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Aquaculture of Tilapia and Pangasius; A Comparative Assessment PDF  | Print |  E-mail

Michael V. McGee, PhD
Caribe Fisheries Inc.
Lajas, PR


Over the last fifteen years production from aquaculture has expanded rapidly to augment supplies from natural fisheries. The FAO predicts that by 2010 aquaculture’s contribution will supplant capture fisheries as the worlds leading source of aquatic products. Intrinsic to this rapid growth has been the emergence of two tropical freshwater species, Tilapia (mainly Oreochromis niloticus) and Pangasius, (Pangasius hypophthalmus) as significant new sources of white fish aquaculture products on the global market. While both species are of tropical origin and characterized by positive attributes including, ease of reproduction, adaptability to intensive culture, acceptability of low input  sustainable feeds, resistance to impaired water quality, and widespread consumer acceptance, specific aspects of their reproduction, management and marketing differ. An assessment of Tilapia and Pangasius as aquaculture species is useful in identifying similarities and differences and provides a means of comparison when considering production of either species.

Tilapia and Pangasius both exhibit excellent qualities as sustainable species for tropical aquaculture. The geographic range for potential culture of the species is identical and encompasses the global tropics in areas where adequate water resources are available. World production of Tilapia has surpassed 2.5 million metric tonnes while Pangasius production, from Vietnam alone, achieved 1.2 million metric tonnes in 2008.  Production increases for both species are expected to continue into the future.

(Include tables indicating current production levels of both species)

Tilapia have been the subject of intensive investigation since their introduction for aquaculture, beginning in the 1950’s. The various species of commercial value have been introduced throughout tropical regions of the world. The widespread utilization of the hormone methyl- testosterone (MT) to achieve the production of all male fry has been a significant factor in permitting development of Tilapia as an aquaculture commodity on global markets. Likewise genetic selection of improved strains has increased yields and production performance while improving product quality.

 Pangasius emerged as a major culture species in the 1990’s and to date, has not achieved a similar level of introduction or research focus, outside of tropical regions of South East Asia. The application of methods for hormone induced spawning has been the principal factor leading to the rapid development of Pangasius aquaculture and its emergence as a globally important aquaculture product. Considerable opportunities appear to exist for improvement of Pangasius as an aquaculture species, potentially resulting from hybridization, genetic selection for positive production traits, as well as increased introduction to suitable culture environments worldwide.


  




Oreochromis nilotica production (FAO)




Breeding and Fingerling Production

Tilapia and Pangasius exhibit markedly different reproductive strategies. Tilapia are mouth brooders and can propagate naturally in diverse tropical aquatic environments. Aspects of Tilapia reproductive strategy include precocious maturation, frequent spawning, extended parental care, and non dependence by fry on specialized food resources. Associated with these characteristics is the relatively low fecundity of females and the energetic costs and benefits of extended parental care. While these attributes facilitate fingerling production under controlled conditions, they also can lead to undesirable reproduction in grow out ponds leading to overpopulation and stunting in mixed-sex populations. Female Tilapia broodstock normally weigh 300 g - 800 g and produce about 1 egg /g of body weight. Males and females are maintained in breeding populations in small ponds or hapas. Fertilized eggs or newly hatched fry are frequently collected and reared under controlled conditions while receiving MT treated feed for 28 days. This technique results in a high percentage of male fry. Fry are transferred to fingerling production ponds prior to final stocking for grow out. Survival of Tilapia fingerlings is normally high assuming proper management and the avoidance of catastrophic bacterial or parasitic infections. Hatchery  production of sex-reversed Tilapia fry requires increased manual labor as well as greater hatchery management skills and the utilization of MT treated feed. 

Pangasius grow to large size and require 2 – 3 years to reach sexual maturity. Adult fish can reach up to 20 kg and live for at least 20 years. Prior to maturity males and females grow at similar rates and no segregation of fish by sex is required during grow out phase of production. Broodfish develop mature gametes while held in ponds and fed commercial feeds but do not naturally reproduce. Hormone induced ovulation and manual stripping of eggs and milt is required to reproduce the species in captivity.  Pangasius are highly fecund and a single female can produce more than 50,000 eggs per kg per spawn. Individual females can spawned up to four times during the breeding season. Pangasius eggs hatch within 24-30 hours and the larva begin to feed 24-30 hours later. Although larval Pangasius can be reared in hatchery tanks better results are achieved through the use of rearing ponds fertilized to enhance the production of small zooplankton. The development of adequate zooplankton populations of appropriate size is the most critical factor to increasing larval survival. Pangasius fry begin to take powdered feed after 5-7 days. Fingerlings of 2.5 – 4.0 cm can be produced in 30 to 40 days.

