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Effects of temperature variation and pellet dimension on settling velocity of fish feed pellets.

Introduction

In order to maximize fish production and reduced waste dispersion, selection of ingredients, their composition and palletizing are of considerable importance. Modeling of waste dispersion is a key factor in regulation of rearing ponds. During feeding, significant amount of waste products (uneaten feed, fecal and soluble excretory material) are produced. Among these the primary reason for impairment of pond ecology is the settled uneaten feed pellets. These pellets not only affect over the benthos communities as well as other living biota (Vezzulli et al., 2003; Beveridge et al., 1991). Earlier studies suggested that 25-30% of dry weight of feed consumed is wasted as fecal matter (NCC, 1990; Butz and Vens-cappel, 1982). Decay of food matter could result in an accumulation of organic matter at pond bottom to manipulate the normal ecological conditions (Carroll et al., 2003; Karakassis at al., 2000). Keeping this in view, a number of models have been reviewed for monitoring the effects of temperature variation and pellet dimension on settling velocity and rate of soaking (Doglioli et al., 2004; Cromey et al., 2002; Perez et al., 2002; Dudley et al., 2000). It is true that settling velocity of uneaten feed pellets and soaking time is very useful tool to predict any model in intensive aqua culturing system. Earlier studies related with dimension of fish pellets involved in either sea water (Vassalo et al., 2006; Chen et al., 1999a) or fresh water (Elberizon and Kelly, 1998) have been recorded but in the present research instead of salinity, two temperature regimes are focused.

Materials and Methods

In the present experiment two diets of different low cast ingredients more given to fish therefore, feed pellets of different length were produced. The proximate compositions of two feeds (DI&D II) are given in Table 1.

Measurement of settling velocity. Three different diameters (3 mm, 6 mm, 9 mm) of two different diets were examined at two ranges of temperature (28-30 [degrees]C and 20-22[degrees]C) as described by Vassalo et al. (2006). Length was taken by the help of a vernier caliper. Plexiglas tube of 120 cm length with a diameter of 10 cm was used to find out the settling velocities of pellets following the method of Chen et al. (1999a). The tube was marked from the top, up to 5 cm for defining floating surface and the time to cover this distance was denoted as floating time ([T.sub.f]). Then from this point, after every 50 cm, the tube was filled with fresh water and fixed vertically at different temperatures. 10 pellets of each length for each diet were examined. Pellets were gently dropped in water with the help of 0.01s chronometer. Time of pellet fall up to 5 cm ([T.sub.f]) and beyond 5 cm to each 50 cm apart was noted. Water in the apparatus was changed for each type of pellet and for temperature ranges. Temperature of water was noted by a thermometer and maintained at the required ranges by adding ice cubes.

Determination of water absorption property of pellets. The weight of feed pellet was not affected by change in temperature and salinity (Chen et al., 1999b), so the water absorption property was recorded at room temperature, during the whole experiment. Ten pellets of each type of dimension were taken. After measuring their length and diameter, weight was taken in dried condition. All the selected pellets were soaked in fresh water for 2, 5 and 10 min of immersion time as indicated by Vassalo et al. (2006). After passing the immersion period pellets were taken out from water and left on absorbing paper for absorption of excess water. Finally all pellets were measured and weighed again to observe the changes in pellet dimension and weight.

Results and Discussion

Settling velocity. The effects of temperature variation and pellets dimension on [T.sub.f] and [V.sub.set] are presented in Tables 2-3. Keeping temperature as a controlling factor, it was observed that time for float ([T.sub.f]) of both diets DI and DII were greater at high range of temperature than lower range of temperature for all tested pellets dimensions (3 mm, 6 mm, 9 mm). On the other hand the settling velocity ([V.sub.set]) did not respond as [T.sub.f] i.e., against high temperature lower [V.sub.set] recorded when compared to lower range of temperature. Furthermore, it is attributed that there was an inverse relationship between [T.sub.f] and [V.sub.set] for all dimensions of pellets (Fig. 1-4).

