*Nandita Ray and Bahni Dhar
College of Fisheries, Central Agricultural University
E mail of first Author: firstname.lastname@example.org.
Phone no : 9436468532, 9774647130, 9436771478
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Address for correspondence :
Phone no : 9436468532, 9774647130, 9436771478
Present address of the author: College of Fisheries,Lembucherra, Agartala
Designation: Field-cum-lab. Assistant. Phone: 0381-2865-264.
Nandus nandus (1822) is a preferred fish in Tripura. Presently its population is declining rapidly and it is now considered as an endangered fish species. So keeping the importance of this species in view, a study has been carried out to unfold its proximate composition such as moisture, protein, carbohydrate, fat and ash and muscle pH. During bioenergetics study it was observed that the fish feeds more in summer season. Microbiology study of fish showed that the fish is in acceptable condition.
Key words: Nandus nandus, Proximate composition, bioenergetics, microbial profile
Nandus nandus (Ham.1822), commonly known as leaf fish is widely distributed in India, Bangladesh, Mayanmar, Pakistan and Thailand including wetlands and beels of Tripura. This fish is also called meni, bheda, nados etc in local languages. The fish is very delicious, costly and widely accepted species throughout eastern India particularly in Tripura. Fish is one of the main food constituents in our diet as it includes essential fatty acids, amino acids and some of the principal vitamins and minerals in sufficient amounts for healthy living(Borgstrom,1961). Protein, fat and water content of fish is important to consumers, scientists and manufacturers from many aspects including nutritional value, seasonal variations and considerations regarding processing (Murray and Burt, 2001). A nutritionist wants to know about the contribution a fish can make to the diet and to health, and the cook must know whether a fish is normally lean or fatty in order to prepare it for the table. A processor, a nutritionist, a cook and finally the consumers all have a direct interest in the composition of fish which is one of the most valuable sources of high grade protein available to man in this hungry world. Fishes show large variations in their biochemical composition from species to species and knowledge on proximate composition of fish will help to evaluate its nutritive value and physiological condition (Brown and Murphy, 1991). There are many reports available on the proximate composition of fresh water fishes but study on composition of this particular fish is this species is scarce. Sea foods may harbour a number of biohazards as well as chemical contaminations such as biogenicamines, biotoxins, pathogenic bacteria and viruses (Gram et al., 2000 and Ashie et al., 1996). For eg. the presence of Staphylococcus aureus a normal flora of skin and mucous membrane of humans can be attributed to human contact during handling and processing (Dalgaard et al., 2006). Several studies have demonstrated many bacterial species encountered in different fish which are potentially pathogenic under certain conditions. (Adedeji et al., 2011). So to determine whether a particular fish is acceptable or not microbiological study is important.
Bioenergetics study helps us to know about food consumption rate, growth rate, percentage of fecal matter excreted. Fisher et al. (1973) have calculated food consumption rate of grass carp in the form of a regression formula under laboratory conditions. Consumption rate is bound to increase with increase in temperature up to an optimum. The portion of the nutrient not excreted as faeces out of the quantity consumed is known as assimilation. Winberg (1956) is of the opinion that total assimilation efficiency is around 80%. The assimilation efficiency varies greatly with the concentration of the nutrient in the diet and feeding level. It is also dependable on the physiological status of the organism, feeding habit, temperature of the medium and special situation in the life history like, maturation, spawning, incubation period of the egg etc. So, bioenergetics study was done to know about the feeding rate, growth rate and other parameters of this fish.
So, the present investigation was carried out to unfold the bioenergetics, proximate composition, microbial status of Nandus nandus, a small indigenous fish species.
Materials and methods :
In the present study, fish was collected from the local fish markets of Agartala during the period 2011. The fishes were collected from Battala, Lake Chowmuhani and Golbazar fish markets where these fishes are available in plenty. A study was done by the following methods given below.
Moisture: Moisture was estimated by following method described by AOAC (2000). A representative fish sample was taken into moisture bottle and dried at 100±5° C in a hot air oven for about 16 hrs. Moisture was calculated by the formula
Moisture (% by weight) = 100(W1- W2)/(W1 –W)
where, W= Weight in gms of the empty dish,
W1 = Weight in gms of the dish with the material before drying.
W2 = Weight in gms of the dish with the material after drying.
Ash content : Ash or total mineral content was estimated following AOAC (2000). A representative fish sample was ignited in a muffle furnace at 550° C to obtain ash.
Total ash (% by weight) = 100 (W2- W)/(W1-W)
Where, W= Weight in gms of the empty dish,
W1 = Weight in gms of the dish with the material before ashing
W2= weight of the dish with ash.
Fat : Fat was estimated following AOAC (2000) using Soxhlet extraction method.
% Total lipid = Weight of fat in the sample / original weight of the sample x 100.
Crude protein percentage: Crude protein was determined by the method of AOAC (2000) microkjheldahl technique.
% Total Nitrogen = 14 x N x X x 250 x 100/1000 x V1 x W,
Where, N = normality of H2SO4,
X= ml of standard H2SO4 required for titration of samples,
V1=ml of digested extract taken for distillation.
