Sturgeons (Chondrostei: Acipenseriformes) display markedly disjunction distributions with a wide distribution in the northern hemisphere. Their unique benthic specializations and conserved morphology, evolutionary age, the variation in their basic diadromous life history, and the large public interest due to their near extinction or critically endangered status make sturgeons and paddlefishes interesting groups for molecular and cytogenetic studies. From altogether 27 acipenseriform species, seventeen species are supposed to be critically endangered, two species are classified as endangered, four species are vulnerable and other species are near threatened or in low-risk (IUCN Red list 2010). Sturgeons are characteristic by a relatively high number of chromosomes in cell nuclei and differences in ploidy levels. Sturgeons displayed a strong tendency for interspecific and inter-generic hybridization under altered environmental conditions as well as under conditions of artificial propagation. Almost 20 inter-specific sturgeon hybrids were described. The decrease of natural populations and tendencies leading to restocking may result in uncontrolled restocking, production of hybrid specimens (even with non-native species) and decrease of natural genetic diversity of species in their original distribution area. Identification of parental species of natural hybrids by modern methods of molecular biology is still not easy. Here, we attempt to briefly summarize the major aspects of sturgeon genetics and cytogenetics related to ploidy levels and interspecific hybridization.

The effect of water temperature and flow on the migration of fish was observed using weekly inspections of a fishpass on the lowland section of the River Elbe (Střekov, Czech Republic) from spring to fall 2003 and 2004. The effect was examined separately for immature (up to 2 years old) and adult fish and also the most abundant species (roach Rutilus rutilus, bleak Alburnus alburnus, chub Squalius cephalus, gudgeon Gobio gobio). More than 13 thousand fish from 23 species were recorded in the fishpass during both years. The highest levels of fish occurrence in the fishpass were observed during the spring spawning migrations of adults (April–May) as well as during the late summer and fall migrations of adult and immature fish (September–November). While the total number of both fish age categories was significantly related to the interaction of water temperature and flow, however, responses of individual species and age categories differed from each other. The numbers of adult bleak, chub and gudgeon increased with higher temperature. The maximum numbers of adult bleak migrated at medium values of temperature (15–20 °C) and flow (140–270 m³ s^-1). The abundances of adult chub and adult plus immature gudgeon were higher with higher flow. The numbers of immature bleak and chub decreased with increasing flow. The numbers of adult and immature roach were influenced only by water flow with maximal numbers migrating under medium values of flow. Generally, we observed that immature fish and small- and middle-sized species required lower values of water flow than adult fish or large species to facilitate their movement. The exception was gudgeon, which required higher values of flow for its migration, a feature that could be related to its bottom dwelling nature or rheophily.

Populations of silver Prussian carp (Carassius gibelio) are known to exhibit different ploidy levels among their individuals. No consistent information is available regarding chromosome number of triploid biotype. Generally diploids have 100 chromosomes while triploids have 150–160 chromosomes. The karyotype of the C. gibelio triploid biotype is characterized by a variable number of small chromosomal elements called supernumerary chromosomes. Here we report the results of a reproduction experiment between a diploid male and triploid female with respect to chromosome numbers of the parents and their offspring. Thirty metaphases of both parents and fifteen individuals of the offspring were investigated. We found variability in chromosome numbers among analysed offspring with a fluctuation from 150 to 159. In comparison, the chromosome numbers of male and female individuals were found to be 100 and 159 respectively. Our results show a high chromosomal plasticity of the Carassius gibelio triploid biotype.

Condition of all fins was assessed in intensively cultured perch (n = 300) in comparison with control pond-reared perch (n = 30). Measurements of maximum fins length as well as a four point photographic scale were used. No damage to any fin was visually observed in the pond-reared group. The first dorsal fin showed the least damage in cultured perch with 93 % of fish demonstrating no erosion. The most affected were paired fins, with only 7 % and 2 % of pectoral and ventral fins, respectively, being non-eroded. No difference between culture systems was found in fin length for the first dorsal and the caudal fin. Pectoral, second dorsal, ventral, and anal fins of intensively cultured perch showed reductions up to 52, 49, 35, and 28 %, respectively. The relationship between fin lengths and standard body length (SL) were described for both groups (SL range 104–170 mm). Results of this study are discussed in relation to aesthetic, welfare and fish survival issues.

The winter diet of the great cormorant (Phalacrocorax carbo) was studied by means of examining regurgitated pellets, individual fish bones and fish remains collected from below the roosting trees in two sites on the River Vltava in Vyšší Brod and at Slapy Reservoir, Czech Republic, and by analysis of stomach contents of birds shot on the River Vltava in Prague. Using diagnostic bones (os pharyngeum, dentale, maxillare, praeoperculare) and own linear regression equations between measured dimension of the diagnostic bone and fish total length (L_T), a total of 1152 fish of 22 species and 6 families were identified in the diet of great cormorants and their sizes were reconstructed. At all three localities on the main stream of the River Vltava, roach (Rutilus rutilus), bream (Abramis brama), bleak (Alburnus alburnus), European chub (Squalius cephalus), European perch (Perca fluviatilis) and ruffe (Gymnocephalus cernuus) made up at least 74.2 % of the cormorants' diet. A great potential for fish stock losses was identified for the River Vltava at Vyšší Brod and in Prague where the loss of fish due to overwintering great cormorants was estimated to be 22 kg ha^-1 and up to 79 kg ha^-1 respectively, i.e. belonging among the highest ever published figures for fish withdrawal caused by great cormorants from any inland waters (carp fishponds excluded). Most probably, both great cormorants and anglers are responsible for the decrease in catches of brown trout (Salmo trutta m. fario) and grayling (Thymallus thymallus) from the River Vltava in Vyšší Brod.

