| Livestock Research for Rural Development 21 (10) 2009 | Guide for preparation of papers | LRRD News | Citation of this paper |
The present study attempts to assess the potential of periphyton vis-a-vis supplementary feeding on growth performance of pearlspot, Etroplus suratensis (mean weight 0.28g) grown in inland saline groundwater ponds for 90 days. Three treatments (1-3) each in replicate of two were maintained. In treatment 1 (Substrate ponds) bamboo poles as substrate were used to increase the submerged surface area (only substrate, no feed). In treatment 2 (feed ponds), fish were fed on a supplementary diet, while no substrate or supplementary diet was used in control ponds (treatment 3). Irrespective of the treatments, all ponds were fertilized with cow dung at 7500 kg ha-1 y-1 at biweekly intervals.
Fish growth in ponds provided with substrate (mean weight 129.7±3.33g; SGR 6.8±0.04) was significantly (P<0.05) higher as compared to feed ponds (mean fish weight 104.5±5.35g; SGR 6.5±0.08) and control ponds (65.1±4.79g; SGR 5.9±0.10), indicating 24% and 100% higher growth, respectively. Length weight relationship (W=cLn) also showed higher exponential value of ‘L’ (n=3.4) in substrate ponds. No significant differences in most of the water quality parameters were observed among different treatments; however, turbidity, NH4-N, net primary productivity, chlorophyll a and epilithic periphyton density remained significantly (P<0.05) lower in substrate ponds as compared to feed and control ponds. Significantly (P<0.05) higher values of periphyton biomass in terms of dry mater (1.6±0.01 mg cm-2), chlorophyll a (10.0±0.64 µg cm-2) and mean periphyton productivity (0.8 mg C m-2 d-1) were observed at a depth of 50 cm, while autotrophic index remained low (88.4) at this depth. No significant variations in sediment chemistry was observed among different treatments; however, alkalinity, NO3-N, organic matter and benthos were significantly (P<0.05) higher in treatment 2, where the fish were fed on supplementary diet. Fish grown in ponds provided with substrate had significantly (P<0.05) higher values (mg g-1 h-1) of digestive enzyme activity (protease 4.7, amylase 2.3 and cellulolytic 2.9). Higher accumulation of muscle protein (175.0 mg g-1), muscle (3.2 mg g-1) and liver (3.9 mg g-1) glycogen and high values of viscero-somatic index (13.4) and hepato-somatic index (2.9) were also observed in fish grown in substrate ponds.
This study thus clearly suggests that provision of substrate in culture ponds resulted in higher growth/ yield of pearlspot, even in comparison with treatment 2 (feed ponds), indicating the usefulness of periphyton in growth enhancement and development of economically viable and eco-friendly fish culture technology.
Key words: Autotrophic index, fish growth, gut enzymes, inland saline ground water, periphyton, water quality
Traditionally phytoplankton is considered very important as the basis of natural food production, influencing both autotrophic and heterotrophic pond food webs. Periphyton has the functions of oxygen and feed production same as phytoplankton, but is considered to be more stable and thus can be utilized more efficiently by many fish species which thrive low in the food chain. Periphyton is the total assemblage of sessile organisms attached to the submerged substrate, which includes not only the algae, fungi and invertebrates, but also detritus and microorganisms (protozoans, bacteria etc.), that swim, creep or lodge among the attached forms (Young 1945). Verdegem et al (2001) through proximate composition have shown higher nutritive value of periphyton under ungrazed conditions (protein 41.4% and fat 7.9%) than under grazed conditions (protein 23-26% and fat 2.7%).
The feasibility of using periphyton based systems has been explored and found to enhance primary production, food availability and fish production as compared to the traditional system of fish culture (Welcomme 1972; Hem and Avit 1994; Konan-Brou and Guiral 1994). Thus, periphyton-based aquaculture could be an important step if aquaculture production by resource-poor farmers is to grow further (Azim et al 2002; Keshavanath et al 2002; Azim et al 2004). In recent trials artificial surfaces substrates are being used in the aquatic ecosystem for the development of periphyton communities for enhancing fish growth/production (Azim et al 2004).
The pearlspot, Etroplus suratensis (Cichlidae) is an important brackishwater edible fish which thrives well both in fresh and brackishwaters. It feeds mostly on decayed organic matter, filamentous algae, dead microorganisms, lab-lab, etc. (Devaraj et al 1975; Keshava and Mohan1988). In the present study, we investigate the effect of periphyton on growth performance of pearlspot in inland saline groundwater and compare it that of supplemental feeding. Usually, activity of digestive enzymes in the gut changes with the feeding habits of the animals (Tengjaroenkul et al 2000). Knowledge of the digestive enzyme profile and other related parameters can be the clue to explain the digestive processess. Since periphyton has been considered to be an important food component, therefore, we also investigate the impact of periphton grazing on hepato-somatic index (HSI), viscero-somatic index (VSI), digestive enzyme activity and carcass composition of fish grown in experimental ponds. Further, along with these investigations, hydrobiological parameters and sediment quality of ponds were also monitored.
Experiment was conducted at the brackishwater fish pond facility of the Department of Zoology and Aquaculture, CCS Haryana Agricultural University, Hisar (Lat. 29o, 10'N; Long 75o, 46'E), India in earthen ponds, each measuring 15m×25m (area 375 m2 with 1.5 m depth), from March to June 2004. Prior to the commencement of treatments, ponds were sun dried and cleaned of all the vegetation. On day 1 (March 1, 2004), bamboo poles (1 meter long and 3.1 cm diameter) were fixed vertically into the ponds to provide substrate for the development of periphyton. Substrates were fixed at the bottom of ponds by digging 20 cm deep holes at an equal distance of one meter, so that a total of 299 poles were used per pond representing a submerged surface area of about 29.1 m2 in each pond. Subsequently, quick lime (CaO at 200 kg ha-1) was applied and ponds were filled with saline water by pumping from deep aquifers. On day 7 (March 7, 2004), first dose of cow dung was applied. To maintain the desired level (75 cm), water was replenished as often as required. Water salinity during the experimental period fluctuated between 12.8 to 13.5 ppt.
