Ecological and toxicological study of the Pontic shad (Alosa immaculata Bennett, 1835) in the Danube River in Serbia

Crnomorska haringa (Alosa immaculata, Bennett 1835) je anadromna vrsta koja veći deo života provodi u jako zagađenom severoistočnom delu Crnog mora, a radi mresta migrira u Dunav. Populacije crnomorske haringe imaju opadajući trend brojnosti, tako da se prema IUCN Crvenoj listi ugroženih vrsta tretira kao ranjiva vrsta (VU). Njen migratorni put radi mresta skraćen je izgardnjom brane Đerdap II do 863 rkm Dunava. Iako je komercijalno značajna, istraživanja na crnomorskoj haringi sprovode se povremeno. Za izradu ovog rada, migranti crnomorske haringe prikupljeni su tokom aprila i maja 2004., 2006., 2007. i 2008. godine na 863 rkm Dunava, neposredno ispod brane Đerdap II. Struktura populacije u odnosu na dužinske klase i dužinsko-težinski odnosi analizirani su na osnovu merenja totalne dužine (TL) i ukupne težine tela (W) jedinki koje su sakupljene u 2004. i 2006. godini. Opseg variranja totalnih dužina tela ulovljenih jedinki iznosio je od 24,2 do 38,7 cm, sa dominacijom klase od 32-32,5 cm. Dobijeni faktori alometrije dužinsko-težinskog odnosa manji su od tri (b<3) za oba pola i za obe sezone uzoraka. Ova studija je imala za cilj da obezbedi i prve podatke o geometrijsko-morfometrijskim karakterima crnomorske haringe, vrednostima gonadosomatskog (GSI) i hepatosomatskog indeksa (HSI) kao i Fultonovog faktora kondicije (K) u Dunavu u Srbiji. Zabeležena je statistički značajna razlika između GSI, HSI i K između oba pola i u obe sezone uzorkovanja. Razlike nisu pronađene samo za vrednosti K između mužjaka i ženki u 2004. godini i za vrednosti GSI i K između ženki uzorkovanih u 2004. i 2006. godini...The Pontic shad (Alosa immaculata Bennett 1835) is an anadromous species that spends most of its life cycle in the heavily polluted northwestern part of the Black Sea and migrates into the Danube River to spawn. Populations of the Pontic shad have a declining trend, and according to the IUCN Red List of Threatened Species the species is classified as vulnerable (VU). Although its migratory way upstream the Danube is shortened to 863 rkm after the construction of the Iron Gate II dam and even though it represents a commercially important fish species in the lower section of the Danube, the research on the Pontic shad was performed only sporadically in this area. For the purpose of this study, Pontic shad migrants were collected during April and May 2004, 2006, 2007, and 2008, immediately downstream from the Iron Gate II dam. The length frequency distribution and length-weight relationship were determined according to the measured total body length (TL) and body weight (W) of individuals sampled in 2004 and 2006. The length-weight allometric factor (b) was lower than 3 (b<3) for both sexes and both sampling seasons. The length frequency ranged from 24.2 to 38.7 cm, with the domination of the length class of 32-32.5 cm. This study was also aimed at providing the very first data on geometric morphometrics, gonadosomatic index (GSI), hepatosomatic index (HSI), and Fulton's condition factor (K) of Pontic shad migrants from the Danube in Serbia. There were statistical differences in GSI, HSI, and K between males and females in both sampling seasons, except for K between males and females in 2004, and for GSI and K between females in 2004 and 2006..

Determination of the development stage of erythrocytes in the common nase (Chondrostoma nasus) using different classification methods.

Fish erythrocytes released from erythropoietic sites are immature. During circulation they increase their own surface while the cell body and nuclei begin to become more elliptical and less spherical during maturaration. The relative abundance of different developmental stages represents an erythron profile which could be a more sensitive indicator of contamination than classic hematological indices. In this study, we analyzed blood smears of the Common Nase (Chodrostoma nasus) with the main goal to identify the determinants of the developmental stage of erythrocytes. Based on parameters developmental stages, erythrocytes are categorized into immature, intermediate or mature. In this investigation we have used four classification methods: the Two Step Cluster analysis, the K-Means Cluster analysis and Neural Neworks - Multilayer Perceptron and an Ordinal Regression Model. Our findings clearly justify that Multilayers Perceptron and ORL models are appropriate to classify the developmental stage of fish erythrocytes

Comparative evaluation of liver enzymes activities in Vimba bream and Common nase living under the same ecotoxicological conditions

