Eastern Pacific Shark Species
By Tara A. Spears
My reason to educate myself about the species and habits of sharks began more than 20 years ago due to a personal encounter with these predators. My sons and I were fishing in south Florida, having an exceptional morning having landed more than 50 fish. By noon it was hot so we put down the rods and dove into the ocean. Foolish idea. As I was handing a cool soda to my youngest son- who was sitting in ankle deep water at the shore- he screams and leaps up, blood running down his back. To this day, he has scars from the 40 puncture marks from the shark bite.
The lesson we learned is that you do not swim where you have been catching fish, as the larger predators are also working the same school of fish. This incident didn’t deter my family from continuing to enjoy ocean water sports- both of my sons are certified scuba divers besides avid fishermen. We understand that every time we go into the ocean, there is a possibility of encountering predators so we take precautions.
According to University of Florida ichthyologist, George Burgess, who has researched sharks for 30 years, “The number of shark attacks could be cut in half if people used more common sense, such as avoiding fishing areas and inlets where sharks gather and leaving the water when a shark is sighted.” Rather than fear, I have respect for these amazing hunters after seeing so many of them live. It is so much more impressive than even the best Discovery Shark Week special!
Physical Characteristics Unique to Sharks:
Unlike ordinary fish, sharks have no bones; their skeleton is made of cartilage, which is a tough, fibrous substance, not nearly as hard as bone. Sharks also have no swim bladder, unlike the bony fish. Instead of scales, sharks have a tough hide-like skin. The shark’s senses are developed to enable it to successfully feed itself. Unlike most fish, the shark has strong olfactory perception. Once the shark picks up a scent, it swims up the trail moving its head from side to side to determine from which direction the odor is emanating. Most sharks possess excellent vision as they rely heavily on sight while hunting for food. Sharks also use the sense of touch to perceive prey: this perception can be split into actual touch or distant touch- where the shark ‘reads’ electrical impulses bouncing off of things in the distance.
Although considered a primitive species, sharks have a relatively large and complex brain. A shark’s brain to body mass ratio is higher than most other fish and is comparable to many other vertebrates, including some mammals. Brain size and complexity vary from shark species to species. The sharks with the largest brain to body weight ratio are active sharks like the dusky shark and the scalloped hammerheads. The sluggish bottom-dwellers (like angelsharks) have relatively smaller, less complex brains.
Sharks of all species continually shed their teeth and grow new ones. They have 40 or more teeth in each jaw. Behind the functional rows of teeth are seven other rows of teeth developing into mature dentures to replace teeth as they are shed or lost. Unlike us, shark teeth are not glued over roots. Amazingly, the shark is equipped with 15 rows of teeth inside their mouth enabling it to replace an old set of teeth within a day with a new set. Sharks replace around 6000 teeth each year yet they never run out teeth.
It’s their Party:
It’s no different for humans that go on safaris or hunt land animals: when you are in the shark’s natural environment, you need to be aware of their behavior and habits. Knowing where in the ocean sharks are likely to dwell, and at what depths they prefer, it’s fairly easy to coexist. Understanding that the different species have unique feeding preferences, water temperature requirements, and seasonal reproduction needs allow you to take precautions. Typically, the majority of shark species will be based around the warmer parts of the ocean, ranging throughout the central tropical regions of the Pacific and Atlantic oceans. There are many more shark species than what I have highlighted in these two articles, but I have chosen the species that either I have personally seen or know to inhabit the coastal area along the Mexican Riviera Nayarit.
Nurse shark: lives around reefs, mangroves, and sand flats. Depth: 0-130 m. size to 400 cm./14 ft
A large shark with a broad flattened rounded head; eyes small, oval; two dorsal fins of similar size; tail fin moderately long, about one-third of its total length. Yellowish brown to grey brown in color.
Oceanic whitetip shark: Oceanic inhabitant to depths of 200m. Grows to 396 cm/13 ft.
Moderately short, rounded snout; serrated upper front teeth broadly triangular; first dorsal fin very large and high, with broadly rounded tip; pectoral fins extremely long with broad round tips; Brownish grey on back, becoming white ventrally; tips of first dorsal fin, paired fins, and caudal fin lobes broadly mottled white; anal fin usually blackish at tip.
