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Effects of Transport Media and Duration on the Mortality and Physiological Responses in Silver Carp Hypophthalm Ichthys Molitrix Fingerlings.

MAHMUD HASAN
Department of Fisheries, University of Dhaka, Dhaka-1000, Bangladesh.

ANWAR HOSSAIN
Department of Fisheries, University of Dhaka, Dhaka-1000, Bangladesh.

SHANKAR C. MANDAL
Department of Fisheries, University of Dhaka, Dhaka-1000, Bangladesh.

WAHIDA HAQUE
Department of Fisheries, University of Dhaka, Dhaka-1000, Bangladesh.

Abstract/ Executive Summary:

This study evaluated the effects of three transport media i.e., well water (WW), pond water (PW) and mixture of the two (WPW; 1 : 1) and durations (1, 3, 6 and 9 hrs) on the mortality and physiological responses in silver carp, Hypophthalmichthys molitrix fingerlings in a transport simulation at 400 g/l loading density. While the total mortality was lower than 9% until 6 hrs of transport, it was very high (49 - 60%) at 9 hrs across all three treatment media. The highest level of cortisol was measured in the fingerlings simulated using WPW while the lowest level was detected in the fingerlings sampled form WW. The level of cortisol observed in the fingerlings simulated using PW was not different from other two media . Between durations, the levels of cortisol observed were significantly different. The highest chloride level was measured in the fingerlings simulated using WW while the lowest level was observed in the fingerlings sampled from WPW. PW did not result in different chloride level from those of WW and WPW. Among duration treatments, while 9 hrs resulted in the lowest level of chloride, the highest level was detected at 1 hr. The results suggest that WW, PW and WPW can be used as medium in transporting well conditioned silver carp fingerlings for 6 hrs with little mortality and less stress effects.

Keywords: Transport, Media, Silver carp, Mortality, Cortisol, Chloride

Location:

Start Date:

End Date:

Program Area: Postharvest and Agro-processing

Commodity: Carp fish

Objectives:

To assess the plasma cortisol and chloride levels as indicators of stress responses.

Methodology:

Silver carp fingerlings (8.94 ± 1.16 cm; mean ± SEM) were obtained from Jagorany Chakra hatchery, Jessore. Fingerlings were well conditioned following methods practiced by the nursers. First, they were transferred from nursery to the conditioning pond (40 x 30 m). After 24 hrs in the conditioning pond, the fingerlings were seined and confined in hapas (size: 5 m²; 200 g/m²) with manual aeration (water splashing) for 30 minutes every morning for 5 days(⁵) . After 30 minutes of aeration, the fingerlings were released back into the conditioning pond. The fingerlings were fed daily wet mustard oil cake (MOC) at 2% body weight (BW) and suspended feeding 24 hrs before loading for transport. Nine aluminum vessels (20 litre) were filled with well water, pond water, and the mixture of well and pond water (1 : 1). Each vessel was stocked with 4 kg fingerlings at 400 g/l for simulation . During simulation 1/3 of the medium was changed at 1.5 hrs interval from each experimental unit to maintain good water quality. A 3 x 4 factorial design was used with three replicates. The experimental variables were transport medium and duration (1, 3, 6 and 9 hrs). The media were given manual aeration by hand agitation. Mortality, plasma cortisol and chloride levels were measured as the indicators of stress responses. Dissolved oxygen (DO), temperature and pH were also monitored before and af ter loading at different periods in the transport vessels. Blood samples (n = 10) were drawn before loading as control (0 time), and 1, 3, 6 and 9 hrs after transport. Dead fingerlings were removed and counted to determine the mortality, and water quality variables were also monitored at the time of fingerling sampling. After each sampling of fingerlings, the water volume was adjusted to maintain the initial loading density. Dissolved oxygen and water temperature were measured using a portable DO meter (HACH sension 6, Loveland, CO, USA), and pH using a pH and ISE meter (Orion 290 A plus, Boston/Baverly, MA, USA). Benzocaine 100 mg/I was used to anesthetize fingerlings before blood collection. Blood was pooled from each treatment into EDTA (100 g/l) heparinized disposable (2.5 ml) syringes by severing the caudal peduncle. Af ter collection the blood was stored into vials on the ice for 1 hr and centrifuged at 5000 x g for 5 min using microcentrifuge. The supernatant plasma was frozen at -20°C until analyzed. The plasma cortisol and chloride levels were measured following Hasan and Bart (⁷). Mortality rate data were transformed into square root before statistical analysis. Treatment means between media and duration were compared using ANOVA followed by Tukey's HSD post hoc for multiple comparisons. Statistical software SPSS version 10.0 was used to analyze the data with the level of significance at p < 0.05.

Source of Information: Dhaka Univ . J. Biol. Sci. 22(1): 55-62, 2013 (January)

Article Link (Online Journal):

Funding Source:

Total Budget (Tk.) :

Achievement/Findings:

Well water, pond water and the mixture of both can be used fat transporting well conditioned silver carp fingerlings for 6 hrs with little mortality. Well water has positive effects in maintaining high plasma chloride level that is crucial for successful transport.

Knowledge Management: Journal