Irrespective of the treatments (1-3) semi-dry cow dung (at 7,500 kg ha-1 y-1) was applied at biweekly intervals to fertilize the ponds. Manure was diluted in pond water (in the ratio 1:3 w/v) before application. Two replicates per treatment were maintained as follows :
Treatment 1 (Substrate) : Ponds with additional substrate, no supplementary feeding.
Treatment 2 (Feed) : Ponds with no additional substrate, only supplementary feeding.
Treatment 3 (Control ) : No additional substrate and no supplementary feeding.
Two weeks after the application of the first dose of organic fertilizer (on March 21, 2004), 30 day old Etroplus suratensis (average body weight 0.28g) were stocked at 10,000 fish ha-1 . The duration of grow out period was 90 days.
The fish in treatment 2 (with supplementary feed) were fed daily twice (between 0800-0900 and 1500-1600 h) on a supplementary diet at 5% BW d-1 (fish meal as the major protein source : 40.0% crude protein, 7.4% fat, 5.8% crude fibre, 35.8% nitrogen free extract, 11.0% ash and 18.5 kJ g-1 energy). Feeding rate was adjusted every 15th day after weighing a representative sample of about 80-100 fish.
The periphyton biomass growing on the substrate was determined in terms of dry matter (DM) and pigment concentration (chlorophyll a and pheophytin a) at biweekly intervals following standard methods (APHA 1998) beginning on day 15 following the application of first dose of fertilizer. From each pond, three poles were selected by random number tables and two 3 cm × 3 cm samples of periphyton were taken at each of four depths (0, 25, 50 and 75 cm below the water surface) per pole. Periphyton samples were collected from the poles following Azim et al (2001a).
One sample out of two (i.e. 3 samples from each replicate pond/depth), was used to determine total dry matter and ash content. Samples from all sampling dates, poles per replicate ponds and per depth were pooled and ashed in a muffle furnace at 550oC for 6h. Dry matter (DM), ash free dry matter (AFDM), autotrophic index (AI) and ash content were calculated following APHA (1998). AI was calculated as follows:
Ash values were also used to calculate periphyton productivity (APHA 1998) and expressed as follows :
Periphyton productivity (mg ash free weight m-2 d-1) = Ash free weight (mg cm-2)×100 /t
Where, t = duration of experiment (90 days).
Out of the remaining 3 samples of each replicate per depth, two were used for
determining periphyton population. Samples from each depth were suspended in 50
ml of distilled water and stored in plastic bottles. Periphyton number was
enumerated using a Sedgwick-Rafter cell according to the procedure described for
planktons and calculated as follows :
N = P×C×100/S
Where,
N = periphyton number cm-2 (whether single celled or multi cellular, counted as one unit)
P = total number of periphyton units counted in 10 fields of Sedgwick-Rafter cell
C = volume of final concentrate sample (ml)
S = area of scraped surface (cm2)
The remaining one 3 cm× 3 cm sample from each replicate was used to determine chlorophyll a and pheophytin a contents following standard methods (APHA 1998).
From each treatment, for comparison, periphyton samples (in replicate of four each 3×3 cm2) growing on the pond walls (epilithic) were also taken twice (at 45 day interval) during the experimental period of 90 days for the study of periphyton population and pigment concentrations.
Water samples were obtained in replicate of four from each pond (i.e. 8 samples from each treatment) before sunrise at 45 day interval (on May 5, 2004 and June 20, 2004) for the study of physico-chemical characteristics (Electrical conductivity, dissolved oxygen, BOD5, carbonates, bicarbonates, alkalinity, chlorides, hardness, Ca++, Mg++, total Kjeldahl nitrogen, NO3-N, NO2-N, NH4-N, o-PO4, SO4, turbidity and TDS) and analysed following APHA (1998). Temperature, pH and salinity were recorded daily. Net and gross primary productivity (NPP and GPP) were determined using light and dark bottle technique following APHA (1998).
Water samples for chlorophyll a and pheophytin a analysis were also collected in replicate of four from each pond by passing a known amount of water (10 L) through Whatman Filter Paper No. 40 and extracted using cold acetone at an interval of 45 days (APHA 1998).
Plankton samples were also collected by passing 20L of water taken from five different locations (4 L from each location) of each pond through plankton net (mesh size 125 µm) at an interval of 45 days. The samples were then carefully transferred to a measuring cylinder and a volume of 50 ml with distilled water was made and preserved in small plastic bottles with 5 per cent buffered formalin (concentrated sample). Plankton numbers were estimated using Sedgwick Rafter cell. One ml of the concentrated sample was placed on to the counting chamber and left to stand for 5 minutes to allow plankton to settle. Ten randomly selected fields of the chamber were counted under a binocular microscope and plankton density was calculated using the following formula:
Identification of plankton to genus level was carried out using the keys of Ward and Whipple (1959), Prescott (1962) and Bellinger (1992).
Sediment samples in replicate of four from each treatment were collected only once at the end of experimental schedule using a cone sampler (area 858.3 cm2) and analysed for physico-chemical (moisture, organic matter, pH, salinity, EC, chlorides, alkalinity, o-PO4 and NO3-N,) and biological characteristics (benthic population) following Piper (1966).
Ninety days post-stocking (June 20, 2004), ponds were completely drained and all the fish were harvested. Total bulk weight and number of fish recovered from each treatment were recorded. Thereafter, weight (g) and length (cm) of the individual fish were also recorded. SGR, condition factor (k) and length-weight relationship (LWR) were calculated.
Length-weight relationship (LWR) of fish was calculated according to the
following equation:
W = c Ln (Logarithmic form of equation is log W = log c + n log L)
Where,
W = weight in kg, c = constant, n = exponential value of length and
L = length of fish in cm.
Plankton
species diversity (d) was determined using the diversity index formula of
Shannon and Weaver (Washington 1984).
Where,
d = species diversity
ni = no. of individuals of ith species
N = total No. of individuals
From each treatment, eight fish were obtained and kept on ice tray, viscera and liver of the fish were extirpated for the determination of viscero-somatic index (VSI) and hepato-somatic index (HSI) respectively. Liver and muscle were processed for the estimation of glycogen (Thimmaiah 1999). Muscle protein was estimated following Lowry et al (1951). Intestine was extirpated and processed for the determination of protease (Walter 1984), amylase (Sawhney and Singh 2000), cellulase (Sadasivam and Manickam 1996) and lipase activity (Thimmaiah 1999).