Pacific sharpnose shark: A common inshore shark that often lives in shallow estuary waters and goes to a depth of 100m. Grows to 154 cm/5 ft.
Slender body with a long pointed snout that is as long as the width of mouth; large round eyes; front teeth on both jaws, with narrow, slanting points; five gill slits; two dorsal fins, first much larger; pectorals broad, triangular; asymmetrical tail fin with large lower lobe, top lobe notched under tip. Grey or grey brown on back and sides, white below; rear edge and upper tip of tail fin broadly black.
Pelagic thresher/Thintail thresher: Oceanic dweller to depths of 700m. Length:365 cm/12 ft.
Body stout, cylindrical; head short, rounded between small narrow eyes, snout elongate, conical; forehead profile,; mouth small ventral; teeth small, pectorals very long, straight, with broad tips; upper lobe of tail extremely long-equal to body length. Blue to grey color with white belly.
Ragged-tooth shark /Smalltooth sandtiger shark/ Bumpytail ragged-tooth shark: Likes rocky shore ocean in depths of 10-530m. Grows to 410 cm/14 ft.
A large shark with a robust body and long, bulbous head with conical snout; large eyes; long mouth; 5 gill slits; all before pectoral; large teeth with prominent dagger-like middle point and 2-3 small points on either side; 2 dorsal fins with 2nd much smaller; asymmetrical tail fin with moderate notch and strong ventral lobe. Medium grey on back, light grey below; young with black tips on dorsal fins.
Scalloped/ Mallethead/ bonnethead shark/Scoophead hammerhead shark: Coastal specie that prefers soft bottom ocean floor to depth of 100m. The size varies among species but generally under 200 cm/6.5 ft
The distinctive mallet shaped snout; the width of the hammer is about 25% of its body length; blade-like front teeth are smooth with 1 slanted point; first dorsal fin moderately large and erect, with the second dorsal fin base about half its length; asymmetrical tail fin notched under tip of top lobe, large lower lobe. Grey on the back and side, white below.
Silky shark: found inshore but more abundant offshore at depth of 0-500 m. Grows to 350 cm./ 12 ft.
Slender-bodied; snout moderately long, flat and slightly pointed; body length in front of height of fin ~ ½ its length; 2nd dorsal and anal fins with long bases and long free rear tips; pectoral long, narrow, curved. Grey to dark grey dorsally, shading to white ventrally, sometimes with faint band of white invading grey of upper abdomen; fins may have dusky tips.
Silvertip shark: Lives coastal-pelagic inshore, common on outer reef slopes. Inhabits water usually less than 20m. deep. Size to 300 cm/ 10 ft.
Snout moderately long and broadly rounded, pectoral fin pointed. Grey, darker on back and shading to white
ventrally; distinctive white tips or margins on first dorsal, tail, and pectoral fins.
Smalltail shark: Inshore shark over mud bottoms, often in shallow estuaries in depths of 5-35 m. Grows to less than 150 cm/5 ft.
A slender, fusiform (spindle shaped) shark with long, pointed snout; large circular eyes; serrated top front teeth with narrow, notched points; first dorsal fin low with bluntly pointed tip; slightly curved, narrow pointed small pectoral fins. Generally grey on back and sides, white on lower parts; tips of pectoral, dorsal, and caudal fins may be dusky or blackish, but are not prominently marked.
S
wellshark: sluggish bottom-dwelling shark that prefers algae covered rocky reefs, depth 0-460m. Size up to 110 cm/ 4 ft
A stocky member of the catshark family; extremely short snout, eyes oval, with ridge above each; yellow- brown with variegated pattern of dark brown blotches, saddles, and spots on body and fins; underside of head and abdomen spotted.
Tiger shark: coastal ocean, stays in deeper water during the day and feeds on shallow reefs at night at depths to 350m. Grows to over 550cm/18 ft.
Head, and body stout but becoming very slender towards tail; very short, blunt snout; large, round eye; mouth large, wide; serrated cockscomb teeth; strong ridge on back between dorsal fins; origin of dorsal fin over posterior corner of pectoral fin; smallish pointed tip dorsal fin; sharp pointed, strongly asymmetric tail that has a large pointed lower lobe, with a low keel along each side of the narrow tail base. Adults are grey with vertical bars on upper half of sides (sometimes faint or absent); young with large dark spots, some coalescing to form bar.
