Gut evacuation in barbel (Barbus sclateri G., 1868) and nase (Chondrostoma willkommi S., 1866)

Abstract– In this study we estimated the rates of summer gut evacuation for two cyprinids with detritivorous-omnivorous feeding habits, Barbus sclateri , Günther 1868 (barbel) and Chondrostoma willkommi , Steindachner 1866 (nase). This study was performed at two sampling stations in the upper Guadalete River (south Spain). A previous study reported differences in the natural diet of both species. The gut evacuation rate was estimated from the regression of gut contents weight against time. Linear and exponential models best described the pattern of gut emptying in the two species. There was no significant difference in the gut evacuation rate between both sampling stations for barbel. However there was a discrepancy related to the model that provided the best fit to empirical data. In contrast, the same model provided the best fit to the empirical data for nase in both sampling stations, but the gut evacuation rate was significantly different in both sampling stations. The results of these study provide the first data of evacuation rates for Iberian freshwater fish species directly measured in the field.     

Khawia sinensis Hsü, 1935 (Cestoda: Caryophyllidea), a tapeworm new to the British Isles: a threat to carp fisheries?

Abstract Khawia sinensis Hsü is recorded for the first time from the British Isles. K. sinensis was recovered from many naturally infected common carp, Cyprinus carpio L., and one tench, Tinca tinca (L.) in 18 localities in England. Prevalence ranged from 4.5 to 100% and intensity of infection from one to 51 worms per fish. The worms were identified as Lytocestidae by the medullary arrangement of the vitelline glands and the cortical position of the testes, and as K. sinensis on scolex characteristics and detailed arrangement and measurements of genital organs. No evidence of pathogenicity was observed, although K. sinensis has been reported as a serious pathogen of cyprinids in overseas fisheries. The potential threat of this tapeworm to carp fisheries in England is discussed.     

Digestion of larval American shad by cyprinids

Cyprinids have pharyngeal teeth for grinding food before swallowing and a continuous gut with no discrete stomach. This digestive tract structure, as well as the feeding behavior traits shown by cyprinids, makes it difficult to identify and measure the amount of food consumed by these fishes. The relations among quantity of food in cyprinid gut, time after feeding and predator size were described by log-linear multiple regression. The number of intact American shad (Alosa sapidissima (Wilson)) larvae eaten in laboratory experiments was estimated by extrapolating the regression for the amount of food in the gut over time for predators of various size. The numbers of larval American shad in guts of fish captured in the Juniata River, Pennsylvania, were not significantly different from those estimated with the equations derived from laboratory data. In view of their abundance in rivers and their potential digestion rate for larval fish, cyprinids can be expected to have a marked influence on reducing the numbers of larval American shad.     

The use of two nature-like fishways by some fish species in the Swedish River Emån

Abstract –  We studied the use of two nature-like fishways by 15 fish species ( N  = 240) in the River Emån in southern Sweden. Use of the fishways for both passage and as a habitat was studied by electrofishing, trap catches and PIT telemetry. Of the 187 PIT-tagged fish, 52 individuals from 10 different species ascended one of the fishways for a total passage efficiency of 74%. For the five species that most frequently ascended the fishways, the passage efficiency was 100% for tench ( Tinca tinca L.) and perch ( Perca fluviatilis L.), 86% for chub ( Leuciscus cephalus L.), 60% for burbot ( Lota lota L.) and 50% for roach ( Rutilus rutilus L.). Individuals that failed to pass the fishways were typically small cyprinids or species that were assumed to have taken up residence in the fishways, such as juvenile brown trout ( Salmo trutta L.) and burbot. The nature-like fishways have re-established longitudinal connectivity for most of the studied species and also functioned as rearing and winter habitat for a number of species.     

Tench farming in China: present status and future prospects

Tench, Tinca tinca (L.) was introduced as a new species to Chinese aquaculture in 1998. Biological characteristics of tench are studied, and propagation techniques are improved at the Hubei Province Fisheries Institute with co-operation with the Research Institute of Fish Culture and Hydrobiology in Czech Republic and Institute of Hydrobiology, Chinese Academy of Sciences. The first successful artificial propagation of tench in China was made in 2000. The number of produced tench larvae increased from 5 millions in 2001 to 20 millions in 2002, and to 200 millions in 2003. The number of juveniles >5 cm reached 12 millions in 2002 and 120 millions in 2003. Total area of ponds with tench culture was 1400 ha in 2002 and 5400 ha in 2003. Main problems that hinder development of tench culture in China are identified, and future prospects of tench farming in China are highlighted. Abundant water bodies for aquaculture and cheap man-power make the export of tench from China to Europe, USA, Australia and Korea a promising activity.     