Fish carcass (initial and final) and supplementary feed samples were analysed following AOAC (1995). Dry matter after desiccation in an oven (at 105oC for 24 hours), ash (incineration at 550oC for 4 hours in a muffle furnace), nitrogen using micro-Kjeldahl method were determined and the crude protein content was estimated by multiplying nitrogen by a factor of 6.25. Crude fat was determined by petroleum ether extraction (Soxhlet's apparatus). Carcass phosphorus was determined spectrophotometrically after acid digestion (nitric acid : perchloric acid 10:1). Per cent nitrogen free extract (NFE) was calculated by substracting the sum of per cent crude protein, crude fat, ash, moisture (% wet weight) and crude fibre from 100. Energy content of fish, fish feed and periphyton were calculated using the average caloric conversion factors of 0.3954, 0.1715 and 0.2364 kJ g-1 for lipid, carbohydrate and protein, respectively (Henken et al 1986).
The data were subjected to ANOVA to test the effect of treatment using the following model :
Yij = µ +Ti + eij
Yij = jth observation of ith treatment
µ = overall mean
Ti = effect due to ith treatment
eij = random error NID (o, σ2)
Arcsine transformation of the data presented in percentage was done before analysis of variance. Means were compared using Tukey’s test as described by Snedecor and Cochran (1982). Coefficient of correlation between different parameters and multiple regression between independent (hydrochemical parameters) and dependent (biological and productivity parameters) was determined.
Fish survival varied between 74 and 79 per cent. ANOVA showed a significant (P<0.05) increase in mean fish weight, biomass and other growth parameters (length, growth per day and SGR) including condition factor in ponds provided with substrate (substrate ponds). Mean fish weight increased from 0.29±0.006g to 129.7±3.33g in substrate ponds (F=34.34, d.f. 2,147, P<0.0001) in comparison with feed ponds (from 0.28±0.007 to 104.5±5.35g) and control ponds (from 0.27±0.007 to 65.1±4.79) (Table 1).
|
Table 1. Effect of substrate and supplementary feeding on growth performance and carcass composition of Etroplus suratensis grown in inland saline groundwater ponds (Duration of experiment–90 days) |
||||||||||||||||
|
Treatments |
Initial fish stock |
Final fish stock (after 90 days) |
Increase in fish mean weight, g (Length cm) |
SGR, % BWday-1 |
Cf, k |
LWR, n |
||||||||||
|
Stocking density 375m2 |
Total Biomass, Kg |
Mean fish weight, g (Length cm) |
Survival, % |
Total Biomass, Kg |
Mean fish weight, g (Length cm) |
|||||||||||
|
Substrate ponds |
375 |
0.11 ±0.002a |
0.29±0.006a (2.40±0.04) |
79.0 |
38.4±0.98a |
130±3.33a (15.5±0.30) |
129a (13.1) |
6.8 ±0.04a |
3.6a |
3.4
|
||||||
|
Feed ponds |
375 |
0.11 ±0.002a |
0.28±0.007a (2.42±0.04) |
78.0 |
30.6±1.57b |
105±5.35b (13.5±0.30) |
104b (11.1) |
6.5 ±0.08a |
4.2a |
3.2 |
||||||
|
Controls |
375 |
0.10 ±0.002a |
0.27±0.007a (2.18±0.04) |
74.0 |
18.1±1.33c |
65.1±4.79c (12.3±0.30) |
64.8c (10.9) |
5.9 ±0.10B |
3.8 a |
3.2 |
||||||
|
Carcass composition, % wet weight |
||||||||||||||||
|
Treatment |
n |
Moisture, % |
Protein, % |
Fat, % |
Ash, % |
Phosphorus, % |
Energy, kJ g-1 |
|||||||||
|
Initial |
4 |
71.8±0.02A |
16.5±0.18D |
3.4±0.16C |
2.8±0.16B |
0.5±0.01C |
6.4±0.09D |
|||||||||
|
Substrate ponds |
4 |
66.0±0.69B |
19.9±0.24A |
4.6±0.06A |
3.3±0.07A |
0.7±0.03A |
7.6±0.07A |
|||||||||
|
Feed ponds |
4 |
66.6±0.57B |
18.4±0.18B |
4.2±0.18AB |
3.3±0.07A |
0.7±0.01B |
7.3±0.06B |
|||||||||
|
Controls |
4 |
66.8±0.20B |
17.4±0.10C |
3.7±0.04 B C |
3.4±0.04A |
0.6±0.01B |
7.1±0.02C |
|||||||||
|
All values are mean±SE of mean Means bearing different superscripts in the same column differ significantly (P<0.05); BW = Body weight; n=number of observation Cf (condition factor) = Wt × 105/L3, where Wt is weight in grams, and L=total length in milimeters. SGR (% BW day-1) = Specific growth rate of weight = [In wt f- in wt i]×100/t, where wt f=final weight of fish (g), Wt i=Initial weight of fish (g), and t=duration of experiment (days). LWR (Length-weight relationship) : Log W=log c + n 1og L, where, W=Weight in kg, c=Constant, n=Exponential value of length, L=Length of fish in cm. |
||||||||||||||||
These results indicate an increase of about 24% in comparison with feed ponds and about 100% in comparison with control ponds. The exponential value ‘n’ of LWR was also high in ponds provided with substrate (n=3.4), followed by feed ponds (n=3.2) and controls (n=3.2).
Carcass composition revealed significantly (P<0.05) high accumulation of protein, fat, phosphorus and energy in fish grown in ponds provided with substrate in comparison with other treatments. Significantly (P<0.05) low values in these parameters were observed in fish carcass grown in control ponds. No differences in ash contents among different treatments were observed (Table 1).