Two new species of Cobitis, C. multimaculata sp. nov. and C. microcephala sp. nov. are described and illustrated from the River Nanliu and the River Beiliu, Guangxi Province, China. Cobitis multimaculata can be distinguished from congeners by its unique colour pattern of scattered, small, elongated, oval blotches on the side of the body; well developed mental lobes; and cardioid lamina circularis. It is similar to C. arenae, but can be distinguished from it by possessing a stumpy body (body depth 6.1–6.6 in standard length in males and 5.7–7.3 in females versus 7.9 in standard length in male and 7.3–9.6 in females), shorter caudal peduncle (caudal peduncle depth 1.4–1.7 of its length in males and 1.6–1.8 in females versus 2.5 in male and 2.3–3.1 in females); and 17–22 small, elongate oval blotches along lateral line (versus 20–25 spots). Cobitis microcephala can be distinguished from congeners by possessing small and solitary irregular spots scattered on the side of the body; a slender and finely serrated (16–18 serrae on the inner margin) lamina circularis; and a much smaller jet black spot on upper half of caudal-fin base

The trout barb Capoeta trutta is native to the Middle East only and little is known of its life-history in Iranian waters. Life history characteristics were examined in 366 specimens collected from the River Meymeh (western Iran) monthly during the reproductive seasons (March-May) of 2008 and 2009. Observed maximum age was 6 years in both sexes, sex ratio (male : female) was 1 : 1.35, and length-weight relationships were TL = 0.0266TW^2.7134(males), TL = 0.0258TW^2.7251 (females), and TL = 0.026TW^2.7217 (entire population). Mean egg diameter (ED) was 1.61 (± 0.03 SE), ranging from 1.6 to 1.9 mm. Mean absolute (AF) and relative fecundity (RF) were 7594 (± 283.04 SE) eggs/female, and 70 (± 241.86 SE) eggs·g^-1 body weight, respectively. AF and ED were found to increase significantly with increasing fish size, whereas RF decreased significantly with both fish TL and weight. Simplified von Bertalanffy growth estimates were also calculated.

Twinning has been reported to be much rarer in sea turtles than in freshwater turtles. However, data from sea turtles were inferred from unhatched eggs only. We hypothesized that the difference in twinning events among turtle taxa resulted primarily from the methods used for recording data. In this study, data have been recorded from 727 clutches of eggs of loggerhead sea turtles Caretta caretta laid between 2002 and 2009 at the Pelagie Islands, Italy (n = 36 clutches) and at Dalaman Beach, Turkey (n = 691 clutches). Twin embryos were found in seven out of 12160 unhatched eggs (twinning rate per unhatched egg: 0.058), but not a single case of hatched or emerged twins was recorded in 3571 eggs. The twinning rate recorded, based on post-hoc procedures, did not underestimate the occurrence of the phenomenon: the odds of obtaining a pair of twins in unhatched eggs were as large (0.92 times) as the odds of obtaining a pair of twins in the total eggs. Compared with other loggerhead nesting sites, and other sea turtle species, no statistical differences were found. However, twinning in C. caretta was found to be 6.9 times rarer than in freshwater turtle species.

We examined 126 wild tortoises to evaluate the shell changes due to sexual dimorphism and ontogenesis by the geometric morphometrics. Adult body shape varies substantially in males and females; adults showed different ontogenetic patterns between sexes: in females the posterior portion of the carapace narrows in the dorsal view, the carapace tends to assume a pyriform shape in the lateral view, and the plastron tends to lengthen of the midline and shows a slight lateral enlargement. Male shape changes towards the posterior portion of the carapace, a bending of the seam between marginal and pleural scutes, allowing the body to assume a hemispherical shape, and ventrally, the plastron narrows strongly, posteriorly. The latter feature was mainly due to the shortening of the anal scutes, probably facilitating copulation by allowing more space to move the long tail. A wider posterior in male angulate tortoises may convey greater stability in male-to-male combat. All the ontogenetic changes suggest a modification of the plastron formula, an important feature for chelonian systematics and taxonomy.

We measured faecal cortisol metabolites of a free-ranging riparian population of red deer to investigate potential effects of season, ambient temperature, precipitations and water level on the annual secretion pattern. Individuals may cope with environmental challenges through the secretion of stress hormones (glucocorticoids) which allows the integration of environmental change and life history traits by means of an adaptive feedback mechanism. Adaptations regard cyclic day-to-day activities, short-term environmental stressors or long-term ecological pressures. We detected a clear seasonal pattern of glucocorticoid metabolites secretion, with higher levels in winter and lower levels in summer. The model relating glucocorticoids secretion to minimum ambient temperature was the best fit to our dataset, although the observed pattern might as well be due to declining nutritional intake and reduction of metabolic rate in the cold season. We observed an improvement of the fit when stochastic events (flash flood) were included in the model, and discussed their role as potential contingent environmental stressors.