The effect of different supplemental feed types in semi-intensive production of common carp fry (Cyprinus carpio) on the structure and dynamics of pond ecosystems

Dobro poznavanje kompleksnih ekoloških odnosa u toplovodnim ribnjacimavaţan je preduslov uspešne šaranske proizvodnje u poluintenzivnom sistemu uzgoja.Poslednjih godina dolazi do intenziviranja proizvodnje šarana u Jugoistoĉnoj Evropi(Srbiji, Bosni i Hercegovini, Hrvatskoj, Bugarskoj i Rumuniji) kroz sve širu upotrebukoncentrovane hrane, peletirane i ekstrudirane, umesto ţitarica. Intenziviranjeproizvodnje ovih riba nosi sa sobom promene u strukturi i dinamici ribnjaĉkogekosistema.U periodu od juna do oktobra u devet ribnjaĉkih objekata na ribnjaku''Kapetanski rit'' na severu Srbije ispitivan je uticaj tri razliĉita tipa dodatne hrane zadvogodišnju šaransku mlaĊ na fiziĉke i hemijske osobine vode, strukturufitoplanktonske, zooplanktonske i bentosne zajednice ribnjaka i rast šarana. Uistraţivanju su korišćena tri tipa dodatne hrane: kombinacija ţitarica u zrnu (kukuruz,pšenica i jeĉam), komercijalna peletirana i komercijalna ekstrudirana hrana sa 25%proteina i 7% masti. Pored toga, analizirana je priroda i jaĉina meĊuzavisnosti razliĉitihkomponenata ribnjaĉkog ekosistema primenom analize redundantnosti (RDA).Tip dodatne hrane nije statistiĉki znaĉajno uticao na pokazatelje kvaliteta vode,izuzev na tvrdoću vode, ali je znaĉajno uticao na brojnost cijanobakterija, zooplanktona,bentosnih organizama i rast šaranske mlaĊi. Tako su jezera sa razliĉitim tipom dodatnehrane bila ujednaĉena u pogledu kvalitativnog sastava fitoplanktonske i zooplanktonskezajednice, dok su se znaĉajna odstupanja javila u kvantitativnom sastavu planktona.Cijanobakterije su bile dominantna grupa fitoplanktonskih organizama u svim jezerima,ali je u proseku njihova brojnost bila najmanja u grupi jezera u kojima je riba hranjenapeletiranom hranom. TakoĊe, proseĉna brojnost Cladocera i Copepoda je u jezerima sapeletiranom hranom bila znaĉajno veća u odnosu na jezera sa ţitaricama iekstrudiranom hranom, a brojnost makrozoobentosa je bila veća u odnosu na jezera saţitaricama. Rast dvogodišnje šaranske mlaĊi je bio znaĉajno manji u objektima u kojima je korišćena kombinacija ţitarica u odnosu na zimovnike sa dodatkom peletirane iekstrudirane hrane izmeĊu kojih nije bilo znaĉajnih razlika...Good understanding of complex ecological relationship in carp ponds is animportant prerequisite for successful common carp production in semi-intensive system.In recent years it has come to an intensification of carp production in South-East Europe(Serbia, Bosnia and Herzegovina, Croatia, Bulgaria and Romania) through the wideruse of industrially compounded feeds, pelleted and extruded, instead cereals.Intensification of production of these fish carries with it changes in the structure anddynamics of the pond ecosystem.The study was conducted from June to October 2009 in nine earthen fishponds atthe carp farm ''Kapetanski rit'' in the north of Serbia. The influence of three differentsupplemental feed types for the two-year carp fry on the physical and chemicalproperties of water, structure of phytoplankton, zooplankton and benthic pondcommunities and carp growth was examined. Three types of supplemental feed wereused: a combination of cereal grains (corn, wheat and barley), commercial pelleted andcommercial extruded feed with 25% of proteins and 7% of fat. In addition using theredundancy analysis (RDA), the nature and strength of the interdependence of variouscomponents of pond ecosystems was analysed.The type of supplemental feed did not significantly affect the quality of water,except the hardness of water, but had a significantly effect on the abundance ofcyanobacteria, zooplankton, benthic organism and the growth of carp fry. Thus pondswith different type of supplemental feed seemed more uniform in terms of thequalitative composition of the phytoplankton and zooplankton communities, whilesignificant discrepancies occurred in the quantitative composition of these communities.Cyanobacteria were the dominant group of phytoplankton organisms in all ponds, buton average their numbers were the lowest in the group of ponds in which pelleted feedwas used. Also, the average number of Cladocera and Copepoda in the ponds withpelleted feed was significantly higher than in ponds in which cereals and extruded feed were used, and abundance of benthic macroinvertebrates was higher than in ponds inwhich cereals were used..