Studies on the Wintering Effects on Growth and Survival of Catla Catla Fingerlings in Polyculture System Employing Greenhouse Technology

The greenhouse experiment was conducted in the six earthen ponds present at Fisheries, Research and Training Institute, Manawan, Lahore for a period of twelve weeks starting from 1st December and lasting up till February 28th. It consisted of two treatments with three replicates: Ponds without greenhouse cover (T1= Control) and ponds with greenhouse cover (T2= Treatment). The treatments replicates were assigned Completely Randomized Design Model (CRD) i.e., completely at random to experimental subjects (Fish). Manuring and Fertilization was carried out only once by addition of cow dung, DAP and urea @ 500 kg, 9kg and 2kg per acre, respectively, as recommended by the Department of Fisheries Punjab. Hence, fertilizer dose applied was 31.25 kg cow dung + 0.56 kg DAP + 0.13 kg urea, respectively as per size of the earthen ponds (0.5 kanal each). No periodical manuring and fertilization was done as the season of experiment is winter. Physico-chemical studies of water including temperature, Dissolved Oxygen and pH were carried out on weekly basis following Eaton et al. (2012).

Bamboo skeleton with 10 feet height at the center were made in an oval shape and were fixed under the guidance of researchers of this project, to all the corners of three randomly selected earthen ponds like a camp. This frame was then covered with a transparent polythene plastic sheet such that it covered all the four sides of the ponds fully and completely to trap the heat inside this cover. Fingerlings of L. rohita, C. mrigala and C. catla were procured from Fish Seed Nursing Farm Farooqabad, district Sheikhupura during September, reared up to November and then shifted to the selected earthen ponds. Stocking density of fish was kept 14,400/ acre; since each pond has an area equal to 0.5 kanal, hence a total of 900 fish fingerlings was added to each pond with a breakup of 300 fingerlings of each selected fish species. Water level was maintained up to the height of four feet in each pond during the entire experiment. Feeding was carried out at the rate of 3% of fish body weight with crude protein level 26.37%, twice a day according to the recommendations of Javaid et al. (1988). Fish growth was monitored on fortnightly basis in terms of wet body weight. During test netting, 10 individuals of each species i.e. L. rohita, C. mrigala and C. catla from each pond were sampled randomly. At the final fortnight, total fish was harvested by draining off the total pond water and weighed to record the total production obtained exactly without any error.

Statistical analysis of the mean values of the data was carried out through SPSS programme (version 16.0) to find out statistically significant differences in growth performance of experimental fish species under both treatments through one-way analysis of variance at P<0.05. The post-hoc separate univariate ANOVAs test as a “step down analysis” after Multivariate analysis of variance (MANOVA) was applied on the experimental data.

The results of physico-chemical parameters of water have been shown in Supplementary Table I. The temperature in T1 remained from a minimum of 15.2 oC to a maximum of 23.1oC while in T2 remained maintained from a minimum of 22.1oC to 26.5oC which actually instigated this research to become successful. The data showed that greenhouse cover pronounced the effect of temperature by intensifying it to a certain level which was satisfactory for fish growth enhancements. This is in accordance with the report of FAO (2011) that C. catla is a eurythermal species that grows best at water temperature between 25-30oC. The dissolved Oxygen in T1 was found in the ranges from 3.05 mgL-1 to 7.69 mgL-1 while in T2 between 2.08 mgL-1 to 6.78 mgL-1. The data showed that greenhouse cover reduced the DO level but not to too much lower extent and even after reduction, the DO was even then in the suitable range required for fish culture operations. The reduced DO values suggested that the photosynthesis rate was reduced in the treatment with greenhouse cover. Similar findings were attained by Vromant et al. (2001) as well as by Frei and Becker (2005) in a study conducted by them who explained that DO reduction may be attributed as a result of amplified mineralization of soil nutrients and their overindulgence into the pond water. The pH for T1 was observed to be from a low level of 8.01 to 8.90 while in T2 from 8.03 to as high as 8.69; which showed not much difference between both the treatment and pH was in suitable ranges.

Table I. Effect of greenhouse cover on ponds on average survival rate (%) of Labeo rohita, Cirrhinus mrigala and Catla catla.