Water salinity during the experimental period fluctuated between 12.8-13.5 ppt. No significant (P<0.05) variation in dissolved oxygen (DO), TDS, carbonates, hardness, chlorides and total Kjeldahl nitrogen was observed among different treatments. Free carbon-dioxide was absent during the entire period of investigations. pH, turbidity, EC, NH4-N, o-PO4, NO2-N, SO4 and BOD5 remained significantly (P<0.05) low, whereas NO3-N remained significantly (P<0.05) high in substrate ponds in comparison with other treatments. A review of the data further indicates that productivity indicating parameters (turbidity and total alkalinity), nutrients (NO2-N, o-PO4 and sulphate), bicarbonate, calcium and BOD5 were significantly (P<0.05) high in feed ponds in comparison with controls and substrate ponds (Table 2).
|
Table 2. Mean values of physico-chemical characteristics of water recorded from different treatment ponds stocked with Etroplus suratensis (Duration of experiment–90 days) |
|||||
|
Parameters |
Treatments |
LSD |
|||
|
n |
Substrate ponds |
Feed ponds |
Controls |
||
|
EC, dSm-1 |
16 |
18.6±0.13b |
19.0±0.28b |
19.6±0.12a |
0.55 |
|
pH |
16 |
7.5–8.4 |
7.5–8.3 |
8.0–8.8 |
– |
|
Dissolved oxygen, mg L-1 |
16 |
6.0±0.23a |
6.6±0.43a |
6.4±0.29a |
0.94 |
|
BOD5, mg L-1 |
16 |
3.6±0.11b |
4.4±0.15a |
4.1±0.11b |
0.36 |
|
Carbonates, mg L-1 |
16 |
4.8±0.57a |
4.5±0.34a |
5.0±0.37a |
1.25 |
|
Bicarbonates, mg L-1 |
16 |
204.0±3.43b |
221.3±2.21a |
204.0±0.48b |
6.76 |
|
Total alkalinity, mg L-1 |
16 |
208.8±2.99b |
227.0±2.01a |
209.0±0.44b |
5.99 |
|
Chlorides, mg L-1 |
16 |
5613.1±9.07a |
5653.6±10.59a |
5838.9±14.24a |
32.79 |
|
Total hardness, mg L-1 |
16 |
3275.0±25.00a |
3262.0±38.59a |
3287.5±20.15a |
82.57 |
|
Calcium, mg L-1 |
16 |
496.8±10.31b |
559.8±10.66a |
494.1±9.00b |
28.54 |
|
Magnesium, mg L-1 |
16 |
498.1±6.87a |
453.3±10.25b |
491.5±8.99a |
25.11 |
|
Total Kjeldahl nitrogen, mg L-1 |
16 |
7.6±0.86a |
9.1±0.87a |
8.8±0.87a |
2.47 |
|
NO3-N, mg L-1 |
16 |
1.1±0.01a |
0.8±0.02b |
0.8±0.01b |
0.04 |
|
NO2-N, mg L-1 |
16 |
1.0±0.01c |
1.1±0.01a |
1.0±0.01b |
0.02 |
|
NH4-N, mg L-1 |
16 |
0.6±0.01c |
1.2±0.01a |
0.9±0.01b |
0.02 |
|
o-PO4, mg L-1 |
16 |
0.2±0.002b |
0.3±0.01a |
0.2±0.01b |
0.02 |
|
SO4, mg L-1 |
16 |
105.6±3.31b |
144.2±8.68a |
121.2±1.84b |
1.40 |
|
Turbidity (NTU) |
16 |
20.9±1.20c |
28.6±0.41a |
24.9±0.55b |
2.78 |
|
TDS, mg L-1 |
16 |
7640.6±69.33a |
8495.3±57.11a |
8025.3±55.30a |
173.48 |
|
All values are mean±SE of mean of eight replicates and two sampling dates (n=16) Means bearing different superscripts in the same row differ significantly (P<0.05) Water temperature during the experimental period ranged between 24.8-31.5oC BOD5 = Biochemical oxygen demand TDS = Total dissolved solids LSD = Least significant difference NTU=Nephelo-turbidity unit |
|||||
Net primary productivity (NPP) and chlorophyll a remained significantly (P<0.05) high in feed ponds in comparison with the substrate ponds and controls (Table 3).
|
Table 3. Mean values of biological parameters and sediment qualities recorded from different treatment ponds stocked with Etroplus suratensis (Duration of experiments–90 days) |
|||||
|
Parameters |
Treatments |
LSD |
|||
|
n |
Substrate ponds |
Feed ponds |
Controls |
||
|
Net primary productivity (NPP), mg C L-1 day-1 |
16 |
0.8±0.05b |
1.0±0.04a |
0.9±0.03b |
0.12 |
|
Gross primary productivity (GPP), mg C L-1 day-1 |
16 |
2.2±0.05a |
2.5±0.07a |
2.3±0.02a |
0.60 |
|
Chlorophyll a, mg L-1 |
16 |
2.2±0.15c |
3.6±0.29a |
2.9±0.27b |
0.69 |
|
Pheophytin a, mg L-1 |
16 |
1.0±0.09a |
1.1±0.07a |
1.0±0.07a |
0.23 |
|
Phytoplankton, numbers L-1 |
16 |
10.0×103±1761a |
13.0×103±1502a |
13.0×103±344a |
3159.0 |
|
Zooplankton, numbers L-1 |
16 |
9.0×103±1220b |
11.6×103±2033a |
8.0×103±1073b |
2259.0 |
|
Phytoplankton d |
16 |
1.4±0.25b |
1.9±0.06a |
1.8±0.08a |
0.45 |
|
Zooplankton d |
16 |
1.6±0.09b |
2.0±0.05a |
1.9±0.14a |
0.30 |
|
Epilithic periphyton density, numbers cm-2 |
16 |
14188.0±3248.0B |
19775.0±3072.0A |
15969.0±2155.0B |
|
|
Epilithic chlorophyll a, mg cm-2 |
16 |
10.3±0.72b |
12.4±1.52a |
10.0±0.13b |
1.13 |
|
Epilithic pheophytin a, mg cm-2 |
16 |
3.8±0.03b |
4.9±0.16a |
2.7±0.12c |
0.90 |
|
Sediment |
|||||
|
Moisture, % |
4 |
41.2±0.41A (40.73-42.19) |
42.1±0.33A (41.41-42.79) |
42.1±0.56 A (40.78-43.11) |
1.23 |
|
Organic matter, % |
4 |
1.4±0.01C (1.40-1.43) |
1.6±0.01A (1.60-1.64) |
1.5±0.01B (1.47-1.51) |
0.06 |
|
pH |
4 |
8.5±0.02 A (8.47-8.55) |
8.6±0.00A (8.54-8.68) |
8.6±0.00A (8.56-8.58) |
0.03 |
|
Salinity, ppt |
4 |
0.5±0.02 A (0.30-0.50) |
0.4±0.00A (0.3-0.4) |
0.4±0.00A (0.3-0.5) |
0.10 |
|
EC, dSm-1 |
4 |
1.7±0.03 A (1.14-1.21) |
1.8±0.02A (1.15-1.17) |
1.8±0.01A (1.13-1.17) |
0.09 |
|
Chlorides, mg g-1 |
4 |
10.4±0.46 A (9.30-11.83) |
10.7±0.48A (9.43-12.01) |
