Dangers posed by fisheries

The Corinthian lying at anchor in Charlotteville, in the north of Tobago.

On 5 Dec 2011, after having been held up for nearly 16 hours by customs and immigration in Charlotteville in the north of Tobago, we sailed to Store Bay in the south of the island. To make the last stretch into the bay, we had to tack against wind and current. Shortly before we reached our anchor spot, our boat was stopped as if held up by an invisible hand. Neither full ahead nor full astern helped. By the light of a flashlight we could see a line with floats – we were caught in an unmarked, illegally set fishing net.

We tried to cut ourselves free, but during our attempt to carefully maneuver out of harm's way, the nylon net wrapped itself around our propeller. On top of everything else, we were now unable to maneuver and in danger of drifting. An underwater high voltage line in the vicinity meant that we couldn't anchor. In the end, a local diver freed us from the net.

We came out of this adventure somewhat poorer but also an experience wiser, yet many marine animals are not as lucky. For them, getting caught in these nets means nothing less than certain death. In the statistics of fishery reports, these deaths are captured as “by-catch”, a term that includes all animals that are accidentally caught during fishing activities, such as in set nets, longlines or bottom trawls. Two well-known, sobering examples are dolphins that are caught in tuna nets or albatrosses that are pulled underwater by longlines; in both cases, the animals die by drowning.

WWF and Greenpeace estimate that each year approximately
300,000 whales and dolphins
100 million sharks
250,000 sea turtles
100,000 albatrosses
are killed as by-catch.

The following day, we freed our propeller from the remainders of the fishing net in several hours of diving. Then we continued our crossing towards Trinidad.

Thorsten Böhnke standing at the bow of the Corinthian, happy about the wind.

We sailed through the night without any incidents, but in the twilight of dawn we saw that we were towing a rope of some sort. This meant another round of swimming for Thorsten. It turned out that the buoy to which the floating line was attached had gotten caught in front of our keel. Approximately half an hour later we had a stick with flags, two styrofoam buoys and over 150 m of nylon rope on board. These objects had probably ripped free from a fishing net and were floating in the ocean.

Parts of a fishing net that we towed with us during the night. At dawn we could free ourselves from the flags, sticks, buoys and nylon rope and collect these objects on board – a small contribution to keeping our oceans clean.

Floating garbage presents a further danger to marine animals. Predators mistake the garbage for food and eat it. Their stomachs fill with indigestible plastic and as a result, the animals starve to death. Seabirds use ropes instead of natural materials to build their nests. At first sight unproblematic, this unnatural building material conceals dangers for the birds – they get entangled in the ropes and strangle themselves when they take off or land.

Large plastic objects, such as the styrofoam buoys that we found, become brittle due to solar radiation and are then broken down into small pieces by wave action. These plastic particles are eaten by tiny animals, zooplankton, and enter the marine food web. Their effects are largely uninvestigated. In the Pacific, we will start a research project about plastic garbage floating in the oceans and then write more about this topic.