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.     

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.     

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.     

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.     

温度对黄金鲈(Perca flavescens)耗氧率和排氨率的影响

在不同水温(15、20、25和30℃)下,对体重(46.1±4.5)g黄金鲈(Perca flavescens)的耗氧率和排氨率进行了测定与分析。结果显示:黄金鲈的耗氧率和排氨率均随温度的升高而显著增加(P<0.01);耗氧率和排氨率与温度的关系可用指数方程拟合,其方程分别为:RO=0.0682 e0.0633t,R2=0.9879;RN=2.4593 e0.0904t,R2=0.9703;随着温度的升高氧氮比(O:N)逐渐降低;耗氧Q10值和排氨Q10值均在20~25℃之间最小。结果表明:在各温度水平下黄金鲈基础代谢消耗底物主要均以蛋白质为主,脂肪其次,然而随着温度的升高,黄金鲈利用糖类和脂肪供能的比例逐渐下降,而蛋白质供能的比例逐渐增加。黄金鲈的最适生长温度为20~25℃。     

Environmental Manipulation of Growth and Sexual Maturation in Yellow Perch, Perca flavescens

Yellow perch, Perca flavescens, exhibit sexually dimorphic growth detected as the fish enter puberty. The purpose of this study was to evaluate the differential influences of photoperiod and temperature on the sexual maturation and dimorphic growth pattern of yellow perch. Four combinations of constant (CP) or natural (NP) photoperiod with constant (CT) or natural (NT) temperature were evaluated (CPCT, CPNT, NPCT, NPNT). Following 6 months of growth, results indicate that (1) CT is the strongest promoter of overall growth regardless of photoperiod. Perch reared under CT were 26.4 ± 8.1 g heavier than perch reared under NT (P < 0.0001). (2) CP also promotes overall growth regardless of temperature. CP perch outgrew NP perch by 7.0 ± 8.1 g (P < 0.0872). (3) NP (decreasing) initiates maturation in yellow perch regardless of temperature. (4) NT is required for late maturational processes. While both NP groups initiated maturation, only NPNT females were able to recruit oocytes to a vitellogenic stage. Only NPNT males were able to sustain spermiation to the end of the study. (5) CPCT confer the best overall growth performance, fully inhibit maturation in both genders, and suppress a sexually dimorphic growth pattern up to 53 g average weight. These results indicate that using a CPCT regime during intensive fingerling production will produce a larger, more uniform fish population that could alleviate losses as a result of cannibalism. Perch that remained immature did not exhibit a dimorphic growth pattern.     

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.     

Nutritional quality of different starches in feed fed to juvenile yellow perch,Perca flavescens

This study determined whether accumulated liver and visceral lipid in yellow perch can be alleviated by feeding an appropriate starch source. We compared the growth performance, nutritional composition and health of yellow perch fed a control diet (no added starch) and three diets with corn, potato or wheat starch (200 g/kg diet) to replace an equal proportion of fishmeal in the control diet. Dietary starch led to increased bulk density, hardness and gelatinization levels of feed pellets compared with the control diet. At the end of an 8‐week feeding, all fish fed the test diets had similar growth rates (p > .05). However, the wheat starch diet resulted in significantly enlarged livers and increased accumulation of lipid in the liver, viscera and whole body (p < .05). This diet also caused significantly higher levels of fasting glucose, aspartate aminotransferase and alkaline phosphatase activities in serum than the control diet. Liver cell diameters were larger, and Kupffer cell numbers were lower in the fish fed the wheat starch than those fed the control diet. Potato or corn starch had less impact on fish health and is considered to be an appropriate carbohydrate sources for yellow perch under the current testing conditions.     

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.     

The population biology of perch, Perca fluviatilis L., in simple fish communities with no top piscivore

Abstract– The population dynamics of perch, Perca fluviatilis L., in the absence of a top piscivore, pike Esox lucius L., were examined in simple fish communities in shallow lakes (mean depth < 1.5 m) in northeast Scotland. Perch in Sand and Lower Lochs were unexploited, whereas perch in Loirston were exploited. Population characteristics were fast growth rates, short life span (< 6 years) and no dominant year classes in Sand and Lower Lochs. The strong 1974 year class in Loirston may have been due to intensive exploitation of older age groups. Abundance of perch, expressed as biomass, was low for European waters, namely 30 kg. ha⁻¹ in Loirston (comprising mainly 1 - to 2-year-old-fish), and biomass of adults (≥ 2 years) was 8.9 kg and 4.7 kg. ha⁻¹ in Sand and Lower Lochs respectively. Recruitment in Sand and Lower Lochs appeared to be governed by water temperature, but the overall low abundance and population stability of perch in the 3 lochs was attributed to cannibalism.     