Mass production of sex-reversed Tilapia fingerlings requires more labor and technical inputs than production of Pangasius fingerlings. The percentage of survival of Tilapia fry under successful culture conditions, particularly if disease outbreaks can be avoided, is normally higher than the percentage survival of Pangasius larva in nursery ponds reared under natural conditions. The higher fecundity of Pangasius permits greater potential yields of fingerlings from a comparative biomass of brood fish than Tilapia. The reproduction and fingerling production techniques for both species are proven and successful, representing no limiting factor to the further expansion of their respective industries. 

Production and Yields

Commercial production of Tilapia and Pangasius is accomplished primarily in ponds and cages. Tilapia yields from intensively managed ponds which include the use of aeration, water exchange and commercial feeds range from 8-15 mt / ha. All male fingerlings are stocked at rates of 1-3 fish / m2 and grown for 5-12 months prior to harvest at 500 – 1000 grams. Pangasius are stocked at higher densities of 60 – 80 fish / m2 and normally grown for 6 - 8 months to a harvest weight of 1kg. Intensive production of Pangasius in ponds can produce yields of 250 – 300 mt / ha. These impressive yields are largely due to the ability of Pangasius to assimilate atmospheric oxygen through the swim bladder rather than depending solely on respiration through the gills. This adaptation provides a distinct advantage to Pangasius as an intensive culture species. The oxygen demand generated by Pangasius is largely satisfied by atmospheric oxygen and reduces the total demand for dissolved oxygen in the pond environment. Aeration and water exchange as utilized in Pangasius ponds are principally applied to avoid environmental deterioration rather than as a method to ensure fish survival.
 Tilapia and Pangasius production in cages is practiced in impoundments, lakes or rivers. Due to increased water volumes, limiting factors imposed by water quality are normally of less significance. Stocking densities of Tilapia normally range from 100 to 400 fish / m3 and yields of 75 – 350 kg / m3 are achieved. Pangasius are stocked in cages at 100-150 fish / m3 and yields range from 100 – 120 kg / m3. Under these conditions production of Tilapia or Pangasius in cages may be nearly equivalent until the carrying capacity of the system is reached, at which point Pangasius are more resistant to the effects of reduced levels of dissolved oxygen.
 
Feeds and Feeding

 Tilapia and Pangasius are both nutritionally low input species. This designation is taken to mean that they can be produced efficiently with reduced levels of animal protein and lipid sources, particularly fish meal and fish oil, incorporated into the feed. This characteristic is of fundamental importance when considering the sustainability of aquaculture species as net producers of higher quality protein. Both species are commercially produced using feeds of 28 – 32% protein, comprised primarily of grain based materials or derivatives. Food conversions for the species are similar and generally range within 1.5 – 2.0 kg / kg of fish produced. Additionally Tilapia and Pangasius can be produced using “homemade feeds” or agricultural by-products and both derive additional nutrition from natural pond productivity. Tilapia tend to feed in the water column by filtering bacteria and phytoplankton while Pangasius consume sediments and detritus to glean nutrition from bacteria and other organisms which colonize the substrate. No known studies have been conducted to determine the relative production of Tilapia and Pangasius under  equivalent conditions of nutrition and environment, therefore no particular advantage for either species can be indicated relating to feed utilization.  The low input diets which are utilized by both species conveys an advantage of sustainability and reduced feed costs resulting in a lower production costs and a more environmentally propitious product for consumers.


Water Quality and Disease Resistance

Under conditions of intensive aquaculture, deterioration of water quality due to high feeding rates and waste generated by fish is the principal limiting factor to production. Tilapia can survive exposure to as little as 0.6 mg / L D.O. for short periods of time and levels of 2.0 mg/ L are adequate to prevent significant stress. However, chronic exposure to D.O. levels below 3.0 mg/L will compromise feed utilization and growth rates as well as disease resistance. Thus, Tilapia are dependent on dissolved oxygen in water. Under conditions of intensive production Tilapia ponds are aerated to increase or sustain dissolved oxygen levels. Although effective, use of mechanical aeration can significantly increase production costs.

Pangasius can utilize a modified swim bladder to absorb oxygen directly from the atmosphere. This imparts an advantage over Tilapia and greatly reduces or eliminates the need for pond aeration. Interestingly, even in heavily stocked Pangasius ponds without aeration, dissolved oxygen levels do not decline to critical levels.  This is possibly due to the utilization of atmospheric oxygen by Pangasius to meet their physiological and metabolic requirements combined with their consumption of soil pond biota and organic matter which normally exerts additional consumptive demands on dissolved oxygen. In this regard the presence of Pangasius in the pond can be considered to potentially improve pond soil and water quality, and carrying capacity due to their ability to use atmospheric oxygen.

