Complex sentence: Predation by sharks, such as the tiger shark, reduced pup survival as the result of human disturbances, ciguatera poisoning, high male to female ratios during the breeding season, and entanglement in fishing nets and debris have killed many animals.
Split into simpler sentences: Predation by sharks, such as the tiger shark, reduced pup survival. As the result of human disturbances, ciguatera poisoning, high male to female ratios occured during the breeding season, and entanglement in fishing nets and debris have killed many animals.