Estimation of the crude protein requirement for juvenile yellow perch Perca flavescens

Recommended dietary crude protein (CP) requirements (210 to ≥360 g/kg) for optimal growth of juvenile yellow perch Perca flavescens (YEP) vary. This study determined the optimal CP requirement for YEP using semi‐purified diets containing essential amino acid ratios of YEP whole body. Six diets were formulated to contain 337, 379, 415, 453, 495 and 540 g/kg CP, but similar gross energy (~20 MJ/kg). Eighteen fish (~5.3 ± 0.5 g each) were stocked per 110‐L tank of a 30‐tank recirculating system, providing five replicates per treatment. Fish were fed sinking feeds at 3% body weight per day, and feed amounts were adjusted every 21 days. After 15 weeks, weight gain increased with increasing CP up to 415 g/kg. Relative growth (RG) and specific growth rate (SGR) increased up to 453 and 415 g/kg, respectively. Feed conversion ratios improved with increasing CP up to 453 g/kg. Protein efficiency ratios decreased with increasing CP. Whole‐body composition did not differ with increasing CP. Protein deposition did not differ beyond 415 g/kg, and apparent net protein utilization of 540CP was the lowest. Broken‐line non‐linear regression of RG conservatively estimated optimal dietary CP to be 457 g/kg, which is supported by the peak (CP456) in SGR.     

An assessment of yellow perch, Perca flavescens, stocking contributions in eastern South Dakota lakes

The success and value of yellow perch, Perca flavescens (Mitchill), stocking programmes are largely unknown because of the difficulties in differentiating between naturally recruited and translocated stocks. To determine stocking contributions of yellow perch, fingerlings and adults were collected from natural rearing ponds in south-eastern South Dakota. Prior to stocking, all fish were marked for 6 h in transfer tanks containing 700 mg L⁻¹ oxytetracycline hydrochloride. Six lakes containing yellow perch populations were supplemented at low, medium and high stocking densities of about 25, 135 or 200 fish ha⁻¹, respectively. Yellow perch populations were subsequently sampled with experimental gill nets during late summer; two lakes were resampled with additional gears (electric fishing, trap nets and cloverleaf traps). Yellow perch were processed for routine measurements, and saggital otoliths were removed to determine the origin of the fish. Stock contribution estimates determined from gill-net samples for Island (low), Oak (low), Twin (medium) and Wall (high) lakes were approximately 18, 5, 41, and 38%, respectively. Samples from other gears provided stock contributions of 15 and 10% for Cavour Lake and 41% for Diamond Lake (high density stockings). Although these results showed that supplemental stockings were successful, variability in stock contributions among populations indicates a need for further assessment of variables that may influence the stocking success of yellow perch.     

Processed soybean meal as an alternative protein source for yellow perch (Perca flavescens) feed