9.9±0.22A (9.44-10.30) |
1.37 |
|
Alkalinity, mg g-1 |
4 |
1.7±0.03 c (1.63-1.77) |
1.8±0.02A (1.76-1.86) |
1.7±0.01A (1.73-1.77) |
0.09 |
|
o-PO4, mg g-1 |
4 |
.003±0.002A (0.003-0.004) |
0.003±0.0002A (0.004-0.005) |
0.003±0.0003A (0.003-0.004) |
0.001 |
|
NO3-N, mg g-1 |
4 |
.03±0.001 B (0.032-0.035) |
0.04±0.001A (0.037-0.042) |
0.03±0.001B (0.032-0.035) |
0.002 |
|
Benthos, numbers m-2 |
4 |
2000.0±115.47 C (2000-2400) |
3000.0±81.65A (2800-3200) |
2400.0±182.57B (2000-2800) |
337.22 |
|
All biological
values of water are mean±SE of mean of eight replicates and two
sampling dates (n=16), while sediment characteristics are mean±SE of
mean of four replicates and only one sampling date (n=4), Figures in
parentheses indicate range. Means bearing different superscripts in
the same row differ significantly (P<0.05). Water temperature
during the experimental period ranged between 24.8-31.5oC |
|||||
Epilithic chlorophyll a and pheophytin a concentrations were also significantly (P<0.05) high in feed ponds in comparison with controls and substrate ponds. No significant (P<0.05) variation in gross primary productivity (GPP) and pheophytin a values was observed among different treatments.
Phytoplankton density (no. L-1) showed no significant variation among different treatments. With regard to zooplankton density, significantly (P<0.05) high values were observed in feed ponds as compared to controls and substrate ponds. Plankton species diversity also remained significantly (P<0.05) higher in treatments 2 and 3 (Table 3).
No significant variations in moisture, pH, salinity, chlorides and orthophosphate were observed among different treatments. However, EC, alkalinity, NO3-N, organic matter and benthos remained significantly (P<0.05) high in feed ponds where the fish were fed on supplementary diet (Table 3).
Mean periphyton density increased with increase in depth up to 50 cm and declined thereafter. Peak values in periphyton density at most of the depths were observed during week 8 (Figure 1).
|
|
|
Figure 1.
Fortnightly variations in mean values (±SE of mean, n=48) of
periphyton density |
Significantly (P<0.05) higher values for mean dry matter (DM), ash free dry matter (AFDM), ash, ash percentage of dry matter, pigment concentrations (chlorophyll a and pheophytin a) and mean peripyton productivity were also observed at 50 cm substrate depth. Variations in chlorophyll a and pheophytin a concentrations had revealed peak values at 50 cm depth during week 4 (Figure 2) and 6 (Figure 3) respectively.
|
|
|
|
|
Figure 2.
Fortnightly variations in mean values (±SE of mean, n=48) of |
Figure 3.
Fortnightly variations in mean values (±SE of mean, n=48) of |
Autotrophic index (AI) decreased with increase in substrate depth from 0-50 cm and thereafter at 75 cm depth an increase was observed (Table 4).
|
Table 4. Periphyton dry matter (DM), ash free dry matter (AFDM), ash contents, ash % of dry matter, periphyton number, total pigment concentration, chlorophyll a, pheophytin a and autotrophic index (AI) at different depths from substrate ponds |
|||||
|
Parameters |
n |
Depth, cm |
|||
|
0 |
25 |
50 |
75 |
||
|
Dry matter (DM), mg cm-2 |
2 |
1.2±0.02b |
1.4±0.03b |
1.6±0.01a |
1.1±0.04c |
|
AFDM, mg cm-2 |
2 |
0.8±0.02ab |
0.8±0.03a |
0.9±0.04a |
0.7±0.01b |
|
Ash, mg cm-2 |
2 |
0.5±0.00bc |
0.6±0.04b |
0.7±0.02a |
0.4±0.05c |
|
Ash, % of DM |
2 |
38.0±1.00a |
43.0±1.2a |
45.0±2.00a |
39.5±2.5a |
|
Periphyton number, units cm-2 |
48 |
12125±1209c |
14916±1253b |
19275±1868a |
12354±1728c |
|
Total pigment concentration, mg cm-2 |
48 |
9.4±0.24bc |
10.7±0.46b |
13.2±0.55a |
7.5±0.45c |
|
Chlorophyll a, mg cm-2 |
48 |
6.6±0.42bc |
7.6±0.82b |
10.0±0.64a |
5.8±0.61c |
|
Pheophytin a, mg cm-2 |
48 |
2.8±0.45ab |
3.0±0.33ab |
3.3±0.32a |
2.3±0.13b |
|
Autotrophic index (AI) |
- |
117.2 |
106.4 |
88.4 |
112.7 |
|
Algal constitute of periphyton Biomass, % |
- |
34-45 |
37-48 |
40-53 |
35-45 |
|
Periphyton productivity, mg ash free weight m-2 day-1 |
- |
0.5 |
0.6 |
0.8 |
0.5 |
|
All values are mean± S.E. of mean; Means bearing different superscripts in the same row differ significantly (P<0.05). |
|||||
Irrespective of the treatments, the plankton communities principally consisted of two groups of phytoplankton (chlorophyceae and bacillariophyceae) and two groups of zooplankton (rotifera and copepoda). Phytoplankton were represented by 9 taxa, 4 belonging to bacillariophyceae and 5 to chlorophyceae. Succession studies showed that Closterium (chlorophyceae) and Synedra (bacillariophyceae) formed the stable community. Zooplankton were represented by 6 taxa, 3 belonging to copepoda and 3 to rotifera. Succession studies showed that Cyclops and Nauplius (copepoda) and Keratella and Brachionus (rotifera) formed the stable community.
