3.3  Yellow Fin Tuna Aquaculture Business Development Analysis

3.3.1 Yellow Fin Tuna Overview

The yellow fin tuna is among the larger tuna species, reaching weights over 180 kg (400 lb), but is significantly smaller than the Atlantic and Pacific bluefin tunas, which can reach over 450 kg (990 lb). They are pelagic fish that inhabit the mixed surface layer of the ocean above the thermocline. Although mainly found in deep offshore waters, yellow fin tuna may approach shore when suitable conditions exist. Mid-ocean islands such as the Hawaiian archipelago, other island groups in the Western Pacific, Indonesia, Maldives islands in the Indian Ocean, Caribbean, as well as the volcanic islands of the Atlantic such as Ascension Island and Saint Helena, often harbor yellow fin tuna close to the shoreline. Yellow fin may venture well inshore of the continental shelf when water temperature and clarity are suitable, and food is abundant.

The yellow fin tuna is among the larger tuna species, reaching weights over 180 kg (400 lb), but is significantly smaller than the Atlantic and Pacific bluefin tunas, which can reach over 450 kg (990 lb). They are pelagic fish that inhabit the mixed surface layer of the ocean above the thermocline. Although mainly found in deep offshore waters, yellow fin tuna may approach shore when suitable conditions exist. Mid-ocean islands such as the Hawaiian archipelago, other island groups in the Western Pacific, Indonesia, Maldives islands in the Indian Ocean, Caribbean, as well as the volcanic islands of the Atlantic such as Ascension Island and Saint Helena, often harbor yellow fin tuna close to the shoreline. Yellow fin may venture well inshore of the continental shelf when water temperature and clarity are suitable, and food is abundant.

A school of yellow fin tuna

Yellow fin tuna often travel in schools with similarly sized companions. They sometimes school with other tuna species and mixed schools of small yellow fin and skipjack tuna. Yellow fin tuna preys on other fish, pelagic crustaceans, and squid. Like all tunas, their body shape is bullet shaped, particularly adapted for speed, enabling them to pursue and capture fast-moving baitfish such as flying fish, sauries, and mackerel, with maximum speed up to 80km/hour.

A new report by an international tuna conservation commission indicates the stock of Atlantic bluefin tuna has plummeted to just 13% of its levels 50 years ago. With decades of overfishing and dwindling population of bluefin tuna, yellow fin tuna becomes more valuable as luxury cuisines and therefore a prime target for aquaculture research, especially because bluefin tuna is much harder to hatch, nurse, and grow to adulthood.

3.3.2 Yellow Fin Tuna Research Effort in Indonesia

Efforts to culture yellow fin tuna has been done in many countries such as Japan, Australia, Panama, USA, and some European countries. In 2001, Indonesian government and Japanese government started a Yellow fin Tuna Hatchery Research Project in Gondol Marine Aquaculture Research Center and Fishery Advisor located in Bali. It was found that tuna aquaculture success is determined mainly by the success of hatching, which has the highest risk of failure. Until now, hatching stage survival rate is very low, with the primary reason of feed management and unsuitable nutrient contents, and tuna fish hitting the basin walls.

3.3.3 Early Yellow Fin Tuna Morphology and Growth

Yellow fin tuna grows slowly at the beginning after hatching, but after a certain period it grows very fast. Right after hatching, yellow fin tuna does not have a mouth. Instead, it has a nutrition sack that would last it for four days. After four days, this sack will be depleted, and a mouth will form, and it has to find its own food to survive. It feeds on rotifers and copepod, and after several days it can feed on certain fish larvae. From day 1 to day 16 it is transparent. Beginning from day 16, it will start to develop silvery scales on its body. It will also begin the rapid growth phase of tuna, where tuna will grow very quickly in terms of both size and weight. However, this is completely dependent of the feed that is given on day 7 to 8, where food given on day 7 to 8 will affect this fast-growing phase.

To solve the issue of fish hitting the basin walls, we propose of growing the juvenile tuna directly inside HDPE cages in the sea, just like what Gondol Marine Aquaculture Research Center and Fishery Advisor did back in 2014 with great success. Membranes will be used on the HDPE cages as a separator of its habitat from open seawater. This will greatly increase the survival rate of the tuna fish, firstly because the size of the HDPE cages is larger than a land basin, the chance of tuna fish hitting the wall is greatly reduced. Secondly, larger swimming area in HDPE cages gives more freedom for tuna fish in swimming, resulting in faster metabolism. These factors combined with less light and less perceived human activity equals less stress and higher survival rate for tuna fish. Thirdly, because membrane is much softer than concrete or plastic wall of a land basin, even on the event the tuna fish hit the membrane, it will not harm the fish. By growing tuna directly inside HDPE cages in the sea instead of in the basin, the survival rate from day 10 to day 26 increased to around 20%, a twentyfold increase from the survival rate of growing juvenile tuna inside a land basin. This practice also have the added benefit of not requiring the operation to build a growing basin inside the decommissioned oil and gas platform, greatly reducing investment cost.

