The term “bycatch” has become a popular one for people interested in sustainable fishing, and became so due to people searching for “dolphin-safe” tuna. Dolphins are known to swim with schools of tuna and have even been used by fishermen as a surface indicator of the presence of tuna, and, as such, have been scooped up and killed with the tuna. Many fisheries have been labeled “unsustainable” because they pull in enormous amounts of bycatch, and not just dolphins. Bycatch in commercial fisheries is a massive waste of ocean life that can threaten entire species. Understanding how to avoid buying seafood that kills a large amount of bycatch can be key to sustainable eating and to keeping good relationships with concerned customers.
Our topic today is the conservation of sea turtles, a particularly captivating and ecologically-important group of seafaring reptiles. All seven species of sea turtles lay their eggs on sandy beaches and feed in coastal waters. Since they must share coastal waters with fishermen, they are tremendously susceptible to being caught as bycatch. It is thought that millions die each year from becoming entangled in nets and lines. Researchers are working with fishermen to find cost-effective and efficient solutions that will reduce sea turtle deaths without impacting the livelihood of coastal communities. They have found awesome success in a very interesting study – adding ultraviolet lights to fishing nets.
An icon for marine conservation
There are few children in the world who would not instantly fall in love when presented with a sea turtle, and not just because they make exceptionally adorable plush toys. These lovable reptiles are gentle and charismatic, graceful yet innocent, a perfect example of the beauty that the sea holds beneath its waves.
The seven species that comprise the world’s sea turtle populations are astounding animals. Many of them travel thousands of miles between nesting grounds and feeding grounds. The leatherback sea turtle can grow to an astonishing 10 feet in length and weigh up to 2,000 pounds, putting a full-grown adult at about the size of a small car. They all spend their entire lives at sea, with the exception of females coming ashore to lay eggs every 2-5 years. Each species prefers a different entrée: green sea turtles graze on sea grasses; leatherbacks consume jellyfish and soft-bodied animals at a fantastic rate; hawksbills munch on sponges and other invertebrates; loggerheads and the Kemp’s ridley prefer crabs.
Fossil evidence has shown us that sea turtles have been on Earth for more than 100 million years, outliving the dinosaurs. But now sea turtles are in trouble. Two of the seven species are endangered and three are considered critically endangered. Their charming image and threatened status has made them an icon for marine conservation.
They are extremely vulnerable to human activity and the threats are numerous. Nesting sites can be destroyed by coastal development. Pollution like plastic bags can resemble jellyfish and be ingested, blocking the intestines and leading to serious injury and even death. Artificial light from cities and towns has been known to disorient baby sea turtles, drawing them into urban areas in their quest for a watery horizon. In some countries they are hunted for meat, shells and eggs. When caught in fishing gear, they can drown.
There is current research into ways that fishermen can help prevent deaths of sea turtles. Since sea turtles wrapped in nets and lines can cause a lot of damage to fishing gear, it is actually very much in the interest of fishermen to find ways to prevent the turtles from becoming entangled.
Sea turtles steer clear of illuminated nets
Researchers have discovered that sea turtles can actually see different types of light than many fish. One study found that green sea turtles stayed clear of nets with green light-emitting diodes (LEDs). The loggerheads and leatherbacks were found to be sensitive to ultraviolet light. While some species of fish can also see UV light, several economically-important fish do not. This is very convenient for the purposes of conservation. Scientists asked the question: would sea turtles actually avoid these lights while traveling underwater?
A very promising study was conducted off the coast of Punta Abreojos, Mexico, which has a large green sea turtle population. Gillnets are the commonly used fishing gear here, a type of net that doesn’t discriminate between fish and sea turtles. Researchers cast 11 pairs of gillnets; each pair had one net fitted with UV LED lights and the other control net was dark. Any and all turtles caught were released. At the end of the study period, 332 green turtles had been caught – 123 in the UV LED nets and 209 in the dark nets. Scientists drew the conclusion that the UV LEDs reduced the number of sea turtles caught by almost 40%.
A second set of similar experiments focused on the effect of the lights on commercially valuable fish. With a total catch of 664 fish caught, 309 were in nets with the lights and 355 in the dark nets, an almost insignificant difference. They even went as far to analyze the market value of the catch in each type of net. The lighted nets contained a value of $15.00/fish, compared with $15.01 for the dark nets. The lighted nets therefore did not decrease the value of the desired catch hardly at all – great news for fishermen and for turtles!
This initial research gives us cause to celebrate. We have the potential ability to save thousands, even millions of sea turtles. One major concern is cost – many fishermen in coastal communities support families and are hard-pressed to find the time and money to invest in a marine conservation project. However, with the cost of UV lights at $2.00 and dropping, fishermen that participate would likely save money by avoiding turtle-caused damage to their gear. Researchers even say that it might even be possible to engineer lights that emit different wavelengths, scaring off turtles but attracting desirable fish species. And we are moving forward with an international effort – further research on the illuminated nets has already begun in Peru, Baja California, Brazil and Indonesia.
Conservation leads to sustainable fisheries
Technology and advancing research are allowing science and conservation to converge with fisheries management. With the result will being more healthy oceans, it is very important that we support these efforts. Healthier ecosystems means healthier fish and shellfish and thus better seafood for us. Support sustainable fisheries by choosing Pucci Foods, a distributor that cares about the health of our oceans.