Departmental Reports


Report of Fishcultural Investigations in South Vietnam


Swingle, Homer, Donavan Moss

Date: 1968

Funding Agency: USAID

Keywords: fisheries, aquaculture, vietnam, devlopment, international, research

Category: International Country Report

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Species of fish most frequently cultured in this country
are common carp, kissing gourami and Tilapia mossambica. In
addition, the chinese carps, consisting of the silver carp,
bighead carp and grass carp,have been introduced and are now
present at several hatcheries. The silver carp was spavmed by
pituitary injection but few fingerlings were produced. The usefulness
of silver carp in Vietnam is still unknown, but it would
give higher production in most ponds as it is a plankton feeder

However, it was thought that the Vietnamese may not like the

fish as well as the common carp. The kissing gourami is

raised in many ponds and is reported to tolerate low pH in

pond waters. A catfish of the genus Pangasius is cultured

in floating bo:tes in the rivers, If methods can be worked

out to spawn this fish, it may be used with considerable success

in ponds,
Tests should be conducted to evaluate these fish for use

in ponds so that the most efficient species and best rates of

stocking, both with and without feeding, will be known. At

present, it is not known exactly how many of each species should

be supplied to fish farmers, The grass carp and probably Tilapia

melanopleura should be evaluated for their ability to utilize

grasses and plant wastes when stocked in combination with the

carps or with Tilapia mossambica,

The snakehead should also be evaluated as a predator to

prevent overcrowding by tilapias. The kissing gourami should

be evaluated for its ability to survive and grow in waters too

acid for other fish species, Pond waters in Vietnam seldom have

a pH higher than 6,5 even with a heavy plankton bloom, The high

acidity appears to come from layers of humus over which the water

flows and also from certain types of soils that contain a large

amount of sulfur, a portion of which is converted to sulfuric acid.

No analyses have been made on hardness or alkalinity or on the

calcium requirements of the bottom soils. Such analyses are

necessary to determine the corrective measures necessary, and

to locate problem areas with respect to fisheries management.

Of the various analyses, that for water hardness (the content

of calcium and magnesium salts) is probably the most informative,

If hardness is above 15 ppm as calcium carbonate, no corrective

measures for acidity are necessary. However, liming is usually

necessary if hardness is below 12 ppm for high production of

fish food organisms, If below 5 ppm, waters do not contain

enough calcium for satisfactory growth of fish. At each Fisheries

Station samples of water should be analyzed for total hardness, alkalinity and pH. Where hardness is very low, samples of bottom

soil should be analyzed for pH and their lime requirements determined.

Salinity of pond waters for those Stations located

near the coast also should be determined. During dry weather,

it appears quite probable that salinity may become too high for

certain species of fish. Minimum water temperatures in all areas

are also necessary for intelligent selection of species most

suitable for culture. Tilapia grow very slowly at temperatures

below l6°C and die at l0°C to l2°C. The minimum temperatures

ranging from 2°C to 8°C for Hatcheries at Cu Chanh, Dong Ha,

Lam Son and Due Trong would appear too low for good growth of warm-water

fishes (Table 1), Minimum temperatures can be misleading, however,

and what is needed are the average monthly maximum and minimum

temperatures to accurately evaluate the period of the year

during which warm-water fishes will make satisfactory growth.

linen this is obtained, it will then be possible to make more

intelligent selections of the fish species to be cultured

in various areas.

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