A Simple Method Of Preventing Dolphin Bycatch

While interactions between marine mammals and fisherman have occurred for centuries, they have increased in both frequency and intensity in recent years due to growing levels of fishing activity around the world. Attempts to reduce these interactions come from two distinct but often overlapping groups: advocates seeking to protect marine mammals, and fisherman seeking to stop marine mammals from destroying gear and interfering with fish.

This paper, published in Ocean & Coastal Management, describes the Dolphin Wall Net (DWN). This is a new method of preventing dolphins from interacting with ring seines (large nets used to surround and capture schools of fish) developed by fishermen in Kerala, India. The authors conducted field studies and interviewed several groups of fishermen, all of whom take part in small-scale fishing operations using non-motorized boats. The fishermen stated that they were seeking a solution that would prevent dolphins from taking fish from nets without harming the dolphins.

As the authors describe, the DWN consists of a 1,000- to 1,500-meter long wall of netting with float line at the top and steel rings on the bottom that is deployed simultaneously with seine nets to prevent dolphins from approaching. The authors observe that the nets not only appear to effectively keep dolphins away but also consist of thick twine and wide webbing that increases acoustic reflectivity, enabling dolphins to detect the net through echolocation so that they do not become tangled in it. Fishermen who were interviewed agreed that the $200 cost to assemble a DWN is well worth it compared to the loss of fish and gear repair expenditures resulting from dolphin attacks.

The DWN may serve as an efficient method for preventing dolphin bycatch and is notable for being developed by small-scale fishermen who want to protect dolphins. Of course, making the process safer for dolphins does nothing to protect the fishes actually being caught. Still, the authors frame it as a positive: “(The DWN) is an eco-friendly conservation aspect followed by fishermen, which indirectly helps to protect the scheduled marine species.” They note that more research should be conducted to assess the merits and demerits of the DWN, but they express hope that it can eventually be adopted by seine fisherman throughout India and around the globe.