Looking at octopus aquacultureーNHK WORLD-JAPAN NEWS

Key Concepts

• Octopus Aquaculture
• Climate Change Impact on Fisheries
• Larval Survival Rates
• Cannibalism in Octopuses
• Tank Redesign for Aquaculture
• Water Flow Dynamics in Tanks
• Octopus Consumption and Demand
• Fisheries Decline
• Technological Innovation in Aquaculture

Octopus Farming: A Solution to Declining Catches

Octopus is a popular and highly valued seafood in various global cuisines, including Asian (especially Japanese), Mediterranean, Mexican, and African. In Japan, it is considered a delicacy, enjoyed in diverse forms such as sashimi, simmered dishes, deep-fried preparations, and the street food takoyaki. Despite its culinary appeal, the global appetite for octopus, coupled with its health benefits (low in calories, high in protein), has led to increased demand.

Challenges in Octopus Catches and Rising Prices

The escalating demand has resulted in a significant decline in wild octopus catches in Japan. This decline is attributed to several factors, including:

• Warming Waters: Climate change is causing ocean temperatures to rise, impacting the food sources available for octopuses.
• Increased Predation: Warmer waters may also lead to an increase in the populations of fish that prey on octopuses.

This reduction in supply, combined with rising global consumption, has caused octopus prices to skyrocket. Consequently, Japan is increasingly reliant on expensive imports.

The Quest for Octopus Aquaculture

In response to these challenges, a Japanese research institute in Hiroshima, the National Fisheries Research Institute, has been dedicated to developing techniques for octopus aquaculture for approximately 10 years. This endeavor is considered a challenging proposition due to the inherent difficulties in raising octopuses from hatching.

Overcoming Larval Mortality: Tank Redesign and Water Flow

A primary obstacle in octopus farming is the high mortality rate of newly hatched larvae. The transcript highlights a critical issue:

• Feeding Difficulties: Newly hatched octopus larvae struggle to consume their feed. The weight of the feed causes both the larvae and the feed to sink.
• Larval Behavior: Larvae naturally tend to rise towards the bright surface of the water. This behavior causes them to miss the sinking feed at the bottom of the tank, leading to weakness and death.

The research team addressed this by redesigning the tanks and manipulating water flow. Their innovative solution involved:

• Upward Water Flow: Creating an upward flow of water by jetting it onto the tank floor. This innovation allows the hatchlings to easily access the feed as it is brought upwards.
• Survival Rate Improvement: By adjusting feed types and other techniques in conjunction with the redesigned tanks, the team achieved a survival rate exceeding 90% for juveniles.

Addressing Cannibalism in Juvenile Octopuses

Another significant challenge encountered as the octopuses grew was cannibalism. To mitigate this, the researchers implemented a structural solution:

• Individual Cubicles: Each young octopus is housed in its own cubicle. This design prevents them from seeing each other, thereby reducing the instances of cannibalism.
• Extended Juvenile Rearing: This method has made it easier to raise young octopuses for periods exceeding 60 days after hatching.

Future Prospects and Ethical Considerations

The National Fisheries Research Institute aims to achieve commercial viability for its octopus farming technology by the end of fiscal year 2028. The transcript acknowledges the significant passion and effort invested by researchers and fisheries in making these breakthroughs.

However, the text also raises an important ethical discussion:

• Animal Intelligence and Sensitivity: There is an ongoing debate about the ethical implications of farming octopuses, given their known sensitivity and intelligence. This topic is expected to remain a subject of discussion.

Conclusion

The research into octopus aquaculture represents a critical step towards addressing the declining wild catches and meeting the growing global demand for this popular seafood. By overcoming significant biological and environmental challenges through innovative tank design and rearing techniques, the National Fisheries Research Institute is paving the way for a more sustainable future for octopus consumption. Nevertheless, the ethical considerations surrounding the farming of such intelligent creatures will continue to be a vital part of the conversation.