Life thrives in the Genkai SeaーNHK WORLD-JAPAN NEWS

Key Concepts

• Genkai Sea: A biologically diverse marine region south of the Sea of Japan, characterized by warm currents.
• Seasonal Spawning: The biological process where marine species, specifically cuttlefish, utilize seaweed and specific structures to lay eggs during early spring.
• Sustainable Fishing Practices: Methods that incorporate the return of egg-laden branches to the sea to ensure population regeneration.
• Marine Biodiversity: The variety of species (rockfish, flounder, yellowtail, red seabream, cuttlefish) coexisting in a specific ecosystem.

Marine Ecosystem of the Genkai Sea

The Genkai Sea, situated south of the Sea of Japan, is sustained by warm currents that foster a highly productive fishing ground. Despite water temperatures hovering around 13°C in February, the region exhibits significant biodiversity. Key species observed during this early spring period include:

• Rockfish: Often referred to as the "fish that welcomes spring."
• Flounder: A bottom-dwelling species that utilizes camouflage in the sand.
• Yellowtail: Large migratory fish, typically reaching lengths of approximately one meter.

Cuttlefish Spawning and Harvesting Methodology

The video highlights a specific interaction between cuttlefish and the local environment during their spawning season, which spans from February to May.

The Spawning Process:

1. Habitat Selection: As seaweed begins to grow in early spring, cuttlefish (averaging 30 cm in length) are naturally drawn to these areas to deposit their eggs.
2. Fishery Technique: Local fishers utilize specialized cages to capitalize on this behavior. They insert holly branches into the cages, which serve as artificial substrates that mimic the seaweed, attracting the cuttlefish.
3. Predatory Dynamics: The environment is highly competitive; the footage captures a large red seabream attacking a cuttlefish as it attempts to enter the trap.

Sustainability Framework: A critical aspect of the local fishing practice is the conservation of the species. After the harvest, fishers return the holly branches—now covered in gray cuttlefish eggs—back into the sea. This methodology ensures that the life cycle is not interrupted and that the population can continue to regenerate for future seasons.

Economic and Ecological Observations

Journalist Tateoka Atsushi notes the efficiency of this traditional method. During a typical outing, a fisher estimated a catch of approximately 100 cuttlefish, noting that this yield occurs when roughly half of the deployed traps are successful. This indicates a high density of marine life in the Genkai Sea during the transition from winter to spring.

Conclusion

The Genkai Sea serves as a prime example of a resilient marine ecosystem where life thrives despite cold temperatures. The synergy between the natural spawning behaviors of species like the cuttlefish and the sustainable, observation-based harvesting techniques of local fishers highlights a balanced approach to utilizing marine resources. By returning egg-laden branches to the water, the local community ensures the continued vitality of the Genkai Sea, marking the arrival of spring with both a harvest and a commitment to future life.