2. Experimental treatment Experimental treatment
Partial Replacement Of Fish Meal with Salt-Marsh Grass (Porteresia coarctata) on Growth Performance and Length-Weight Relationship of Macrobrachium rosenbergii Kunal Mondal, Subhra Bikash Bhattacharyya*, Rajrupa Ghosh*, Sufia Zaman*, Subhasmita Sinha** and Abhijit Mitra* Department of Marine Science, University of Calcutta, 35 B. C. Road, Kolkata , India *Attached to Department of Oceanography, Techno India University, EM-4, Sector V, Salt Lake, Kolkata , India **Kakdwip Research Centre of Central Institute of Brackishwater Aquaculture (ICAR), Kakdwip , West Bengal, India Correspondence:
Introduction
Freshwater prawn (Macrobrachium rosenbergii) is one of the most commercially important species in the fisheries sector of India as a source of animal protein and foreign exchange earner. It has recently been identified as an important shellfish species for culture in South-Asian countries after significant losses in penaeid shrimp culture in mid- 1990’s due to viral diseases (Paez-Osuna 2001, Moss et al. 2001). Fish meal makes up a major part of the formulated feed for any carnivorous fish species as a protein source. However, the recent scarcity, rising cost and uncertain consistency in supply of fish meal have increased the efforts to search for the alternative protein sources to fish meal in aquaculture by the fish nutritionists and feed manufacturers. On this background, the present study aims to evaluate the effect of partially replacing fish meal with salt-marsh grass (Porteresia coarctata) as ingredient in prawn feed preparation. The salt-marsh grass is another cheapest source of protein(~11%), widely available in the intertidal mudflats of Sundarbans.
Fig. 1: Salt-marsh grass vegetation on intertidal mudflat
Methods
Collection and processing of plant material: Live and healthy P. coarctata leaves were collected from the intertidal mudflat in the mangrove belt of Kakdwip region (21o52'35.7'' N latitude and 88o11' 55.0'' E longitude) during low tide condition (Fig. 2) and the collected materials were washed and finally processed to make powder.
2. Diet preparation and experimental prawn farming: Control and experimental diets were formulated and the culture experiment of M. rosenbergii was conducted during April to November 2012 in farm condition at Kakdwip region of Indian Sundarbans (Fig. 2)
3. Analysis of growth performance and length-weight relationship: The growth performance parameters were analyzed according to the method outlined by De Silva & Anderson, 1995 and L-W relationship was calculated following the conventional formula, W= a. TLb (Ricker, 1973)
Salt-marsh grass
A salt-marsh grass is a vital biotic component of the marshy ecosystem found along the coastal and deltaic zones (Fig.1). They are highly productive floral species and have wide range of salinity tolerance. In the present study, the salt-marsh grass P. coarctata is the marsh grass species that has been used as one of the ingredient for prawn feed preparation. Apart from its nutritional value, the species has ecological value as it brings stability to the newly formed island. It is also referred to as pioneer species in the process of ecological succession.
Results
Table 1: Growth performance Table 2: Length-weight relationship
Parameters
Experimental treatment
Control treatment
Condition factor
1.22 ± 0.1a
1.14 ± 0.12b
Survival (%)
65.73 ± 5.41a
58.28 ± 5.92b
Specific growth rate (%)
1.40 ± 0.15a
1.33 ± 0.14b
Feed conversion ratio
1.81 ± 0.25a
2.02 ± 0.39b
Final body weight (gms)
72.04 ± 3.14a
61.76 ± 4.98b
Muscle protein content at harvest (%)
67.41 ± 1.02a
64.17 ± 1.33b
Experimental treatment
Control treatment
W= x TL2.968
W= x TL2.890
Fig. 2 Map showing the culture location
Conclusion
The deltaic complex of Sundarbans in the lower Gangetic region offers a unique opportunity for the culture of M. rosenbergii.
The present study reveals the upgradation of growth performance and related success indicators of M. rosenbergii culture due to the use of P. coarctata based feed (Table 1&2).
We conclude from this study that partial replacement of fish meal by P. coarctata as feed ingredient can give better results and it can be recommended to the local fish farmers for ecofriendly aquaculture which can pave the avenue of alternative livelihood in the coastal zone where mangroves are widely distributed.
Kakdwip
Study design
To screen salt-marsh grass (P. coarctata) from Indian Sundarbans for its protein content in context to prawn nutrition.
To prepare formulated feed using P. coarctata powder as one of the ingredient.
To study the effect of P. coarctata based feed on growth performance and length-weight relationship of the cultured species (M. rosenbergii)
Planning of alternative livelihood programme through ecofriendly and sustainable aquaculture practice in Sundarban islands.
*Figures with different superscripts in the same row are significantly different (p<0.01)