Light intensity preference of juvenile pikeperch Sander lucioperca (L.)

Light intensity preference of the pikeperch was tested in 1‐m² tanks divided into four lateral compartments with a hole in the middle to allow the fish to move between compartments. Two experiments were carried out with both 0+ and 1+ pikeperch: one testing intensities from 25 to 300 lx and the other from 1 to 50 lx. Light preference was observed individually for 5 days at 8, 11, 14 and 17 h. On the first and fifth day, the preference was tested without differences in light intensity (control). In both experiments, both age groups showed preference for the lowest available light intensity. Preference for low light intensity in pikeperch may be related to innate activity and feeding behaviour and to avoidance of harmful effects of light. It is suggested that under aquaculture operations, pikeperch should be reared under very dim conditions.     

The use of tannic acid to remove adhesiveness from pikeperch, Sander lucioperca, eggs

The studies conducted in 2003–2004 focused on the possibilities of applying a tannic solution to remove adhesiveness from pikeperch eggs. Spawners were caught in Lake P?tnowskie (central Poland) and then transported to the Gos?awice Fish Farm. After initial selection, the fish were weighed, measured and stimulated with human chorionic gonadotropin. Gametes were obtained 5 days after the first injection. The weight and diameter of the eggs, and the commercial fecundity of individual females were determined. The eggs were fertilized with the dry method. After the addition of water, the eggs were mixed for 4 min, and then divided into 20 g portions. After determining the number of eggs in the various portions, the adhesiveness removal procedure was performed. Three concentrations of tannic acid solution (500, 1000, 1500 mg L^?1) and three exposure times (0.5, 2, 5 min) were applied. The eggs were incubated in Weiss jars. The studies indicated that both the solution concentration and the exposure time significantly (P<0.05) impacted pikeperch egg hardening, the degree of adhesive removal and embryo survival. The tannic acid solution concentration of ≤500 mg L^?1 applied for 0.5–2 min was not effective; the eggs clumped and it was impossible to separate them even with intensive mixing. Better results were obtained using higher tannic acid concentrations and/or by lengthening exposure time. The adhesiveness of pikeperch eggs disappeared completely after 5 min exposure to tannic acid solution concentrations of 500–1500 mg L^?1 or after 2 min exposure to solution concentrations of 1000–1500 mg L^?1. In these variants, the embryo survival rate to the eyed‐egg stage was 78.0–84.0% (2003) and 82.3–84.7% (2004). However, high tannic acid concentration had a negative impact on the pikeperch larvae hatching. The greatest decrease in survival rate was observed in groups exposed to a tannic acid solution of 1500 mg L^?1 for 2 and 5 min periods. Thus, the optimum method for removing pikeperch egg adhesiveness was to apply a solution of tannic acid at a concentration of 500 mg L^?1 for 5 min or 1000 mg L^?1 for 2–5 min.     

Temperature dependent growth and yield of pikeperch, Sander lucioperca, in Finnish lakes

Abstract  A non-linear growth model was used to evaluate the effects of temperature and age on annual length increments of pikeperch, Sander lucioperca (L.), in seven lakes in Finland. Length increments were derived by back-calculation using the Fraser–Lee method. Annual length increments increased from age 1 to age 3 and then decreased, while at the same time length increments and air temperature had positive correlation until age 12. Age- and size-structured yield per recruit models were used in two lakes to evaluate the effects of temperature and gillnet mesh size on pikeperch yield. In these two lakes maximum yield could be obtained with 60 and 70 mm (bar length) gill nets. In the second lake, as typically in Finland, 45–50 mm gill nets are the most frequently used. The use of larger mesh size gill nets would increase pikeperch yield from 685 to 1000 g per recruit based on the present mean temperature. In both lakes increase in temperatures would increase yield if mesh size is simultaneously increased. Higher pikeperch yield can be expected in the future because of climate warming.     

Investigations on the effect of formalin and iodophor on embryo and larvae development in pikeperch,Sander lucioperca

ABSTRACT

An experiment was conducted to evaluate the effects of incubating pikeperch, Sander lucioperca, eggs in formalin and iodophor solutions for 15 min on embryo survival, the hatching rate, as well as on the rate of misshaped larvae, in order to develop methods for egg surface disinfection. Embryos in the morula stage, in the epiboly stage, and at the beginning of heart beat and blood circulation tolerated formalin concentrations up to 1,500 ppm for 15 min. However, they were very susceptible to iodophor treatment, as >0.1% iodophor solution (=13 ppm active iodine) significantly decreased the percentage of ready-to-hatch embryos and the percentage of hatched larvae. These data of this study recommend the use of formalin at a concentration of up to 1,500 ppm to disinfect pikeperch eggs.     

