The Interannual Variability of the Fall Size of Young-of-The-Year Chub (Squalius cephalus): Influence of Phenology, Growth Patterns and Abiotic Factors

Long-term surveys confirm the rapidity of environmental and biological changes undergone by endangered species but that also concerned relatively “tolerant” species, especially common rheophilic species such as European chub (Squalius cephalus, Linnaeus 1758). As many organisms, fish are highly vulnerable during their first life stages. Body size is a determinant factor for ecosystem functioning and for fish to survive to predators or to winter conditions. While numerous studies has already demonstrated the large variability of autumnal size of fish hatched during the year, few have focused on the factors explaining these interannual variations and on the growth patterns underlying these distributions. Using otoliths of young-of-the-year (YOY), we studied how the interannual variability in fall sizes of chub might be related to varying phenology, temperature, hydrology and growth patterns. YOY were sampled in three sections of the same reach of the Rhône River with contrasted hydrological regime: an artificial deep lotic channel (the tailrace of Bollène), a bypassed section with both lotic and lentic areas (former river channel before dam construction) and a reservoir with lentic deep waters. Sampling was performed on each sector during two thermally distinct years. Temperature had an important effect on both phenology and growth rate but it was not expressed similarly among river sections. Fish hatched earlier in the warmer year. Fish sizes were positively correlated with growing degree-days, but with distinct relationships between years and sections. The growth was faster in the warmer year, and in the warmer section, but differences in growth patterns varied between sections. In the bypassed section, the difference was slight, almost not significant, even if temperatures were very different between the 2 years considered. Autumnal variations in size could be explained either by an earlier phenology or by a faster growth due to higher temperatures occurring during the final part of the growing period. Our results were in accordance with general theory’s predictions relating individual growth to temperature, but they also showed that other factors might mitigate the influence of temperature on fish early life stages.

Comparative study of the fatty acid composition of light/dark mixture musculature of five freshwater fish from the region of Dezful, Iran

Fatty acid composition of fish is one of the key factors for the evaluation of fish nutritional value and it could be different based on fish species, habitat, nutrition and etc. The aim of the present study was to evaluate the fatty acid composition of five commercially important freshwater fish species taken from fisheries sites at Dez River, Iran. The fish samples included Heckel’s Orontes barbell, Luciobarbus pectoralis (Heckel, 1843), Chub, Squalius cephalus (Linnaeus, 1758), Common carp, Cyprinus carpio (Linnaeus, 1758), Brond-snout, Chondrostoma regium (Heckel, 1843) and Longspine scraper, Capoeta trutta (Heckel, 1843). The determination of fatty acid contents of the fish fillets were conducted by means of Gas chromatography. Results showed that Luciobarbus pectoralis fillets had the highest amount of fatty acids (43.49%). Cyprinus carpio had the highest amount of saturated fat (SAF) (29.43%) whereas the Luciobarbus pectoralis fillets had the highest MUFA (Monounsaturated fatty acid) (18.51%). The Squalius cephalus fillets possessed the highest amount of PUFA (polyunsaturated fatty acid) (1.87%). The Chondrostoma regium fillets revealed the highest n-6 (1.1%) while the Squalius cephalus fillets had the highest omega 3 (1.87%). The results of the present study showed that these freshwater fish are good sources of n-3 fatty acids, especially EPA and DHA, and could be considered as a valuable nutritional source.

The fishes of the Bolaman Stream, Northern Turkey

In this study, the fish species inhabiting the Bolaman Stream drains to the Black Sea from the Fatsa coast (Ordu Province, Turkey) was reported for the first time. The study was caught out non-periodically by sampling from seven stations in the Bolaman Stream between July 2017 and November 2018. Fish samples were captured with an electroshock device. With this study, it was determined that the fish fauna of the Bolaman Stream is represented by 10 species in five families (Acheilognothidae, Cyprinidae, Gobiidae, Leuciscidae, and Salmonidae). These species were as follows, respectively Rhodeus amarus, Barbus tauricus, Capoeta banarescui, Neogobius fluviatilis, Ponticola turani, Alburnus derjugini, Squalius cephalus, Vimba vimba, Alburnoides fasciatus, and Salmo coruhensis.

Organosomatic indices and leukocyte formula of chub (Squalius cephalus L) from the Suturlija River

Coefficients of organs, along with haematological characteristics, represent an important means of monitoring the health and condition of fish. Organosomatic indices show the state of organ systems and individual organs. They manifest as changes in size, which are reflected through a decrease or increase, under the influence of environmental factors. Chub individuals from the Suturlija River were used for analysis. The paper analyses the Fulton's condition factor, heart, liver, and spleen coefficients as a condition factor. Furthermore, the values ​​of total length, standard length, and body weight were determined for all individuals. Also, certain haematological parameters were analysed in the paper: total leukocyte count and differential blood count. A total of 19 chubs caught from the Suturlija River were analysed. The obtained result of Fulton's condition factor (1.53) indicates favourable habitats for chub individuals in the Suturlija River. The results of organosomatic indices are without major variations between individuals (CSI = 0.184, SSI = 0.992, HSI = 0.133). The mean leukocyte count was 45.857x109/l, with the highest proportion of lymphocytes in the differential blood count.