Long-term examination of health conditions in monoculture of communally tested amphimictic diploid, diploid gynogenic and triploid tench, Tinca tinca (L.)

Amphimictic diploid (2n), induced triploid (3n) and meiotic gynogenic (MeiG) tench populations were established in 1998 by mass propagation. After separate nursing, fish were group-marked by freeze branding and 200 specimens per population were stocked into an experimental earthen pond for communal test until present. Parasitological and haematological (haemoglobin content Hb, haematocrit PCV and differential leukocyte count) examinations were performed every spring and autumn in the 2+ category, once sex could be registered macroscopically. Altogether 9 genera and/or species of parasites were detected on skin, 7 genera and/or species on gills, 1 genus in eye and 1 species in gut. The highest invasion extensity was recorded in the MeiG tench in the majority of examinations till the age of 4+. The courses of PCV and Hb values for 2n and MeiG populations showed high similarity while those for 3n population were slightly decreased and sex-related differences proved to be insignificant within populations in the majority of examinations. Differential leukocyte counts showed significant differences (p<0.05) of 3n vs. 2n and/or MeiG considering lower proportions of lymphocytes and higher proportions of segmented neutrophils in the majority of cases.     

Genetic studies in tench (Tinca tinca L.): high incidence of spontaneous triploidy

A high incidence of spontaneous triploidy was found in tench broodstock hormonally treated to induce spawning but without positive response. Triploidy was also observed in random samples of fingerlings from four tench lines. Triploidy was evaluated by counting Ag-stained NORs in erythrocyte nuclei and was confirmed in 62.5% of the broodstock and in a range from 0.00% to 34.62% in fingerlings. Discrimination of tench diploids and triploids based on differences in shape and length of pelvic fins was tested in the broodstock and also in stocks of earlier artificially induced triploid tench by means of the above-mentioned cytogenetic approach and shown to be a rapid method with a high accuracy (96.43%). Natural disposition for egg overripening is one of the possible causes of highly frequent spontaneous triploidy in the analyzed samples. Genetic predisposition, i.e. occurrence of a recessive allele responsible for the failure of the 2nd polar body extrusion when homozygous, was hypothesized as another possible cause of spontaneous triploidy, based on analysis of the relationships among the tench lines.     

Influence of nutrition on the lipid quality of pond fish: common carp (Cyprinus carpio) and tench (Tinca tinca)

Like marine fish freshwater fish are an important source of essential fatty acids for human nutrition. However, the fatty acid composition of pond fish can vary considerably and strongly depends on that of the ingested food. Investigations on the fatty acid composition of common carp (Cyprinus carpio) and tench (Tinca tinca) have shown that different methods of rearing and feeding cause substantial variations in the proportions of the n-6 and n-3 polyunsaturated fatty acids of these fish species. Carp reared on the basis of natural food in ponds exhibit high contents of n-6 as well as n-3 fatty acids in their muscle triacylglycerols. On the other hand carp fed supplementary wheat in ponds resulted in somewhat lower levels of these essential fatty acids. High amounts of n-3 fatty acids can be found in carp fed high-energy diets containing high levels of fish oil. Analogous results were obtained in experiments with tench reared under different nutritional conditions. While rearing on the basis of only natural food in ponds as well as feeding supplementary wheat yielded in similar levels of n-3 and n-6 polyunsaturated fatty acids, higher contents of n-3 fatty acids were recorded in tench fed pellets. High levels of n-3 polyunsaturated fatty acids in foodstuffs have positive effects on human health. Experiments with different cultured fish species proved that the fatty acid composition of the edible parts can be influenced by the diet. Therefore, a finishing diet with a suitable fatty acid profile can be used to improve the nutritional quality of fish products of farmed origin.     