白梭吻鲈3个群体的遗传结构比较

为了加强良种选育工作,切实做好亲本遗传管理,防止近交衰退的发生,利用20个微卫星分子标记对白梭吻鲈(Sander lucioperca)新疆野生群体及山东和苏州2个养殖群体的遗传结构进行检测。结果表明,20个微卫星标记中18个有扩增产物,14个呈现多态性;每个位点的等位基因数为2~6个,平均等位基因数为3.6个,3个群体的平均等位基因数为2.57~3.36,平均观测杂合度为0.5085~0.5621,平均多态性信息含量为0.3931~0.4764,表明3个白梭吻鲈群体的遗传多样性处于中等偏低水平,遗传多样性大小为:新疆群体苏州群体山东群体。群体的Fst为0.1798,表明群体间有一定的遗传分化。在白梭吻鲈人工繁殖与养殖过程中,必须加强亲本遗传结构监测并维持一定数量的亲本规模,以利于其产业的持续发展。     

Effects of brewer’s yeast extract on growth performance and health of juvenile pikeperch Sander lucioperca (L.)

Juvenile European pikeperch, Sander lucioperca, were fed commercial feed (group C) or experimental feed supplemented with NuPro^® nucleotide‐rich Saccharomyces cerevisiae yeast protein (extract obtained through a cell wall removal process) in doses of 20, 40 or 60 g kg^?1 feed (groups N2, N4, N6) for 8 weeks. Growth, non‐specific immunity parameters, histological structure of the liver and intestine, proximate whole‐body composition and blood biochemical parameters were assayed. It was noted that brewer’s yeast extract has immunomodulatory proprieties. NuPro^® in doses of 40 and 60 g kg^?1 feed strongly stimulated non‐specific (innate) cellular and humoral immunity in pikeperch. The experimental feed did not have a significant impact on pikeperch growth (P > 0.05). The proximate composition of the fish bodies and the hepatosomatic and viscerosomatic (VSI) indices were also not affected, which indicated that the tested diets had no negative impact on the metabolism or deposition of nutrients in fish tissues. The lower levels of transaminases AST and ALT, which were noted in the groups with the two highest doses of NuPro^® (P < 0.05), might indicate improved liver function. It was also demonstrated that the brewer’s yeast extract stimulates the absorption activity of intestinal epithelial cells.     

Fertilizing ability of gametes at different post‐activation times and the sperm–oocyte ratio in the artificial reproduction of pikeperch Sander lucioperca

The time period during which oocyte and spermatozoa retain their fertilizing ability after contacting with water was evaluated in pikeperch (Sander lucioperca). In addition, success of in vitro fertilization was examined regarding to the sperm‐to‐oocyte ratio (SOR). In the first trial, oocytes were placed in Petri dishes containing 5 ml of the hatchery water, to which freshly collected and pooled sperm were added to each sample at 0, 15, 30, 60, 90, 120, 150 and 180 s post oocyte activation. The oocytes retained their fertility for at least 30 s after contacting with water. The second trial tested the maximum time period during which spermatozoa retained fertilizability after contacting with water. Milt (50 μl) was collected from each male and added to 5 ml of water in Petri dishes. Thereafter, oocytes were added at 0, 5, 15, 30, 60 and 75 s post‐sperm activation. Delays exceeding 10 s affected negatively the fertilization success. The third trial examined the optimum SOR; in which was found that 100 × 10³ spermatozoa per oocyte were the minimum ratio to ensure fertilization rates above 70%. Overall, the data clarified some biological interactions of gametes in the artificial propagation of pikeperch.     

