Ivica Aničić

First record of palmetto bass (Morone saxatilis x M. chrysops) in the Croatian part of the river Danube

On October 19, 2010, a male specimen of palmetto bass (Morone saxatilis x M. chrysops) was caught by commer- cial fishing net in the Croatian section of the river Danube (302 mm TL and 331 g). It was in its third year of age (2+). A condition factor of 1.20 was based on the total length. Six specimens of prey fish were found in its gut (22.97 g altogether). Morphometric and meristic traits of this palmetto bass are presented and its possible threat to the fish community is dis- cussed.

Microsatellite-based genetic variability and differentiation of hatchery and feral common carp Cyprinus carpio L. (Cyprinidae, Cypriniformes) populations in Croatia.

Common carp production has an important status in Croatian aquaculture. In addition, the sport fishing of common carp in open waters is very popular, but it is often based on stocking from fish farms. Using fifteen microsatellites, 243 individuals from 5 hatchery and 5 feral populations have been analyzed. A total number of 148 alleles were recorded. However, the mean number of alleles per locus was remarkably low. Pairwise FST values (0.026-0.130) were significant (P<0.01), demonstrating differentiation among populations. The Markov chain method test showed that all the popula- tions deviated from HWE (P <0.05). After sequential Bonferroni correction only the Vrana lake was in HWE in all the loci but MFW20. The factors that may result in genetic divergence and significant reduction of the observed heterozygosity are discussed. AMOVA results for 10 populations indicate that the percentage of the variation among populations was 6.26%, which is lower than the variation within populations (91.04%).

The common carp Cyprinus carpio in Croatia (Danube and Adriatic basins): a historical review

This review provides the first historical account of the ecology and biology of common carp Cyprinus carpio in the Danube and Adriatic basins of Croatia, and emphasises the species’ economic relevance and management implications. As a semi-native species that is native to the Danube but translocated across the Adriatic Basin, carp plays an important role for aquaculture, recreational and artisanal fisheries. However, original strains have now disappeared, and because of genetic pollution in inland waters there is an increasing demand for restoring populations of the now rare and threatened wild carp, making conservation measures a priority. Translocations of carp across water bodies of the Adriatic Basin mostly for food supply did not prove successful in the long term, as the resulting ecological impacts may have been higher than the expected economic advantages. Measures for the prevention of further (uncontrolled) carp re-stocking are therefore necessary and this will require closer collaboration between scientists and environmental managers.

Growth and Gonad Changes in Stony Sea Urchin, Paracentrotus Lividus (Lamark, 1816) Fed Artificially Formulated Feed and Benthic Macrophyte Diet

This study reported the efficiency of artificially formulated feed and benthic macrophyte diet on growth and gonad development of cultured stony sea urchin, Paracentrotus lividus (Lamark, 1816). An initial sample of 720 individual urchins was gathered in coastal area of SE Adriatic, near Dubrovnik, Croatia and for the purposes of the experiment, was held in a flow-through system. Sea urchin were fed four test diets A, B, C and D. Diet A consisted of seaweeds collected in the natural habitat of sampled sea urchin, artificial diets B, C, and D contained a different ratio of ingredients. The feed mixtures differed in respect to corn meal content; B (22%), C (30%) and D (35%) as well as the distribution of fish meal content; B (15%), C (5%) and D (0%). Prior to the commencement of feeding, sea urchins in all groups were starved for 15 days. During the period of starvation, recorded total urchin weight, gonadosomatic index (GSI) and gonad weight values for all experimental groups, showed a declining trend except in the control group, where they stayed the same. After 30 days, the declining trend of morphometric values was recorded for treatment A and the control group. During the two months of the intensive feeding conditions in the regimes with artificially prepared feed, B, C and D a growing trend was recorded for all morphometric values, and it was particularly evident in the treatment C. In the last month of the experiment, a significant decline in the GSI and gonad weight values were observed for the groups, A and the control. The differences among the artificially formulated feeds expressed through increase of GSI and gonad mass values revealed that the best among them was artificial feed C whose variance in consistence of essential nutritional components fits between prepared feeds B and D. Based on the results of our study we conclude that the artificially formulated feed is adequate food for sea urchins in a controlled environment, especially when it contains a smaller animal protein component (510%) and a larger share of plant components (over 90%).

Effects of dietary vitamin C and soybean lecithin in the nutrition of brown bullhead ( Ameiurus nebulosus L.) fingerlings

The effects of different forms of vitamin C and soybean lecithin on growth performance, feed utilization and body composition of brown bullhead (Ameiurus nebulosus, Lesuer 1819) were evaluated during a 9-week growth trial. A special interest was to investigate a possible combine effect of these nutritional components. The diets used contained three forms of vitamin C (crystallized ascorbic acid, encapsulated L-ascorbic acid and Ca-L-threonate) (100 mg/kg) with and without the combination of soybean lecithin. Besides control diet (K), one more diet was supplemented with soybean lecithin (L) only. One-hundred-ninety-two brown bullhead of about 45 g initial body weight was randomly divided in 24 tanks (115 L each). Testing conditions included 8 fish per tank, with triplicate tanks for treatment. All diets with supplemented components had higher final weight. Specific growth rate, feed conversion rate and condition factor were significantly higher with encapsulated vitamin C diets (CC, CCL), followed by the results of enriched ascorbic acid diets. Vitamin C and lecithin supplementation showed positive influence on significantly higher number of erythrocytes, haematocrit, triglycerides and total protein. Vitamin C content of muscle and liver tissue was not uniform and was significantly higher in AAL, CCL, CC and AA feeding groups. The fatty acids profile of muscle and liver tissue showed that phospholipids from soybean lecithin and vitamin C diets enhanced the quality of usable part of the fish body. Combine supplementation of vitamin C and soy lecithin indicated positive production effects, but did not cause a statistically significant difference.

Long-term analysis of fish assemblage structure in the middle section of the Sava River – The impact of pollution, flood protection and dam construction

At the beginning of the 20th century, the middle section of the Sava River in Croatia was unaffected by major human activities and rich in ichthyofauna. The Sava River was important for commercial and recreational fishing for the local population, which still remains today. However, the 1920s mining industry was established in Slovenia, which emitted carbon dust into the Sava River. At the same time, the construction of embankments to mitigate flooding started in the middle section. Furthermore, in the 1980s, the Krško nuclear power plant (NPP), and in the 2010s, the Krško hydropower plant (HPP) were built in Slovenia. These activities could have an impact on the composition of fish communities downstream from the major sources of disturbances. Therefore, the main aim of this paper were to analyze the changes in fish assemblages of the Sava River from 1978 to 2017, prior to and after the construction of Krško NPP and HPP at the Medsave site on the Sava River, 20 km downstream from the major construction operations. Collected data were divided into four sampling periods (SP): SP1, from 1978 to 1980; SP2, from 1991 to 1994; SP3, from 2001 to 2006, and SP4 from 2011 to 2017. Besides alien fish species, water quality and hydromorphological modifications were identified as significant stressors. In SP1 and SP2 limnophilic and eurytopic fish groups were predominant, and 26 different fish species were identified, but in SP3 and SP4 rheophilic fish groups become dominant, and the diversity has declined to 21 species. Threatened species blageon, Telestes souffia seems to be missing from the main course of the Sava River in last 20 years. It can be concluded that disturbances in the fish assemblage pattern have coincided with the presence of multiple stressors of human origin.