Effect of different dietary fat content and fat type on the growth and body composition of intensively reared pikeperch Sander lucioperca (L.)

Two, 42‐day feeding experiments were carried out in aquaria working in a recirculation system, to determine the influence of the different dietary fat levels and fat sources on the growth and body composition of pikeperch fingerlings. In the first experiment three levels of dietary fat (F0: 60; F1: 120; F2: 180 g kg^?1) were tested, compared with a commercial diet (Trouvit, 240 g kg^?1 fat content). F1 and F2 were formulated by adding fish oil. Best growing and feed conversion ratio was obtained with the commercial control diet, which produced also the highest total body fat (117 g kg^?1) while respective values of fish fed on the other three diets varied between 74.1 and 85.1 g kg^?1. Different feeds had no significant differences in crude protein content of the fish body. In the second test, besides feeds F0, F1 and F2, two additional feeds were formulated containing 127 g kg^?1 (L1) and 178 g kg^?1 (L2) crude fat (from linseed oil). Dietary fat levels and fat sources had significant effect neither on growth nor on feed conversion ratio. Chemical composition of the whole body did not change significantly due to the different feeds. Linseed oil had a decreasing effect on the sum of saturated fatty acids and increased the oleic and the α‐linoleic acid proportions in fillet. However, total polyunsaturated fatty acid (PUFA) proportion remained constant.     

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 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.     

Effects of turbidity on feeding of the young-of-the-year pikeperch (Sander lucioperca) in fishponds

The effect of water turbidity on the prey selection and consumption of the young-of-the-year (YOY) pikeperch in the planktivorous feeding stage was studied. Attention was paid particularly to the question of how the food selectivity depends on the size of YOY pikeperch and how the turbidity affects feeding in different size classes. Studies were carried out in ponds of two fish farms in Estonia over 4 years. Small cladocerans were the most preferred prey in the smallest pikeperch size class. In larger size classes, the most selected prey were the large cladocerans. Water turbidity affected the prey selection of the planktivorous pikeperch significantly. In more turbid environments, the larger zooplankters were more positively selected than the smaller ones. Turbidity decreased both total zooplankton consumption and Fulton's condition factor of fish only in the largest size class of pikeperch. The effect of turbidity on foraging and growth, and thus on the size of juvenile pikeperch of a particular year class is substantial under conditions where juveniles cannot shift from planktivory to piscivory.     

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.     

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.     

Effect of two medicinal herbs (Astragalus radix and Lonicera japonica) on the growth performance and body composition of juvenile pikeperch [Sander lucioperca (L.)]

The aim of this study was to determine the impact of feeding juvenile pikeperch diets with medicinal herb adjuvants on the growth performance, proximate body composition, fatty acids profile (whole fish, muscle tissues, viscera) and cytological and histological indicators of the liver and middle intestine. The fish (mean body weight of ca. 110 g) were fed diets with a 0.1% supplement of Astragalus radix (group A), Lonicera japonica (group L) or a mixture of these herbs ( A. radix + L. japonica ; group A/L) for 8 weeks. The herbal supplementation was not noted to have had an impact on the analysed indicators of fish growth performance, condition or feed conversion ratio ( P >0.05). Statistically significant intergroup differences were noted in the value of the hepatosomatic index, hepatocyte size, their nucleus and nucleus/cytoplasm diameter ratio ( P <0.05). Significant intergroup differences were also noted in the appearance of the hepatic parenchyma. Statistically significant intergroup differences were also noted in the protein content of the whole fish body. The analysis of the proximal composition of the fish viscera, in turn, indicated significant differences in the fat content ( P <0.05). Among the analysed group of fatty acids (saturated – SFA, monoenoic – MUFA, polyenoic – PUFA) contained in the whole fish, the fillets and the viscera, significant intergroup differences were noted with regard to SFA (viscera) and MUFA (whole fish) ( P <0.05). The total PUFA content was stable, although significant intergroup differences were noted with regard to a few of the acids that belong to this group ( P <0.05).     