Biological characteristics of pikeperch, Sander lucioperca, during spawning migration in a Baltic Bay

Abstract  Protection of pikeperch, Sander lucioperca (L.), during its pre-spawning migration is a hotly debated issue in the Baltic as fishing regulations to protect these stocks are based on anecdotal information. To improve understanding of pikeperch migration and improve the setting of regulations, fish were sampled with a fyke net and gill nets during the migration period (April to June) at the entrance of a spawning bay, and changes in length, sex ratio and gonadosomatic index (GSI) were analysed. Catches were greatest at the beginning of the period and consisted mainly of mature fish. From the beginning of spawning migration in April to late May, daily mean length of pikeperch decreased and then increased rapidly in early June. Sex ratio was equal at the beginning of migration, but was dominated by males thereafter. Pikeperch caught during June had already spawned.     

Out-of-season spawning of pike perch (Sander lucioperca L.) without the need for hormonal treatments

The provision of fry and fingerlings, independent of the natural spawning season, can facilitate the implementation of innovative rearing strategies also in pike perch ( Sander lucioperca L.). As strict pharmaceutical acts or codes of conduct for organic aquaculture can constrain fish farmers in inducing spawning with hormonal applications, this study intended to develop protocols for advanced and postponed spawning just by simple photo-thermal treatments. After spending between 31 and 61 days at temperatures below 10 °C, different groups of pike perch spawners were treated with light and temperature programmes to advance spawning. Reproduction could be induced successfully 2 months before the natural spawning season when the mating pairs spent 43 or more days below 10 °C, followed by a maturation phase of 44–68 days at 15 °C and 16 h illumination per day. Advanced spawning could be documented for 32 out of 35 females (91%) that underwent photo-thermal treatments. Mean commercial fecundities up to 24% and average rates of developing eggs of 65% were observed in advanced spawning groups. Coldbanking of mature females allowed to postpone spawnings for 2 and 3 months. However, no egg development could be recorded in these treatment groups.     

Size-dependent predator–prey relationships between pikeperch and their prey fish

Abstract –  Predator–prey interactions in aquatic food webs depend on the sizes of both predator and prey. In the present study, size-dependent interactions between >70 mm total length pikeperch Sander lucioperca (L.) and four different prey species in the biomanipulated Bautzen Reservoir were investigated. Gape widths of 597 pikeperch were measured, and the stomach contents of 806 specimens were analysed. Additionally, total lengths (TL) and body depths of 1448 prey fish were determined. The highest prey length to predator length ratio (PPR) was 0.63. Total lengths of piscivorous pikeperch and total lengths of prey fish [pikeperch, ruffe Gymnocephalus cernuus (L.) and roach Rutilus rutilus (L.)] were positively and linearly related. This was not the case for prey perch ( Perca fluviatilis L.) as all size groups of pikeperch fed strongly on age-0 perch. This study coupled with results of previous studies suggests that predation by pikeperch can have a major impact on the population dynamics of especially perch.     

The effects of dietary long‐chain essential fatty acids on growth and stress tolerance in pikeperch larvae (Sander lucioperca L.)

The nutritional requirements of pikeperch larvae have been sparsely examined. Dietary polyunsaturated fatty acids, arachidonic acid (ARA), eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) may affect growth and physiological stress response in marine fish larvae, but these mechanisms have not received as much attention in freshwater fish. Pikeperch larvae were reared on Artemia from day 3 until 21 days posthatch. Artemia were enriched with six formulated emulsions, with inclusion of either fish oil, pure olive oil (POO) or olive oil supplemented with various combinations of ARA, EPA and DHA. Larval tissue FA was significantly related to the content in the diets, but larval growth was similar for all treatments. When exposed to stress by confinement in small tanks with culture tank water or saline water (15 g L^?1.), mortality in larvae treated with POO was significantly higher than in the remaining treatments while tissue cortisol contents in these fish seemed lower. The findings of a lower stress response in larvae fed POO may be related to the lower tissue content in these larvae of essential fatty acids especially DHA but also EPA and ARA.     