Total and specific enzyme activity values for protease, amylase and cellulolytic were significantly (P<0.05) higher in fish grown in ponds provided with substrate, followed by feed and control ponds. Though specific protease activity was higher in fish grown in ponds provided with substrate, the values were not significantly different than the fish fed on supplementary diet. No significant (P<0.05) variation in lipase activity among different treatments was observed (Table 5).
|
Table 5. Effect of substrate and supplementary feeding on digestive enzyme activity, muscle protein, muscle glycogen, liver glycogen, viscero-somatic index and hepato-somatic index of Etroplus suratensis grown in inland saline groundwater ponds (Duration of experiment–90 days |
||||
|
Parameters |
Treatments |
|||
|
Substrate Ponds |
Feed ponds |
Controls |
LSD |
|
|
Total protease enzyme activity, mg g-1 h-1 |
4.7±0.02a |
3.2±0.01b |
2.1±0.01c |
0.05 |
|
Specific protease enzyme activitya |
1.6±0.02a |
1.6±0.02ab |
1.5±0.02b |
0.08 |
|
Total amylase activity, mg g-1 h-1 |
2.3±0.07a |
1.8±0.05b |
1.5±0.06c |
0.21 |
|
Specific amylase activityb |
1.1±0.03a |
0.9±0.03b |
0.8±0.03c |
0.10 |
|
Total cellulolytic activity, mg g-1 h-1 |
2.9±0.09a |
2.3±0.03b |
1.9±0.06c |
0.22 |
|
Specific cellulolytic activityc |
1.4±0.01a |
1.2±0.02b |
1.0±0.02b |
0.07 |
|
Total lipase activity, mg g-1 h-1 |
3.2±0.17a |
3.3±0.44a |
3.1±0.51a |
1.38 |
|
Specific lipase activityd |
1.5±0.09a |
1.7±0.20a |
1.7±0.24a |
0.65 |
|
Muscle protein, mg g-1 |
175.0±1.08a |
168.3±0.47b |
156.0±1.47c |
3.49 |
|
Muscle glycogen, mg g-1 |
3.2±0.08a |
2.8±0.04b |
2.4±0.08c |
0.24 |
|
Liver glycogen, mg g-1 |
3.9±0.14a |
3.1±0.04b |
2.3±0.03c |
0.29 |
|
Viscero-somatic index (VSI) |
13.4±0.65a |
12.1±0.57a |
8.3±0.46b |
1.89 |
|
Hepato-somatic index (HSI) |
2.9±0.06a |
1.4±0.09b |
1.0±0.16c |
0.36 |
|
All values are mean±SE of mean of eight observations (n=8) Means bearing different superscripts in the same row differ significantly (P<0.05) a µg of tyrosine liberated/mg of protein/min, b µg of maltose liberated/mg of protein/min, c µg of glucose liberated/mg of protein/min. d micromole fatty acid liberated/mg of protein/h |
||||
Similarly, muscle protein, muscle glycogen, VSI and HSI values were also significantly (P<0.05) enhanced in fish grown in ponds provided with substrate, followed by feed ponds and controls (Table 5).
In the present study, provision of substrate resulted in 24% higher growth as compared to feed ponds and almost 100% as compared to control ponds. Jana et al (2004, 2006) have reported 35.4 per cent higher growth in Mugil cephalus and 72.5% in Chanos chanos when grown in inland saline groundwater ponds with substrate.
Since Etroplus suratensis is an omnivore and bottom feeder, feeding mostly on algae growing on substrates and the associated bacterial and zooplanktonic biomass (Keshava and Mohan 1988), periphyton growing on the additional substrate might have also been directly exploited by the fish resulting in high fish growth/yield as also reported by Horn (1989) and Huchette et al (2000). The values of 'n' of LWR for fish grown in ponds provided with substrate were also higher than in other treatments. Further, the values were > 3 indicating that Etroplus suratensis grown in inland saline groundwater ponds (12.8-13.5 ppt salinity) follows the cube law and inland saline groundwater of high hardness appears to be conducive for its optimum growth.
Only minor differences in water quality parameters were observed among different treatments. pH remained alkaline in all the three treatments. Total Kjeldahl nitrogen, alkalinity, turbidity, NH4-N, NO2-N, o-PO4, SO4, BOD5, chlorophyll a , plankton density and epilithic chlorophyll a values were significantly (P<0.05) higher in ponds with supplementary feeding. In general, the values of these parameters, were low in ponds provided with substrate, indicating the utilization of nutrients and incorporation of planktonic flora and fauna in periphyton growth. Low ammonia (NH4-N) levels in ponds provided with substrate is also supported by Ramesh et al (1999) and Jana et al (2004 and 2006), concluded that enhanced bacterial biofilms on substrates might have reduced ammonia levels through the promotion of nitrification. Reduction in NH4-N and turbidity levels and absorption of particulate organic matter by the periphyton may be attributed to the biofilter properties of the periphyton.
Plankton density was low in ponds provided with substrate. High chlorophyll a concentration also coincided with the phytoplankton population. Azim et al (2001a), Keshavanath et al (2001a) and Jana et al (2004 and 2006) reported low values of chlorophyll a in ponds provided with substrate, which may be attributed to the incorporation of phytoplankton in periphyton production or to the grazing pressure exerted by the growing fish. Multiple regression analysis of data showed a significant (P<0.05) positive correlation of NPP with turbidity (r=0.37), alkalinity (r=0.30), total Kjeldahl nitrogen (r=0.30), o-PO4 (r=0.34) and chlorophyll a (r=0.40), clearly revealing that ponds were in high trophic status.
Periphyton biomass measured in terms of periphyton density, DM, AFDM and pigment concentrations (Chlorophyll a and pheophytin a) significantly (P<0.05) increased with depth up to 50 cm; a decline thereafter in their values indicates that the euphotic zone was only up to 50 cm. These findings are in accordance with those of Konan-Brou and Guiral (1994), Azim et al (2001b) and Keshavanath et al (2001b) and also with the studies of Jana et al (2004, 2006) on Mugil cephalus and Chanos chanos.