Variations in fatty acids composition of pikeperch (Sander lucioperca) liver with respect to gonad maturation

Abstract –  We examined seasonal variations in liver condition factor, total lipid and fatty acid composition of maturing pikeperch ( Sander lucioperca) from Lake Eğirdir, Turkey. The spawning of pikeperch in Eğirdir Lake started in March, continued very fast during May and gradually ended in July as determined by measuring the gonadosomatic index. The total lipid content of male and female liver reached its highest level in September and November (the end of dense feeding period during which temperature decreased sharply), but declined to the lowest level in May (just after spawning). The highest level of liver condition factor was observed in January and March during which gonads mature rapidly. Palmitic acid was the predominant saturated fatty acid (SFA) in female and male liver. The ratio of monounsaturated fatty acids (MUFA) was higher than that of polyunsaturated fatty acids (PUFA) in both sexes. Docosahexaenoic acid (22:6 n -3), eicosopentaenoic acid (20:5 n -3) and arachidonic acid (20:4 n -6) were the predominant PUFA. Seasonal variations in PUFA were more evident than that in other fatty acids. PUFA, especially the n -3 fatty acids ratio, increased to the maximum level during the sharp decreases in temperature (in November). However, the amount of PUFA decreased to the lowest level in reproductive period. The results suggest that the ratio of pikeperch liver fatty acids is influenced by gonad maturation and temperature variations and that pikeperch requires a large amount of PUFA and the n -3 fatty acids for the development of gonads.     

Supplementing the feed of pikeperch [Sander lucioperca (L.)] juveniles with MacroGard and its influence on nonspecific cellular and humoral defense mechanisms

This study examined the influence of β‐1.3/1.6‐glucan (MacroGard) on the innate immune system in healthy pikeperch (Sander lucioperca) juveniles. MacroGard was fed in a pelleted ration of 1 or 2 g kg^?1 feed for 6 weeks. The control group of fish was fed feed with no supplement. Blood, pronephros and spleen samples for the study of nonspecific cellular and humoral defense mechanisms were collected from 10 fish from each group. No changes were observed in either the behaviour or the health of the fish throughout the rearing period. Fish mortality was not noted in any of the groups. Additionally, the supplementation of feed with MacroGard did not have a significant impact on the fish growth rate as expressed in both absolute and relative values (P>0.05). The condition of the fish from the experimental group did not differ from that of the control group specimens, and the feed conversion ratios were also very similar (P>0.05). The results showed that MacroGard administered in two doses significantly (P<0.05) activated the metabolic activity and potential killing activity of spleen phagocytes, compared with the control‐fed pikeperch. The highest phagocyte activity was observed with a dose of 2 g kg^?1. The proliferative response of pronephros lymphocytes indicated a similar pattern. MacroGard significantly increased proliferative response of lymphocytes stimulated by mitogens (P<0.05). MacroGard also significantly increased the lysozyme activity and total immunoglobulin levels in the serum. In this study neither significantly different ceruloplasmine activity or total protein level in serum were observed. The result showed that MacroGard at the optimal dose of 1 g kg^?1 feed and a twofold higher dose does not have a negative influence on the hepatocytes or increased nonspecific cell‐ and humoral‐mediated immunity in healthy pikeperch.     

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.     

Influence of β-hydroxy-β-methylbutyrate on nonspecific humoral defense mechanisms and protection against furunculosis in pikeperch (Sander lucioperca)

Studies have shown that in both in vitro and in vivo tests, β‐hydroxy‐β‐methylbutyrate (HMB) increases the nonspecific cellular and humoral immune response and protection against diseases in animals. The present study examines the influence of HMB on nonspecific humoral defense mechanisms and protection against furunculosis in pikeperch (Sander lucioperca). β‐hydroxy‐β‐methylbutyrate was fed in a pelleted ration of 50 mg kg^?1 feed day^?1 for 4 weeks. Blood was drawn from 12 HMB‐fed and control‐fed pikeperch. The lysozyme and ceruloplasmin activities in the plasma, total immunoglobulin (Ig) levels, and total serum protein were analysed prior to and then after 2 and 4 weeks of HMB ingestion. After 4 weeks of HMB ingestion, a challenge test was performed by injecting the fish with live pathogenic Aeromonas salmonicida bacteria. β‐hydroxy‐β‐methylbutyrate at a dose of 50 mg kg^?1 feed resulted in a statistically significant (P<0.05) increase in the lysozyme activity of the plasma, total Ig, and serum protein levels. Additionally, reduced mortality (40%) after the in vivo challenge with pathogenic A. salmonicida suggested that HMB‐activated nonspecific protection against furunculosis in pikeperch.     