The goal of this study was to compare conventional soybean meal (SBM) with modified SBM (MSBM) after chemical and enzyme pretreatment to potentially reduce the antinutritional factors (ANF), as a fishmeal (FM) replacer at 50% or 100% in the diets of yellow perch (Perca flavescens). Half of the SBM and MSBM diets contained an enzyme cocktail (of phytase and carbohydrate‐degrading enzyme), and the other half received no enzyme supplementations. Fingerlings (297; initial weight, 11.01 ± 0.19 g) were randomly distributed over nine treatments, in triplicate, and fed these isonitrogenous diets (crude protein 410 g/kg) that included replacing FM with SBM at 50% or 100% without or with enzyme supplementations (S50, S100, S50+E or S100+E, respectively), MSMB at 50% or 100% without or with enzyme supplementations (MS50, MS100, MS50+E or MS100+E, respectively) or a control FM‐based diet. After 10 weeks, the growth performance, feeding efficiencies, proximate composition, intestinal/pyloric caeca digestive enzymes and liver metabolic/antioxidant enzymes in P. flavescens were measured. The highest (p < 0.05) growth performance and nutrient utilization parameters (protein efficiency ratio and protein productive value, PPV) were observed for the MS_50+E group, which was not statistically different to parameters for the control and MS₅₀ groups, and significantly (p < 0.05) higher than all other groups. The lowest and highest growth performance and feed conversion ratios, respectively, were observed in the S100, S100+E and MS100 groups. The highest protease activity (in both intestine and pyloric caeca) was observed for the control group, but was significantly similar to MS₅₀, MS_50+E and S_50+E groups. The lowest value was observed for 100% replacement of FM protein by SBM and MSBM fed groups. However, inclusion of exogenous enzymes in feed showed positive effects in MS_50+E (compared to MS₅₀) for PPV, lipid productive value and amylase activity in the intestine. Activity of protein metabolism enzymes (i.e., alanine transaminase and aspartate aminotransferase) in the liver was the highest in the control group, which was similar (p < 0.05) to the MS_50+E and MS₅₀ groups. Antioxidant enzymes (catalase, superoxide dismutase and glutathione peroxidase) in the liver were the lowest in the control group, which was significantly similar (p < 0.05) to the group given the feed with 50% replacement of FM protein. Complete (100%) replacement of FM protein exhibited the highest antioxidant enzyme activity. Conclusively, performance of the MS₅₀ and MS_50+E groups was similar to the FM group and better than SBM group; therefore, MSBM with high protein and low ANFs has considerable potential as an alternative to FM in aquafeed.     

Effect of light intensity,prey density,and ontogeny on foraging success and prey selection of larval yellow perch (Perca flavescens)

Light intensity has been shown to influence the foraging success of larval fish. However, the effect of light intensity on larval foraging is likely variable and influenced by both the density and characteristics of planktonic prey. In this study we examined the influence of light intensity of 0.1, 2.0, and 60 μmol·s^?1·m^?2 Photosynthetically Active Radiation (PAR) on foraging of yellow perch (Perca flavescens) larvae at two prey densities. We fed them with a mixture of zooplankton taxa common to lakes inhabited by yellow perch. In addition to light intensity and prey density, the effect of larval yellow perch size was examined by using fish ranging from 9 to 15 mm. The results of our study indicated that yellow perch larvae are well adapted to feed at a wide range of light intensities, as there was no difference in foraging success at investigated light intensities. Increasing prey density from 25 to 150 (zooplankton·l^?1) significantly improved the foraging success of larval yellow perch. However, the influence of prey density on foraging success was dependent on fish length. Improved foraging success at increased prey densities occurred only for individuals with a total length >10 mm. Overall, prey selection by fish larvae was influenced by light intensity, prey density, and fish length. However, the factors that influenced selection for specific prey types differed. Our study, combined with evidence from other field and laboratory work, highlight the need for a better understanding of the influence of prey density on foraging throughout ontogeny.     

Evaluation of two soybean meals fed to yellow perch (Perca flavescens)

Aquaculture of yellow perch (Perca flavescens) has been increasing, yet there have been few nutritional studies and no evaluations of alternative protein sources in diets. Solvent‐extracted, dehulled soybean meal (SBM) and expelled‐extruded soybean meal (exSBM) were fed to yellow perch to evaluate their effectiveness in replacing dietary fish meal (FM) in isonitrogenous practical feed formulations. Both soy ingredients were incorporated in graded amounts from 100 to 730 g kg⁻¹ of the diet. Feed consumption, weight gain, feed efficiency (FE) and survival were significantly affected by type of soy ingredient, concentration and the interaction of the two main effects. Consumption was significantly lower in fish fed diets containing 400, 600 and 730 g kg⁻¹ compared to fish fed diets containing lower concentrations. Weight gain was significantly lower in fish fed diets containing 600 g kg⁻¹ and FE significantly lower in fish fed diets containing 500 g kg⁻¹ compared to fish fed the control diet or lower concentrations of soy ingredients. Most fatty acid concentrations were affected by feeding exSBM compared to fish fed the control diet, but long chain fatty acids remained at relatively high concentrations. Based on feed consumption, weight gain and FE data, yellow perch are able to effectively utilize both soy ingredients in practical diets. A conservative recommendation of 300 g kg⁻¹ diet appears appropriate for growout diets.     