Galanin and β-endorphin as feeding regulators in cyprinids: effect of temperature

The effects of intracerebroventricular (ICV) and intraperitoneal (IP) administration of galanin and β-endorphin on food intake have been studied in satiated tench held at 21 ± 2 °C. Food intake was evaluated at 0–2 h and 2–8 h after injection. The same treatments were carried out in tench and goldfish acclimated to 10 ± 1 °C. Central administration of either galanin or β-endorphin significantly increased food intake at 2 h and 8 h after injection in tench acclimated to 21 ± 2 °C, but no change in feeding was observed after IP treatments. Low temperature (10 °C) significantly reduced food intake in both tench and goldfish, and neither central nor peripheral administration of galanin or β-endorphin was found to modify feeding. The results indicate that galanin and opioids play a role in the central regulation of feeding in tench, but the stimulatory effect of these neuropeptides did not reverse the feeding inhibition produced by exposure to low temperature.     

Biology of the tench, Tinca tinca (L.), in an Irish lake

Abstract. During the summer of 1986 a fyke-netting programme in Lough Leane, Killarney, County Kerry, for tench, Tinca tinca (L.), yielded 142 tench of which 107 were retained for analysis. Age, growth, feeding and fecundity studies were carried out on these fish.
The trophic status of Ross Bay in Lough Leane, which is known to have been eutrophic since 1971, is thought to be responsible for the improved growth of the tench when compared with two other Irish lakes, Coosan Lough, County Westmeath and College Lake, County Cork.
The meristic data recorded for Lough Leane tench show variations from those listed by Lelek (1987) for tench from other European waters. These variations may be related to the low water temperatures which curtail tench spawning in Ireland, particularly in Lough Leane.     

Induced meiotic gynogenesis in tench, Tinca tinca (L.) using irradiated heterogenic sperm

Effects of the starting time and duration of cold shock, as well as the source of heterogenic sperm on the percentage of viable gynogenic larvae (PVGL) in tench were studied. The DNA in sperm of red common carp (Cyprinus carpio var singuonensis) was inactivated by ultraviolet radiation prior to use to induce meiotic gynogenetic development in tench. In experiment 1, tench eggs were cold-shocked for 30 min starting at 1, 3, 5, 7, 10 and 15 min post activation. In experiment 2, cold shock began 5 min after activation and lasted for 10, 20, 30, 40, 50 min, respectively. Each experiment was run in triplicate using 3 tench females, and one group not treated with cold shock was included in each experiment to serve as a control group. In experiment 3, sperm of bigmouth buffalo (Ictiobus cyprinellus), red common carp or grass carp (Ctenopharyngodon idella) was used to induce gynogenesis in tench with a 20-min cold shock starting 5 min post activation. The results showed that PVGL from the control group was very low (0.11–0.47%). In experiment 1, the highest average PVGL (9.60%) was observed when cold shock treatment was applied 5 min post activation. When cold shock treatment was started 5 min post activation, duration of cold shock affected PVGL. Cold shock lasting 20 min resulted in the highest average PVGL (12. 57%) among the selected duration of cold shock studied in experiment 2. The average PVGL was 2.3, 8.6, and 9.3%, respectively, for eggs induced by sperm of bigmouth buffalo, red common carp and grass carp. Average PVGL was significantly lower for eggs induced by sperm of bigmouth buffalo, compared with that for eggs induced by sperm of the other two species. However, average PVGL were similar for eggs induced by sperm of red common carp and grass carp. In summary, the optimal conditions for gynogenesis in tench include the use of irradiated sperm of grass carp to activate the eggs and cold shock of 20 min starting 5 min post activation. Since female tench grow much faster to a larger size than male tench, gynogenesis of tench holds great potential for production enhancement.     

Changes in commercially exploited populations of tench, Tinca tinca (L.) in lakes of Northeastern Poland

Commercially exploited tench populations in 755 lakes in the Northeastern part of Poland were observed on the basis of the fishing data from 1951 to 1994. The observations were analyzed in five size categories of water reservoirs, whose total area reached over 123,900 ha. The analyses were performed according to the parameter of a commercial fish catch per area unit, taking into consideration the number of months per year when the lakes were exploited. Statistically significant differences were determined in the mean value of the tench catch parameter between the different size categories of lakes. Similar time-related differences were observed. In the lakes >100 ha the relative tench catch gradually declined in the successive time intervals. Tench was the rarest in catches from lakes <50 ha. The complete disappearance of tench from commercial catches occurred first as early as the late 1960s in lakes <200 ha. The largest quantities of tench stocking material were introduced to the lakes from 1951 to 1972. The amount of stocking material per 1 ha of stocked lakes decreased for larger lakes. The average frequency of tench stocking in the analyzed lakes was higher in larger lake size categories. On the other hand, in each lake size group the frequency of stocking was found to have declined along with the average volume of the stocking material in the subsequent 11-year-long periods.     