Effects of varying dietary fatty acid profile on growth performance, fatty acid, body and tissue composition of juvenile pike perch (Sander lucioperca)

Pike perch (Sander lucioperca) has been identified as specie destined to diverse European inland aquaculture, but knowledge on the nutritional requirements is weak. Therefore, we investigated the effect of varying dietary fatty acid (FA) profile by partial replacement of fish oil (FO) with vegetable oils on growth, FA and body composition of juvenile pike perch. An extruded basal diet containing 59 g kg^?1 crude lipids (FO) was added with 60 g kg^?1 FO, 60 g kg^?1 linseed oil (LO) or 60 g kg^?1 soybean oil (SO). The resulting dietary FA composition differed mainly in the triglyceride fraction and was characterized by highest amounts of linolenic acid (18:3 n‐3) in the LO diet and linoleic acid in the SO diet. Diet enriched with FO contained highest contents of highly unsaturated FA 20:5 n‐3 (eicosapentaenic acid) and 22:6 n‐3 (docosahexaenic acid). Pike perch were held in a recirculation system and each feeding group (in triplicate) was fed with experimental diets at a daily rate of 35 g kg^?1 of biomass for 57 days by automatic feeders. Weight gain and specific growth rate of experimental feeding groups ranged between 18.47 and 19.58 g and 1.37–1.45% day^?1 and was not affected by the dietary composition indicating that FO can be replaced by vegetable oils without negative impact on growth performance. In contrast to the whole body and muscle composition, liver tissue was affected by the varying diets. Liver tissues of fish fed diets enriched with vegetable oils showed significantly increased lipid contents of 162 (LO) and 147 (SO) g kg^?1 and indicate decreased lipid utilization compared with fish fed FO diet (liver lipid content 112 g kg^?1). Nevertheless, hepatosomatic index of pike perch was not influenced by dietary lipid composition. The FA profile of pike perch was generally determined by the dietary FAs.     

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.     

Importance of the relative levels of dietary arachidonic acid and eicosapentaenoic acid for culture performance of gilthead seabream (Sparus aurata) larvae

The effect of different arachidonic acid (ARA) dietary contents at several dietary eicosapentaenoic acid (EPA) levels on the growth, survival and biochemical composition of gilthead seabream larvae was studied to better define the importance of this fatty acid as a function of EPA. Larvae of 18 days were fed one of the five isonitrogenous and isolipidic microdiets with three different EPA (0.3%, 2% and 4%) and ARA amounts (0.1%, 0.6% and 1.2%). Although a dietary increase in either ARA or EPA alone did not improve survival significantly, the increase in both fatty acids significantly enhanced growth and survival, suggesting an optimum dietary value of EPA:ARA close to 4:1.2. Dietary ARA was more efficiently incorporated into larval tissues than EPA. Increased dietary EPA or ARA contents reduced the incorporation of ARA or EPA into larval lipids, indicating their competition as substrates for different enzymes. The possible negative effect of further elevation of dietary ARA and its competition with EPA for phospholipids synthesis deserves further studies in marine fish larvae.     

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.     

The application of tannic acid to the elimination of egg stickiness at varied moments of the egg swelling process in pikeperch,Sander lucioperca (L.)

The aim of this article was to analyse the process of pikeperch, Sander lucioperca, egg swelling and to apply tannic acid to eliminate egg stickiness at different moments of the swelling process on artificially obtained eggs. The first experiment involved observation of egg swelling process and the second determined the effect of temperature (12, 14 and 16°C) on the egg swelling rate. The third experiment involved elimination of egg stickiness in a tannin solution (0.75 g L^?1) where eggs were submerged in a solution for 0.5, 1, 2 and 5 min – 5, 10, 15, 20, 25 and 30 min following gamete activation. The results indicate that the pikeperch egg swelling process lasts 30 min. It was found that the temperature did not affect the process duration. The results of the third experiment showed that the effectiveness of tannic acid application in egg stickiness elimination increases with time. The best result was obtained in groups of eggs submerged for 1 and 2 min (86.5% and 80.5% of larvae were obtained respectively) 30 min following the gamete activation. The results presented in this study for the first time indicate the possibility of highly effective procedure of egg stickiness elimination with tannic acid in pikeperch aquaculture.