Emergence of larval yellow perch, Perca flavescens, in South Dakota lakes: potential implications for recruitment

Abstract  Temporal patterns in length frequency distributions and hatch dates were described for larval yellow perch, Perca flavescens (Mitchill), captured in surface ichthyoplankton trawls from late April to mid-June 2000 to 2002 in six South Dakota, USA lakes. Fewer than 15 larval yellow perch were collected in four of six lakes during 2002, suggesting that in some cases factors prior to, during or immediately after hatching likely play a critical role in the perch recruitment process. When larval yellow perch were encountered in larger numbers, temporal trends in total length (TL) frequencies indicated that only a single cohort was produced annually in each lake. Most yellow perch in these lakes hatched between 29 April and 17 May, and most hatching occurred during 5–11 days each year. Larval TL was not related to hatch date. The apparent prevalence of relatively short hatch periods in these yellow perch populations probably increases the risk of catastrophic losses resulting from periods of poor environmental conditions.     

Comparison of exploited and unexploited yellow perch Perca flavescens (Mitchill) populations in Nebraska Sandhill lakes

Exploitation can have a pronounced effect on fish populations. Yellow perch, Perca flavescens (Mitchill), populations in Nebraska Sandhill lakes were sampled in 1998 and 1999. Three of the 29 lakes containing yellow perch have been closed to fishing for at least 10 years. Unexploited yellow perch populations had fast growth rates, but age structure was similar to exploited populations. For unexploited lakes combined, mortality and condition were not different from exploited lakes. However, one unexploited lake, Marsh Lake, had the fastest growth, highest proportion of older fish and highest condition of all populations sampled. This lake had low interspecific competition and high invertebrate abundance, which likely resulted in fast growth and high condition. However, size structure and growth were also related to lake productivity. Although exploitation may affect yellow perch populations, other factors (food availability, predators and lake productivity) also play an important role in structuring these populations. Regardless, these results indicate the potential of yellow perch in Nebraska Sandhill lakes given no exploitation.     

Effects of dietary protein to metabolizable energy ratios and total protein concentrations on the performance of yellow perch Perca flavescens

Juvenile yellow perch Perca flavescens were fed semipurified diets with varying protein to metabolizable energy ratios (PME, g protein MJ⁻¹ metabolizable energy) and nutrient densities in three experiments to determine recommended dietary protein and energy concentrations. Experiment 1 fish (18.6 g) were fed diets containing 450 g crude protein kg⁻¹ dry diet and 14.5–18.8 MJ ME kg⁻¹ dry diet for 10 weeks. No differences were found in the growth of experiment 1 fish fed the different diets. Experiment 2 fish (21.9 g) were fed diets containing 15.7 MJ ME kg⁻¹ dry diet and 210–420 g crude protein kg⁻¹ dry diet for 8 weeks. Fish fed the diet containing 340 g kg⁻¹ protein (diet PME = 22) exhibited the greatest weight gain. Experiment 3 fish (27.1 g) were fed diets with a PME of 22 and varying nutrient density (yielding 205–380 g crude protein kg⁻¹ dry diet) for 8 weeks. No differences were found in the growth of experiment 3 fish. Yellow perch fed the semipurified diets exhibited increased liver fat content, liver size and degree of liver discoloration compared with fish fed a commercial fish meal-based diet. Liver changes may have resulted from high dietary carbohydrate levels. We conclude that a protein level of 210–270 g kg⁻¹ dry diet is suitable for juvenile yellow perch provided that the dietary amino acid profile and carbohydrate content are appropriate for yellow perch.     

