NORTH-WESTERN JOURNAL OF ZOOLOGY 10 (1): 158-166 ©NwjZ, Oradea, Romania, 2014 Article No.: 131404 http://biozoojournals.ro/nwjz/index.html A contribution to understanding the ecology of the large spot barbel - sexual dimorphism, growth and population structure of Barbus balcanicus (Actinopterygii; Cyprinidae) in Central Croatia Petar ŽUTINIĆ1,*, Dušan JELIĆ2, Mišel JELIĆ1 and Ivana BUJ1 1. University of Zagreb, Faculty of Science, Division of Biology, Rooseveltov trg 6, 10000 Zagreb, Croatia. 2. Croatian Institute for Biodiversity, Prva breznička 5a, 10000 Zagreb, Croatia. *Corresponding author, P. Žutinić, E-mail’s: [email protected], [email protected] Received: 22. March 2013 / Accepted: 5. November 2013 / Available online: 31. December 2013 / Printed: June 2014 Abstract. Recent morphological and genetic studies on the genus Barbus in the Danube basin area (Kotlík et al. 2002) have led to division within the Barbus petenyi species complex and description of a new species, Barbus balcanicus. As a contribution to a better understanding of ecology of this newly described species, during 2007 authors studied the age structure, growth rate and sexual dimorphism in the population from the Ilova River basin. The overall sex ratio in the population was close to expected 1:1. Age estimation of captured specimens identified males aged 0-2 years and females aged 0-3 years. Length and weight change over age shows that there is no difference in growth rate between males and females. The population age structure suggest that females live longer (3+) than males (2+), thus explaining the sexual dimorphism in the body size. Males reach sexual maturity at around 67 mm of the total length (TL) and females at approximately 82 mm TL. Mean condition factor (Kmean) for all age classes is high (~1.2-1.3) and shows similar values. The results from unpaired two-tailed t-tests for all 26 morphometric characters show statistically significant differences between males and females (p<0.001). However, when comparing the morphometric ratios, 9 out of 28 have shown statistically significant differences (6 ratios with p<0.001; 3 ratios with p<0.005). Key words: Barbus balcanicus, central Croatia, ecology, morphometry, growth, age structure. Introduction Pliocene (Kotlík & Berrebi 2002). B. balcanicus was described as one of those three species based on its The genus Barbus contains more than 20 species unique genetic and morphological characteristics (Kottelat & Freyhof 2007) of which many have (Buonerba 2011). It inhabits mountainous and broad distribution, but some species in the Medi- submountainous streams and rivers, rarely lakes terranean region have very narrow distribution and accumulations, of the Dinaridic massif on the area and are endemics (Tsigenopoulos et al. 1999, Balkan Peninsula. Beside the Danube basin, con- 2002, Tsigenopoulos & Berrebi 2000, Machordom specific populations were recorded in the Isonzo & Doadrio 2001). Even though there is still a lack River basin (Adriatic drainage) in Italy and Slove- of data about the ecological characteristics of nia, and in rivers of the Aegean Sea drainage in many European barbels, they are separated into the north Greece (Kotlík & Berrebi 2002, Tsi- two ecophenotypic groups: rheophilic (riverine) genopoulos et al. 2002). Similar to other barbel group which contains smaller species (total body species (Britton & Pegg 2011), it is a demersal spe- length TL = 20-25 cm), and fluvio-lacustrine type cies that lives in fast and moderately fast streams which includes larger species (total body length with gravel bottom, usually retaining in riffles and TL > 50 cm) (Tsigenopoulos et al. 1999). waterfalls. During the spawning season (May to Formerly classified as Barbus petenyi, the large July) B. balcanicus migrates to the upper parts of spot barbel, now recognized as Barbus balcanicus, the stream searching for waterfalls and faster well was recently described by Kotlík et al. (2002). It is oxygenated currents to spawn. More detailed data a small rheophilic species with widespread distri- on the environmental characteristics of individual bution in the mountainous area of the Danube populations of this species are very scarce, and for (rivers Sava, Drina, Archar, Krupaja, Nera and the Croatian area, until now, practically non exis- Vlašina Lake), the Adriatic (river Soča) and the tent. Observations on morphological characters Aegean (rivers Gallikos, Vardar, Loudias and Ali- highlight conformation features of the species or akmon) basins (Tsigenopoulos et al. 2002, Kottelat subspecies in a given geographical area revealing & Freyhof 2007, Marić et al. 2012). Recent genetic any differences in terms of body size (Bănăţean- studies revealed that B. petenyi complex comprises Dunea et al. 2009). On the other hand, these data at least three species which have separated during are important for understanding the species life Ecology of Barbus balcanicus in central Croatia 159 