Volume 50 (2021): Issue 1 (March 2021)

Accumulation of metals (Fe, Zn, Cu, Mn, Pb, Cd and Ni) in the muscles and gills of Oreochromis niloticus, Oreochromis aureus and Tilapia zillii was assessed based on seven locations in the Qahr El-Bahr area in Lake Al-Manzalah. The average accumulation of metals was in the following order: Tilapia zillii > Oreochromis aureus > Oreochromis niloticus. To determine the risk of fish consumption, the estimated daily intake, carcinogenic, non-carcinogenic and relative risk indices were calculated. The results indicate that the intake of individual metals through the consumption of fish is almost safe for human health, whereas the intake of combined metals poses a high potential health risk to consumers. Assessment of carcinogenic risk of Cd and Ni from the consumption of tilapia species indicates that consumers are at risk of cancer. The contribution of Pb and Cd to the overall relative risk index ranged from 34% to 41%. Of the three species studied, Oreochromis niloticus is relatively safe for consumption as it poses the least health hazard, while Tilapia zillii is more predisposed to accumulate metals in its tissues. Histopathological changes were observed in the muscles, gills and liver of Oreochromis niloticus as a result of heavy metal accumulation in these organs.

Metabolic activities such as breathing and digestion, resulting from natural functions of the body through oxidation, lead to the formation of free radicals that cause cancer, premature cardiac aging and some chronic diseases. Antioxidants are substances that remove free radicals and prevent cell damage. Seafood significantly contributes to the elimination of free radicals, especially owing to its high quality nutrient content. In this context, the objective of the study was to determine the radical antioxidant capacity and the total amount of carotenes in razor clams. The IC₅₀ (mg g⁻¹) value of the DPPH radical sweeping effect varied over the months (p < 0.05), showing the highest value in June, gradually decreasing from September and reaching the lowest level in February. The total amount of carotenoids also varied, with the highest value in September (p < 0.05). The total amount of chlorophyll ranged from 6.15 μg g⁻¹ in August to 66.71 μg g⁻¹ in December.

The present study investigated the trophic ecology of two species living in an alluvial lake ecosystem in terms of season, length groups, sex, and mouth morphology. The fish were caught in a coastal lake area between December 2014 and March 2016 using a seine. In general, C. aquaedulcis was the most important prey for S. abaster, accounting for 10.99% of all prey, while amphipods accounted for 54.04% of the S. acus diet. Amphipods were the most frequently consumed prey in autumn, while C. aquaedulcis was the most important prey in spring. This result indicates that the species preferred similar prey groups and generated food competition depending on the season. The short-length group contained samples of S. abaster with empty guts, whereas S. acus in the same group consumed C. aquaedulcis. Length group II and III of individuals indicated that both species consumed amphipods and juvenile Syngnathus sp. Thus, the two species had statistically different preferences in terms of prey length. The mouth width of S. abaster was larger than that of S. acus. In conclusion, zooplankton constituted the main prey for both species in the lake and the morphological differences between the mouth apparatus of the species were due to the differences in feeding habits.

One of the economically important species is Penaeus kerathurus (Forskål, 1755), which is widespread in the Mediterranean ecosystem. This paper presents results of research on reproductive biology of Penaeus kerathurus in the Sea of Marmara. A total of 1404 specimens were dissected to determine the maturity stages, reproduction time, and length at first reproduction. The female-to-male ratio was 1:0.9. A high percentage of mature females was determined in April, May and July. Moreover, the value of the gonadosomatic index (GSI) decreased after July. The spawning period was observed between April and July, and its intensity increased in July. The carapace length at first sexual maturity was determined to be 39 mm.

European huchen (Hucho hucho) is a representative of large and rare migratory salmonid fish, which has become endangered due to extensive anthropogenic changes in freshwater ecosystems. Numerous broodstocks of the European huchen have therefore been established throughout the species’ range in recent years to supplement wild fisheries of this species. Unfortunately, this conservation management strategy entails a number of potential ecological and genetic risks associated with the release of farm-raised fish into wild populations. A comprehensive and feasible genetic monitoring protocol for broodstocks maintained for the production of restocking material is therefore essential in the sustainable management of critically endangered fish species. The current paper presents phylogenetic characteristics of four selected huchen broodstocks across Central and Eastern Europe. Genetic comparisons of the studied broodstocks were based on ten microsatellite DNA markers. The effective population size (Ne), the individual assignment test, the Principal Coordinates Analysis (PCoA), the allele sharing distance (DAS) and the Bayesian clustering analysis were applied in this study. Moreover, five selected fragments of mitochondrial DNA were used for molecular verification of species membership and genetic purity of examined specimens.

The first data on the Lemanea genus in Serbia come from the late 20th century. Only one species, L. fluviatilis, was reported from 10 localities in Serbian riverine ecosystems between 1991 and 2017. Extensive research on this genus was performed in April–November 2017–2019, surveying 150 localities in 97 upland and mountain rivers. During this study period, the Lemanea genus was recorded at 14 localities in 12 rivers, while it disappeared from five previously reported localities. A total of four taxa were identified: Lemanea fucina, L. rigida, Lemanea sp. and L. fluviatilis. Lemanea fucina and L. rigida were recorded in Serbia for the first time. L. fluviatilis was the most common taxon. Our research confirmed that Lemanea species prefer similar specific environmental conditions. These species were found in temperate, soft or moderately hard, well-oxygenated and weakly alkaline waters, with low, moderate or high conductivity, and in waters with low content of inorganic nutrients. Due to their sensitivity to changes in environmental conditions, Lemanea species are exposed to negative anthropogenic impact leading to the degradation of their habitats. Intensive construction of small hydropower plants has threatened most habitats of the Rhodophyta species in the last few years.