The effect of dipeptide,Lys‐Gly,supplemented diets on digestive tract histology in juvenile yellow perch (Perca flavescens)

The aim of the present study was to evaluate the effects of three formulated diets: wheat‐gluten‐protein‐based diets supplemented with Lys‐Gly dipeptide (LG) or free lysine and glycine (FL), a control diet without lysine supplementation (C) and commercial starter Bio Oregon (BO) for on the growth and digestive system morphology of yellow perch. After 48 days of experimental feeding, fish fed LG diet showed the highest body mass. Fish fed LG diet showed the highest number of gastrin/cholecystokinin positive cells and the lowest number of CD3‐positive cells. The brush border of anterior intestine was the most PepT1 immunopositive in fish fed LG diet, the weakest in fish fed C diet. The largest hepatocytes were observed in fish fed BO, while the smallest in those fed FL diet, the difference being statistically significant. Relative hepatocyte cytoplasm volume occupied by lipids was higher in fish fed BO and FL compared to those fed C and LG. Number of proliferating cell nuclear antigen‐positive hepatocyte nuclei did not significantly differ among experimental groups. These results indicate that wheat‐gluten‐protein‐based diets supplemented with dipeptide Lys‐Gly (LG) were appropriate for yellow perch.     

Comparative susceptibility among three stocks of yellow perch,Perca flavescens (Mitchill), to viral haemorrhagic septicaemia virus strain IVb from the Great Lakes

The Great Lakes strain of viral haemorrhagic septicaemia virus IVb (VHSV‐IVb) is capable of infecting a wide number of naive species and has been associated with large fish kills in the Midwestern United States since its discovery in 2005. The yellow perch, Perca flavescens (Mitchill), a freshwater species commonly found throughout inland waters of the United States and prized for its high value in sport and commercial fisheries, is a species documented in several fish kills affiliated with VHS. In the present study, differences in survival after infection with VHSV IVb were observed among juvenile fish from three yellow perch broodstocks that were originally derived from distinct wild populations, suggesting innate differences in susceptibility due to genetic variance. While all three stocks were susceptible upon waterborne exposure to VHS virus infection, fish derived from the Midwest (Lake Winnebago, WI) showed significantly lower cumulative % survival compared with two perch stocks derived from the East Coast (Perquimans River, NC and Choptank River, MD) of the United States. However, despite differences in apparent susceptibility, clinical signs did not vary between stocks and included moderate‐to‐severe haemorrhages at the pelvic and pectoral fin bases and exophthalmia. After the 28‐day challenge was complete, VHS virus was analysed in subsets of whole fish that had either survived or succumbed to the infection using both plaque assay and quantitative PCR methodologies. A direct correlation was identified between the two methods, suggesting the potential for both methods to be used to detect virus in a research setting.     

Changes of plasma steroid concentrations associated with spontaneous or induced ovulation in yellow perch Perca flavescens

This study examined the changes in plasma steroids during natural (Experiment 1) and induced (Experiment 2) final maturation in yellow perch Perca flavescens. In experiment 1, ovulating yellow perch were stripped of eggs and blood samples collected to determine the concentrations of testosterone (T), estradiol-17β (E2), and 17,20β-dihydroxy-4-pregnen-3-one (17,20βP). Eggs from individual females were weighed and fertilized. Fertilization rate was determined at the embryo eyed stage. In experiment 2, females were randomly assigned to one of the following treatment groups: (1) saline (0.7% NaCl), (2) des-Gly¹⁰[D-Ala⁶] LHRH-ethylamide (100 μg LHRHa/kg), and (3) LHRHa plus 17,20βP (100 μg LHRHa/kg + 2 mg 17,20βP/kg). Fish were injected intraperitoneally with two doses at a two-day interval. Blood was collected prior to injections and at the time of ovulation/spawning and concentrations of T, E2, and 17,20βP (free and conjugated) were determined. In experiment 1, low concentrations of 17,20βP were recorded at spawning. In experiment 2, all surviving fish injected with LHRHa (5 of 5) released their eggs spontaneously during the week following injections. None of the surviving control fish (0 of 5) ovulated during this period, whereas only 1 of 3 surviving fish injected with LHRHa + 17,20βP released eggs. In the control group, concentrations of E2 and 17,20βP did not show significant differences over the experimental period, whereas plasma T concentrations increased significantly. In fish injected with LHRHa, the concentrations of T and 17,20βP increased significantly after the first injection but then declined at ovulation/spawning. It also appears that 17,20βP was conjugated to its sulfated form. Mortality reached 62.5% in the group injected with LHRHa + 17,20βP indicating that this treatment was severe. Thus, LHRHa alone appears highly effective in inducing ovulation in yellow perch. This revised version was published online in July 2006 with corrections to the Cover Date.     