cycle, describing its ecological valence, and accu- rate determination of the population state, which is the basis for defining the level of vulnerability and proposing measures for its protection. There- fore, the aim of this study was to gather informa- tion on the environmental characteristics and life cycle of the large spot barbel in Croatia, as a con- tribution to a better understanding of this species and a basis for comparison with its conspecific populations. Materials and methods Figure 1. Map of Ilova river drainage with locations The study was based on a sample of 77 individuals of the where Barbus balcanicus was found. large spot barbel caught at five locations on the Ilova River and its tributaries in the central Croatia (Fig. 1). The regulates the water flow to nearby ponds. Typical sub- ecological characteristics of the Toplica River (locations A strate ingredients of the Ilova River are sand and mud, and E) are a winding water flow through the forest and but the bottom substrate beneath the dam is anthropo- distinct changes in the depth of the flow, while the bot- genically altered due to paved coastal access and residual tom is covered with pebbles and mud. The terrain is stone blocks that reduce the river width. Beside the large sloped, allowing rapid water flow, and the roots and spot barbel, 35 fish species from 10 families (Jelić et al. stumps from the surrounding trees create hidden holes 2009) were recorded in the Ilova River. where the fish can dwell. Similar ecological features are Gender of every specimen of the large spot barbel present on location B (Rijeka River), except that the sub- was determined by gonad inspection. Age class was de- strate consists of smaller sized pebbles, less mud and termined by collecting 10 scales from the anterior part of slower stream flow. The fish are dwelling in deeper holes each fish between the lateral line and dorsal fin. Annuli (the maximum depth of 1 meter), sheltered by the tree (growth zones) on the scales were counted on the micro- stumps and roots. The substrate at location F (Rijeka film projector and their thickness was measured in mi- River) consists of a mud and sand combination, the ter- crometers. rain is quite laid and thus the water flow is much slower. Altogether 26 morphometric characters (Fig. 2; modi- Location C (Ilova River) is situated below the dam that fied from Lampart-Kałužniacka & Heese 2000, Domagała Figure 2. Diagram of measured morphometric characters. Abbreviations: TL, Total length; SL, Standard length; Lc, head length; pan, distance between the snout and anal aperture; pA, preanal distance; pV, preventral dis- tance; pP, prepectoral distance; pD, predorsal distance; Van, distance between the ventral and anal fin; lpC, length of caudal peduncle; lD length of dorsal fin base; lA, length of anal fin base; lC, length of caudal fin base; lP, length of pectoral fin base; lV, length of ventral fin base; P-V, distance between pectoral fin base and ventral fin base; P-A, distance between pectoral fin base and anal fin base; H, maximum body height; hco, maximum head height; h, minimum body height; laco, maximum body width; lac, maximum head width; io, interorbital distance; prO, preorbital distance; poO, postorbital distance; Oh, horizontal diameter of eye. 160 P. Žutinić et al. & Kirczuk 2004, Corsini et al. 2005, Szlachciak & Stra- kowska 2010, Takács 2012) were measured on each specimen with a caliper of 0.1 millimeter accuracy. For weight determination a digital scale with precision of 0.1 gram was used. In addition, the ratio between 19 mor- phometric characters (Lc, pan, pA, Van, pV, pP, pD, lpC, lD, lA, lC, lP, lV, P-V and P-A) and a standard body length (SL), the ratio between 8 morphometric characters (hco, h, laco, lac, io, Oh, prO and poO) and maximum body height (H), and the ratio between the maximum head width and the maximum body width (lac/laco) were calculated. Fish growth was determined from the length-weight relationship expressed by curve interpolation: W = aSLb (W = fish weight in grams, a = intercept on the x-axis, SL Figure 3. Length distribution of Barbus balcanicus = standard fish length in millimeters, b = exponent of the by sexes. arithmetic form of the weight–length relationship and the slope of the regression line in the logarithmic form). Coef- ficient b was used to describe the growth of barbel popu- lation in the Ilova River basin. The R2 value (coefficient of determination), which reveals how the assessed value on the curve fits the data (Treer 2008), was obtained by curve interpolation. The curve is more reliable as the R2 is closer to the theoretical value of 1. Fish condition is calculated on the basis of fish body length and weight, using the mean condition factor (Kmean). Kmean represents the mean condition factor for a given length derived from the respective weight–length relationship (Froese 2006), making it suitable for compari- son of different populations of the same species.