To further increase the survival rate, reducing cannibalism is the logical next step. Extra care must be given on feed distribution and nutrition during this sensitive period to keep the fish sated. If cannibalism can be reduced significantly, it is believed that the survival rate from day 10 to day 26 can be further improved from 20% to about 60%, another threefold increase.

3.3.4 Late Yellow Fin Tuna Morphology and Growth

From day 26 onwards, yellow fin tuna grows very fast. From 4cm at day 26, it can grow to 12cm at day 50. The diet consists larvae or live fish of smaller sizes, we recommend milkfish larvae because it can be produced on site as a consistent source of feed.

After 50 days, feed should be changed to live fish. At this stage, yellow fin tuna appetite is ferocious, each fish requiring about 5-10% of its bodyweight in feed daily. A typical tuna aquaculture business spends around 60-75% of its total cost in feed. To reduce this cost, we recommend several fish capture devices placed around the cage so that fish can be caught easily to satisfy the needs of feed of the yellow fin tuna, which potentially could reduce the cost of feed by 80%. Within 1 year, yellow fin tuna can grow up to 20-30kg. At this stage, it can breed by itself, with breeding month mostly occurring in August and September.

3.3.5 Hatching and Growing Yellow Fin Tuna

As we see above, the critical point in the survival rate of yellow fin tuna from hatch to juvenile is between day 10 to 26, where it drops from 65% all the way down to less than 1%. Therefore, in order to maximize the survival rate, yellow fin tuna will be hatched directly in HDPE cages in the sea. This is to: 1) build its natural adaptability in seawater from the very beginning, 2) avoid death of yellow fin tuna hitting hard basin walls, 3) provide larger swimming area for yellow fin tuna, 4) reduce stress from moving the tuna from basin to HDPE cages (because the tuna is already in HDPE cages), as well as the stress from human activity and excessive light, and 5) minimize the operational distance of caring for tuna larvae.

Aquatec invented a special HDPE cage where all stages of yellow fin tuna hatchery and growing are done in the sea. Each unit of Yellow Fin Tuna Hatchery and Growing System consists of:

1.  2.5m in diameter HDPE membranes inside octagonal cages

o  Water volume  : 60m³

o  Harvest density for yellow fin tuna  : 1,800kg

Tuna eggs are sifted with a special device and the good ones (the floating ones) are put inside 2.5m in diameter HDPE membranes inside octagonal cages to hatch. Once hatched, tuna larvae are grown for 16 days and given rotifers and copepods as food.

2.  4 octagonal HDPE cages 6.1m in Diameter with membranes, assembled together (knock-down) inside a round HDPE cage

o  Water volume  : 450m³

o  Harvest density for yellow fin tuna  : 13,500kg

After 16 days, the 2.5m in diameter HDPE membranes are opened, letting tuna larvae to enter the octagonal HDPE cages 6.1m in diameter with membranes. Tuna larvae are then grown up to day 50 to become juvenile tuna and given leftover tuna eggs alongside rotifers, copepod, and other fish larvae. Extra food is given from day 7 up to day 26 to optimize survival rate.

3.  1 round HDPE cage 22m in diameter (knock-down) with UHMWPE knotless net 6m deep inside a semi-round HDPE cage

o  Water volume  : 2,200m³

o  Harvest density for yellow fin tuna  : 66,000kg

After 50 days, octagonal HDPE cage membranes are opened, releasing juvenile tuna into the round HDPE cage 22m diameter with knotless net. The knock-down octagonal HDPE cages 6.1m diameter are then disassembled and taken out. Juvenile tuna of 12 cm is grown inside round HDPE cage 22m in diameter until it reaches baby tuna stage of approximately 2kg each in approximately 150 days (day 200).

4.  1 semi-round HDPE cage, 45m x 33.5m with knotless UHMWPE net 12m deep

o  Water volume    : 15,000m³

o  Max. harvest capacity for yellow fin tuna  : 450,000kg

After baby tuna reaches 2kg, round HDPE cage 22m knotless net are opened, releasing the tuna into the semi-round HDPE cage 45m x 33.5m. The knock-down round HDPE cage 22m in diameter is then disassembled. The tuna is then grown inside semi-round HDPE cage 45m x 33.5m until it reaches 30kg each in approximately 18 months.

The list (non-exhaustive) of activities in yellow fin tuna aquaculture operation are as follows:

1.  Getting Yellow fin Tuna as Brood Stock

Small yellow fin tuna size 2-10kg can be caught by local experienced fishermen using a specialized technique to minimize damage to mouth. Catching yellow fin tuna can be made easier by placing several fish aggregation devices in the area. Fish aggregation device accumulates small fish which in turn act as a food source that attracts tuna fish. Lots of fish aggregation devices placed in an area can stop tuna fish from migrating away, making the area a constant supply of tuna brood stock if caught responsibly.