Myxobolus neurophilus Guilford 1963 (Myxosporea: Myxobolidae): a common parasite infecting yellow perch Perca flavescens (Mitchell, 1814) in Saskatchewan,Canada

The goal of this study was to identify a myxosporidian parasite infecting the central nervous system of yellow perch Perca flavescens (Mitchell, 1814) observed while investigating a fish kill in Saskatchewan, Canada. Fish were collected from seven different lakes, from two distinct watersheds. Sixty-four per cent (54/86) of yellow perch contained myxozoan pseudocysts located throughout the spinal cord and brain. Myxospores measured 16.5 μm (range 16.2–16.8) long and 8.2 μm (range 7.9–8.4) wide and contained two pyriform, mildly dissymmetrical, polar capsules measuring 7.7 μm (range 7.3–8.1) long and 2.7 μm (range 2.4–3.0) wide. The polar capsules each contained a single polar filament, with 7–9 turns per polar filament coil. Sequencing of the 18S SSU rDNA gene demonstrated >99% similarity to Myxobolus neurophilus. In 60% of infected fish, there was a mild to moderate, non-suppurative myelitis or encephalitis, or both, associated with myxospores. Axonal degeneration was present in rare cases. These findings extend the geographical distribution of M. neurophilus and suggest it may be widespread in yellow perch populations in Saskatchewan.     

The role of prostaglandins in the control of ovulation in yellow perch,Perca flavescens

Previous studies have shown that 17α,20β-dihydroxy-4-pregnen-3-one (17α,20β-P) can induce both germinal vesicle breakdown and ovulationin vitro of yellow perch (Perca flavescens) oocytes. The stimulation of ovulation can be blocked by indomethacin and restored by the subsequent addition of several primary prostaglandins (Goetz and Theofan 1979). In the present investigation, medium levels of prostaglandin F (PGF) and E (PGE) were measured by radioimmunoassay duringin vitro 17α,20β-P-induced ovulation of perch oocytes. PGF levels increased significantly (compared to controls) from 30 to 36h of incubation. Hourly samples taken through the time of ovulation revealed that the increase in PGF was very closely correlated to the time of ovulation though it did not preceed it. Cortisol, testosterone, estradiol-17β, 17α,20α-dihydroxy-4-pregnen-3-one and 17α-hydorxyprogesterone did not increase PGF levels by 48h of incubation, however, several other progestational steroids including 20β-dihydroprogesterone (20β-P) and progesterone did. 17α,20β-P, 20β-P and progesterone also stimulated an increase in PGF in spontaneously ovulating oocytes (in which all oocytes ovulated including controls), indicating that the increase in PGF was not merely a result of the physical process of ovulation but was related to the presence of the steroid. Based on work supported by the National Science Foundation under grant DCB-8517718 and DCB-8718178.     

Weaning of juvenile pikeperch, Stizostedion lucioperca L., and perch, Perca fluviatilis L., to formulated feed

Weaning success of pond‐cultured pikeperch and wild‐caught perch (mean length 51 and 48 mm respectively) was evaluated using different weaning techniques and different formulated feeds. Juveniles that were fed formulated feed grew as well as or better than juveniles that were weaned successively using zooplankton or yolk. Four different formulated feeds (agglomerated marine larvae feed, marine larvae feed, trout feed and a semi‐moist feed) were evaluated regarding specific growth rate (SGR), condition factor and a subjective stomach fullness estimate. The agglomerated marine larvae feed gave significantly better weaning performance than the other feeds regarding all parameters (SGR = 7.3% day^?1 and 3.4% day^?1 for pikeperch and perch respectively).     