As tropical species Tilapia and Pangasius do not tolerate water temperatures below 14 C for extended periods. Growth rates are reduced and disease resistance is decreased. Neither species can be recommended for commercial production in areas where water temperatures are below 20 C for extended periods of time. .

 Tilapia and Pangasius are generally resistant to disease during the grow-out phase of production under adequate culture conditions. Deteriorated water quality, handling, or low water temperatures can lead to increased potential for parasitic and/or bacterial infections. Both species, as fry or fingerlings are more susceptible to disease outbreaks which can lead to significant mortalities. Common disease problems include protozoan infestations on the skin or gills, and bacterial infections resulting from handling or environmental stress. As scaleless fish Pangasius are highly susceptible to the protozoan parasite Icthyopthirius multifilus when water temperatures remain in the range of 20 C, a temperature preferred by the parasite. Pangasius are excitable and tend to exhibit higher stress levels than Tilapia as related to capture or handling. No specific catastrophic diseases of bacterial or viral origin have been reported for either species.


Environmental Impact

Tilapia are native to Africa and are among the most widely introduced aquaculture species in the world. Due to their ability to reproduce in nearly any tropical freshwater environment they have established feral populations in most regions where they are commercially cultured. The existence of self-sustaining populations of Tilapia alters the original ecosystems they colonize. Tilapia are omnivorous feeders and can be predaceous on smaller fish and crustaceans as well as affecting habitats due to nest building activity and territorial behavior. Despite this, Tilapia introductions have been considered to have positive impacts when socio-economic factors as well as environmental issues are assessed.
Pangasius (P. hypophthalmus) is native to the Mekong River drainage which encompasses regions of China, Laos, Cambodia, Thailand and Vietnam. Pangasius exhibit an annual spawning migration to specific upstream areas of the river and have not been reported to reproduce naturally outside of these environments. Prior to the application of hormone spawning techniques, the collection of Pangasius fry from the river for aquaculture purposes was implicated in the reduction of the natural fishery and secondary impacts on additional  species. This problem has been resolved by the development of hormone induced spawning techniques for the species and governmental restrictions on fry collection and the harvest of wild stocks.
 Pangasius has been introduced for aquaculture purposes throughout much of South East Asia as well as Bangladesh and India.  It has not been introduced to the Western Hemisphere with the exception of Puerto Rico and Florida, USA where it is cultured as an aquarium species. In Puerto Rico grow out trials, conducted since 2002, indicate that Pangasius can be successfully cultured in the western tropics and that it does not reproduce naturally under these conditions. Pangasius are omnivorous and ingest detritus and sediments to obtain nutrition from particulate organic matter, microbial biomass and benthic invertebrates. They have not been observed to be predaceous on other fish. It is likely that Pangasius can contribute to increasing and diversifying aquaculture production in the Western Hemisphere without significant negative environmental impact. This possibility should be investigated by using appropriate protocols for the introduction of new aquaculture species.
 Aquaculture effluents represent an additional area of environmental concern. Increased oxygen demand, nutrient loading and sedimentation are potential results of discharge from any commercial aquaculture operation. The rapid and dramatic growth of the Pangasius aquaculture industry in Vietnam has raised concern regarding environmental impacts associated with such large scale production. Currently there are on-going international efforts to develop and implement aquaculture guidelines or standards for both Tilapia and Pangasius which provide management and engineering solutions to these environmental concerns as well as addressing issues of drug and chemical usage, product safety, and social issues among others.

Processing and Product Quality
Tilapia are processed as whole gutted fish or filets. Scales are removed from whole fish and small pin bones above the rib cage are removed from filets. Gutted whole fish typically yield 80 % of live weight. Filet yield is around 33 %. Tilapia flesh is nearly white with some red flesh along the lateral line. Treatment of filets with carbon monoxide gas to maintain the appearance of freshness in frozen filets is often applied. Tilapia is typically exported as whole gutted frozen fish and frozen or fresh filets. The meat is of flaky texture with a mild flavor. Seasoned or breaded filets represent the major value added Tilapia product for mass distribution although additional products are continually being developed.
Pangasius have no scales or pin bones and are typically exported as skinless, boneless filets. Larger fish may be cut into rounds.  Yields are around 80% for gutted whole fish and 34% for boneless filets. Flesh color varies from white, cream, yellow or rose depending on feed type, environment, and processing. Whiter filets are associated with higher quality and price, although specific markets exist for other grades as well.  Production of white filets is associated with the use of floating feeds and good water quality. Yellow flesh is associated with an increased reliance on non commercial or natural food sources. The flesh is of mild flavor with a medium firm flaky texture. Numerous value added products are produced from Pangasius, particularly for established Asian markets. Pangasius filets from commercial processors are often subjected to infusion of sodium tri-polyphosphate (STP) solution at levels of 10-20% by weight. This additive improves the appearance and shelf life of frozen filets while increasing profits for the processor. The widespread use of STP is a factor in maintaining the relatively low market price of Pangasius filets on international markets.  

