Chapter 1: Understanding Bycatch and Its Impacts

Bycatch, the unintended capture of non-target species during fishing, poses significant threats to marine ecosystems. With the global population on the rise, the need for food security intensifies. The United Nations aims to eradicate hunger by 2030, and fish play a pivotal role in addressing this challenge by providing essential nutrients, including omega-3 fatty acids.

However, fishing practices contribute to serious environmental issues. Ghost nets, which are discarded fishing nets left in the ocean, account for approximately 10% of marine debris. Each year, an estimated 500,000 to 1 million tons of such waste enter our oceans, endangering marine wildlife.

The ecological ramifications of bycatch are extensive, disrupting food webs and threatening both commercial and subsistence fishing communities. For instance, a fishing ban on knife fish in the Yangtze River has been implemented to facilitate their recovery.

Given the gravity of these consequences, minimizing unnecessary animal deaths is crucial. Thus, reducing bycatch is imperative, and various strategies have been proposed to achieve this goal.

Acoustic Deterrents

Acoustic deterrents leverage sound to influence marine animals' behavior. For instance, specific sound frequencies can deter sharks from approaching fishing gear. While effective, these acoustic cues often need to be paired with other sensory signals for maximum efficacy.

In addition to artificial sounds, natural calls, such as those from killer whales, can effectively deter certain shark species, though their effectiveness may vary regionally.

Olfactory Deterrents

Olfactory cues, or smells, can also play a vital role in deterring bycatch. Chemicals from decomposing sharks can repel other sharks, while different bait types can minimize bycatch rates. For instance, using squid instead of fish can reduce shark captures, depending on their dietary preferences.

Visual Deterrents

Visual deterrents involve the use of lights and colors to influence animal behavior. Green LEDs have shown promise in reducing shark bycatch significantly, but further research is needed to validate these findings. Techniques such as using scaring lines can also deter seabirds from approaching fishing gear.

Electrosensory Deterrents

Electrosensory deterrents exploit the ability of some marine animals to sense electrical fields. Ferrite and neodymium magnets can repel certain shark species, while SMART hooks, which incorporate magnetic properties, have shown mixed results in reducing bycatch.

Echolocation Reflection Deterrents

Echolocation reflection deterrents exploit the natural hunting techniques of dolphins and porpoises. By modifying fishing nets to reflect echolocation signals, these animals may be able to detect and avoid traps more effectively, although more research is necessary to confirm these findings.

Chapter 2: Taking Action to Reduce Bycatch

The second video titled "Bycatch - Explained" provides insights into the issue of bycatch and its implications for marine ecosystems.

Conclusion

The reduction of bycatch can be achieved through a combination of acoustic, olfactory, visual, and electrosensory deterrents, as well as by reflecting echolocation signals. While some methods have demonstrated effectiveness, others require further evaluation. Integrating various sensory cues may enhance the overall success of these strategies.

Practical Steps for Individuals

Here are some actionable steps you can take to contribute to bycatch reduction:

• Immediately return bycatch to the water
• Utilize fishing gear designed to target specific species
• Avoid fishing in overfished areas
• Stay away from regions with high bycatch potential

What measures can you adopt in your fishing practices? Share your ideas to inspire collective action against bycatch!

References

This article is informed by:

Lucas, S., & Berggren, P. (2022). A systematic review of sensory deterrents for bycatch mitigation of marine megafauna. Reviews in Fish Biology and Fisheries, 1–33.