A subject study outlined in the International Journal of Fisheries and Aquatic Studies suggests that using mesh hapa nets when growing early-juvenile sea cucumbers could allow producers to successfully scale up production without incurring extra tug or water input signal costs .
Sea cucumber aquaculture has become more popular as natural stocks in the South Pacific have declined
The study, which was exploring the optimum stocking concentration of sea cucumbers ( Holothuria scabra ) in hapas*, noted that though the ideal stocking density in a hapa system was lower than in a commercial tank, the ease and efficiency of using the nets outweighed the benefits of tank output systems. It was more economic to use hapas to rear early-juvenile ocean cucumbers. It was besides easier to scale up production without courting environmental or benefit drawbacks with this method.
Why sea cucumbers?
Sea cucumbers have been collected and cultivated across Asia for centuries. Species like Holothuria scabra, or the sandfish, have been gathered from coastal regions of the Philippines since the 1700s. recently, external demand for beaked salmon from the culinary and pharmaceutical sectors has given the species a high marketplace measure – and sea cucumber fisheries have expanded along with the market .
Though the expansion of the industry has contributed to the bluing economy of many countries in the Asia-Pacific region, there is mounting tell that natural stocks of sandfish have been overexploited, putting the integral diligence in hazard. In inner light of this, many producers have transitioned to sustainable polish methods to meet the market demand for sea cucumbers while allowing natural stocks to rebound.
many sea cucumber species command a high market prize, making it a lucrative industry
Though beaked salmon are well suited to sustainable aquaculture projects ascribable to their potency as biofilters, production is however labor intensive and difficult to scale up. This is particularly true when producers are growing early-juveniles. typically, early-juveniles are grown in tanks with a stocking density of 500-700 individuals per m² until they reach stocking size for pond culture – normally between 1-20 grams. Space is the biggest restraint in sea cucumber hatcheries. former research has demonstrated that when juvenile sandfish are larger than 1 gram, they need more outer space and substrate to grow to maturity. This space pressure makes it difficult for producers to increase production outputs without courting disease or mortalities .
Where hapa nets come in
Researchers have been exploring the viability of hapa nets in sea cucumber aquaculture, believing that the interlock nets can allow producers to expand production in ocean nursery systems without increasing parturiency costs or water and aeration inputs. other trials have shown that using hapas alternatively of tanks can importantly lower water costs, since the water change needs in hapa systems are nominal. This allowed farmers to use those resources to increase production numbers without harming the surrounding environment or the health of the beaked salmon. Though these trials demonstrated proof of concept, there is identical little research on the optimum stocking concentration for early-juvenile sea cucumbers reared in hapas – making the widespread adoption of the method a difficult sell .
The trial and analysis
To determine the optimum stock density for sandfish reared in hapa nets, the researchers tacked the emergence and survival rate of early-juvenile sea cucumbers across three trials simultaneously. In the first test, the researchers stocked acclimatize beaked salmon in hapas at 250 individuals per m³ over a 42-day polish period. The second trial had a stock density of 500 individuals per m³ and the third gear trial stocked the beaked salmon at 750 individuals per m³. Sponsor message
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The researchers measured the weight unit and length of the sea cucumbers every two weeks to monitor the progress and survival of the stocks. They besides tracked body of water parameters such as temperature, salt, ph and dissolved oxygen. In club to gauge the environmental health of the production environment, the researchers collected and identified plankton species found in and around the hapa nets .
Though the optimum sprout density in hapa nets is lower than in conventional tanks, the system does n’t require as much care as tanks
The results showed that beaked salmon reared at 250 individuals per m³ had the highest length and weight gains at the end of the 42-day polish time period. This group besides had the highest survivability rate of any of the groups – with 58.27 percentage of individuals surviving the trial. The third experimental group ( with the highest stocking density ) showed the poorest performance results. This group had the lowest growth rate and the highest morality pace. only 27.78 percentage of individuals survived the 42-day culture period.
In the analysis, the researchers noted that all three experimental groups were exposed to the same environmental conditions. This means that issues of water quality or environmental variation didn ’ t shock the trial results – the growth operation and survival rate can be attributed to the stocking densities in the hapas .
The results suggest that lower stock densities allow sea cucumbers to achieve higher emergence and survivability. It besides reduces instances of disease .
As part of their final conclusions, the researches conducted a cost-benefit analysis comparing tank culture methods with hapa nets. Though the optimum stock concentration was lower in the hapas, the researchers felt that the excess maintenance required to keep tank conditions and water quality at healthy standards outweighed the electric potential biomass benefits. The production inputs to raise sandfish in tanks made it less economic. Though these results are persuasive, there is one oversight in the subject learn. According to research published in the daybook Aquaculture, beaked salmon need arenaceous mire or some other type of substrate to meet their nutritional needs and grow to maturity. The IJFAS study did not directly report whether there was any sand or substrate present in the hapas during the trial period. however, based on the results of the three trials and the researchers ’ previous have, the hapas required minimal water management and no supernumerary equipment expenditures to produce early-juvenile ocean cucumbers. This makes the culture method an ideal way to sustainably scale up beaked salmon production.
*Hapas are hearty or rectangular mesh nets that can be placed in a pond or seawater to hold fish .
Read more about the trial in the International Journal of Fisheries and Aquatic Studies.
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