Reciprocal hybrids of tench Tinca tinca (L.) × bream Abramis brama (L.), and tench × carp Cyprinus carpio L., and some characteristics of their early development

Reciprocal hybrids between tench Tinca tinca (L.) and carp Cyprinus carpio L., and tench and bream Abramis brama (L.) were produced artificially. The survival of all these hybrids during embryogenesis was quite high. The highest survival rate (over 60%) at the eyed stage was observed for tench and bream hybrids (both sex combinations). The hatching rates of these hybrids were also over 60%. The number of larvae with some abnormalities (i.e. deformed body) was low. In contrast, the hatching rates of tench and carp hybrids were very low (0.2%). From over 1000 fertilized eggs, only three specimens started swimming, and only one specimen survived to juvenile stage. Embryos of hybrids and their parental species differ in morphological features. These differences were also visible in the juveniles. Body parameters of juvenile hybrids produced from three species had intermediate values in comparison to parental fish.     

Response of juvenile tench (Tinca tinca L.) fed practical diets with different protein contents and substitution levels of fish meal by soybean meal

A basal practical diet for juvenile tench (Tinca tinca) was formulated and elaborated to test several protein contents and substitution possibilities of fish meal (FM) by soybean meal (SBM) in a 90‐day trial with 5‐month‐old juveniles (30.54 mm TL, 0.30 g W). A factorial design included nine feeding treatments: three protein contents (50%, 40% or 30%) and three levels of replacement (0%, 25% or 45%) of FM protein by SBM protein. In addition, a commercial carp feed was used as reference. Final survival ranged from 98.2% to 99.4%. The 50% dietary protein with 0% or 25% replacement and 40% dietary protein with 25% replacement diets enabled higher growth (P < 0.05) and lower FCR (P < 0.05) than the rest of practical diets. Fish fed 50% dietary protein had similar growth than those fed carp feed (63.8% protein). Deformed fish averaged 1% for the practical diets and 87.6% for the carp feed. The basal practical diet has showed to be feasible and levels of 40–50% dietary protein with 25% replacement of FM protein by SBM protein can be recommended for juvenile tench aged 5–8 months.     

Decapsulated Artemia Cysts: A Suitable Dietary Supplement for Juvenile Tench (Tinca tinca L.)

There are no specifically formulated dry foods for tench (Tinca tinca L.), which forces farmers to use diets formulated for other fish species. This has major drawbacks, such as high mortality, slow growth, and body deformities. A 120 day experiment was performed with five-month-old juvenile tench (initial mean weight: 0.388 g; total length: 31.78 mm) to evaluate decapsulated Artemia cysts as a supplement to a dry diet for other fish species. Three treatments, differing in the daily supplement, were tested: 1,800 freshly hatched nauplii, 1,800 cysts, and 300 cysts per g of tench biomass. Final survival ranged between 95.3% and 97.9%. Juvenile tench that received the supplement of 1,800 decapsulated Artemia cysts had a specific growth rate (1.28), weight (1.83 g), and total length (52.30 mm) significantly higher than those with the same amount of nauplii. The lowest supplement (300 cysts/g of fish biomass) allowed significantly lower growth and higher condition coefficient (1.40) than the rest. Animals with body deformities (1.06%) were only recorded in the groups that received the lowest cyst supplement. Results showed Artemia cysts are a suitable dietary supplement for juvenile tench, being an advantageous alternative to live nauplii.     

Genetic and structural characterization of the growth hormone gene and protein from tench, Tinca tinca

The analysis of the tench growth hormone gene structure revealed a comparable organization of coding and non-coding regions than other from cyprinid species. Based on the performed mRNA and amino acid sequence alignments, gh tench is related to Asian than to European representatives of Cyprinidae family. Second aim of the work was to characterize and predict protein structure of the tench growth hormone. Tinca tinca GH share many common features with human GH molecule. The Tench GH protein binds to the growth hormone receptor (GHR) using two regions I and II that are situated at opposite sites of molecule. Binding site I is placed in the central part of T. tinca GH and H 189 amino acid in the middle region of the IV helix is crucial for GH–GHR interactions.     

