GROWTH RATE AND FECUNDITY OF BLEAK (ALBURNUS ALBURNUS (L.) IN THE SAND-PIT LAKE CHEPINTSI (BULGARIA)

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1 GROWTH RATE AND FECUNDITY OF BLEAK (ALBURNUS ALBURNUS (L.) IN THE SAND-PIT LAKE CHEPINTSI (BULGARIA) G. Raikova-Petrova 1, M. Iliev 1, I. Petrov 2 1 University of Sofia, Faculty of Biology, Department of General and Applied Hydrobiology, 8, Dragan Tzankov blvd., 1164 Sofia, Bulgaria; 2 Forest Research Institute, BAS, 132, Kliment Ohridski blvd., 1756 Sofia, Bulgaria Correspondence to: Galerida Raikova-Petrova galerida@abv.bg ABSTRACT The population status of bleak (Alburnus alburnut (L.) in sand-pit lake Chepintsi near Sofia by using some biological factors as growth rate, condition and fecundity was investigated. The maximum age, length and body mass of bleak were 3 years, 12.7 mm and 20 g, respectively.the first, second and third age group were 5.77%, 63.46%, 30.77% respectively. The linear and body mass growth rate were described by the equations: SL= R (r=0.88); W=0.1499L (r=0.95), respectively. The condition coefficient of bleak (k) was the lower than that for other populations from different water bodies. Also the populations from different water basins were compared by the body mass at the same length. Fecundity was eggs, the average was eggs. The fecundity-length and fecundity-weight relationship were described by the equations: F=387.32L (r = 0.46); F=1368.4W (r = 0.59) respectively. Keywords: bleak, fecundity, growth rate, sand-pit lake Chepintsi Introduction The bleak (Alburnus alburnus (L.) is a common freshwater species in Bulgaria, but hasn t been investigated. Data for the growth rate and fecundity in Batak dam, the age and body mass in Piasachnik dam and Gorni Dabnik of the bleak was published by (18) (4) (8). The purpose of this article is to determine the growth rate, condition and fecundity of the bleak from sand-pit Lake Chepintsi. Materials and methods The sand-pit lake Chepintsi is located in the Northeastern part of the Sofia valley. Its area is 0.24 km 2. The material was collected in 2007 and A total of 52 bleaks were captured by guil net with mesh size mm, fishing rod and spoon-net with mesh size 2 mm. The standard length (L ±1mm), body mass (W ±1g), gutted body mass (W ±1g) and gonad mass (w ±0.1g) were measured. The age was determined by the scales at magnification of 17.5x. The back calculation of the length (L) and body mass (W) were established by the equations L = R and W = L respectively. The coefficient of condition k was calculated by the body mass at the same lengths (10, 20 cm) according the relevant equations (9), (10).The individual absolute fecundity (F, number of eggs) was determined gravimetrically (1) (5). The relationship between the fecundity, length and body mass was described by the equations F = L, r = 0.46; F = W, r= 0.59, respectively. The relative fecundity (RF) was calculated as an index F/W (14) and as coefficient b (or b in %) from the equation F= a+bw (18) (19). Results and Discussion The material was divided in 7 size classes (Table 1). Individuals from size class cm (38.46%) and cm (28.86%) predominated. This is most likely due to the large number of predatory fish species and especially the perch. The lengths and the annual growths of the bleak in the Chepintsi sand-pit are presented in Table 2. As the age increased the linear growth was constantly decreasing. The maximum linear growth during the first year was 5.36 cm. Table 3 presents the average body mass and the fish growths. The weight growths didn t show a tendency of increasing or 212

2 decreasing with the age. The maximum weight growth was 3.76g. Size composition of bleak catch from Chepintsi Size composition size class (cm) scale radius (r, graduation) average length (L,cm) average body mass (W, g) Gutted weight body mass (g) n % 3,1-4 1,2 3,7 2,2 1,9 2 3,85 4,1-5 1,3 4,2 2,5 2,2 1 1,93 8,1-9 2,93 8,6 7,27 5, ,46 9,1-10 3,01 9,45 9,83 7, ,85 10,1-11 3,13 10, ,5 4 7,69 11,1-12 3,6 11,8 16, ,61 12,1-13 3,9 12, ,4 5 9,61 TABLE 1. TABLE 2. Beak calculated lengths (L 1, L 2, L 3, cm) and average annual growths in the end of each vegetation season of different bleak generations from Chepintsi. Generation (year) Age group W 1 W 2 W 3 Fish number , ,61 9, ,57 7,86 10, ,96 6,82 8,79 3 Average length 5,36 8,05 9,78 Growth t = L (n) - L (n-1) 5,36 2,69 1,73 52 TABLE 3. Average fish body masses (W 1, W 2 and W 3, g) and average annual growths in the end of each vegetation season of different bleak generations from Chepintsi. Generation (year) Age group W 1 W 2 W 3 Fish number , ,93 9, ,59 6,79 12, ,89 5,22 8,35 3 Average body mass 3,34 7,1 10,18 Growth t = W (n) - W (n-1) 3,34 3,76 3,08 52 The bleak linear and weight growth rate in Chepintsi was relatively low compared to this of the other water basins from the range of the species (Table 4 and Table 5.). The bleak from Chepinci is on sixth place from all 28 populations from its whole range, i.e. it has a relatively slow growth rate. The main reason for this are the food competitors like Zebra mussel (Draisena polimorfa), common roach (Rutilus rutilus), the bream (Abramis brama)and the small perch (Perca fluviatilis). Table 6 shows that for the same randomly chosen average length (3, 5, 10, 15 cm) the average body masses of the bleak in Chepinci at the first two sizes were larger than these from Batak dam, and at 10 and 15 cm were heavier. The table also illustrates very well the conclusion of (13) to use this method when comparing the condition at different populations, and not the Fulton s coefficient (13), (17), (18), (19). SPECIAL EDITION/ON-LINE YEARS OF ACADEMIC EDUCATION IN BIOLOGY