High ash content (38-45%) of periphyton recorded in the present studies may be attributed to the suspended particles entrapped by the periphyton community. Low turbidity in ponds provided with substrate in comparison to other treatments further supports this view. The algal content of the periphyton can be deduced from the relationship between ash free dry matter (AFDM) and chlorophyll a concentration. The periphyton autotrophic index (AI) values showed that 1.0 mg of chlorophyll a is equivalent to about 117.2, 106.4, 88.4 and 112.7 mg of AFDM at 0, 25, 50, and 75 cm depths, respectively indicating high autotrophic association in periphyton at the surface (0 cm). Huchette et al (2000) and Azim et al (2001a) reported that AI fluctuated between 150 to 300 and 190 to 350 respectively under ungrazed conditions. In the present study, due to grazing pressure exerted by the stocked fish, autotrophic index values remained low and ranged between 88.4-117.2. AI values decreased with increase in substrate depth from 0-50 cm and thereafter at 75 cm an increase was observed, which may be attributed to low penetration of light (beyond euphotic zone) resulting in low autotrophic association and an increase in AI values. These results are similar to those reported by Azim et al (2001a). The decrease in AI values may be due to an increase in productivity in terms of chlorophyll a at 50 cm depth. The increase in chlorophyll a concentration may be attributed to rejuvenation of autotrophs and constant grazing by the fish at this depth. Hatcher (1983), Hay (1991) and Huchette et al (2000) also stated that productivity increases when periphyton community are constantly grazed by the fish. If one mg of chlorophyll a can be derived from 65-85 mg algal dry matter (Reynolds 1984; Dempster et al 1993) this may indicate that algae constitutes 34-45, 37-48, 40-53 and 35-45 per cent of periphytic biomass at different depths (0, 25, 50, 75 cm, respectively). The bulk of the periphyton (47-66%) in the present study is thus not of an algal nature, confirming the importance of periphyton for attracting heterotrophs and trapping organic matter.
A review of sediment chemistry also indicates higher values of NO3-N, alkalinity, organic matter and benthic population in treatment 2 where the fish were fed on supplementary diet. High population of benthos in feed ponds may be attributed to the availability of organic matter.
Digestive enzyme activities in fish respond to changes in the quality and quantity of nutrients intake (Coway et al 1981). High intestinal enzyme activity coupled with high growth has been observed in fish grown in ponds provided with substrate, followed by feed ponds and controls. Studies of Verdegem et al (2001) on proximate composition of periphyton had revealed significantly (P<0.05) higher protein (41.4%), fat (7.9%) and energy (21.2 kJg-1) content in samples collected from ponds without fish (ungrazed condition) as compared to the samples obtained from ponds stocked with fish (grazed condition), indicating the high nutritive value of periphyton. High digestive enzyme activity (especially protease) in the gut of fish grown in ponds with substrate is a clear response to periphyton as a protein source. High growth of fish indicates that periphyton can be used as an alternative to supplementary diet as it has high nutritive value. High HSI values and higher accumulation of muscle and carcass protein, muscle and liver glycogen also support high growth in fish grown in ponds provided with substrate. Fish maintained in treated ponds also had higher accumulation of fat as indicated by high VSI and carcass fat content.
Though significant differences among different treatments were not observed,
provision of substrate increased fish survival. However, more data is needed to
support these results. It has also been observed that in addition to increasing
food supply, the presence of substrate appears to reduce stress by acting as a
shelter or hiding place. Elevated swimming activity is energetically expensive
and any increase in activity level lead to an increased metabolic expenditure.
Kuhlmann and Koop (1981) reported that eels kept in silo (with housing) grew
much faster than when the eels were kept in boxes with no housing. Wahab et al
(1999 a,b) and Keshavanath et al (2001a) have also observed higher survival of
fish in ponds provided with substrate, making periphyton-based systems
particularly worthy of consideration for fry/fingerlings production.
The findings of this study indicate that periphyton based production technology offers considerable potential for enhancing aquaculture production without any deleterious impact on pond ecosystem.
Significantly higher weight gain of fish in ponds provided with substrate as compared to feed ponds where the fish were fed on supplementary diet, is a clear indication of economic viability of the technology.
Trials need to be conducted in farmers ponds to further support these results.
This study was supported in part by a grant from C(b) Zoo-9 ICAR (NATP-World Bank) and C(g) Zoo-10 OA.
AOAC (Association of Official Analytical Chemists) 1995 Official methods of analysis. Association of Official Analytical Chemists Inc., Arlington, USA, p.684.
APHA (American Public Health Association) 1998 Standard Methods for the Examination of the Water and Wastewater, 18th edition. American Public Health Association, Washington, DC.
Azim M E, Rahaman M M , Wahab M.A., Asaeda T, Little D C and Verdegem M C J 2004 Periphyton based pond polyculture system : a bioeconomic comparion of on-farm and on-station trial. Aquaculture 242 :381-396
Azim M E, Verdegem M C J, Rahman M M, Wahab M A, van Dam A A and Beveridge M C M. 2002 Evaluation of polyculture of Indian major carps in periphyton-based ponds. Aquaculture 213 :131-149
Azim M E, Wahab M A, van Dam A A, Beveridge M C M, Milstein A. and Verdegem M C J 2001a Optimization of fertilization rate for maximizing periphyton production on artificial substrates and the implications for periphyton-based aquaculture. Aquaculture Research 32: 749-760
Azim M E, Wahab M A, van Dam A A, Beveridge M C M and Verdegem M C J 2001b The potential of periphyton-based culture of two Indian major carps, rohu, Labeo rohita (Hamilton) and gonia, Labeo gonius (Linnaeus). Aquaculture Research 32: 209-216
Bellinger E G 1992 A key to common Algae. The institute of water and environmental management, London.
