GROWTH-PATTERNS OF PIKE (ESOX-LUCIUS L) LARVAE AND JUVENILES IN SMALL PONDS UNDER VARIOUS NATURAL TEMPERATURE REGIMES

A detailed analysis of early growth of pike was conducted in small ponds at low stocking density, under six natural temperature regimes. From the day of first feeding, young pike achieved a total length of 70 mm (i.e. a fresh weight close to 2 g) after 25 to 36 days (above 7-degrees-C) of extensive rearing on invertebrate diets. Total length (TL,mm) was linearly related with degree-days (DD) according to the relationships: TL = 5.292 + 0.118 DD (larval period), and TL = 0.487 + 0.147 DD (early juvenile period). These equations could be used to estimate growth on the basis of water temperature profiles and, therefore, to take appropriate management decisions. Increments in total length up to 2.0 and 5.6 mm day-1 were measured during the larval and early juvenile periods, respectively. Specific growth rates declined from 22.2 to 17.4% day-1 during the larval period (at 15-degrees-C) and from 24.1 to 16.0% day-1 during the early juvenile period (at 19-degrees-C). These data, obtained under conditions of near-maximum growth, confirm the extremely rapid growth rate of pike during early life stages.