Statistically it is proven by general linear model (GLM). Analysis of variance for floating time (Tables 4-5) indicated significant differences (P<0.05) for pellets dimension within each temperature regime (28-30[degrees]C, 20-22[degrees]C). The interaction between pellets dimension and temperature regimes was significantly affected over time for floating pellets on water surface. Tables 6-7 show response of pellets in terms of settling velocity ([V.sub.set]) (Fig. 5-8). Again a highly significant difference was noted for pellets dimension and temperature regimes (P < 0.05), however, the interaction between pellet size and temperature regimes did not significantly affect over [V.sub.set].

Water absorption property of pellets. Table 8 shows immersed pellets weight increment with reference to time of immersion i.e., 2, 5 and 10 min. None of the pellets of diet DI exhibit any change in dimension after three different times of immersion. However, in case of diet DII 3 mm size pellets were dissolved or loosed their dimension when immersed for 5 and 10 min due to having small diameter than diet DI. On the other hand percent weight increments for diet DI were noted maximum for pellets size of 3,6 and 9 mm after 10 min of immersion i.e., 33.33, 55.55 and 38.46%, respectively, when compared to dry pellets and 2 and 5 min of immersion time. Totally different trends were observed for diet DII in this context. With comparison to dry pellets weight increment of 100%, 50% and 66.66% were recorded for 3, 6 and 9 mm of pellets size, respectively, after 2 min of immersion.

The same increasing pattern of weight enhancement was noted for DII pellets having the same pellet size i.e., 100% after 5 min and 150% after 10 min. The differences between the weight increment values of DI and DII showed that as the diameter of pellets increases, their water absorption property decreases (Chen et al., 1999a). It was also noted that more or less all under observed pellets of diet DII were dissolved or disintegrated into its constituents revealing greater absorption properties as compared to diet DI. The role of formulated diets definitely contributes in rate of production. Feed manufacturers have diverted their efforts towards the physical qualities including settling velocity and soaking or immersion time. According to linear law of stokes, a particle falls in water with its settling velocity with respect to its dimension, density and viscosity. Among these, the viscosity is highly influenced by temperature, solute concentration and hydrostatic pressure. In present feed trial smaller pellets size of diet DII (3 mm) were dissolved or loosed their dimension when immersed for 5 and 10 min while more pellets of diet DI show any change in dimension after three different times of immersion. These results were in line with the findings of Thomas and Vander Poel (1996), who claimed that small diameter pellets (3 mm) were found to be more susceptible to breakage than larger diameter pellets (6 mm). The differences between diet DI and DII can be attributed to variations in formulation because of the water soaking ability of different ingredients. It shows that the diet DII is more friable than diet DI. Doglioli et al. (2004) focused on behaviour of pallets made for salmon aquaculture and potentially applied and described a model.

In present research, a comparison was undertaken between two diets DI and DII to investigate the settling velocity and time for immersion. The findings were indicated that an inverse relationship exist between [T.sub.f] and [V.sub.set] for all dimensions of pellets. As far as immersion time is concerned (2, 5 and 10 min) none of the pellets of diet DI exhibit any change in dimension after three different times of immersion. However, for diet DII 3 mm sized pellets were dissolved when immersed for 5-10 mins due to smaller in size. These results conclude that two diets have no similar pattern of [T.sub.f] and [V.sub.set], although Wood (1987) found a relationship between pellet hardness and friability. Relationship between the under observed parameters are generally only found where the feed ingredients and pellet producer are same as suggested by Thomas and Vander Poel (1996).

The outcome from Tables mean velocities to sink for diet DI (3 mm) were 0.077 m/s in water having two temperature ranges followed by 0.087 m/s. 0.16 m/s and 0.100 m/s for 6 mm and 0.097 m/s and 0.104 m/s for 9 mm respectively.

For pellets size of 3 mm of diet DII 0.041 m/s, 0.046 m/s were calculated with the increasing trend for 6 mm, 9 mm i.e., 0.058 m/s, 0.059 m/s and 0.063 m/s, 0.067 m/s, respectively. When comparing these results with the results of earlier studies the similar attributions are found.

