n.

any of numerous elongate mostly marine carnivorous fishes with heterocercal caudal fins and tough skin covered with small toothlike scales

a person who is ruthless and greedy and dishonest

a person who is unusually skilled in certain ways

"a card shark"

Cascading effects of the loss of apex predatory sharks from a coastal ocean
The effects of fishing on sharks, rays, and chimaeras (chondrichthyans), and the implications for marine ecosystems
Sharks and Rays of Australia
Sharks of the World
Standardized diet compositions and trophic levels of sharks
Rates of mitochondrial DNA evolution in sharks are slow compared with mammals
Sharks and Rays of Australia.
...and conservation of the world’s sharks and rays
Intrinsic rebound potentials of 26 species of Pacific sharks
Sharks and rays of Australia