Elasmobranch

Elasmobranchs (Subclass Elasmobranchii) are cartilaginous fish characterised by: a skeleton entirely of cartilage (no bone), 5–7 pairs of exposed gill slits (no opercular cover), placoid scales (dermal denticles), urea-based osmoregulation, internal fertilisation (males have claspers), and ovoviviparous or viviparous reproduction in most species. They include approximately 1,200 species of sharks and 600 species of batoids (skates and rays). Most elasmobranchs are apex or mesopredators. Their slow growth, late maturity, and low fecundity make them extremely vulnerable to overfishing.