Gowen et al. (1989) quoted results from unpublished data of velocities of 0.09 to 0.15m/s and used a settling velocity equal to 0.12 m/s in developing waste dispersion models. Findlay and watling (1994) provided data on several North America pellet types or sizes and quoted settling rates of 0.055 m/s and 0.155 m/s for 3 mm and 10 mm dry pellets, respectively. Elberizon and Kelly (1998) showed settling velocities of freshwater salmonid pellet diets ranging from 0.05 to 0.12 m/s for 2 mm and 8 mm pellet sizes, respectively.

The floating time since the ANOVA test showed that it significantly affects settling velocity. The reason for this fact may be because of the observed weight increment of pellets immersed in the water at the surface before they start to fall. The soaking experiment provides a quantitative estimate of this process, pointing out that the phenomenon is greater for smaller particles. Thus, it could be said that the influence of temperature and salinity on the settling velocity is indirect via [T.sub.f] the lesser the percentage of uneaten feed. However, a quantitative calculation of this link is very hard to achieve but knowing the [T.sub.f] value provides a valuable piece of information for model calibration and validation processes.

Finally, the present study provides important information for aquaculture wastes dispersion modeling. A realistic dispersion model would then have to consider: (a) the diameter of the actual feed distributed to fishes: (b) the seasonal variation of temperature. Collaboration with farmers, nutritional data collection and hydrological measurements will be useful to improve aquaculture impact predictions. Two temperature ranges show the seasonal temperature variations which have a significant influence or the settling velocity and floating time.

References

Beveridge, M., Phillips, M., Clarke, R. 1991. A quantitative and qualitative assessment of wastes from aquatic animal production. In: Agriculture and Water Quality, Advances in World Aquaculture, D. Brune and J. Tomusso (eds.), vol. 3, pp. 506-533, World Aquaculture-society, Baton-Rouge, LA, USA.

Butz, I., Vens-Cappell, B. 1982. Organic load from the metabolic products of rainbow trout fed with dry food. In: Report of the EIFAC Workshop on Fish-Farm Effluent, J. S. Alabaster (ed.), EIFAC Technical Paper, 41, pp. 73-82, FAO, Rome, Italy.

Carroll, M., Cochrane, S., Fieler, R., Velvin, R., White, P. 2003. Organic enrichment of sediments from Salmon farming in Norway: environmental factors, management practices, and monitoring techniques. Aquaculture, 226: 165-180.

Chen, Y., Beveridge, M., Telfer, T. 1999a. Physical characteristics of commercial pelleted Atlantic Salmonfeed consideration of implications for modeling of waste disperson through sedimentation. Aquaculture International, 7: 89-100.

Chen, Y., Beveridge, M., Telfer, T. 1999b. Settling rate characteristics and nutrient content of the faeces of Atlantic salmon, Salmo salar L., and the implications for modelling of solid waste dispersion. Aquaculture Research, 30: 395-398.

Cromey, C., Nickell, T., Black, K. 2002. DEPOMOD modelling the deposition and the biological effects of wastes solids from marine cage farms. Aquaculture, 214: 211-239.

Doglioli, A., Magaldi, M., Vezzulli, L., Tucci, S. 2002. Development of a numerical model to study the dispersion of wastes coming from a marine fish farm in the Ligurian Sea (Western Mediterranean). Aquaculture, 231: 215-235.

Dudley, R., Panchang, V., Newell, C. 2000. Application of a comprehensive modeling strategy for the management of netpen aquaculture waste transport. Aquaculture, 187: 319-349.

Elberizon L., Kelly L. 1998. Settling measurements of parameters critical to modelling benthic impacts of freshwater salmonid cage aquaculture. Aquaculture Research, 29: 669-677.

Findlay, R.H., Watling, L. 1994. Towards a process level model to predict the effects of Salmon net pen aquaculture on the benthos. In: Modelling Benthic Impacts of Organic Enrichment from Marine Aquaculture, Canadian Technical Report of Fisheries And Aquatic Siences 1949: xi, pp., 47-79.