The present study was carried out to investigate the differences in some enzymatic components of liver in vimba bream (Vimba vimba) and common nase (Chondrostoma nasus). For this purpose, 33 healthy vimba bream and 20 common nase were collected from commercial catches on the Danube River, near Belgrade (1172-1173 rkm), in 2016. The blood samples were taken and after separation of serum, the values of Aspartate aminotransferase (AST) and Alanine aminotransferase (ALT) enzymes activities were measured. Based on obtained results, the values of AST and ALT enzymes activities were slightly lower in the common nase compared to vimba bream, which is a possible indicator of better health and physiological status, and greater resistance to environmental pollutants present in the habitat. This difference was, however, not statistically confirmed. Considering that the selected fish were captured by the same method, having a similar ecology, living in similar habitats and under similar ecotoxicological conditions, it is not surprising that the differences in the activity of the measured liver enzymes were minimal. Since common nase is important bioindicator species, similar results could indicate that vimba bream could be considered as replacement species for this types of research, if future studies indicate the decline or endangerment of common nase populations

Reproducibility of age determination by scale and vertebra in pontic shad (alosa pontica eichwald, 1838), from the Danube

Specimens of Pontic shad (Alosa pontica Eichwald, 1838) were collected during April and May of 2006 in the Danube River (rkm 863) just downstream of the Iron Gate (Djerdap) II dam. Twenty-eight scales and 30 vertebrae were prepared and given to five interpreters with fish aging experience of from 3 to 30 years and with shad aging experience of from 0 to 12 years. Interpreters with experience in shad age determination showed lower values for the index of average percent error (IAPE) and an index of coefficient of variation (ICV). In regard to within-interpreter reproducibility, no significant differences were found between scale and vertebrae as structure for age determination. The most experienced reader showed the lowest value for IAPE, while the least experienced reader showed the highest value for IAPE. The results of this work indicate that experience in age determination by particular structure had more impact on age determination precision than specificity of structure, scale or vertebra. More work is needed on adopting standard protocols that must include some sort of common interaction between responsible age readers

Temporal analysis of electroretinographic responses in fishes with rod-dominated and mixed rod-cone retina

Photoreceptor content of fish retinas could be accessed by comparative electroretinographic (ERG) studies using flickering light stimuli that could separate rod-mediated vision where critical flicker frequency (CFE, frequency when the eye loses its ability to resolve individual light pulses) is usually less than 15 Hz from cone-mediated vision. Four fish species inhabiting different photic environments (small-spotted dogfish shark - Scyliorhinus canicula, eel - Anguilla anguilla, painted comber - Serranus scriba, Prussian carp - Carassius gibelio) were investigated. Dogfish shark b-wave amplitudes significantly decreased at low frequency of stimulation and CFF was reached at 3.2 Hz. A similar effect on the b-wave amplitude was observed in the eel, but CFF occurred at around 20 Hz. Conversely, b-waves of painted comber and Prussian carp remained unaltered under intermittent low-frequency stimulation, and CFFs were around 25 and 30 Hz, respectively. Additional support in accessing the receptor content of fish retinas was given by the characterization of the OFF-response (d-wave) after light adaptation. Monotonous time course of the b-wave dark adaptation indicated a rod dominated retina of the dogfish shark. Observed results indicate that the dogfish shark possesses preponderantly rod retina, that of the eel is rod-dominated, while Prussian carp and painted comber have cone-rich retinae

Age, growth, and length-weight relationship of common nase (Chondrostoma nasus) in the Danube River near Belgrade (Serbia).

Growth parameters, length-weight relationship, and condition of the common nase (Chondrostoma nasus) in the Danube River near Belgrade were analyzed on a sample (n=30) from the commercial catch, caught between March and May 2017. The total body length of the sampled individuals ranged from 268 to 401 mm, and body weight from 195 to 875 g. Age was determined from scales and individuals aged 5+, 6+ and 7+ were present in the sample, in approximately the same percentage. The regression coefficient of the length-weight relationship was b = 3.28. The value of b > 3 indicates a positive allometry, which denotes that the weight growth rate is greater than the length growth rate. The Fulton’s condition factor ranged from 0.90 and 1.36, with the mean value of 1.07. The parameters of the von Bertalanffy growth function were L∞ = 697.84, k = 0.08, and t0 = -1.72. The estimated phi-prime growth performance index (j') was 4.60. The lengths were back-calculated using the method of Monastyrsky, and the greatest relative growth increment was observed in the first and second year of life

Age, growth, and length-weight relationship of common nase (Chondrostoma nasus) in the Danube River near Belgrade (Serbia).

