UNCORRECTED PROOF Short Communication Growth of the common carp (Cyprinus carpio) introduced into the Mediterranean Vransko lake By T. Treer, B. Varga, R. Safner, I. Anicˇ ic´ , M. Piria and T. Odak Faculty of Agriculture, University of Zagreb, Zagreb, Croatia Introduction The common carp (Cyrpinus carpio) is a popular species both for aquaculture and angling. Consequently, along with the rainbow trout (Oncorhynchus mykiss), carp were introduced into many waterbodies throughout the world. Common carp is among the few species whose introductions have been gener- ally considered as beneficial (Holcˇik, 1991), except in North America and Australia (Jhingran and Natarajan, 1976; Harris, 1995). Shortly after World War II when there was still a food shortage, the idea to introduce the common carp to improve the fisheries in the fresh-water Mediterranean Vransko lake in southern Croatia, just a kilometer from the Adriatic sea, was well received. This lake belongs to the Dalmatian division, the most specific of all the Euro-Mediterranean subregions because of its five endemic genera and many endemic species (Economidis and Banarescu, 1991). Prior to carp stocking, the most numerous fish in the lake were eel (Anguilla anguilla) and gray mullet (Mugil cephalus) (Morovic´, 1964). Habekovic´ (1973) summarized all introduced carps (Table 1); it is evident that 97.5% were of fish-farm origin. The remainder were wild from the river Drava. Both groups come from north Croatia, part of the Danube basin distribution of carp. According to the contemporary data based on experience alone, the carp grew rapidly during the first years of introduction into the Vransko lake, but growth decreased soon afterwards (Treer, 1989). There are several studies on the growth of wild common carp populations. Talaat and Olah (1986) and Balon (1995) describe their growth in the Danube basin. Recently, several thorough papers on the same subject were published in Australia (Vilizzi and Walker, 1995, 1998, 1999, Vilizzi et al., 1998). Common carp growth in Vransko lake was analyzed only once (Treer et al., 1995), based on catches between the years 1979 and 1982. Data also exists on condition factor (CF) of carps caught between the years 1961 and 1963 (Habekovic´, 1973). The present study investigates recent growth of com- mon carp in Vransko lake, as in 1980s the Prussian carp (Carassius auratus gibelio), probably introduced by anglers, plays an important role in the lake ichthyofauna (Treer, 1989). Holcˇik (1980) stated that populations of Prussian carp influenced the common carp populations along the lower and middle Danube, while Paller et al. (1991) found a reduced mean CF of introduced populations and ascribed it to the competitiveness of the fish species. The present paper studied whether, the interaction had the same effect in Vransko lake. Materials and methods Carp were caught by angling in Vransko lake in autumn 1999 (September and November). The lake is situated in southern Croatia, 1 km from the Adriatic sea. It is oligotrophic, with high alkalinity and high quantities of magnesium and calcium, low chemical oxygen demand and low quantities of nitrogen and phosphorus. Mild climate allows for a long growing season from May to September, with water temperatures exceeding 20 °C (Treer, 1988). Of the 70 specimens caught, 39 were male, 28 were female and, three were of undetermined sex. Measures were taken of total length (TL in cm) and weight (W in g). Scales for age determination were taken from above the lateral line, below the anterior part of the dorsal fin. Scale growth rings were read by microscope, with a video camera connected to the computer screen (SCION SCION image program). Back-calculation of growth in length was studied by using the Fraser–Lee formula and a correction coefficient for common carp of c ¼ 2.382 (Talaat and Olah, 1986). The von Bertalanffy growth function (VBGF) was used to fit the values of growth in length, and phi-prime (U¢) was used to study overall growth performance (Sparre and Venema, 1992): L t ¼ L 1 ð1  e Kðtt0Þ Þ U 0 ¼ ln K þ 2 ln L 1 where L t ¼ length at age t, L ¥ ¼ the ultimate length that an average fish would achieve if it continued to live and grow, K ¼ the growth coefficient that determines how fast the fish approaches L ¥ ,t 0 ¼ hypothetical age for L t ¼ 0 and U¢ ¼ overall growth performance. Absolute annual length increments (i n ), average absolute length increments (  l 19 ) and real growth rate (L 9 ¼ 9  l 19 ) in cm during the first 9 years of life were computed as suggested by Z ˇ ivkov et al. (1999). To establish a length–weight relationship, the commonly used W ¼ aL b was applied (Ricker, 1975) where W ¼ weight in grams, L ¼ total length in cm, and a and b are constants. CF was calculated as: CF ¼ W  L 3  100 Using the measurements of 436 carps to compare these results with those of the authors who used fork length (Vilizzi J A I 4 7 5 B Dispatch: 18.4.03 Journal: JAI CE: Svalli Journal Name Manuscript No. Author Received: No. of pages: 4 PE: Priya J. Appl. Ichthyol. 19 (2002), 1–5 Ó 2002 Blackwell Verlag, Berlin ISSN 03175–8659 Received: May 5, 2002 Accepted: January 26, 2003 U.S. Copyright Clearance Centre Code Statement: 0175–8659/2002/1703–0001$15.00/0 www.blackwell.de/synergy