Gowen, R.J., Bradbury, N.B., Brown, J.R. 1989. The use of simple models in assessing two of the interactions between fish farming and marine environment. In: Aquaculture: A Biotechnology in Progress, N. De Pauw, E. Jaspers, H. Ackefors and N.Wilkins, (eds.), vol. 1, pp. 1071-1080, European Aquaculture Society, Bredene, Belgium.

Karakassis, I., Tsapakis, M., Hatziyanni, E., Papadopoulou, K., Plaiti, W. 2000. Impact of cage farming offish on the seabed in three Mediterranean coastal areas. ICES Journal of Marine Science, 57: 1462-1471.

NCC, 1990. Fish Farming and the Scottish Freshwater Environment, Report prepared for the Nature Conservancy Council (NCC) the Institute of Aquaculture, University of Stirting, Institute of Freshwater Ecology, Penisuik, and the Terrestrial Ecology, Banchory, pp. 285, Nature Conservancy Council, Edinburgh, UK.

Perez, O.M.,Telfer, T.C., Beveridge, M.C.M., Ross, G.L. 2002. Geographical Information Systems (GIS) as a simple tool to aid modeling of particulate waste distribution at marine fish cage sites. Estuarine Coastal Shelf Sciences, 54: 761-768.

Thomas, M., Van der Poel, A.F.B. 1996. Physical quality of pelleted animal feed 1. Criteria for pellet quality. Animal Feed Science and Technology, 61: 89-112.

Vassallo, P., Doglioli, M., Rinaldi, F., Beiso, L. 2006. Determination of Physical behaviour of feed pellets in Mediterranean water. Aquaculture Research, 37: 119-126.

Vezzulli, L., Marrale, D., Moreno, M., Fabiano M. 2003. Sediment organic Matter and meiofauna community response to long-term fish farm impact in the Ligurian Sea (Western Mediterranean). Journal of Chemistry and Ecology, 19: 431-440.

Wood, J.F. 1987. The functional properties of feedEraw materials and their effect on the production and quality of feed pellets. Animal Feed Science and Technology, 18: 1-17.

Mohammad Shoaib *, Aasia Karim, Samreen Imtiaz and Saima Naz

Department of Zoology, University of Karachi, Karachi 75270, Pakistan

(received May 22, 2012; revised Marchl 1, 2013; accepted April 22, 2013)

* Author for correspondence;

E-mail: drmshoaib11273@yahoo.com

Table 1. Proximate composition of two feeds

Diet I                              Diet II

Ingredients        Percent values   Ingredients     Percent values

Rice polish        20               Rice protein    35
Rice bran          15               Corn gluten     30
Fish meal          20               Wheat bran      20
Sun flower meal    20               Fish meal       15
Wheat bran         10
Bone meal          10
Wheat flour        5

Proximate values

Crude protein      29               Crude protein   16.9
Fats               11.3             Fats            9.7
Moisture           5.7              Moisture        6.3

Table 2. Settling velocity ([V.sub.Set]) and floating time
([T.sub.f]) for three different dimensions of fish feed pellets
of DI (3.5 mm, diameter) with reference to two temperature regimes

S.No.               Temperature
                    (28-30[degrees]C)

        3 mm                      6 mm

        [T.sub.f]   [V.sub.set]   [T.sub.f]   [V.sub.set]
        (sec)       (m/s)         (sec)       (m/s)

1       1.2         0.071         1.1         0.095
2       1.68        0.068         1.02        0.085
3       1.56        0.077         0.8         0.087
4       1.36        0.08          0.6         0.081
5       1.52        0.079         0.56        0.094
6       1.62        0.081         0.89        0.092
7       1.23        0.069         0.92        0.088
8       1.38        0.09          1.02        0.087
9       1.6         0.071         1.96        0.085
10      1.51        0.084         0.72        0.08

Mean    1.46        0.077         0.95        0.16
        (0.16)      (0.007)       (0.39)      (0.24)

S.No.   Temperature               Temperature
        (28-30[degrees]C)         (20-22[degrees]C)

        9 mm                      3 mm

        [T.sub.f]   [V.sub.set]   [T.sub.f]   [V.sub.set]
        (sec)       (m/s)         (sec)       (m/s)

