A review of the freshwater crabs of Turkey (Brachyura, Potamidae)

The present status of freshwater crabs (Decapoda, Brachyura) in Turkey is reviewed in this study, with the purpose of identifying the exact number of species, their conservation status, and their distribution. In previous records, it was reported that Turkey has nine freshwater crab species belonging to the genus Potamon: Potamon bileki Pretzmann, 1971, P. ibericum (Bieberstein, 1809), P. hueceste Pretzmann, 1962, P. persicum Pretzmann, 1962, P. magnum Pretzmann, 1962, P. potamios (Olivier, 1804), P. setiger Rathbun, 1904, P. rhodium Parisi, 1913, and P. mesopotamicum Brandis, Storch & Türkay, 1998. However, there was no detailed information on species distribution in Turkey. This review is intended to update the distribution of species in the country, and it revealed that populations of three more freshwater crab species (P. karpathos, P. fluviatile and P. hippocrate) also occur; thus, there are currently 12 freshwater crab species in Turkey. In addition, this review provides a distribution map and identifies possible threats to each species. This review can serve decision makers in the development of management strategies to better protect the environments of these species that are facing growing anthropogenic impacts.

Impact of a polyunsaturated fatty acid supplement on enriching the nutritional value of brine shrimp nauplii, Artemia sp.

The first aim of the study was to determine the impact the commercial product S.presso (INVE Aquaculture, Belgium) had on enriching the proximate composition of brine shrimp (Artemia sp.). The second aim of the study was to develop a better enrichment protocol for preparing enriched brine shrimp larvae. Two different enrichment protocols were investigated; the supplement was administered in either one (0.5 g L-1) or two equal (0.25 g L-1) doses. Using S.presso to enrich brine shrimp nauplii with polyunsaturated fatty acids resulted in higher levels of total lipids and higher quantities of docosahexaenoic acid DHA and eicosapentaenoic acid EPA deposition. Additionally, the enrichment supplement did not lead to overall lowered protein content values caused by increased hydrolytic activity that likely facilitates digestion in larval fish as they shift to exogenous feeding.

Tolerance of roach for modified water mineralization levels and temperatures expressed by biochemical indicators

Changes in the activity of Na+/K+-ATPase, lactate dehydrogenase, and succinate dehydrogenase in the white muscles and gill petals of roach, Rutilus rutilus (L), were studied for the combined actions of water mineralization and water temperature. It was established that decreased mineralization to 260.0 mg dm-3 and increased water temperature to 32°C increased aerobic processes in roach tissues. A sharp increase in water temperature and changes in water mineralization significantly affected the tolerance and physiological state of fish and could impact their abundance in waterbodies.

Structure of the FindFish Knowledge Transfer Platform

As consumer awareness increases in Poland, fish consumption is on an upward trend. While new technologies permit meeting increasing demand, they significantly increase the pressure on fish supplies. As a result, many fish stocks are over-exploited, which threatens marine ecosystems. Declining fisheries, increasing fishing operating costs, and the necessity of making longer fishing expeditions at greater distances that often end with catches of fewer or less valuable fish mean that in some fisheries sectors are currently running at the margins of profit or at a loss. At the same time, the European Union’s fisheries policy aims to create more selective and sustainable fisheries, to implement limitations through fishing quotas, and to ban the recognition of discards. The aim is to ensure that individual fish species are protected while providing the European Union with stable, secure supplies of fresh fish. The FindFish Knowledge Transfer Platform project was launched to provide solutions for challenges facing commercial fisheries. Its purpose is to provide fishers with a knowledge transfer platform and a numerical forecasting system for the marine environment of the Gulf of Gdansk. By combining in-situ research, environmental data, fish catch data, and numerical calculations, this tool will improve the accuracy of targeted fishing while reducing by-catch. The system will provide more reliable data on fish stocks and facilitate more efficient resource management.

Diel differences in the exploitation of shallow inshore habitats by three small bottom-dwelling fishes with implications for their monitoring in a large lowland river

Sampling small-bodied fish species in large lowland rivers poses numerous difficulties often resulting in the underestimation of their true distribution and abundance. Some of these drawbacks might be overcome by using additional sampling gears and adapting sampling strategies to the biological specifications of the target species. The results of a two-year, repeated survey on a single location on the Vistula River (southern Poland) revealed that nighttime beach seining proved to be very effective in collecting specimens of three imperiled species: Romanogobio belingi, Romanogobio kesslerii, and Sabanejewia baltica. It was found that these species were 4.3-8.8 times more abundant in nighttime than in daytime collections. The abundance of all three species peaked at dusk and gradually decreased in subsequent hours. In conclusion, nighttime beach seining is recommended as a supplementary sampling technique for small bottom-dwelling fish species in large lowland rivers.

Impact of the surgical implantation of acoustic transmitters on the condition and health of pikeperch (Sander lucioperca (L.))