Reproductive performance of indoor‐reared pikeperch (Sander lucioperca) females after wintering in outdoor earthen ponds

Photo‐thermal induction of gonadal maturation in completely controlled conditions is still not well explored in pikeperch. Thus, wintering intensively reared breeders in outdoor pond conditions might be rather suitable alternative to use these fish for larvae production. In this study, we compared the propagation success of indoor‐reared [recirculating aquaculture systems (RAS)‐reared fish, RRF] and wild (WCF) pikeperch females wintering them in outside earthen ponds. Each group was composed of six females and four males which were artificially propagated following hormonal induction with human chorionic gonadotropin. Beside the main parameters of reproductive success, fatty acid composition of dry eggs and mortality during early larviculture were assessed. The only statistically significant difference among reproductive parameters was found in latency time, which was significantly lower in RRF. Fatty acid profiles of dry eggs were rather similar between the groups; however, significant difference was noticed in phospholipid fraction in EPA/AA (eicosapentaenoic acid; C20:5n‐3/arachidonic acid; C20:4n‐6) ratio which was, on average, five times higher in the RRF (5.1 ± 3.8) than in WCF (0.9 ± 0.3). Significantly lower mortality was seen in the larvae originating from wild breeders (13.4 ± 1.7% and 27.0 ± 4.9% for WCF and RRF respectively). Wintering indoor‐reared females in outdoor pond conditions led to appropriate gonadal maturation, and ovulation occurred in all examined females. The lower quality of larvae was likely caused by suboptimal broodstock nutrition, which should be studied further, with special consideration given to the EPA/AA ratio and the phospholipid content and composition of the diet.     

Effect of feeding regime and temperature on ongrowing results of pikeperch (Sander lucioperca L.)

This study aimed to determine the effect of feeding rates and water temperatures on the growth, feed utilization and size heterogeneity changes in subadult pikeperch. Fish with an average weight of 84±19 g were fed with a commercial trout diet for 18 weeks at a water temperature of 20 °C and 25 °C. Four feeding rates (PSFR) were predicted at both temperatures, which corresponded to 1.0%, 1.25%, 1.50% and 2.0% of body weight per day (bw day⁻¹) for the first, and to 0.8%, 1.0%, 1.2% and 1.4% of bw day⁻¹ for the second 9 weeks respectively. At the end of the experiment, the individual weight averaged 273±82 g. Pikeperch showed a better growth rate [specific growth rate (SGR)] and apparent feed conversion rates (AFCR) at the higher temperature. Thermal-unit growth coefficient (TGC) was better at the lower temperature. The values of SGR, TGC and AFCR significantly increased with increasing PSFR at both temperatures. The values of TGC plotted against the computed feeding rates allowed estimation of the maximum feeding rates (1.25% and 1.15% of bw day⁻¹ for pikeperch of 150–180 g at 25 and 20 °C respectively). Size heterogeneity changes were affected neither by the feeding rate nor by temperature.     

Impact of fish size,water temperature,and MS‐222 concentration on inducing general anesthesia in pikeperch (Sander lucioperca)

The aim of the study was to determine the optimum concentration of MS‐222 for given size groups of pikeperch and water temperatures. The study considered three size groups of pikeperch (body weight [BW] 8.56, 15.72, 52.91 g), an MS‐222 water solution (50, 100, and 150 mg/L), and two temperatures (20 or 23°C). It was revealed that the optimum MS‐222 concentration depended largely on the size of the pikeperch and on water temperature. For fish with a BW <10 g the recommended concentration is 100 mg/L but only at 23°C. For fish with a BW of 10–40 g at an immersion temperature of 20°C the safe MS‐222 concentration ranges from 100 to 150 mg/L. However, at a temperature of 23°C the recommended concentration of the anesthetic is 100 mg/L. Similarly for larger fish, that is, fish with a BW >40 g, the optimum MS‐222 concentration at a water temperature of 20°C is in the range of 100–150 mg/L, but at a temperature of 23°C is it approximately 100 mg/L. Additionally, when exposure to the anesthetic is shorter (several min), a concentration of 150 mg/L is also safe for juvenile pikeperch of this size.     

Effect of dietary protein, lipid and carbohydrate ratio on growth, feed efficiency and body composition of pikeperch Sander lucioperca fingerlings