1       0.52        0.098         0.63        0.079
2       0.47        0.089         0.61        0.08
3       0.4         0.1           0.71        0.078
4       0.42        0.094         0.4         0.087
5       0.7         0.094         0.45        0.079
6       0.46        0.104         0.7         0.087
7       0.64        0.095         0.51        0.093
8       0.38        0.104         0.77        0.075
9       0.59        0.105         0.74        0.082
10      0.62        0.096         0.59        0.076

Mean    0.52        0.097         0.61        0.087
        (0.11)      (0.005)       (0.12)      (0.005)

S.No.               Temperature
                    (20-22[degrees]C)

        6 mm                      9 mm

        [T.sub.f]   [V.sub.set]   [T.sub.f]   [V.sub.set]
        (sec)       (m/s)         (sec)       (m/s)

1       0.75        0.082         0.49        0.113
2       0.42        0.107         0.51        0.107
3       0.7         0.092         0.35        0.097
4       0.73        0.083         0.37        0.092
5       0.51        0.097         0.32        0.106
6       0.54        0.105         0.27        0.092
7       0.43        0.1           0.39        0.094
8       0.6         0.102         0.41        0.118
9       0.37        0.104         0.53        0.123
10      0.36        0.133         0.46        0.098

Mean    0.54        0.104         0.41        0.104
        (0.14)      (0.01)        (0.08)      (0.01)

Values in subscripts are standard deviations.

Table 3. Settling velocity ([V.sub.set]) and floating time
([T.sub.f]) for three different dimensions of fish feed pellets
DII (2mm, diameter) with reference to two temperature regimes

S.No               Temperature
                   28-30[degrees]C

       3 mm                      6 mm

       [T.sub.f]   [V.sub.set]   [T.sub.f]   [V.sub.set]
       (sec)       (m/s)         (sec)       (m/s)

1      1.93        0.043         1.56        0.077
2      1.86        0.042         1.48        0.061
3      1.63        0.047         1.06        0.058
4      1.74        0.039         1.2         0.051
5      1.89        0.041         1.02        0.057
6      1.91        0.038         1.4         0.058
7      1.34        0.041         1.23        0.051
8      1.82        0.045         1.19        0.06
9      1.96        0.037         1.27        0.057
10     1.83        0.084         1.1         0.053

Mean   1.79        0.041         1.25        0.058
       (0.18)      (0.01)        (0.17)      (0.007)

S.No   Temperature               Temperature
       28-30[degrees]C           20-22[degrees]C

       9 mm                      3 mm

       [T.sub.f]   [V.sub.set]   [T.sub.f]   [V.sub.set]
       (sec)       (m/s)         (sec)       (m/s)

1      0.96        0.057         1.19        0.032
2      0.84        0.063         0.77        0.04
3      0.77        0.064         0.8         0.051
4      0.86        0.065         1.19        0.049
5      0.87        0.061         0.78        0.05
6      0.81        0.058         0.83        0.051
7      0.92        0.059         1.01        0.041
8      0.89        0.061         0.92        0.052
9      0.96        0.074         0.96        0.048
10     0.79        0.071         0.78        0.054

Mean   0.86        0.063         0.92        0.046
       (0.06)      (0.005)       (0.16)      (0.006)

S.No               Temperature
                   20-22[degrees]C

       6 mm                      9 mm

       [T.sub.f]   [V.sub.set]   [T.sub.f]   [V.sub.set]
       (sec)       (m/s)         (sec)       (m/s)

1      0.43        0.071         0.51        0.063
2      0.54        0.058         0.49        0.062
3      0.49        0.043         0.54        0.064
4      0.59        0.062         0.5         0.078
5      0.46        0.057         0.51        0.068
6      0.52        0.061         0.55        0.071
7      0.56        0.064         0.54        0.068
8      0.46        0.052         0.49        0.064
9      0.6         0.064         0.55        0.072
10     0.51        0.059         0.41        0.065

Mean   0.51        0.059         0.50        0.067
       (0.05)      (0.007)       (0.04)      (0.004)

Values in subscripts are standard deviations.

