Using Buoys To Keep Seabirds From Becoming Bycatch

“Bycatch” refers to the accidental catching of species of non-human marine animals not intended to be caught and killed for human use. Often, this happens as a result of bottom trawling—a fishing practice where a large net is towed along the ocean floor by a ship, thus scooping up crab, shrimp, flounder, and other “desirable” bottom-dwelling species. Other similar practices include gillnet and longline fisheries. Respectively, these involve setting large nets where the mesh is wide enough for fish to get their heads but not their bodies through (thus they become stuck at the gills), and setting a giant fishing line with up to 5,000 smaller lines, all baited with hooks and set for anywhere from a few hours to several days.

While they are efficient at capturing target animals, these practices are also imprecise and indiscriminate. Huge numbers of sea turtles, dolphins, and various marine megafauna are also ensnared and killed, despite having little to no commercial value. These animals are often merely discarded, dying for nothing. For vulnerable and endangered megafauna especially, these practices pose tremendous conservation challenges and are a primary driver of population decline in several species. Less discussed, however, is the impact of these practices on seabirds, despite the fact that an estimated 400,000+ seabirds are killed every year as bycatch in gillnet fisheries alone. Worse still, several methods proposed to reduce this number are ineffective or unpopular among fishers — and as a result, are politically unattainable.

In a recent paper, a team of conservation researchers tried a novel approach to reducing the number of seabirds killed as bycatch, focusing specifically on long-tailed ducks in the Baltic Sea. Historically, techniques to deter these birds relied on scaring them away from the nets once they were already underwater. As mentioned, these methods simply didn’t work—they did not reduce bycatch and therefore the problem remained. One way used flashing white LED lights attached to the nets and in some cases actually made the problem worse. With this in mind, the researchers in this paper attempted to solve the problem from the top down: instead of trying to deter the ducks once already underwater, they planted a device on the surface meant to take advantage of many bird species’ instinctual aversion to “looming eyes.” Specifically, fear responses to looming stimuli are known to activate the collision-risk signal in many birds’ brains and other research shows that very obvious eyespots are more likely than other visual cues to trigger this response. Below is a picture of the buoy design for reference. It was mounted on a standard fishery buoy and fixed on top of a small turbine to catch the wind, which would then cause unpredictable and erratic movements to reduce the chance of the birds simply getting used to the buoy.

To test its effectiveness, the researchers set up an experiment where they first watched a small area of the sea for several months to determine the typical abundance of long-tailed ducks in the area. They later installed several buoys at varying distances from the gillnet and tracked duck abundance for several weeks afterward, measuring carefully how many ducks were in the area as well as other variables that might influence that number, such as weather conditions, wind speed, the state of the sea, and others. Complex statistical analyses and a machine learning algorithm showed that the prototype of the device tested in this paper could reduce the abundance of long-tailed ducks by approximately 20-30% within a 50-meter radius.

To be sure, the authors of this study caution that replication and further testing of the buoy is needed to draw any hard conclusions. Nevertheless, they are excited by the possibility that their device may be effective in saving nearly 7,000 long-tailed ducks every year in the Baltic Sea. Moreover, although this study focused on the ducks, other seabirds may also experience similar benefits. Although they did see some evidence of the ducks habituating to the buoys, the researchers note that this may have simply been due to the seasonality of ducks in the area, rather than long-term ineffectiveness of the buoy.

In a world where humans continue to eat and use non-human animals in various ways, the welfare of these animals is critical. Perhaps one day, we may move past this practice, but in the meantime, harm reduction both moves us closer to that cruelty-free reality and improves the existence of animals alive today. The innovation presented in this paper is one example of such an approach. Potentially reducing the number of seabirds killed as bycatch in the Baltic Sea by nearly a third in a given year is a tremendous gain for those animals. Further advances may raise that number higher still—an optimistic, hopeful, and very possible future for animal welfare advocates and the long-tailed ducks. Ultimately, extending this idea further to many more species in many different contexts offers a chance to significantly reduce the amount of suffering experienced by non-human animals stuck in the middle of it all.