The most important components of the sprat’s diet are micro- and mesozooplankton – copepods, cladocerans and rotifers. The diet of the herring is dominated by micro- and mesozooplankton in the first period of life, but older fish consume mainly mysidaceans (macrozooplankton) (Załachowski et al., 1975 and Wiktor, Selisistat chemical structure 1990). The copepods in the sprat and herring diet are represented mostly by Pseudocalanus minutus elongatus, Acartia spp. and Temora longicornis ( Załachowski et al., 1975 and Wiktor, 1990). Copepods are the most abundant zooplankton species

in the Baltic Sea and adjacent waters. Numerous environmental factors – most importantly, temperature – govern essential physiological and metabolic processes in copepods. Together with food quality and concentration, this affects mortality CHIR99021 rates (Hirst & Kiørbe 2002), egg production (Halsband-Lenk et al. 2002) and the growth and development rates of these animals (Twombly and Burns, 1996, Campbell et al., 2001, Peterson, 2001, Hirst and Kiørbe, 2002, Leandro et al., 2006a and Leandro

et al., 2006b). In copepods, stage durations decrease and growth rates increase significantly with temperature, causing the animals to develop faster (Leandro et al., 2006a and Leandro et al., 2006b). Temperature also has a very important influence on moulting rates in juveniles (Hirst & Bunker 2003). Experiments on the growth rate of T. longicornis suggest that this parameter is directly proportional to food concentration ( Harris and Paffenhöfer, 1976a, Harris and Paffenhöfer, 1976b and Klein Breteler et al., 1982) and is strongly influenced

by food quality ( Klein Breteler et al. 1990). The development of T. longicornis has also been found to accelerate with temperature ( McLaren, 1978, Martens, 1980, Klein Breteler and Gonzalez, 1986, Hay et al., 1988 and Fransz et al., 1989). However, the combined effect of food concentration and temperature as a function of these parameters on the growth and development rates of T. longicornis at each of the model stages (naupliar, C1, C2, C3, C4, C5) is Phosphoglycerate kinase established in this paper. Recently, quantitative expressions describing the effects of temperature and food concentration on the growth and development of P. minutus elongatus and Acartia spp. were presented by Dzierzbicka-Głowacka, 2004, Dzierzbicka-Głowacka, 2005a and Dzierzbicka-Głowacka, 2005b) and Dzierzbicka-Głowacka et al., 2006 and Dzierzbicka-Głowacka et al., 2009a. The experimental data given by Klein Breteler and Gonzalez, 1986, Klein Breteler et al., 1982 and Klein Breteler et al., 1990were sufficient to do likewise for T. longicornis. The present work advances the idea of establishing the combined effect of temperature and food concentration on the development and growth of the naupliar stage and copepodid stages (C1, C2, C3, C4, C5) of T. longicornis.