The effect of lysine‐supplemented wheat gluten‐based diet on yellow perch Perca flavescens (Mitchill) performance

Formulation of nutritionally complete and cost efficient diets for yellow perch (Perca flavescens) is a prerequisite for successful intensive culture of this species. One of the objectives of this study was to determine the optimum diet for the grow‐out phase of juvenile yellow perch. Fish at the size of 12.9 ± 4 g were individually marked with passive integrated transponders (PIT)‐tags and randomly distributed into six 400 L tanks, 45 fish per tank. This experiment included lysine‐deficient [(?) Lys] and lysine‐supplemented [(+) Lys] wheat‐gluten‐based diets in triplicate groups. Our experiment showed that the mean weight of fish fed (+) Lys diet (83.9 ± 1.5 g) was significantly larger than fish fed (?) Lys diet (68.6 ± 5.2 g) (P < 0.05). This experiment also showed that the blood plasma concentration of free lysine in (+) Lys group was significantly higher than in (?) Lys group (P < 0.05) and the same trend appeared also in methionine concentrations. The concentration of Lys in deficient group of fish, 3 h after a meal was lower compared with levels of Lys 24 h post‐feeding (P < 0.05). Lysine deficiency in diet resulted in significantly higher level of serine, and a similar trend occurred in small and large fish.     

Phylogenetic analysis and molecular methods for the detection of lymphocystis disease virus from yellow perch, Perca flavescens (Mitchell)

Lymphocystis disease is a prevalent, non-fatal disease that affects many teleost fish and is caused by the DNA virus lymphocystis disease virus (LCDV). Lymphocystis-like lesions have been observed in yellow perch, Perca flavescens (Mitchell), in lakes in northern Alberta, Canada. In an effort to confirm the identity of the virus causing these lesions, DNA was extracted from these lesions and PCR with genotype generic LCDV primers specific to the major capsid protein (MCP) gene was performed. A 1357-base pair nucleotide sequence corresponding to a peptide length of 452 amino acids of the MCP gene was sequenced, confirming the lesions as being lymphocystis disease lesions. Phylogenetic analysis of the generated amino acid sequence revealed the perch LCDV isolate to be a distinct and novel genotype. From the obtained sequence, a real-time PCR identification method was developed using fluorgenic LUX primers. The identification method was used to detect the presence/absence of LCDV in yellow perch from two lakes, one where lymphocystis disease was observed to occur and the other where the disease had not been observed. All samples of fin, spleen and liver tested negative for LCDV in the lake where lymphocystis disease had not been observed. The second lake had a 2.6% incidence of LCD, and virus was detected in tissue samples from all individuals tested regardless of whether they were expressing the disease or not. However, estimated viral copy number in spleen and liver of symptomatic perch was four orders of magnitude higher than that in asymptomatic perch.     

Changes in yellow perch (Perca flavescens) growth associated with the establishment of a walleye (Stizostedion vitreum) population in Canadarago Lake, New York (USA)

Abstract – Piscivorous fish can affect prey growth in two ways: directly by reducing prey density and indirectly by inducing predator-avoidance behaviors. We investigated these two pathways in yellow perch ( Perca flavescens ) growth responses to walleye ( Stizostedion vitreum ) stocking in Canadarago Lake, New York (USA) using a 25-year time series. Before walleye stocking, yellow perch growth rate was low and independent of body size. As walleye abundance increased, yellow perch growth increased and became size-dependent. The switch to size-dependent growth occurred in 1 year, indicating a rapid behavioral response to predators. Mean growth rate increased more gradually and was linearly related to walleye density, indicating a slower numerical effect of walleye on yellow perch densities. Although the net effect was an increase in perch growth, small perch growth initially decreased as walleye became established. Therefore, the combination of numerical and behavioral effects produced a complex pattern of size-dependent changes in growth of yellow perch.