Aquaculture Europe 2015

October 20-23, 2015

Rotterdam, Netherlands

COMPARATIVE STUDY OF TWO DIFFERENT INTENSIVE POND REARING TECHNOLOGIES OF EUROPEAN CATFISH (SILURUS GLANIS)

Z. Nagy1,2*, D. Gál1, M. Havasi1, Cs. Hancz2
1 Research Institute for Fisheries and Aquaculture. 5540 Szarvas. Anna-liget 8. (Hungary)
2 Kaposvár University. 7400 Kaposvár. Guba S. u 40. (Hungary)
E-mail: nagyz@haki.hu

Introduction

Rearing of European catfish (Silurus glanis) in polyculture is a common practice for more than a century in Eastern- and Central Europe (Linhart et al. 2002). The aquaculture production of European catfish has doubled in the last decade (200: 755 t; 2013: 1480 t) owing to its exceptional growth potential and high meat quality. The production of catfish is carried out in intensive systems in a large measure. Good water quality has primary importance, which we can affect by species combination, stocking density, technology, feeding etc. (Milstein 1993). The aim of this study was to compare the intensive rearing of catfish in monoculture ponds and in floating cages put in polyculture ponds.

Material and methods

The 6 months long experiment was carried out in 4 earthen ponds with concrete wall between May and October 2013 at Research Institute for Fisheries and Aquaculture, Szarvas, Hungary. Each of the ponds had a surface area of 300 m2 and a depth of 1.2 m. In this study European catfish, common carp and silver carp were used in two treatments with two replications: monoculture (M1,2) and polyculture (P1,2). European catfish in monoculture was stocked with average weight of 47.5 g and 46 g, the stocking density was 0.26 and 0.25 kg m3-1. In P1,2 ponds a net cage (2 m x 6 m x 1.5 m) was put for European catfish which were stocked with average weight  of 45.5 g and 46 g, respectively, the stocking density was 5.2 kg m3-1. Common carp and silver carp were stocked outside of the cage with average weight of 36 and 34 g of carp and 1 kg of silver carp. The stocking density of common carp and silver carp was the same (0.07 kg m3-1). Skretting feed with 43 % protein content was fed to catfish with a daily ration of 2.5% and common carp in P1,2 ponds was given wheat daily, according to appetite. Daily ration was corrected weekly based on sample fishing.  Samples from the water column were taken also weekly.

Results

In M ponds the average final weight of catfish was 534.8 g. In P ponds the average weight of catfish was 404.6 g, the average weight of carp and silver carp were 303.25 g and 2.27 kg, respectively. Significant difference (p<0.05) in the average weight of catfish was found between the treatments. The average values of FCR and SGR of catfish were 1.74 g g-1 and 2.27 % in polyculture treatment and 1.19 g g-1 and 2.54 % in monoculture. FCR and SGR of common carp were 2.38 g g-1 and 2.23 %, respectively.

Water quality parameters are shown in Table 1. Significant differences were found between the parameters in NO2-N, TON, TP and TSS values (p<0.05). Different N-forms showed increasing tendency from the start of the experiment to August. The values of TP showed increasing tendency from the start of the experiment to the end of it. The TSS showed great fluctuation in all ponds during the experiment.

Conclusions

Against to the previous expectations, average weight of catfish was significantly smaller in treatment P, than in treatment M which might be caused by the high stocking density in cages. Difference in values of FCR (1.19 vs. 1.74 g g-1) also support this assumption. Our average daily weight gain results correspond to data published by other authors (Stevič et al. 1993; Treer et al. 1989) attained in experiments conducted in cages. Higher values of NH4-N observed in P ponds, where wheat was offered to carps daily, can be explained by bioturbation   of the sediment that also was observed by Ritvo et al. (2004). The bioturbation can also cause higher values of NO3-N and NO2-N in the water column (Cline et al. 1994) that was not observed in our experiment.

Acknowledgement

The support of the "Quality Changes in the traditional pond fish farming structures; development of new, complex breeding, feeding and management technology environment" project (GOP-1.1.1-11-2011-0028) is gratefully acknowledged.

References

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