Table 4. Two way analysis of variance for floating time of diet DI

Source          DF   SeqSS     Adj SS   Adj MS   F       P

Pellets         2    3.2891    3.2891   1.6445   40.93   0.000
Temperature     1    3.1878    3.1878   3.1878   79.33   0.000
Pellets x       2    1.4014    1.4014   0.7007   17.44   0.000
  Temperature
Error           54   2.1699    2.1699   0.0402   --      54
Total           59   10.0482   --       59       --      --

DF = degree of freedom; Seq SS = sequential sum of square; Adj SS
= adjusted sum of square; MS = means of square; F = F ratio; P =
probability ratio.

Table 5. Two way analysis of variance for settling
velocity of diet DI

Source          DF   SeqSS       Adj SS      Adj MS

Pellets         2    0.0048632   0.0048632   0.0024316
Temperature     1    0.0009362   0.0009362   0.0009362
Pellets x       2    0.0002077   0.0002077   0.0001039
  Temperature
Error           54   0.0042231   0.0042231   0.0000782
Total           59   0.0102302   --          --

Source          F       P

Pellets         31.09   0.000
Temperature     11.97   0.001
Pellets x       1.33    0.274
  Temperature
Error           --      --
Total           --      --

DF = degree of freedom; Seq SS = sequential sum of square; Adj SS
= adjusted sum of square; MS = means of square; F = F ratio; P =
probability ratio.

Table 6. Two way analysis of variance for floating time of diet DII

Source          DF   SeqSS     Adj SS   Adj MS   F        P

Pellets         2    4.0049    4.0049   2.0024   66.43    0.000
Temperature     1    5.7722    5.7722   5.7722   191.49   0.000
Pellets x       2    0.5189    0.5189   0.2594   8.61     0.001
  Temperature
Error           54   1.6277    1.6277   0.0301   --       --
Total           59   11.9237   --       --       --       --

DF = degree of freedom; Seq SS = sequential sum of square; Adj SS
= adjusted sum of square; MS = means of square; F = F ratio; P =
Probability ratio.

Table 7. Two way analysis of variance for settling velocity of
diet DII

Source          DF   SeqSS       Adj SS      Adj MS

Pellets         2    0.00476     0.0047      0.0023805
Temperature     1    0.0001908   0.0001908   0.0001908
Pellets x       2    0.0000492   0.0000492   0.0000246
  Temperature
Error           54   0.0021071   0.0021071   0.0000390
Total           59   0.0071082   --          --

Source          F       P

Pellets         61.01   0.000
Temperature     4.89    0.031
Pellets x       0.63    0.536
  Temperature
Error           --      --
Total           --      --

DF = degree of freedom; Seq SS = sequential sum of square; Adj SS
= adjusted sum of square; MS = means of square; F = F ratio; P =
probability ratio.

Table 8. Mean weight increase (%) of pellets of DI and DII as a
function of different immersion times (2, 5 and 10 minutes)

Before immersion

Diet I          Diet II

L(mm)   W(gm)   L(mm)   W(gm)

3       0.6     3       0.1
6       0.9     6       0.2
9       1.3     9       0.3

After immersion
Time in minutes

    2                 5                 10

L   W     MWI     L   W     MWI     L   W     MWI

3   0.7   16.66   3   0.8   25      3   0.8   33.33
6   1.2   33.33   6   1.3   44.44   6   1.4   55.55
9   1.4   7.69    9   1.7   30.76   9   1.8   38.46

    2                 5                 10

L   W     MWI     L   W     MWI     L   W     MWI

3   0.2   100     3   0.2   100     3   0.1   **
6   0.3   50      6   0.4   100     6   0.5   150
9   0.5   66.66   9   0.6   100     9   0.6   100

L, length; W = weight; MWI = mean weight increase (%), ** =
dissolved completely.
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Author:Shoaib, Mohammad; Karim, Aasia; Imtiaz, Samreen; Naz, Saima
Publication:Pakistan Journal of Scientific and Industrial Research Series B: Biological Sciences
Article Type:Report
Geographic Code:9PAKI
Date:Nov 1, 2013
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