Pond Dynamics/Aquaculture CRSP Aquanews ~ Fall 2002

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Culture of Mollusks to Improve Human Protein Intake in the Amazon Region

by Fernando Alcantara and Salvador Tello, Instituto de Investigaciones de la Amazonia Peruana, and Christopher C. Kohler, Susan T. Kohler, and William Camargo N., Southern Illinois University, Carbondale

Mollusks Offer an Alternative to Fish-based Aquaculture
he Amazon River region contains a high biodiversity of aquatic organisms hence an excellent potential for commercial aquaculture. The sustainability and expansion of aquaculture in Amazonia will be fostered by establishing new species for cultivation. Invertebrates, in particular, have received minimal attention in this regard. Several species of mollusks (gastropods and bivalves) have been exploited irregularly by the ever-declining commercial fishing industry in the Amazonian region. Currently, research is underway by the Instituto de Investigaciones de la Amazonia Peruana (IIAP) in Iquitos and Pucallpa, Peru, to develop simple technologies to culture aquatic and giant terrestrial gastropods as an alternative form of polyculture or integrated aquaculture.

Adult Pomacea bridgesi.
[Image courtesy of <www.applesnail.net>.]

By: Stiyn Ghesquiere
Churo is a Promising Candidate
Applesnails (Pomacea spp.)—and among them P. maculata, or churo, as it is known in Peru—are the largest known freshwater gastropods, reaching lengths of 155 mm and diameters of 135 mm (Pain, 1960). This aquatic organism lives in the floodplain of the Amazon region (Cobos, 1998), preferring the zone where water mixes in the major and minor rivers (hardness from 35 to 256 mg l-1) as well as in their tributaries (Villacorta, 1976). It is a species of periodic reproduction (Cobos, 1998), depositing its eggs in clusters outside the water on hard surfaces (e.g., trees, shrubs, wood debris), most frequently in the flooding months (rainy season). The number of eggs produced per female at each spawn varies according to body size, ranging from 233 to 1,425 eggs (Cobos, 1998; Rojas and Mori, 1976; Villacorta, 1976). Ontogenic development takes from twelve to sixteen days (Alcántara et al., 1996) and hatching rate is 87% (Cobos, 1998). Churo is omnivorous, feeding either on fresh or partially decomposed organic matter, including floating macrophytes (e.g., water lettuce or huama–Pistia stratiotes, duckweed–Lemna minor), rooted plants (e.g., gramalote–Paspalum spp.), tree leaves (e.g., renaco–Ficus guianensis, cetico–Cecropia spp., tangarana–Paniculata tachigalia, catahua–Hura crepitans and quinilla–Vochysia lomatophylla) and shrubs (e.g., ñejilla–Bactris sp. and water chestnut or rayabalsa–Montrichardia spp.) in the natural environment (Cobos, 1998).

Churo is a hardy species that readily adapts to controlled environments and reproduces in captivity. The egg-laying characteristics facilitate egg collection under culture conditions. In Iquitos, churo culture is conducted by IIAP in aquaria or in cement tanks slightly filled with water (15 cm depth). These are covered with a lid made of a wooden frame layered with a fine metallic mesh to provide a suitable surface for oviposition. Two weeks later, the eggs hatch and the juveniles fall into the water. At this time they are fed lettuce (Lactuca sativa, Villacorta, 1976; Sáenz, 2001), eggplants

Pomacea eggs on tree trunk near Iquitos, Peru. [Image courtesy <www.junglephotos.com>.]

Photo By: Roger Harris
(Solanum melongena), zapallo (Cucurbita pepo) and taro or pituca (Colocasia esculenta). In a six-month culture period, they reach a weight of 35 g and a length of 6.5 cm, with an average food conversion ratio (FCR) of 2.9. Further, Alcántara and Nakagawa (1996) conducted nutrition experiments using artificial feeds, obtaining variable yields between 8.1 to 31.8 kg m-2 in seven months of culture, with individuals averaging weights from 39 to 98 g.