Selective behaviour of a tench, Tinca tinca (L.), stock in different light–substrate combined conditions

Two physical factors light or substrate (fibre glass, artificial vegetation, gravel and mud) were determined in a 24 m long artificial channel to have importance on the distribution of 33 tench 2+, mean size 11.8±0.9 cm S.L. For this purpose in five trials tench could select between the half of the channel occupied by their preferred light intensity (inferior to 10 lux) combined with the less preferred substrate (fibre glass) or the half with the combination of one of the substrates considered and higher light conditions (40 lux). Fish preferred, with a 100% frequency, the optimal light-less preferred substrate when compared with the combinations fibre glass, gravel and mud. When artificial vegetation was the substrate considered, tench selected the combination preferred substrate – non-optimal light intensity with a 98.26±2.68% frequency. This result changed when increasing light intensity up to 150 lux, avoiding the shading effect. We demonstrated that light has a bigger influence than substrate in juvenile tench habitat selection under controlled conditions.     

Changes in commercially exploited populations of tench, Tinca tinca (L.), in littoral zones of lakes of northeastern Poland

Commercially exploited tench, Tinca tinca, (L.) populations in 480 lakes in the northeastern Poland were analyzed on the basis of the fishery data from 1949 to 1994. The long-term changes in tench catch were studied in four categories of lakes with respective proportions of littoral zones (<30, 31–60, 61–90 and <90% of total lake area). The analyses were performed with using relative catch (kg ha⁻¹ month⁻¹) of tench. Mean relative catch of tench for 1949–1994 ranged from 0.36 kg ha⁻¹ month⁻¹ in lakes with smallest littoral zone (>30%) to 0.93 kg ha⁻¹ month⁻¹ in lakes with the largest littoral (<90%). Mean relative catch increased with increasing proportions of littoral zones in lakes. However, long-term trends in mean relative catch of tench showed decreasing tendencies in all lakes. The beginning of these tendencies was found about ten years earlier in lakes with smaller littoral (<60%) in comparison to lakes with larger littoral zones (>60%). Mean stocking rates of tench (number of 1-year-old fish per ha of littoral) for 1949–1994 were not significantly different in lakes of studied categories. However, lakes with proportionally less littoral zone had reduced stocking efficiency estimated as number of stocked fish per ha of littoral to require 1 kg ha⁻¹ month⁻¹ of tench.     

Grazing Selectivity of Red Abalone Haliotis rufescens Postlarvae on Benthic Diatom Films under Culture Conditions

The gut contents of Haliotis rufescens postlarvae that had grazed on a diatom film grown in PVC buckets were analyzed to determine selectivity in feeding. Species composition and abundances were compared to that of the surrounding film. Diatom samples were oxydized and mounted permanently, or observed directly by the squash technique under phase contrast microscopy. The surrounding flora yielded 111 taxa, while 64 species appeared in the gut contents. A high proportion of Pinnularia biceps v. minor and Navicula incerta (and others) in the gut contents, which were rare or absent from the samples of the surrounding flora, indicated grazing selectivity by the postlarvae. An analysis of similarity confirmed that samples from the gut contents could be grouped together and that they were clearly different from the surrounding flora.     

Efficiency of capture of tench, Tinca tinca L. by trammel nets of monofilament and multifilament net twine combinations

Efficiencies of different trammel net types on capture of tench, Tinca tinca L. were investigated in Lake Beyşehir in Turkey between April 1998 and August 1999. Nets with an inner wall of monofilament and outer walls of multifilament (type A) were more efficient than the other net types (type B, monofilament inner and outer walls; type C, multifilament inner wall and monofilament outer walls; and D, multifilament inner and outer walls). Type A nets were 2.08, 1.79 and 1.08 times more effective than the types D, C and B for catching tench. Monofilament inner walls of trammel nets were on average 1.85 times more effective than multifilament inner walls. No significant difference in catching efficiency of monofilament and multifilament outer walls was found ( P >0.05). The average size of tench caught in monofilament trammel nets was higher than those caught in multifilament trammel nets, although not significantly different.