The aim of the study was to determine the impact the surgical implantation of acoustic transmitters (AT; implantation incisions were sutured with tissue adhesive) had on the condition and health of pikeperch, Sander lucioperca (L.), (initial body weight of approximately 600 g). After tagging, the fish were held for 42 days in recirculating aquaculture systems. During this period, no negative effects were observed stemming from the implantation of AT on fish growth, condition, survival, or foraging effectiveness. The procedure also did not have a negative impact on hematological indicators. Among the 13 biochemical blood plasma indicators analyzed, only glucose level in the fish tagged with AT was significantly lower than that in the control group (P≤0.05). The rate of wound healing and the condition of the implantation incisions raised no concerns. Three weeks following the AT implantation procedure the incisions were closed and no infection was noted. Short-term AT retention (42 days) was 83.3%, and the fish shed the tags in the first two weeks following implantation.

Lake Hańcza – a new site for signal crayfish (Pacifastacus leniusculus Dana) occurrence in Poland

Crayfish catches were conducted using traps in Lake Hańcza, which is the deepest lake in Poland. Two crayfish populations were found to co-exist in the lake: spiny-cheek crayfish (Orconectes limosus Raf.) and signal crayfish (Pacifastacus leniusculus Dana), which is a new species for this lake. Signal crayfish dominated the samples at 98.5% of the specimens caught. The crayfish occurred at depths of 1-10 m. The mean total body length of the male and female signal crayfish (TL) was 99.5 ± 17.8 mm and 96.5 ± 11.7 mm, respectively, while the average body weight (BW) was 38.7 ± 24.9 g and 26.8 ± 9.5, respectively. Chelae were damaged in 4.5% of the individuals. Fishing efficiency (catch per unit effort – CPUE) was 0.96 crayfish trap−1 night−1. Selected characteristics of the population and of individual signal crayfish from Lake Hańcza were compared with those of the two closest neighboring populations of this species in lakes Mauda and Pobłędzie. The confirmed occurrence of the relatively large signal crayfish population in Lake Hańcza excludes this lake as a possible site for native noble crayfish (Astacus astacus L.) restoration.

Assessment of the impact of the timing of first feeding with live and formulated feeds on the survival and growth of larvae Atlantic sturgeon (Acipenser oxyrinchus Mitchill) in recirculating systems

The aim of the study was to determine the optimum timing of the first feeding of live and formulated feeds and its impact on the survival and growth of larval Atlantic sturgeon, Acipenser oxyrinchus Mitchill, reared in recirculating systems. The first experiment compared the rearing effects on larvae that were provided live feed (Artemia sp.) at first feeding on 6, 9, and 12 days post hatch (DPH). The timing of the first feeding with live feed had an impact on the specific growth rate, the final body weight, and the coefficient of body weight variation. The most advantageous rearing parameter values were noted in the group given their first feeding 9 DPH (P < 0.05). The second experiment compared the results of rearing larvae that were first given formulated feed on days 20, 25, and 30 post hatch. The highest specific growth rate and final body weight were obtained by the group of fish given their first feeding of formulated feed on day 20 post hatch (P < 0.05). The timing of the first feeding did not impact fish survival, which was above 76% (P > 0.05) in all groups. The results of the experiment indicate that the optimum timing of Atlantic sturgeon first feeding on live feed was nine DPH, and on formulated feed it was 20 DPH.

Effects of replacing fish meal with sunflower meal on growth performance, body composition, hematological and biochemical indices of common carp (Cyprinus carpio) fingerlings

The aim of the present study was to evaluate the effects of replacing fish meal with sunflower meal had on common carp, Cyprinus carpio L. fingerlings. A total of 455 fish with an average weight of 3.03 ± 0.36 g were distributed in 15 fiberglass tanks and fed five isonitrogenous and isoenergetic diets with replacement levels of 0 (control), 25, 50, 75, and 100% of fish meal with sunflower meal for 10 weeks. Based on the results, the highest and lowest final weights were observed at 25 and 100%, respectively, although the differences at 50 and 75% were not significant compared to the control. Significant differences were observed in body composition excluding ash content. Differences in all hematological indices among treatments were not significant, but in plasma biochemical indices, there was a significant decline in triglyceride levels at 100%, and cholesterol was significantly higher in the control. The results of the current study demonstrate that replacing fish meal with sunflower meal is possible up to 75% for common carp fingerlings without negative impacts on growth, body composition, or hematological and plasma biochemical indices.

The largest Baltic population of sea trout (Salmo trutta L.): its decline, restoration attempts, and current status

The sea trout, Salmo trutta L. population in the Vistula River was the largest in the Baltic Sea. Its primary spawning grounds were located in the Carpathian tributaries in the upper river basin. The fish ascended to spawn in two runs: in winter when the fish were immature and spent nearly a whole year in the river, and in summer when mature fish ascended the river and spawned within a few months. This work presents the fisheries and stocking history and scientific studies of this population from the late nineteenth century. The consequences of the most important changes in the sea trout habitat are tracked from construction in the upper river basin in the 1940s and the damming of the river in its middle reaches in Włocławek in 1969. Despite intense stocking that has been conducted for over one hundred years, catches have declined from over 100 tons to nearly zero in recent years. The current state of the population and the possibilities of restoring it are discussed in light of genetic studies.