W=weight of sample,
Since average nitrogen content of the fish protein is 16% so 1 gm nitrogen= 100/16= 6.25g protein Hence,% protein = % total nitrogen x 6.25 (conversion factor).
Carbohydrate: Carbohydrate was estimated using anthrone following (AOAC 2000) method. The absorbance was measured at 620nm in spectrophotometer.
Glucose (in mg) 100
—————- x Dilution factor x ————–
Weight of fish (g) 1000
Total plate count: Total bacterial count in the fish sample was estimated following APHA (2001). The method used was spread plate technique using Nutrient agar as the culture media. The prepared plates are inoculated and kept in incubator for different time intervals. The bacterial count was expressed as colony forming unit/gram (cfu/g).
No of colonies/weight of fish sample x dilution factor.
Bioenergetics study: Bioenergetics study was done by following the methodology of Brett and Groves (1979). It was performed for a month taking 30 nos of fishes (Weight range = 12.90±3.11 gm). During this study, the amount of food consumed by the fishes, their growth rate, percentage of excreted faecal matter etc. are observed.
Results and discussion:
The bioenergetics study on N. nandus shows that the rate of food consumption is usually larger during the summer months. Similar result was also noted by Brett (1995). Mabaey (1971) observed greater growth rate in male tilapia when Tilapia mossambica fed with artificial diets. Tesch (1977) worked on the eel with reference to management and biology and found greater growth in female fishes. He pointed out that during winter period the fishes feed quantitatively poor and in other cases the fishes do not feed at all and use the stored energy. Interestingly the present observation noticed that during winter months the rate of food consumption was significantly lower than the summer months. But the percent calories input lost (23.986±2.041) through fecal matter in winter was much greater than the summer (16.766±1.41). Further, the caloric value of fecal matter during winter was 7.489±0.692 kcal/gm, while in summer it was much less(4.891±0.292 Kcal / gm).Therefore it appears that both the temperature and season not only affect the rate of food consumption but also affect the degree of loss of faecal matter. Hence, it may be stated that both the temperature and season affect the process of digestion as well as assimilation either directly or indirectly. During summer months, the caloric value of fish tissue was 5.762±0.412kcal/gm, while in winter it was only 4.017±0.766 kcal/gm. Further in summer, total wt gain in dry wt was 0.811±0.017gm. The line chart shows (Fig 1) comparison between the bioenergetics study during the summer and winter months. Hence, it indicates that summer temperature greatly influences the feeding rate as well as digestion while winter causes poor feeding rate in the fishes. As a result stored food is being exploited as energy resource. (Brett 1971).
Proximate composition study:
The main constituent of fish flesh is water, which usually accounts for about 80 %of the weight, average water content of the flesh of fatty fish is about 70 per cent. The moisture content of Nandus was estimated to be 79.74. This fish has got ash/mineral content of 5.7. The small indigenous fishes are reported to be rich in minerals as they are consumed whole. They supplement minerals and micronutrients in our diet (Thilsted et al.,1997). Fat content in Nandus was estimated to be 2% and carbohydrate 0.208%. Furthermore, some nutritional components of fish have functional effects on human health. For example, fish oil is one of the most important natural sources of polyunsaturated fatty acids including eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), which have been proven to have useful effects on human health (Saoud et al., 2008; Rafflenbeul, 2001). The composition, however, varies greatly from species to species and also from individual to individual depending on age, sex, environment and season (Huss, 1988; 1995). The crude protein content was estimated it was found to be 52.5%. pH of muscle of Nandus nandus was 6.58. A similar study on biochemical composition of 26 small indigenous fish species of North-east India including N. nandus was carried out by Karthikeyan et al (2007).
The total plate count study of N. nandus(Ham.1822) shows a value of 2.3 x 104 cfu/gm which is within the acceptable limit for a fresh fish.
Finally, it is expected that the studied parameters like moisture, crude protein, fat, ash, carbohydrate, pH etc will be helpful for nutritionists of fish biology for knowledge on the nutritional importance of this fish. The microbiology study also gives the status of good condition of this fish. The bioenergetics study reveals that this fish feeds more in summer.
Summary : Nandus nandus(leaf fish) found in ponds, beels, lakes in Tripura. It has also good consumer preference. But now a days the fish is showing a declining trend. So the present study is aimed to get overall picture about the food consumption pattern, proximate composition and microbiological status of Nandus nandus(leaf fish). During this study, it is found that the fish feeds more in summer months and less in winter months. The growth rate is more in summer months and less in winter. The caloric value of the faecal matter is more in winter than in summer months. The study of proximate composition shows that the fat content is low and protein content is good. The mineral content is 5.7. During microbiology study shows that the total microbial flora in the fish is within the acceptable level. So keeping all these points in view, it is needed to protect this species in the actual habitat from further declination. Otherwise, the present condition of this fish may lead to exhaustion of the species if appropriate measures are still not initiated.
I heartily acknowledge Professor A.K Roy, College of Fisheries for his very useful moral support and guidance for doing this work.
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