snout. They are a greyish or brownish color, interdorsal ridge present, and are very strong swimmers.

The sandbar shark is also called the thickskin shark or brown shark. It is one of the biggest coastal sharks in the world, and is closely related to the dusky shark, the bignose shark, and the bull shark. Sandbar sharks usually have heavy-set bodies and rounded snouts that are shorter than the average shark's snout. Females reach sexual maturity around the age of 13 with an average fork-length (tip of the nose to fork in the tail) of 154.9 cm, while males tend to reach maturity around age 12 with an average fork-length of 151.6 cm.

Like other shark species, this sandbar shark has electroreceptors, hundreds of specialized pores located on and around its head. This sensory system detects the electric fields all animals give off with every heartbeat or movement of a muscle. Sharks use this incredible ability to locate even buried prey, like stingrays on the seafloor. Large sharks can detect an electric field at about three feet (one meter).

The sandbar shark eats many fishes, including menhaden, eels, flatfish, other sharks, goatfish, skates, octopus squid, and crustaceans. 

These sharks are viviparious, yolk-sac placenta. Mating occurs from spring through early summer, and females carry the developing young for 9 to 12 months. They retreat to shallow nursery grounds to give birth to 8 to 12 young, depending on the size of the mother. Pups are about 8.6 inches long at birth.

Electric ray or Pacific Torpedo Ray

The Pacific electric ray (Torpedo californica) is a species of electric ray in the family Torpedinidae, endemic to the coastal waters of the northeastern Pacific Ocean from Baja California to British Columbia. The electric ray, also called torpedo, torpedo fish, numbfish, or crampfish, any of the rays of the families Torpedinidae, Narkidae, Narcinidae, and Hypnidae, named for their ability to produce electrical shocks. It generally inhabits sandy flats, rocky reefs, and kelp forests from the surface to a depth of 200 m (660 ft), but has also been known to make forays into the open ocean.

Measuring up to 1.4 m (4.6 ft) long, the Pacific electric ray has smooth-rimmed spiracles (paired respiratory openings behind the eyes) and a dark gray, slate, or brown dorsal coloration, sometimes with dark spots. Its body form is typical of the genus, with a rounded pectoral fin disc wider than long and a thick tail bearing two dorsal fins of unequal size and a well-developed caudal fin.

These large flattened rays often lie partially buried on sandy seafloors, where they use a specialized sensory system to detect the electrical stimuli of potential prey and then attack them by ambush. The predator wraps its body around a halibut or mackerel and uses special kidney-shaped organs to produce a stunning electric charge of up to 50 volts.

The only electric ray found off western North America, the Pacific electric ray occurs as far south as Sebastian Vizcaino Bay in Baja California, and as far north as the Dixon Entrance in northern British Columbia. It is most common south of Point Conception, California, with the rays north of the Point perhaps representing one or more separate populations.