Over-fishing

What is it? Over-fishing occurs when the catch is at a rate greater than natural reproduction can sustain. Worldwide, we are removing 180 billion pounds of fish and shellfish every year! By-Catch - non-target fish species and invertebrates of no commercial value –Unwanted fish and other animals are usually thrown back into the sea dead, injured, or so weakened that they are easily killed by predators. –At least one fifth of marine catch is by-catch.

Methods of Commercial Fishing Long Lines –Up to 15 miles long lines with many hooks attached to branched lines. Problem: Any kind of fish may be caught and fish may bleed to death before they are brought up. Drift Net Trawling –Nylon nets that hang suspended in the water for up to 30 miles! Problem: These often break free of the ship and become “ghost nets” floating in the ocean entangling and killing other marine life. Bottom Trawls –A bag shaped net that is drug over the sea bed to catch bottom-dwelling fish Problem: rips up sea grasses and other benthic habitats, increasing sedimentation An area twice the size of the United States is trawled every year. Purse Seine Nets –Nets that are drug behind boats. The two sides are pulled together to capture the fish. Problems: Fish are often crushed to death by all the fish on top of them. This is how tuna were caught, which drowned many dolphins

year old piece of coral picked up in a bottom trawl.

Effects of Over-fishing 70% of the world’s fish species are either fully exploited or depleted (not able to be commercially caught anymore). Industrial fishing has reduced populations of large fish by 90% in the past 50 years! –Specific examples include the Pacific Cod, Atlantic sturgeon and Rockfish. –The Pacific Red Snapper populations has declined by 99.3% in the past 25 years! Commercial harvested fish populations could be gone in the next 40 years!

More Effects Biodiversity decreases –By depleting certain species, other “non-valuable” species take over, killing off the others even more. Causes problems in food chains –Ex: The Stellar Sea Lion’s population has decreased by 90% and is now endangered because they eat the Pacific Cod 1 in 5 people on Earth depend on fish as their primary source of protein. Could be detrimental to the 200 million people living in these developing nations.

What are we doing to help? Many areas have law and regulations as to what type of fishing is allowed. Using new technology that reduces the amount of by-catch while increasing yield –By-Catch Reduction Trawls –Species Excluding Nets –Circle Hooks Marine Reserves where fishing is prohibited. Laws require fish sellers to identify the source of seafood. –Be an informed consumer: only buy products from well- managed fisheries

By-Catch Reduction Trawl The SLED (Sea Lion Exclusion Device) is designed to reduce the number of marine mammals such as seals and sea lions that are trapped in the trawl nets of squid-fishing boats. The device allows sea lions to escape through the top hatch, while squid pass through a metal grid and get caught at the end of the net.

Species Excluding Net These type keep the fish and by-catch alive, so that they can be returned to the ocean alive and unharmed if need be.

Circle Hooks Will almost always catch the fish’s jaw even if they try to swallow it. This allows for the fisherman to release the fish unharmed. Increases catch by 20%. Catches Sea Turtles and Marine Birds less than “J” hooks.