Ecology and environmental protection

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=1.3487+2.6601R (r=0.88); W=0.1499L 1.8499 (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 7 168 eggs, the average was 1 707 – 12 284 eggs. The fecundity-length and fecundity-weight relationship were described by the equations: F=387.32L+4365.7 (r = 0.46); F=1368.4W-3151.9 (r = 0.59) respectively.

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

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 compo-nent 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 mini-mum is in November (0.56%). Feeding activity during the breeding season is decreased. The low value of vacuity index (5.94%) shows goo...

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