By Claire Preston
Last time we talked about the fishing technique called purse seining – one of the most common means of catching fish in the pelagic (surface and sub-surface) zones of the ocean. This time we will investigate gillnets, a fishing method that is used near the surface, mid-water, and on the bottom of the ocean to catch many different species of fish, and incidentally they catch many species that fisher harvesters don’t intend.
Gillnets can be comprised of single, double, or triple netting walls, using a nearly invisible nylon monofilament line that will either entangle or enmesh fish before they are hauled to the surface. As you can probably imagine, these monofilaments are quite small, so inevitably they have a high rate of incidental catch (bycatch), including a number of endangered species, like sea turtles and sharks. In fact, the gillnet fishing industry poses a significant threat to the sea turtle population, as gillnets are a major cause of sea turtle mortality. A gillnet fishery off the coast of California is causing a threat to three species of sea turtle, including the critically endangered Pacific leatherback. What makes this industry even more dangerous for these species is that modern vessels allow fish harvesters to travel greater distances into the sea, therefore setting their nets in locations that were once beyond their reach.
This is yet another excellent reason why it is important to manage our fisheries to not fish in places and at times where sea turtles (and other endangered species) are common. This is important because as fishing industries advance and expand, sea turtle populations may face greater risks from fishing nets .