3 Fig. 1. Relationship between the lengths and fecundity of bleak from Chepintsi Fig. 2 Change of the absolute fecundity in different weight classes of bleak from Chepintsi Bleak linear growth rate in different water basins from its range Average body length (mm) of different age (years) Author and locality Lake Balaton (3) Stream Stropnice (7) Lake Leginskie (11)) Lake Qyeren (2) Danub Rive (7) sand-pit Lake Chepintsi -our data River Ohre near Karlovi Vary (7) Danub Rive Czech Republic (12) Piasuchnik Dam (4) Danub Rive Jofin (7) River Labe near Decin (7) Sainte-Croix Dam Reservoir (6) River Vltava near Podbaba (7) Danub Rive Rusovets (7) Batak Dam-1974 (17) River Vltava near Mechenice (7) West Dvina (16) Danub Rive Vulche gurlo (7) Miedzyodrze (9) Gorni Dubnik Dam (8) Batak Dam-1971/1972 (17) River Fresching (10) River Beek (10) Vranov Dam (12) Slapi Dam-1957 (12) Lipno Dam-1952/1962 (12) Brno Valley Reservoir (15) Slapi Dam (12) ТABLE

4 TABLE 5. The bleak growth rate in different water basins from the species range Author and locality Average body mass (W, g) sand-pit Lake Chepintsi -our data Batak Dam-1974 (17) Gorni Dubnik Dam (8) Batak Dam-1971 (17) TABLE 6. Average body masses of the bleak calculated at the same body length values by the equations W = kl n. Water basin and author W=kL n Average body masses (W,g) at the same length (3,5, cm) W 3 W 5 W 10 W 15 Batak Dam (17) W= L sand-pit Lake Chepintsi -our data W=0.1499L Relative fecundity in different weight classes of the bleak from Chepintsi. Weight class ( g ) Body mass (W, g) Fecundity (eggs) Relative fecundity (RF) Number (n) 5, , , TABLE 7. The reason for this is the fact that the fish body mass doesn t depends only on living conditions, but also on the start body mass, i.e. on the selfregulating rate of alometric W L growth. The smaller the start body mass, the larger the rate, and vice versa. For example when L = 5 cm in Chepinci, the average bleak body mass was 2.9g, in Batak dam it was 1.5 g, and when the length was L = 15 cm in the first case W was just 22.5 g and 41 g in the second. The absolute fecundity of the bleak ranged from 1707 (at length, body mass and age respectively 8,9 cm, 8 g and 2 years) to spawn eggs (at length, body mass and age 9.7 cm, 10 g and 2 years). The average weighted fecundity of the population was 6473 spawn eggs. Fig. 1 and Fig. 2 illustrated the relationship between the length and fecundity and the average absolute fecundity by weight classes. With increasing of the length (L) and body mass (W) there was a clear trend towards increasing the absolute fecundity (F). Calculated by equation F = W in random body mass (5, 10, 15 g), the fecundity is F 5 = 3690 eggs, F 10 = eggs, F 15 = eggs. The relative fecundity of the bleak in size classes ranged from 788 to 104 (Table 7). The relative fecundity of the bleak from Batak (18) was near 2.1 times less than this one from Chepintsi. Acknowledgements We are grateful to the funding provided by National Scientific Fund Project U-B-406/06. REFERENCES 1. Anohina, L. (1969): Zakonomernosti izmenchivosti rosta rib. M., Nauka, p Backe-Hansen (1982) SE Norway. Fauna Norv., Ser. A3: Biro (1975) Annal. Biol. Tihany, Hungaria, 42: Boiadjiev, А. (1969) Izv. Na Opitna stancia sladkovodno ribovudstvo, Plovdiv, 6, Brilinska, М., Brilinski, E. (1974) Tipovie metodiki izssledovanii produktivnosti rib v predelah ih arealov, I, Vilnus, Mintis, Chappas et al. (1987) Annls. Limnol., 23, 3: Chitravadivelu. (1974) Vestn. Ceskoslov. Spol. Zool, 35, 4: SPECIAL EDITION/ON-LINE YEARS OF ACADEMIC EDUCATION IN BIOLOGY

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