Coway C N, Cooke D J, Matty A J and Adron J W 1981 Effects of quantity and quality of dietary protein on certain enzyme activities in rainbow trout. Journal of Nutrition 111 : 336-345 http://jn.nutrition.org/cgi/reprint/111/2/336
Dempster P W, Beveridge M C M and Baird D J 1993 Herbivory in tilapia Oreochromis niloticus (L.) : a comparison of feeding rates on periphyton and phytoplankton. Journal of Fish Biology 43 : 385-392
Devaraj K V, Shantharam B and Shetty H P C 1975 A comparative study of the food of juveniles of the pearlspot, Etroplus suratensis (Bloch) collected from estuarine and freshwaters. Mysore Journal of Agricultural Sciences 9: 479-481
Hatcher B G 1983 Grazing in coral substrate ecosystems. In : Barnes D J (Editor), Perspectives on coral substrate. Brain clouston publishers, Manuka, Australia, pp. 164-179
Hay M E 1991 Fish seaweed interactions on coral substrates : effect of herbivorous fishes and adaptations of their prey. In Sale P F (Edition), The ecology of fishes on coral substrates. Academic Press, London, England, pp. 96-119
Hem S and Avit J L B 1994 First results on “acadjas enclos” as an extensive aquaculture system (West Africa). Bulletin of Marine Sciences 55: 1038-1049
Henken A M., Lucas H, Tijseen P A T and Michiels M A M 1986 A comparison between methods used to determine the energy content of feed, fish and faecal samples. Aquaculture 58 : 195-201
Horn M H 1989 Biology of marine herbivorous fishes. Oceanography and Marine Biology Annual Review 27 :167-272
Huchette S M H, Beveridge M C M, Baird D J and Ireland M 2000 The impacts of grazing by tilapias (Oreochromis niloticus L.) on periphyton communities growing on artificial substrate in cages. Aquaculture 186 : 45-60
Jana S N, Garg S K, Arasu A R T, Bhatnagar A, Kalla and Patra B C 2006 Use of additional substrate to enhance growth performance of milk fish, Chanos chanos (Forsskal) in inland saline groundwater ponds. Journal of Applied Aquaculture 18(1):1-20
Jana S N, Garg S K and Patra B C 2004 Effect of periphyton on growth performance of grey mullet, Mugil cephalus (Linn.) in inland saline groundwater ponds. Journal of Applied Ichthyology 20: 10-17
Keshava S J P and Mohan J M 1988 Feeding habits of the pearlspot, Etroplus suratensis (Bloch) in the Nethravati-Gurpur Estuary. In : Proceedings of the first Indian Fisheries Forum, Asian Fisheries Society. Indian Branch, Mangalore, pp. 203-206
Keshavanath P, Gangadhar B, Ramesh T J, van Dam A A, Beveridge M C M and Verdegem M C J 2002 The effect of periphyton and supplemental feeding on the production of the indigenous carps Tor khudree and Labeo fimbriatus. Aquaculture 213: 207-218
Keshavanath P, Gangadhar B, Ramesh T J, van Rooij J M, Beveridge M C M, Baird D J, Verdegem M C J and van Dam A A 2001a Use of artificial substrates to enhance production of freshwater herbivorous fish in pond culture. Aquaculture Research 32: 189-197
Keshavanath P, Ramesh T J, Gangadhar B, Beveridge M C M, van Dam A A and Verdegem M C J 2001b On farm evaluation of Indian major carp production with sugarcane Bagasse as substrate for periphyton. Asian Fishery Science 14: 367-376
Konan-Brou A A and Guiral D 1994 Available algal biomass in tropical brackishwater artificial habitats. Aquaculture 119 : 175-190
Kuhlmann H and Koop H 1981 New technology for rearing elvers in heated waters. Proceedings of World Symposium on aquaculture in heated affluents and recirculation systems, Stavanger, 30 May 1980, 1 :302-308
Lowry O H, Rosebrough N J, Farr A and Randall R J 1951 Protein measurement in the folin phenol reagent. Journal of Biological Chemistry 193 :265-275
Piper C S 1966 Soil and plant analysis. Hans. Publishers, Bombay, India, pp. 401.
Prescott G W 1962 Algae of the Western Great Lakes Area. Wm. C. Brown Co., Dubuque, IA.
Ramesh M R, Shankar K M, Mohan C V and Varghese T J 1999 Comparison of three plant substrates for enhancing carp growth through bacterial biofilm. Aquaculture Engineering 19: 119-131
Reynolds C S 1984 The Ecology of Freshwater Phytoplankton. Cambridge University Press.
Sadasivam S and Manickam A 1996 Biochemical methods. New Age International (P) Ltd. Publishers, pp. 126-128.
Sawhney S K and Singh R 2000 Introductory Practical Biochemistry. Narosa Publishing House, pp. 452.
Snedecor G W and Cochran W C 1982 Statistical methods. Iowa State University Press, Ames. 1A, 507pp.
Tengjaroenkul B, Smith B J, Caeeci T and Smith S A 2000 Distribution of intestinal enzyme activities along the intestinal tract of cultured Nile tilapia, Oreochromis niloticus L. Aquaculture 182: 317-327
Thimmaiah S K 1999 Standard Methods of Biochemical Analysis. Kalyani Publishers, India, pp. 545
Verdegem M C J, van Dam A S, and Azim M E 2001 Nutritive value and utilization of periphyton, pages 17-19 in P. Keshavanath and M.A. Wahab (Editors) Peryphyton-based Aquaculture and its Potential in Rural Development. Summary of an EC-INCO-DC Funded Workshop, Dhaka, Bangladesh, 29-31 January 2001.
Wahab M A, Azim M E, Ali M H, Beveridge M C M and Khan S 1999a The potential of periphyton-based culture of the native major carp calbasu, Labeo calbasu (Hamilton). Aquaculture Research 30 : 409-419
Wahab M A, Manan M A, Huda M A, Azim M E, Tollervey A G and Beveridge M C M 1999b Effect of periphyton growth on bamboo substrates on growth and production of Indian major carp, rohu (Labeo rohita). Bangladesh Journal of Fish Research 3: 1-10
Walter H E 1984 Methods of Enzymatic Analysis. Verlag Chemie, Weinheim, p.238
Ward H B and Whipple G C 1959 Freshwater Biology, John Wiley and Sons, pp. 1248
Washington H G 1984 Diversity, biotic and similarity indices. Water Research 18: 653-694
Welcomme R L 1972 An evaluation of acadja method of fishing as practised in the coastal lagoons of Dahomey (West Africa). Journal of Fish Biology 4: 3955
Young O W 1945 A limnological investigation of periphyton in Douglas Lake, Michigan, Trans. American Microscopy Society 64: 1
Received 20 August 2008; Accepted 17 July 2009; Published 1 October 2009