The market size (proportional to culture period) can be reduced considerably to fit the requirements of international markets. Marketing the product as escargot (in Europe), for example, reduces the market size of the snails to only 4 cm in length, requiring only 2- to 3-months growth.

Another possibility is to use a value-added method such as canning, which IIAP and Southern Illinois University Carbondale under PD/A CRSP sponsorship have successfully produced using brine as the preservation media. This product is readily consumed by the locals to prepare cebiche de churo, a traditional dish. An economic study performed by IIAP determined profit margins of 58, 62 and 93%, at low (1,000 m-2), medium (5,000 m-2), and high (10,000 m-2) stocking densities, respectively. Thus, the culture and processing of churo offers excellent potential to produce animal protein at a very low production cost.

Other potential candidates that deserve research effort are the Amazonian soft-shell clams (Anodontites spp.) locally named tumbacuchara, which possess very fast growth of visceral mass compared to the shell, which is

Half-grown bivalve locally named "tumba-cuchara," Anodontites sp. (13.4 mm length, and 8 months old), found in a recently drained fish culture pond at IIAP Pucallpa.

Photo By: William Camargo
surprisingly very thin (Fig. 3). This bivalve has been reported to grow up to 10 cm in less than seven months in fishponds (stocked with paiche–Arapaima gigas) at high densities at IIAP, Pucallpa (M. Rebaza, personal communication), Lago de Sauce, Tarapoto (Campos, personal communication), and other localities of the Peruvian Amazon. The natural habitat of these bivalves is also very diverse. They are present in white (high silt) and black (high tannin) waters, in meanders, and in waters with considerable flow rates. The soft-shell clams have been reported in the Amazon, Itaya, and Tapiche Rivers, near Iquitos, and are probably widely distributed throughout the entire Amazon region. Surprisingly, they are rarely present in the largest local markets (Iquitos and Manaus, Brazil), and little information is available regarding their consumption by the riverside people. Some regional Peruvian dishes, however, incorporate this bivalve in diverse combinations such as cebiche (marinated clams and/or fish), picante (hot sauce) with rice, and picante with yucca. Accordingly, this resource could become another important alternative to diversify aquaculture in a resources-rich region where, unfortunately, some inhabitants are malnourished (Amazon Alliance, 2000) because of lack of knowledge of all the alternatives available.

References

Alcántara, B.F. and N. Nakagawa, 1996. Cultivo preliminar del churo Pomacea maculata. Perry 1810. (Gasterópoda, Ampullariidae). Folia Amazónica, 8(2): 29-33.

Alcántara, B.F., N. Nakagawa, and E. Zamora, 1996. Características del desove del churo Pomacea maculata, en ambiente controlado. Folia Amazónica, 8(2): 7-11.

Amazon Alliance. 2000. Peru: Indigenous March Planned to Initiate Government Dialogue. July, 2000. <http://www.amazonalliance.org/update/2000/upd_jul00_en.htm>.

Cobos, M., 1998. Bioecología del churo Pomacea maculata, en el Caño Liverpool. Río Marañón. Tesis para optar el título profesional de Biólogo. Facultad de Ciencias Biológicas. Universidad Nacional de la Amazonía Peruana, Iquitos, Peru. 92 pp.

Pain, T., 1960. Pomacea. (Ampullaridae). On the Amazon River System. J. Conch. 24(12):421-32.

Rojas, J. and L.L. Mori, 1976. Aspectos bioecológicos del churo Ampullaria canaliculata D’Orbigni. Centro de Investigaciones de Recursos Naturales Amazónicos, Iquitos, Peru. 29 pp.

Sáenz, B.O., 2001. Dietas de origen vegetal y composición corporal del "churo" Pomacea sp., en Iquitos – Perú. Tesis para optar el título profesional de Biólogo. Facultad de Ciencias Biológicas. Universidad Nacional de la Amazonía Peruana, Iquitos, Perú. 61 pp.

Villacorta, M., 1976. Algunas consideraciones bio-ecológicas del churo Pomacea maculata. Tesis para optar el título profesional de Biólogo. Facultad de Ciencias Biológicas. Universidad Nacional de la Amazonía Peruana, Iquitos, Perú.

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