2.  Getting and producing tuna feed

For tuna larvae, rotifer, copepod, and milkfish larvae can be produced using standard techniques. For juvenile and adult tuna, fish capture devices (such as lift-net of 25-30m in diameter) can be used to catch fish and squids every day to provide feed. On a good day, one fish capture device can produce more than 500kg of fish and squids.

Some facilities to grow milkfish is also needed to get milkfish larvae for tuna larvae and tune juvenile feed, as well as to get milkfish for adult tuna feed.

3.  Tuna breeding effort

Getting yellow fin tuna from fisherman is not practical for industrial scale aquaculture operation in the long term. Although cheap, supply is not always constant, and sizes are not uniform. Therefore, tuna breeding effort must soon start in order to provide the operation with constant and reliable supply of tuna fish in the future. It begins with harvesting tuna eggs, hatching tuna eggs, then nursing the hatched tuna larvae.

Yellow fin tuna eggs can be harvested using a sift shaped like a cone. Good tuna eggs are floating, while bad tuna eggs are submerged. Bad tuna eggs can be used as tuna feed as long as it is fresh.

Good tuna eggs with hatch by itself. After they hatched, nursing can be done directly inside HDPE cages like explained above.

4.  Transportation to destination

To minimize fish stress due to moving the fish from cage to boat, and to minimize transportation cost, the whole semi-round HDPE cage 45m x 33.5m can be transported directly to final destination by dragging it using a boat. The long, semi-round shape of the cage minimizes water drag to save fuel. Up to 3 semi-round HDPE cages can be tied together and dragged all at once using a boat. With this, the process of freezing the fish for transportation is eliminated as well, delivering high quality live fish to the market.

5.  Marketing

The price of yellow fin tuna scales linearly with quality. High quality yellow fin tuna should be marketed in countries that prizes quality such as Japan in order to get the best price possible. Efforts to get quality certifications in Japan and live delivery must be prioritized to fetch the best auction price in Japanese fish market.

6.  Continuous research

Yellow fin tuna aquaculture currently does not yet exist in Indonesia, and yellow fin tuna research is by no means comprehensive. Therefore, continuous research is needed to implement the science-based aquaculture and improve the efficiency and profitability of the operation.

7.  Brood stock management

For long term aquaculture operation, brood stock management and genetic selection must be implemented to get the best quality yellow fin tuna for aquaculture.

3.3.6 Equipment Needed to Hatch and Grow Yellow fin Tuna

For tuna aquaculture operation on a decommissioned oil and gas platform, the equipment needed are as follows:

1.  Office equipment:

a.  Generators, electrical equipment, cables, etc

b.  Desks, chairs, filing cabinets, etc

c.  Lights, air conditioner, communication system, monitoring system, etc

d.  Computers, printers, etc

e.  Office consumables

2.  Laboratorial equipment:

a.  Basins, pipes, etc

b.  Water circulation system

c.  Laboratory tools

d.  Monitoring system

3.  One set of Yellow Fin Tuna Hatchery and Growing System, each consists of:

a.  HDPE floating dock that connects the decommissioned oil and gas platform to semi-round HDPE cage

b.  1 semi-round HDPE cage, 45m x 33.5m with knotless net

c.  1 round HDPE cage 22m in diameter with knotless net (knock-down) inside a semi-round HDPE cage

d.  4 octagonal HDPE cages 6.1m in Diameter with membranes, assembled together (knock-down) inside a round HDPE cage

e.  2.5m in diameter HDPE membranes inside octagonal cages

4.  Two sets of Round HDPE Cage 20m in Diameter, for growing milkfish as tuna feed

5.  Two sets of large fishing boats to catch fish as tuna feed

3.3.7 Yellow Fin Tuna Production

One semi-round HDPE cage 45m x 33.5m with net depth of 12m can produce 450 tons of yellow fin tuna per harvest cycle. Growth from 12cm to 2kg requires around 12 months, growth from 2kg to 10kg requires around 10 months, and growth from 10kg to 30kg requires an additional 10 months. The harvest cycle is therefore around 1.6 years if grown from caught up yellow fin tuna bought from fishermen (2-5kg), 2.6 years if grown from 12cm (from hatchery), or a full 3 years if grown from the hatching of the egg.

It is estimated that the Food conversion rate (FCR) of Tuna is around 20. This means that in order to produce 450 tons of yellow fin tuna, around 9,000 tons of live fish must be provided as tuna feed per harvest cycle (2-3 years). Near the end of the harvest cycle, around 16 tons of live fish must be provided daily to feed 450 tons of yellow fin tuna that is about to be harvested. At this time, the two sets of large fishing boats must be fully operational to supply live fish. The two sets of round HDPE cage 20m in diameter growing milkfish act as a buffer to supply live fish in times when the fishing boats fail to deliver the necessary amount of fish needed to feed the yellow fin tuna.

3.3.8 Cost Estimation For Yellow Fin Tuna Production

Below are the cost estimation for yellow fin tuna production: