Workers remove the liver from a shark for processing at Keel Harbour, Ireland on July 3, 1954. The sharks were killed off Keem Bay because they made holes in the fishing nets and their bodies had commercial value.Haywood Magee/Corbis

There are five top reasons sharks are in trouble today. All of them are human-related, and most are decades-old anti-shark practices that are only now just seeing a turning tide.

Top of the list is the onset of industrial fishing, which for more than 60 years has drastically depleted many shark populations. Commercial fisheries targeting sharks exist throughout the world. Sharks are primarily targeted for their fins, meat, liver oil, and cartilage.

Shark Week: The Good and Bad Since Last We Met

A dragger hauls in a net with Spiny Dogfish Shark (Squalus acanthias), Yellowtail Flounder (Limanda ferruginea), Atlantic Cod fish (Gadus morhua), and Little Skate (Leucoraja erinacea) from Stellwagen Banks, off the New England coast.Jeffrey Rotman/Corbis

Bycatch is the part of the catch that is not targeted but caught and killed by commercial fishing gear. In essence it is unregulated and often unreported, and contributes to the mortality for many shark species worldwide.

Glass containers filled with shark fins at a store in Chinatown on August 24, 2011, in San Francisco. California State Assembly Bill 376 banned the sale, purchase or possession of shark fins in California starting Jan. 1, 2013.Justin Sullivan/Getty Images

The value of shark fins has escalated in recent years, and the minimum value of the global shark fin trade has been estimated at US$400 to US$500 million a year. Shark fins are primarily used in the Asian dish shark fin soup.

ANALYSIS: US Shark Fin Soup Appalling and Widespread

A tasselled wobbegong shark is seen eating a brown-banded bamboo shark on the fringing reef of Great Keppel Island on Australia's Great Barrier Reef in this August 1, 2011 handout.Australian Research Council's Centre of Excellence for Coral Reef Studies/Tom Mannering/Corbis

Globally, the existing state of management for sharks is inadequate to protect these animals. Shark conservation and management is a piecemeal approach of varying measures at the domestic, regional, and international levels.

ANALYSIS: State vs Fed Clashing on Shark Protections

Tourist snorkeling with small blacktip sharks (Carcharhinus limbatus) and a variety of colorful reef fish including the brilliantly colored Pacific double-saddle butterflyfish (Chaetodon ulietensis) during a lagoon safari trip in Bora-Bora Lagoon.Michele Westmorland/Corbis

Sharks get a bad rap and are often portrayed as mindless killers in the movies. The truth is, sharks play an important role at the top of the ocean food chain and their depletion has risks for the health of the marine environment.