Survival (%) of the L. rohita, C. mrigala and C. catla fingerlings was calculated by counting total fish at the end of the experiment which remained 65%, 57% and 22% under Treatment 1 and 69%, 73% and 75% in Treatment 2, respectively. The overall Survival rate of total fish in T1 and T2 was observed to be 48% and 72% which is a very prominent difference and made this research a remarkable victory (Table I). Fish growth was determined on fortnightly basis for six fortnights in terms of wet body weight; the results have been presented in Table II. The post-hoc test; multivariate analysis of variance (MANOVA) was applied to test the effect of (with or without) greenhouse system on the weight gain by three selected fish species in polyculture system (Supplementary Table II). Initially,

Table II. Effect of greenhouse cover on ponds on body weight (g, mean ± SD) of Labeo rohita, Cirrhinus mrigala and Catla catla on fortnightly basis for six fortnights.

there was no significant difference in weights of carps in both treatments but gradually statistically significant differences were obtained between the body weights of three carps. There was no significant difference between the initial weights of carps of both treatments as regards C. mrigala and C. catla, however, only L. rohita differed significantly in body weight gain during 1st fortnight. The 2nd fortnight MANOVA results revealed that there were statistically significant differences obtained between the body weights of L. rohita and C. catla of two treatments (F= 7.321, p= .001) while that of C. mrigala remained non-significant. The post-hoc test (MANOVA) also revealed that body weight of two carps i.e. L. rohita and C. catla were significantly higher in T2 (with green house) as compared to T1 (without green house) at p < .05. Significant differences for all three species i.e. L. rohita, C. mrigala and C. catla were also observed during 3rd fortnight and found to be F= 26.402, p= .000. The body weights of three species differed significantly at the end of 4th, 5th and 6th fortnights at p < .05 and the weights of all the three species were higher in T2 as compared to T1 as is evident from Supplementary Table II. Mean fish body weight increase of C. catla was non-significant with L. rohita but was significant with C. mrigala in T1 while in T2, Mean fish body weight increase of C. catla was non-significant with both the other species and remained at the highest. The greenhouse cover had a positive effect on the growth of C. catla in the polyculture system with the other major carp species.

Fish culture under the greenhouse technique represents an important alternative method of maintaining water temperatures within the acceptable range for fish survival and thereby obtaining high growth rates with low feed conversion rates, due to the effect of temperature on fish metabolism and consequently on food consumption. Our research has been supported by the studies taken up by García-Trejo et al., 2016; Hashem et al., 2011; Alatorre-Jácome et al., 2011. In our experiment, water temperature of fish ponds was increased by using the technique of greenhouse cover. Due to increase in temperature in T2 from 7 to 11 degrees as compared to T1, the survival rate (%) of the carp fingerlings calculated by total counting at the end of the experiment was achieved up to 72% as compared to T1 in which it was only 48%. However, in conventional nursery ponds, the survival rate of C. catla is normally lower than that for L. rohita and C. mrigala. As can be seen in T1 (without greenhouse cover) the survival rate of C. catla remained at 22% only as compared to L. rohita which was highest with 69% followed by C. mrigala with 57% survival rate. But this study showed that under greenhouse cover (T2), the survival rate of C. catla was enhanced up to 75% which was even higher than the L. rohita (69%) and C. mrigala (73%) which made this study a success. Green and Fisher (2004) research also supported our study and proved that higher temperature at 28°C has better impacts on growth, duration and maximum swimming speed of marine fish species Amphiprion melanopus as compared to temperatures lower than 25°C. Moreover, the growth data in T1 showed that L. rohita attained a maximum average body weight up to 16.7 g which was comparable with C. catla with maximum weight up to 16.2 g, however, C. mrigala showed better performance than both having 20.0 g at the end of twelve-week experiment. On detail study of data obtained from T2, it was observed that all three fish species have higher growth rates as compared to T1. L. rohita had attained a maximum average body weight up to 28.7 g (1.7 times higher than in T1), C. mrigala was at 31.8 g (1.6 times higher than in T1) and C. catla was at 39.3 g (2.4 times higher than in T1). Among all three carp species cultured in Polyculture system, it was revealed that the performance of C. catla was much higher with greenhouse cover.

The study concluded that greenhouse technique has provided amplified survival rates along with magnified growth rates with respect to all the three major carp species cultured in polyculture system, however, the lead remained with C. catla which showed maximum growth rates with greenhouse cover. This technique represented a valuable substitutive method for sustaining the water temperature within the desirable ranges in the cold seasons. However, the main focus of this learning can be visualized from the results shown by C. catla where not only the survival rates have been improved but also enhanced growth rate and overall increased production was obtained in comparison to L. rohita and C. mrigala.

There is supplementary material associated with this article. Access the material online at: https://dx.doi.org/10.17582/journal.pjz/20200421070402

The authors have declared no conflict of interest.