Mohammad Mustafizur Rahman
Aquaculture Research Team, ESFRI, National Fisheries Research and Development Institute, Gangnung, Gangwon, 210-861, Korea.
Marc Verdegem
Department of animal Science, Aquaculture and Fisheries Group, Wageningen University, Wageningen, The Netherlands.
Md Abdul Wahab
Faculty of Fisheries, Bangladesh Agricultural University, Mymensingh, Bangladesh.
Md Yeamin Hossain
United Graduate School of Agricultural Sciences, Kagoshima University, Kagoshima, Japan.
QtaeJo
Aquaculture Research Team, ESFRI, National Fisheries Research and Development Institute, Gangnung, Gangwon, Korea.
Swimming, Grazing, Behaviours, Rohu, Common carp
Fisheries Faculty Field Laboratory, Bangladesh Agricultural University, Bangladesh.
Animal Health and Management
The experiment was carried out between November 2003 and January 2004 in six rectangular tanks [area: 1 m2 (2.5 m 0. 4 m ), height : 0.9 m ] at the Fisheries Faculty Field Laboratory, Bangladesh Agricultural University, Bangladesh. In each tank, the two short sides were constructed from concrete and the two long sides were made from glass, allowing direct observation of fish throughout the whole tank. In the tanks, pond condition was simulated: the bottom received pond sediment and the tanks were filled with pond water. The heights of the sediment and the water column in each tank were 10 and 70 cm respectively. If the turbidity in the tank became too high, preventing observation of all areas with in the tank, the water was diluted with pond water. All tanks were treated with CaCO3 at a rate of 250 kg ha-1 (25 g tank-1), decomposed cow manure at 1250 kg ha-1 (125 g tank-1), urea at 31 kg ha-1 (3.1 g tank-1 ) and triple super phosphate at 16 kg ha-1 (1.6 g tank-1) 1 week before fish stocking. All glass walls were covered by bamboo mats to minimize sunlight penetration other than via the water surface. Bamboo mats were only removed when recording fish behaviour. The study was set up as a factorial experiment with three factors: factor 1, time (two levels: light and dark conditions): factor 2. common carp density (three levels: 0, 1 and 2 common carp tank-1 ); and factor 3, feed addition (two levels: with and without artificial feed). The combinations of factors 2 and 3 resulted in the following six treatments: rohu alone without formulated feed, rohu alone with feed. rohu plus 0.5 common carp m-2 without feed, rohu plus 0.5 common carp m-2 with feed, rohu plus 1 common carp m-2 without feed and rohu plus 1 common carp m-2 with feed. All treatments were performed in triplicate. Factor 1 was only considered during behavioural observations and data analysis. Because we had only six tanks, we assigned the treatments randomly to the tanks. The experiment was repeated three times, considering time observations as blocks in the analysis of variance (ANOVA). Between repetitions, the tanks were completely emptied and cleaned. All tanks were stocked with three rohu. Rohu and common carp stocked in the tanks were of similar total length, ranging between 17 and 19 cm, and ranging in weight between 66.5-68.3 and 79.9- 82.0 g respectively. Fish were always stocked between 19:00 and 20:00 hours. After stocking, an acclimatization period of 1 week was included before starting behavioural observations through video recording. A 30% protein diet containing fish meal (protein: 57.5%. inclusion in feed 37%). rice bran (14%.47%), mustard oil cake (14%. 15%) and vitamin pre-mix (0%, 1%) was applied daily at 15 g kg -08 day-1 at 10:00 hours from the day of stocking until the day of harvesting. Water quality parameters viz., temperature, dissolved oxygen, pH, nitrate nitrogen, total ammonia nitrogen, total nitrogen, phosphate phosphorous (PO4 -P) and total phosphorous, were determined before stocking. harvesting and recording behaviours. Plankton and benthic macroinvertebrates were sampled at the beginning and at the end of the experiment. Periphyton biomass was sampled at the end of the experiment. For plankton collection, a 5-L sample was passed through a 10 µm-mesh plankton net. Each concentrated plankton sample was then transferred to a plastic bottle and diluted to 100 mL with 5% buffered formalin solution. Plankton numbers were estimated in a Sedgewick-Rafter (S-R) cell (Graticules. Kent. UK). A 1mL sample was placed in the S-R cell and left for 10 min to allow the plankton to settle. The plankton in 10 randomly selected fields in the S-R cell was identified up to the genus level and counted under a microscope. The biovolumes of plankton, periphyton and benthic macroinvertebrates were calculated based on length and shape measurements. At the end of the experiment, tanks were drained and all fish were harvested and weighed to the nearest 0.1 g to determine specific growth rate (% body weight day-1). Water quality, natural food availability and fish growth data were collected to check whether the simulated tank environments were representative for the pond environment. All data were checked for normality before analysis. Only behavioural per cent data had to be arcsine transformed before analysis, but non-transformed data are shown . All behaviour data were analyzed through 2 x 3 x 2 factorial ANOVA using the computer statistical package SAS, applying a complete random block design. Factors were common carp density (three levels), artificial feed (two levels) and time (two levels). The effects of common carp density and artificial feed and their interactions on grazing, swimming, resting and social behaviours of rohu and common carp are discussed in a separate article. The present paper discusses only the effects of time (day and night) and the interaction effects among time. com- mon carp density and artificial feed. If a factor was significant. differences between the means were analyzed using the Tukey test for unplanned multiple comparisons of means (P<0.05 level of significance). The light period (day) included observations at 08:00, 11:00, 14:00 and 17:00 hours. and observations at 20:00. 23:00.02:00 and 05:00 hours were considered to be the dark period (night). Each of the four observations per period (day or night) were analyzed separately and then summed together to obtain day and night behaviour. Water quality, natural food availability and fish growth were analyzed using two-way ANOVA. In none of the cases was there a Significant block effect and therefore the block effect is not reported in the tables.
Aquaculture Research, 2008, 39, 1383-1392
Journal