sentences:  Among the reasons for this drop off are overfishing and the rise in demand for shark fins.Researchers attribute this growth in demand to the increase in shark fins as an expensive delicacy (such as in shark fin soup) and are calling for a ban on shark finning, a practice in which the shark's fins are cut off and the rest of the animal is thrown back in the water to die.Hammerheads are among the most commonly caught sharks for finning.