Markets

Tilapia and Pangasius are freshwater aquaculture species which have achieved commodity status on world seafood markets. This represents a major shift from the traditional dependence on capture fisheries and clearly defines the trend to a greater reliance on aquaculture to meet the demand for fish and shellfish products into the future. Tilapia sales on world markets reached over 2 billion USD in 2008, while Pangasius exports from Vietnam alone represented sales of $ 1.2 billion USD. The major export market for Tilapia is the United States. Frozen Tilapia products are exported from Asia while fresh product, primarily filets are principally obtained from Central and South America.
   
The global market for Pangasius has developed extremely rapidly over the last 10 years. Currently product from Vietnam is exported to over 107 countries. The production boom in Vietnam coincided with the signing of a free trade agreement with the USA. The Vietnamese began exportation of Pangasius to the USA as catfish. Despite the fact that Pangasius are catfish, the increasing popularity and low cost of Pangasius resulted in domestic catfish producers acting to convince the U.S. Congress to pass legislation banning the sale, as catfish, of any species other than the native genus Ictalurus. The U.S. Dept. of Commerce enacted additional regulations which established tariffs up to 64% on imported Pangasius.  This effectively halted expansion of the export market for Pangasius from Vietnam in the United States.  Ironically the restriction of Pangasius imports resulted in increased imports of Tilapia which currently outsell Pangasius in the US market.  Vietnam was able to successfully open significant new markets in Europe and Russia where Pangasius currently outsell Tilapia.

Large scale production in Vietnam, and additional production by neighboring countries including China, has resulted in the marketing of Pangasius filets at low prices which largely contribute to its rapid growth and acceptance on world markets. Recent increases in production costs associated with rising feed and energy costs has temporarily destabilized the Vietnamese industry while an adjustment to higher market prices is ongoing. This will likely permit increased opportunities for development of Pangasius farming in other countries, including the tropical regions of the Western Hemisphere. Production from this area has the potential to compete for the US market since the tariffs imposed on Pangasius imports currently apply only to product from Vietnam.

Fig. 3 Distribution of Tilapia production worldwide. FAO   






 
















Summary


 The economic success of Tilapia and Pangasius as aquaculture species and their ascendance to commodity items on world seafood markets are indicators of the transition of seafood supplies from traditional capture fisheries to sustainable aquaculture based production. Both species reflect the desirable characteristics which define appropriate and sustainable aquaculture and both products are well accepted by consumers.
This comparative assessment indicates that Pangasius exhibits potential advantages in terms of reproductive capacity, resistance to low dissolved oxygen, and production yields. Tilapia retain an advantage based upon increased distribution and familiarity among policy makers, researchers, aquaculturists and consumers. Both species are adapted to utilize low input feeds and likely can be produced with nutritionally adequate grain based diets in the future. The development of aquaculture standards for both Tilapia and Pangasius will assist with defining the methods and means to improve these industries while securing their sustainable futures. Tilapia and Pangasius occupy similar market niches as freshwater whitefish aquaculture products although little direct competition for market share has occurred to date. Current trends project continued increases in production of both species.
In conclusion, not all aspects of a comparative assessment of Tilapia and Pangasius can be clearly determined at this time. Research is needed to further clarify and define these comparisons in a more quantitative way as well as establishing long term sustainable production parameters for these two globally important aquaculture species.



Table 1.  Comparative Assessment of Tilapia and Pangasius

Characteristic        Tilapia        Pangasius

Taxonomic Family        Cichlidae        Siluriidae

Native range            North Central Africa    South East Asia

Environment              freshwater tropical    freshwater tropical

Reproduction            mouth-brooder        egg-scatterer

Age of Reproduction        4-5 months        2-3 years

Size at Maturation        100 grams        2-3 kilos

Maximum size               3kg            30 kg

Broodstock size (avg.)     0.5 kg                       6 kg

Fecundity (avg.)         1 egg/g                  50 eggs /g

Egg Yield per Female (avg.)    500 eggs        500,000 eggs

Spawning            pond, tank or hapa     hormone induced

Fry rearing            tank, hapa (sex reversal)        pond, hapa

Fingerling rearing        tank, hapa, pond            pond

Hormone Utilized        methyl testosterone                           hCG, Ovaprim, other

Harvest Size            0.3- 1.0 kg                0.8 – 1.2 kg

Grow out period                       6-12 months                                           6-12 months

Yield ponds (mt per ha)                10 (avg)                                        100 (avg)

Yield cages (kg per m3)              75 – 300                100-120

 
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