The influence of the structure of the common carp and grass carp population on the growth and cyprinid polyculture production indexes


Agricultural University,Tirana, Albania

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The experiment is done in cultivation plant of cyprinid fish family in Klos, Elbasan, during March 2012-May 2013. Two ponds are used to do the test, each with a surface of 0.3ha. Stocking was done with one year olds. We have applied two structures of ponds population with five species of cyprinid family, the control polyculture and the test polyculture. The analysis of data for grass carp showed that in the control polyculture the “b” intercept value was 2.9778, thus a negative allometric. In the test polyculture the value of this index was b=3.2106 (r = 0.928), thus a positive allometric. In the two polyculture variants applied in this study, the “b” values coefficient in the length-weight relation for “common carp population” resulted to be negative allometric. For the control polyculture the value “b” calculated was 2.6762 (r = 0.981), whereas in the test polyculture this index had the value 2.924 (r = 0.984). The value of this index for the bighead carp grown in control polyculture was 3.0914 (r = 0.978). This number is found in the interval between the isometric value (b = 3.0) and allometric positive values (b>3.0 up to 3.5). For the population of bighead carp grown in test polyculture the value of “b” was 3.3708 (r = 0.987), thus a positive allometric. For the population of silver carp cultivated in control polyculture the “b” value was 3.0554 (r = 0.960), whereas for the silver carp grown in the test polyculture the “b” value was 3.1037 (r = 0.974). The final medium weight of common carp in the test polyculture was 141g greater compared with the polyculture. The difference of medium weight between two variants for bighead carp was 257g, for silver carp 204g and for grass carp 149g, always in favor of the populations included in the test polyculture.

Keywords: common carp, bighead carp, silver carp, grass carp, control polyculture, test polyculture

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