Common and Applied Hydrobiology

Contemporary study of the age-size composition, L-W relationship and condition factor of the population of Salmo trutta from Iliyna River, Bulgaria was made. Classical methods for assessment of fish age, condition and population structure were applied. Five age groups were found. The maximum age, length and weight of the caught trout was 5 years, 24.7 cm and 199 g. The most abundant was the 2nd age group43.2% of the population and the less numerous was the 5th age group composed from 2.7% of the individuals in the population. The fish catch was divided in 17 size classes. The most abundant were the size classes 15.1-16 and 16.1-17 with six individuals each. The first and the second age groups were with highest size range with 5 and 6 size classes respectively. Power function describes the regression between the length and the weight of the fish (W=0.0162L2.9444, r=0,999). Fulton’s Condition Factor was 1.84, showing the wellbeing of the population. DOI: 10.29011/CRHR-121.100121

The population of the European chub (Squalius cephalus L.) from Lesnovska Rier consists 1 to 5 years old fish. The most abundand is the first age group (45,8%). The largest in size is a 5 years old individual with body length 235 mm and body weight 476 g. First and fifth age groups exibit highest size range. The following size groups are the most numerous: 7,1-8; 8,1-9 and 18,1-19 cm. The relation between the fish body length (L) and the scale radius (R) is described by the equation L=2,504R + 0,233; r=0.99. The von Bertalanffy's linear and weight growth equations are respectively: L t =76.6 [1-e-0.0677 (t+0.419) ], r = 0.999 and W t = 7164, 5 [1-e-0.0698 (t+0.4686) ] 3,036 , r= 0.999. Based on the Hohendorf's coefficients (L max : L ∞ = 0,38 and W mах :W ∞ = 0,07) it is established that the studied population doesn't sufficiently use its growth potential due to overfishing of the largest individuals. The condition factor defined by the Fulton's equation is 2.98. Mor...

The present work includes part of the first studies of element composition and metals concentrations in the plankton and fish tissues and organs from Iskar Reservoir, Bulgaria, determined by x-ray fluorescent analysis. The levels of heavy metals varied significantly among fish species and organs. The results showed that the mean concentrations of heavy metals were higher in internal organs and gills than muscles of fish. The samples for the plankton analysis were executed at different stations in the ecotone zone between Iskar River and Iskar Reservoir and in the middle of the reservoir. The results show substantial spatial heterogeneity. The highest concentrations of heavy metals in plankton were registered in the upper ecotone.

RAIKOVA-PETROVA, G., D. ROZDINA, R. MARINOVA, I. PETROV, E. NIKOLOVA and S. ILIEVA, 2015. Heavy metal content and element composition of Alburnoides bipunktatus Bloch in Iskar River. Bulgaria. Bulg. J. Agric. Sci., Supplement 1, 21: 196–201 Altogether 28 specimens of Alburnoides bipunctatus from the middle stream of Iskar River were studied to determine the element composition, distribution and deposition of heavy metals in tissues and organs of the species. An x-ray fl uorescent analysis was used. Twenty one out of the 32 surveyed elements were found. The highest concentration of elements was found in the fi ns, gill caps and gills. The level of Pb, Zn, Cd and Cu in certain tissues and organs is higher than the maximum allowed concentrations for the same metals. The highest levels of Cd were found in the muscles (4 mg.kg–1) and internal organs (3 mg.kg–1) of 3–4 years old fi sh. The highest level of Zn was established in the fi ns and gill caps of 3–4 years old specimens (147 mg.kg...

ROZDINA, D., G. RAIKOVA-PETROVA, R. MARINOVA and E. UZUNOVA, 2008. Food spectrum and feeding of Barbus cyclolepis Heckel from the middle stream of Maritza River (Bulgaria). Bulg. J. Agric. Sci., 14: 209-213 To assess the food spectrum of Barbus cyclolepis altogether 101 specimens were investigated. Food of the barbel consists of 14 food components. The occurrence frequency and the index of dominance were the highest for Chironomid larvae with 78.95% and 42.11% respectively. Plant detritus is established as a significant component in the feeding of the species with 55.79% occurrence frequency and 23.16% index of dominance and is the most important nutrient during the summer season. Variation of index of dominance and fullness index during the year is also investigated. The maximum values of fullness index are established in August (4.8%) and the minimum is in November (0.56%). Feeding activity during the breeding season is decreased. The low value of vacuity index (5.94%) shows good ...

Among the parasitic taxa studied for their metal accumulation properties, especially Acanthocephala and Cestoda proved to be promising sentinels for metal pollution. However, studies on metal accumulation are still sparse for other parasite groups, mainly due to their small body size. In the present study, we collected the relatively large-sized monogenean Mazocraes alosae Hermann, 1782 from the gills of Pontic Shad (Alosa immaculata Bennet 1835) from its spawning region – the Danube River. The host tissues gills, muscle, intestine and liver, the monogeneans as well as the nematode Hysterothylacium aduncum (Rudolphi, 1802), in the cases of coinfected fish, were analysed for the elements As, Cd, Co, Cu, Fe, Mn, Pb, Se and Zn. All elements (except of As) were found in higher concentrations in monogeneans and nematodes compared to host muscle tissue. High bioconcentration factors were obtained for toxic elements such as Cd and Pb with concentrations being approximately 12 and 251 times...