Fishing and Dolphins: Better Education for Better Prevention

Wild dolphins are frequently found entangled in fishing lines and other marine debris. And unfortunately, this can have serious consequences. However, these consequences are studied far too infrequently, simply because it is difficult to track the fate of a dolphin that has been caught in such traps and survived to tell the tale.   In rare cases, dolphins can be successfully freed from fishing lines, released back into the wild, and then examined after their death to better understand the causes of death and the long-term effects of entanglement in fishing lines. This was the case for a young bottlenose dolphin that was rescued off the coast of Indian River Lagoon, Florida, a few years ago . A monofilament fishing line had wrapped around its upper jaw. Once freed, it was immediately released back into its natural habitat, though with visible aftereffects. A year after its rescue, photos and observations indicated that the young dolphin, now independent, was in a concerning state of health. Despite a healed jaw, its ribs were very visible, and it had a prominent post-nucal depression. And unfortunately, more than two years after his rescue, the animal’s carcass was found with numerous injuries likely resulting from a predator attack. However, this was probably just the end of the story. Despite a half-full stomach, the animal was emaciated, indicating that it had been suffering long before the attack. And a necropsy did indeed reveal repeated encounters with fishermen. In addition to the primary trap, which had caused significant and permanent bilateral deformation of the maxillary dental arch, external evidence of propeller scars and a fishing hook found embedded in the laryngeal mucosa attested to regular encounters with fishing gear.

The effects of fishing can therefore have repeated and long-term consequences for the animals.

And, as with many other dolphins and cetaceans, contact with fishing gear and nets may have restricted the mammal’s movements and impaired its ability to find food. This may have led to malnutrition or undernutrition, weakness caused by tissue damage, pain, or distress, and systemic infections, inevitably resulting in death. While the rapid response to free this dolphin may have initially saved the animal’s life, it did not prevent it from repeatedly finding itself in the same situation, which ultimately led to its death. Better prevention efforts targeting fishermen to limit these interactions could have extended its life well beyond the two years it lived. It is important to educate fishermen on the importance of retrieving their lines when dolphins are present and of properly stowing fishing gear to reduce the risk of these harmful interactions with cetaceans. This would benefit all parties—fewer injured or dead cetaceans, as well as less damaged fishing gear.