recreationally, blue sharks are considered a sport fish, and large individuals provide a challenge for fishermen. most commercially caught blue sharks are considered bycatch. it is estimated that 10 to 20 million are killed each year, possibly having a negative impact on world populations. the salmon, mackerel, and sardine fisheries are affected by blue shark predation on catches, and entanglement in nets. the fins of blue sharks are sold to asian markets and are used to make shark-fin soup.