Monday, March 27, 2017

28/03/2017: Grouper farming: current bottleneck and new technology

by Huey-Lang Yang, Research Professor, National Cheng Kung University, Taiwan

Groupers are fish of several genera in the subfamily Epinephelinae of the family Serranidae

They are wild and spread globally in many warm water oceans, and can be quite large, such as the giant grouper (Epinephelus lanceolatus), which can commonly weigh up to 400kg.

Unlike other commonly farmed fish, grouper is a demersal fish that usually does not swim continuously, thus, it is an efficient and suitable fish for culture.

At least elven species of grouper have been farmed and the fertilised eggs of the following ten species are commercially available in Taiwan, such as giant grouper:

(E. lanceolatus), longtooth grouper (E. bruneus), coral trout (Plectropomus leopardus), red spotted grouper (E. akaara), orange spotted grouper (E. coioides), brown marbled grouper or tiger grouper (E. fuscoguttatus), Malabar grouper (E. malabaricus), camouflage grouper (E. polyphekadion), greasy grouper (E. tauvina), and polka dot grouper (Cromileptes altivelis).

Two species, such as E. coioides and E.malabadicus, have been successfully induced spawning, but other species are still unstable, such as E. bruneus, E. lanceolatus and P. leopardus.

The cultured fingerling has replaced the wild catch fingerling for most of the grouper farming. Grouper as a bottom fish is generally cultured in earthed ponds and shallow floating net cages in Southeast Asia.

The current culture system is fragmented and separated into at least four stages: brood stock farm supplies the fertilised eggs; hatchery supplies hatched larvae, nursery provides various size fingerlings to grow out farm.

All the stages have their own knowhow-based farmer’s experiences.

Current key bottleneck and disease

The stable supply of fingerling has facilitated the grouper farming in the past twenty years and about 100,000 tonnes of grouper was produced in Taiwan, China and south Asia at 2013.

However, high-density farming and repeated use of farming sites with non-responsible farming management has created drastic problems which has caused the industry to suffer many unsolvable problems in the past several years.

One of the major constraints is the disease, many diseases have already occurred such as VNN (Viral Nervous Necrosis, disease caused by NNV) which infects the brain and nervous system at the larvae and post-larval stage and has resulted total morality of larvae of all culture grouper species.

At the grow-out stage, NNV and Irido viruses and bacterial pathogens, such as Vibrio spp, Photobacterium, Aeromonads and Streptococcus as well as parasites are the main pathogens, especially, when fish are under stress.

Disease is not only causing mortality, it is also related to escalated production cost, unstable harvest, inferior fish quality, and damage to the farming environment.

Antibiotics and chemical drugs are currently used to treat disease, but unfortunately, this practice also causes the outgrowth of antibiotic resistant bacteria.

Many countries around the world have tightened regulation on the use of antibiotics in aquaculture, but this rule is just palliatives and difficult to abide, as farmer needs solution.

About the Author: 

Dr H-L Yang obtained his Ph.D. at UC Davis in Bacteriology and post-doctoral traning at Columbia University in USA.

Dr Yang was the CEO of Merit Ocean Biotech. Inc. that was established in 2011 after receiving his virus free indoor hatchery system.

Prior to this, he has worked as director of Institute of Bitoechnology and director of University Centre for Bioscience and Biotechnology at National Cheng Kung Univ, senior research fellow at Academia Sinica and director of Molecualr Biology at Development Centre of Biotechnology.

Fifteen years ago, Dr Yang shifted his research interest from bio-medicine of mammals to bio-medicine of fish and founded the R&D team of grouper with the intention of ameliorating the disease-related mortality of warm water aquaculture.

Dr Yang’s significant accomplishments were recognised by the Taiwanese government, and have obtained several domestic and international awards including the Distinguished Contribution in Science and Technology by Executive Yuan (cabinet), award of successful example of investment in R&D on Biotechnology and the Innovation award (Ministry of Agriculture).

International awards include the TWAS (The Academy of Sciences of Developing Country, a UN support organisation of the Academy of 68 developing countries) prize in Agricultural Sciences (2009), and he was elected as VIP in aquaculture of 2011, by China “Advance in Aquaculture” magazine.

Read the full article HERE.

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