It is becoming increasingly important to monitor zoobenthic biodiversity in seas that are under industrial and anthropogenic pollution pressure, such as the Black Sea and the Marmara Sea. This study covers crustacean species in the Turkish waters of the Black Sea and the Marmara Sea, both of which are closed systems. Sampling was carried out in July–August 2019 and yielded 32 crustacean species from the Black Sea and 77 species from the Marmara Sea. In the Marmara Sea, two species [Kupellonura mediterranea and Leucon (Macrauloleucon) siphonatus] represent new records for the Turkish waters, and 12 species [Cirolana cranchii, Cumella (Cumella) pygmaea, Cyathura carinata, Cymodoce truncata, Eurydice pulchra, Gammaropsis sophiae, Harpinia truncata, Iphinoe serrata, Iphinoe trispinosa, Liocarcinus pusillus, Nebalia strausi and Synchelidium maculatum] are new to the Marmara Sea. The following species: Gammaropsis palmata, Pontocrates arenarius, and Synchelidium haplocheles are new records for the Black Sea. The order Amphipoda dominated in both seas in terms of the number of species and the number of individuals.

Macrophytes are one of the main components of the aquatic ecosystem. They are used in several countries as metrics for the ecological assessment of hydrosystems. The objective of our study was to evaluate the suitability of the Macrophyte Biological Index for Rivers (IBMR) to determine a trophic level in the upper Oum Er Rbia basin (Morocco) and to understand physicochemical parameters of water that govern the distribution of macrophyte species. CCA analysis was used to relate the distribution of macrophytes to hydrochemical parameters of water. The CCA analysis shows that the distribution of macrophytes was more correlated with abiotic parameters (EC, WT and DO) than nutrient parameters (PO₄-P, NO₃-N, NO₂-N, NH₃-N and COD_Mn). The recorded values of IBMR in the upper Oum Er Rbia basin indicate that the trophic level of the studied rivers ranged from “moderate” to “very high”. Pearson's correlation coefficient showed that the IBMR is more correlated with the abiotic parameters such as WT and EC and does not show any significant correlation with the content of PO₄-P and NH₃-N in water, which makes the IBMR index unreliable for assessing the trophic status related to phosphate and ammonia concentrations in our lotic waters.

The present study was carried out to determine gonadal stages and quality of pearl oyster meat (Pinctada imbricata radiata, Leach, 1814) in Izmir Bay (Turkey). Pearl oyster samples were collected from the study area at a depth of ~5 m between February 2013 and January 2014. The highest and lowest temperature was measured in July and January as 27°C and 14.2°C, respectively. The maximum chlorophyll a value of 4.640 μg l⁻¹ was calculated in May and the lowest value of 1.009 μg l⁻¹ was recorded in April. Individuals reached their first maturity in April. Spawning activity was observed from June to September and the gonad index (GI) was at the highest level during those months. The development was observed from April to February. The overall female to male ratio was 1.32:1 (p < 0.05) and it did not affect the GI (p > 0.05). There is a strong positive correlation between the GI and temperature (p < 0.05). The highest condition index (CI) was recorded in May as 12.31 ± 0.51, whereas the lowest one in January as 7.37 ± 0.22. As a result, this study revealed that the pearl oyster population in the region is characterized by high reproductive activity, especially during the summer months.

The abundance and distribution of microphyto-plankton and related physicochemical factors were assessed monthly in Obhur Creek, the central Red Sea. Sampling was carried out near the entrance, the middle and end parts of the creek. During the course of the present study, the Red Sea was characterized by predominantly oligotrophic conditions. Nutrient concentrations were relatively higher in the end part of the creek compared to the two other study sites. Chlorophyll a was also low throughout the year (average: 0.35 ± 0.32 mg m⁻³), except in May when it showed clear peaks at open-water and middle sites of the creek (1.85 and 1.04 mg m⁻³, respectively). Phytoplankton abundance followed a similar pattern to that of chlorophyll a with considerably higher abundance at these sites in May (3063.27 × 10³ and 1082.34 × 10³ individuals m⁻³, respectively). This unusually higher abundance was mostly due to the proliferation of the diatom Pseudo-nitzschia cf. delicatissima (Cleve) Heiden. Silicate concentrations were statistically significantly correlated with total phytoplankton. A total of 220 phytoplankton species were recorded during the study period (117 diatoms, 99 dinoflagellates and four cyanophytes). Diatoms dominated in the phytoplankton abundance (75%) and were followed by dinoflagellates (20%), while cyanophytes accounted for a minimal proportion. Of all phytoplankton species observed during the study, 21 diatom and four dinoflagellate species were considered as new records for the Red Sea, and two diatom and 14 dinoflagellate species were listed as harmful algal species worldwide.