Body size - Subclass Elasmobranchii

Body size

When compared with bony fishes, sharks as a group have always been relatively large. Modern sharks range from the 15 g, 17 cm Dwarf Lantern Shark, Etmopterus perryi (Etmopteridae), and several sharks in the 22–25 cm range (e.g., dalatiid pygmy sharks,Squaliolus laticaudus and S. aliae; proscyliid Pygmy Ribbontail Catshark, Eridacnis radcliffei) to the 4000 kg, 10 m Basking Shark,Cetorhinus maximus, and the 12,000+kg, 12+m long Whale Shark, Rhincodon typus (Rhincodontidae), the largest fish in the world. At least 90% of living sharks exceed 30 cm in body length, 50% reach an average length of about 1 m, and 20% exceed 2 m (Springer & Gold 1989). Maximum sizes of sharks, particularly the maximum size reached by the superpredatory White Shark (Lamnidae), is a subject plagued by misinformation and exaggeration.

Large size is intimately linked with the feeding and reproductive ecology of sharks. As predators on other fishes, including other elasmobranchs, large size confers an advantage in terms of greater swimming speed during pursuit or long-distance cruising, and allows for larger mouth size and larger jaw muscle attachment. Such traits make sharks effective predators on smaller fishes and also decrease their own vulnerability to predators, either via rapid escape or active defense.  

It is suggested that sharks larger than 1 m long are relatively immune to shark predation, and it is not surprising that birth sizes of many sharks are close to the 1 m critical length (e.g., Sand Tiger, Odontaspididae; White and Longfin Mako, Lamnidae; Dusky, Carcharhinidae). Sharks that give birth to smaller young often have relatively large litters or short intervals between reproduction (e.g., Atlantic Sharpnose, Carcharhinidae; Scalloped Hammerhead and Bonnethead, Sphyrnidae). Predation also affects nursery ground location and interacts with growth rate. Sharks that drop their pups in offshore or beachfront areas that are frequented by large sharks tend to have relatively rapid growth rates of 30–60 cm during the first year (e.g., Thresher, Alopiidae; Shortfin Mako; Blue, Tiger, Spinner, and Sharpnose, Carcharhinidae; Bonnethead).

Sharks that release their young in relatively predator-free inshore nursery areas such as bays, sounds, estuaries, or shallow reef flats tend to grow only 15 cm in the first year Hammerhead and Bonnethead, Sphyrnidae). Predation also affects nursery ground location and interacts with growth rate. Sharks that drop their pups in offshore or beachfront areas that are frequented by large sharks tend to have relatively rapid growth rates of 30–60 cm during the first year (e.g., Thresher, Alopiidae; Shortfin Mako; Blue, Tiger, Spinner, and Sharpnose, Carcharhinidae; Bonnethead). Sharks that release their young in relatively predator-free inshore nursery areas such as bays, sounds, estuaries, or shallow reef flats tend to grow only 15 cm in the first year (e.g., Bull, Sandbar, and Lemon, Carcharhinidae; Scalloped Hammerhead) (Branstetter 1990, 1991).