Pikeperch Sander lucioperca fingerlings were fed nine practical diets containing three levels of protein (P=34%, 43% and 50%), lipid (L=10%, 16% and 22%) and carbohydrate (C=10%, 15% and 20%) for 10 weeks in a recirculating water system at 23°C. Dietary treatments were distributed by orthogonal design with dietary energy content ranging from 15.5 to 23.1 MJ kg^?1 diet. Significant differences (P<0.05) in weight gain (%) and feed efficiency (FE) were observed after feeding trial. Relatively low growth and FE were found in fish fed diets containing 34% dietary protein level compared with that of fish fed diets with 43–50% protein levels, suggesting that 34% dietary protein probably is below the protein requirements of pikeperch fingerlings. Fish fed diets containing P43L10C15, P43L22C20 and P50L16C20 had significantly (P<0.05) higher weight gain and FE than fish fed the diets containing other dietary P/L/C ratios. There was no significant difference in weight gain and FE between fish fed diets of P43L10C15, P43L22C20 and P50L16C20. These results may indicate that pikeperch require at least 43% of dietary protein for adequate growth and FE, and considering the fish growth and feed ingredient cost P43L10C15 diet is more cost‐effective formulation for pikeperch fingerling. However, protein efficiency was not significantly affected by dietary P/L/C ratio.     

Movements,recapture rate and length increment of tagged pikeperch (Sander lucioperca) – a basis for management in large lakes

Movements, site fidelity, exploitation rate and total length (TL) increment of pikeperch, Sander lucioperca L., were studied by tagging 3977 pikeperch, of 334 mm mean TL, in Lake Mälaren in 1994. Fish were recaptured in gillnets, trap nets and to a lesser extent with rod and line. Total recapture rate was 30.4%, with 50% of the recaptures made within 8.4 km of the release site. Movements were restricted during summer, whereas movements from shallow to deeper basins were frequent in autumn. The yearly TL increment was estimated at 99 mm for fish 300 mm long at release and 42 mm for fish of 400 mm at release. The results have direct implications for future management, as the mortality of undersized fish in the fishery; the strong site fidelity and fast growth indicate that fishery closures may be an effective measure to attain a larger stock of fish above the size limit.     

Effect of partial or total replacement of forage fish by a dry diet on the quality of reproduction in pikeperch, Sander lucioperca

The aim of this preliminary study was to evaluate the influence of different feeding regimes on the quality of reproduction in pikeperch. Three diets were tested: forage fish (FF), a commercial dry feed (DD) and a mix of both (FD).  The diets were given to fish throughout a complete reproductive cycle. During the spawning season, couples were injected with human chorionic gonadotropin (hCG) and let to spawn on nests. Proportion of running males, spawning and hatching success and larval quality (weight, length, body protein, total lipid, fatty acid and lipid class compositions and resistances to osmotic shock and starvation stress tests at hatching) were evaluated. The proportion of running male was lower in the DD group than in the FF and FD groups (54% for DD against 76–89% for FF and FD). In addition, 25%, 62.5% and 75% of injected couples gave spawning that hatched in DD, FF and FD groups respectively. Larval quality parameters were not significantly different between treatments. The results indicate that overall quality of reproduction was higher in FF and FD treatments than in DD. It suggests that the dry feed used was not totally adequate for pikeperch reproduction. Relations between breeder reproductive performances and the feed compositions are discussed.     

A new classification of pre‐ovulatory oocyte maturation stages in pikeperch,Sander lucioperca (L.), and its application during artificial reproduction

This study aimed at improving the reproduction effectiveness and synchronization of ovulation in the pikeperch, Sander lucioperca (L.), during induced spawning, which is one of the main bottlenecks in the aquaculture of this species. For this purpose, a new categorization of maturation stages in pre‐ovulatory oocytes was applied. It is generally based on two morphological indicators: germinal vesicle migration or its breakdown (GVBD) and different oil droplet coalescence rates. This categorization covered seven stages (from I to VII) – from the end of vitellogenesis to ovulation. The categorization was verified by controlled reproduction with the use of hormonal stimulation (500 IU of hCG per kg of female body weight) and low spawning temperature (12 °C), which extended the latency time. In addition, some morphological indicators (pseudo‐gonadosomatic index, Fulton's condition coefficient) of females were calculated in order to determine their usability in determining the maturation stage. However, these indicators proved to be ineffective for this purpose, further highlighting the need to determine the maturational stages in pre‐ovulatory oocytes to synchronize ovulation in pikeperch. During the experiment, ovulation seemed to be synchronized among the experimental treatments. Statistical differences were found in terms of latency time between experimental groups at different maturity stages (II – 78–98 h; III – 57–78 h; IV – 48–58 h; V – 32–49 h; VI – 5–30 h) according to the proposed classification. This classification and the results presented in the study significantly improved the synchronization of ovulation, which may positively affect the effectiveness of pikeperch production under controlled conditions.