Growth parameters, length-weight relationship, and condition of the common nase (Chondrostoma nasus) in the Danube River near Belgrade were analysed on a sample (n=30) from the commercial catch, caught between March and May 2017. The total body length of the sampled individuals ranged from 26.8 to 40.1 cm, and body weight from 195 to 875 g. Age was determined from scales and individuals aged 5+, 6+ and 7+ were present in the sample, in approximately the same percentage. The regression coefficient of the length-weight relationship was b = 3.28. The value of b > 3 indicates a positive allometry, which denotes that the weight growth rate is greater than the length growth rate. The Fulton’s condition factor ranged from 0.90 and 1.36, with the mean value of 1.07. The parameters of the von Bertalanffy function were L∞ = 697.84, K = 0.08, and t0 = -1.72. The estimated phi-prime growth performance index (') was 4.60. The lengths were back-calculated using the method of Monastirsky, and the greatest relative growth increment was observed in the first and second year of life

Difference in element accumulation and histopathology of Pontic shad (Alosa immaculata) migrants caught in the Danube River in interval of one decade

Pontic shad (Alosa immaculata) is an anadromous species that lives in the Black Sea and Sea of Azov and migrates into the Danube, Don and other rivers to spawn. It is still economically important fish species in the Danube River. As the North-Western part of the Black Sea is heavily polluted investigation was performed to determine heavy metal and element accumulation in muscle tissue of Pontic shad as well as to record the level of histopathological changes. Pontic shad specimens were caught on 863 river kilometer of the Danube and the first investigation was performed during 2007 and repeated one decade later in the period 2017-2019. Element analysis was performed by inductively-coupled plasma – optic emission spectroscopy (ICPOES). In both sampling periods, only concentrations of arsenic (As), copper (Cu), iron (Fe), magnesium (Mg), strontium (Sr), and zinc (Zn) were above detection limit. Higher concentrations of As, Cu, and Zn were detected in 2007, while higher concentrations of Fe, Mg, and Sr were measured in 2019. Differences in concentrations of these elements, between sampling periods, were statistically significant. The gills of sampled fish were assessed using histopathology as a marker of general fish health state, using semi-quantitative scoring system. The histopathological results revealed different pattern of histopathological alterations in the gills of fish sampled during two distinct time periods. According to the method used, there were no difference in total gill histopathological index, but alterations were specific for fish sampled at two time points. Hyperemia and hyperplasia of respiratory epithelium dominated in fish sampled at the year 2007, while necrosis of branchial tissue prevailed in fish sampled a decade later

Reproducibility of age determination by scale and vertebra in pontic shad (Alosa pontica Eichwald, 1838), from the Danube

Specimens of Pontic shad (Alosa pontica Eichwald, 1838) were collected during April and May of 2006 in the Danube River (rkm 863) just downstream of the Iron Gate (Djerdap) II dam. Twenty-eight scales and 30 vertebrae were prepared and given to five interpreters with fish aging experience of from 3 to 30 years and with shad aging experience of from 0 to 12 years. Interpreters with experience in shad age determination showed lower values for the index of average percent error (IAPE) and an index of coefficient of variation (ICV). In regard to within-interpreter reproducibility, no significant differences were found between scale and vertebrae as structure for age determination. The most experienced reader showed the lowest value for IAPE, while the least experienced reader showed the highest value for IAPE. The results of this work indicate that experience in age determination by particular structure had more impact on age determination precision than specificity of structure, scale or vertebra. More work is needed on adopting standard protocols that must include some sort of common interaction between responsible age readers.U ovoj studiji analizirana je primenljivost starosne determinacije pomoću krljušti i pršljenova kod Alosa pontica Eichwald, 1838 iz Dunava. Neophodno je više studija o sačinjavanju standardnih protokola koji bi bili evaluirani od strane kompetentnih stručnjaka.Projekat ministarstva br. 14304

Growth parameters of vimba bream (Vimba vimba) in the Danube River near Belgrade (Serbia).

Age, growth, and length-weight relationship of the vimba bream (Vimba vimba) were analysed on a sample of 43 individuals from a commercial catch, caught between March and May 2017 in the Danube River near Belgrade. Total body length of the sampled fish ranged from 26.3 to 34.5 cm, and body weight from 223 to 554 g. Age of the sampled fish, determined from scales, ranged from 5+ to 8+, with the largest percentage of individuals in the age class 6+. The regression coefficient of the length-weight relationship was b = 3.28, which indicates a positive allometry. The parameters of the von Bertalanffy function were L∞ = 543.82, K = 0.09, and t0 = -2.41. The estimated phi-prime growth performance index (') was 4.44. The Fulton’s condition factor ranged from 1.04 to 1.42, with the mean value of 1.23. The length-at-age was back-calculated with the method of Monastyrsky, and the greatest relative growth increment was observed during the first two years of life