2. MATERIALS AND METHODS

2.1 Selection of ponds

The fingerling production demonstration activities were carried out in seven ponds located at four government farms representing four administrative division. Location, water area, identification number of ponds assigned and number of production cycles achieved are given in Table 1. Though exact pond areas are given in this table, for convenience and uniformity, later stocking rates, production etc. were converted to 1000m².

TABLE 1
SUMMARY OF DEMONSTRATION PONDS AND CROPS

Fingerling production technology applied in these ponds was based on the principle of semi-intensive polyculture system and the practice of Bangladeshi and Hungarian fish seed producers, but modified to a improved technology.

2.2 Pond preparation

For pond preparation, residual fish, insects and their larvae etc. were removed from the selected ponds by dewatering or by application of poisons (0.25 ppm Phostoxin or 5.0 ppm Rotenone) or by repeated netting. Between the production cycles residual fish were also eliminated by the application of either of the above methods. A gap of, at least 3 days, was maintained between poisoning and liming. Quicklime (CaO) was spread on the bottom after dewatering or sprinkled in diluted form on the pond water. Empty ponds were partially replenished on the next day and dry poultry manure (in some cases, in addition to manure urea and TSP) was spread on water surface except for of pond 3.1 and 4.1 where cowdung was used. Table 2 presents summary of pond preparation and maintenance.

TABLE 2
PRE-AND POST-STOCKING MANAGEMENT DETAILS

2.3 Stocking

Altogether eight species viz., grass carp (Ctenopharyngodon idella), silver carp (Hypophthalmichthys nobilis), catla (Catla), mrigal (Cirrhinus mrigala), calbaush (Labeo calbasu), Thai shorputhi (Puntius gonionotus), mirror carp (Cyprinus carpio var. specularis) and common carp (Cyprinus carpio var. communis) were stocked in various densities and ratios. The overall stocking densities ranged between 7200 and 18900 pre-nursed fry per 1000 m² (Table 3). Stocking ratios were usually decided on the basis of food requirement of various fish species, utilization of different trophic levels of the ponds and artificial feed that could be used.

TABLE 3
FRY STOCKING AND FINGERLING PRODUCTION DETAILS

2.4 Pond maintenance

Unlike the traditional practice, fortnightly heavy fertilization (80 kg of cowdung, 2.25 kg of urea and 2.25 kg of triple superphosphate per 1000 m²) and daily small quantities of manure and fertilizer were applied to maintain a rich plankton population as natural food for the fish (Table 2). Dry poultry drops was used in majority of ponds. Stomach contents of slaughtered ruminants was applied daily as manure in pond 5.2 and cowdung in pond 3.1. Making of deviation from other ponds, pond 4.1 was manured fortnightly in the corner like the traditional practice here.

The pond bottom was raked daily to stir the upper layer of the mud to help release any trapped gases and to aerate the pond bottom.

2.5 Feed preparation and feeding

Food supply was established on phyto and zooplanktons produced by frequent manuring and on artificial feeds in the demonstration ponds (Table 4). Mixture of soaked rice bran and mustard oil cake was fed in pond 4.1 (Feed type I). Dough type feeds containing fresh (coagulated) blood or fish meal, mustard oil cake and wheat bran (Feed type II), and mixture of ground duckweed and the traditional feed ingredients, wheat bran and mustard oil cake (Feed type III) was used in other ponds managed in 1990. But in 1991 all the applied feed ingredients (MOC, W/RB, CB, FM & DW) were mixed and administered together (Feed type IV). The dough type feeds contained at least 1/3 of the feed wet component (cattle blood, ground duckweed or soaked wet mustard oil cake). However, depending on the pre supposed requirement of fingerling, availability of feed ingredients and accuracy of management, the ratio of feed ingredients were changed from time to time as it is shown in Table 4. Floating duckweed was given when grass carp fry were big enough to consume it.

Feed was provided once in the morning and in the afternoon, in equal portions. Dough type feeds were administered on feeding trays made of polyethylene sheet fixed on bamboo frame. Traditional feed applied in pond 4.1 was dispersed from along the dikes.

TABLE 4
FEEDING RATIONS IN DEMONSTRATION PONDS
(KG/1000M2)

MOC = Mustard Oil Cake
W/Rb = Wheat/Rice Bran
CB = Cattle Blood
FM = Fish Meal
GD = Ground Duckweed
FD = Floating Duckweed

2.6 Sampling and harvesting

Sampling was done frequently to monitor growth and health condition. At the end of about 5th – 7th week when the fingerlings attained or exceeded 10 g average individual weight (10 cm), feeding was stopped and the ponds were harvested within 2 days.

2.7 Survey of locally used fish seed production technologies

A survey on the fish seed production methods/practices adapted in different parts of the country, was conducted. Production data of 8 fish seed producers were collected from Faridpur, Kumarkhali, Kushtia, Natore and Sreemongal. The selected farmers possessed approximately 380 bigha (51 ha) water surface area. A similar survey was conducted in the nearby area of Jessore (representing 195 bigha or 26 ha fish pond) where an advanced technology of fish seed production was being applied. Results of the survey conducted are summarized in Table 5.

TABLE 5
SUMMARY OF THE SURVEY CARRIED OUT ON PRIVATE FINGERLING PRODUCTION FARMS

I.: Faridpur, Kumarkhali, Kushtia, Natore, Sreemongal
II.: Jessore
* The prenursed fry (Dhani) are not sold but used in the same farm for stocking for fingerling production ponds. Production cost of Dhani is = Tk.0.05/pc