Importance of maternal size on the reproductive success of perch,Perca fluviatilis,in small forest lakes: implications for fisheries management

Abstract Abundance, sex ratio and size structure of perch, Perca fluviatilis L., populations were studied in two forest lakes. The influence of maternal size on the amount and quality of eggs and larvae was investigated, and the effect of the spawning stock’s length structure on population egg and fry production was evaluated. The importance of large females was essential for the reproduction of perch. Large perch spawned more and bigger eggs that had higher hatching percentage resulting in considerably higher fry production. Larvae of large females were heavier and survived longer with bare yolk sac reserves. The relation between egg dry weight and female length differed between the study lakes suggesting varying maternal influence in different environments. Decrease in the share of large individuals in a perch population can substantially reduce the amount and quality of larvae produced. The results can be applied to improve the sustainability of perch fisheries.     

Density and temperature dependence of gill net catch per unit effort for perch, Perca fluviatilis, and roach, Rutilus rutilus

Abstract  The densities of perch, Perca fluviatilis L., and roach, Rutilus rutilus (L.), were estimated in six and three lakes, respectively, using mark–recapture and ranged from 25–1064 perch ha⁻¹ and 865–2749 roach ha⁻¹. Effects of fish density, net type and water temperature on catch-per-unit-effort (CPUE) were analysed by generalised linear models (GLM) and generalised additive models (GAM). GAMs were fitted to estimate the simultaneous linear and nonlinear effects of temperature and density on CPUE. These models showed significant nonlinear effects of density on CPUE – mostly for perch, and also for both species at high densities. The models also revealed that both species had distinct density–temperature criteria of expected maximum CPUE and zero CPUE values. Because of the nonlinear relationship between CPUE and density, it was concluded that CPUE should be used with caution as a proxy of density.     

东海北部和黄海南部鲐鱼年龄和生长的研究

本研究采用2002年11月～2003年8月在东海北部和黄海南部海域(30°～34°N、126°E以西)所获取的鲐鱼渔获样品,合计采集777ind,通过对鲐鱼耳石生长轮的观察和基础生物学测定,研究了鲐鱼的年龄和生长。结果表明叉长与体重的关系雌雄间没有显著性差异;所鉴定鲐鱼年龄组成为1～3龄鱼,共3个年龄序列,并补充20世纪80年代4～5龄鱼对鲐鱼的生长规律进行研究,采用Walford方法拟合,其生长参数K、L∞、t0分别为0.31993、451.3514和-1.20307;鲐鱼的生长拐点年龄为2.7yr,拐点体重为450g,拐点叉长为320mm。比较分析东海群系鲐鱼的渔业生物学历史状况,在目前所能观察得到的鲐鱼年龄段内(1～3龄),东海区鲐鱼个体平均叉长比20世纪80年代的都要小;与闽南、粤东近海地方群系的相比,东海群系的平均叉长在鲐鱼的整个生长阶段都明显的大。     

东海北部和黄海南部鲐鱼生长特性及合理利用

采用2002年11月~2003年8月在东海北部和黄海南部区域(30°~34°N、126°E以西范围)所获取的鲐鱼(Scomberjaponicus)样品,通过观察鲐鱼耳石生长轮和基础生物学测定,研究了鲐鱼的年龄和生长;再依据不完全β函数渔获量方程,计算、分析在不同开捕年龄和不同捕捞强度下的单位补充量渔获量(Yw/R)的变化情况。结果表明,采用Walford方法拟合的鲐鱼生长方程,其生长参数K、L∞、t0分别为0.320、451.4和-1.203。比较不同时期鲐鱼的生长情况显示,20世纪60、80年代和21世纪初期鲐鱼的生长较接近,而20世纪70年代的鲐鱼生长情况与其他3个时期的鲐鱼生长相差较大。比较不同海域鲐鱼的生长情况显示,随着纬度的增加,鲐鱼的个体有增大的趋势,经分析很可能与海水温度有关。根据历史资料推算出鲐鱼的最大年龄(tλ)为9龄;根据最近的采样,推算出鲐鱼的开捕年龄和补充年龄都为0.4年,鲐鱼的自然死亡率为0.355,捕捞死亡率为2.27。利用上述参数,动态综合模型模拟的结果显示,该资源过度捕捞已很严重。若保持当前捕捞强度,则必须把开捕年龄限制在2.9龄;若能同时改变捕捞强度和开捕年龄,则可以把当前的开捕年龄限制在2.0龄,捕捞死亡率降到1.3,这样鲐鱼资源才能够得到保护与合理利用。     

维生素K3对草鱼生长、体成分和凝血时间的影响

以酪蛋白和脱脂豆粕为蛋白源,糊精为糖源,玉米油和豆油为脂肪源的半纯化饲料为试验饲料,研究了维生素K3对草鱼(Ctenopharyngodon idellus)成活、生长、体成分、血清中钙磷含量及凝血时间的影响。试验饲料中的维生素K3共设7个添加梯度,分别为0,0.5,1.0,2.0,5,10,20mg/kg,每一梯度设3个重复,每个重复60尾初始体重3.5g左右的草鱼,在(25.0±3.0)℃的流水系统中养殖11周。结果表明:维生素K3对草鱼增重率、特定生长率、饲料系数、成活率和体成分均没有显著性影响(P>0.05);维生素K3对血清中的钙磷浓度也无显著性影响;凝血时间显著性受饲料中维生素K3含量影响,饲料中缺乏维生素K3会延迟凝血时间。对饲料中维生素K3含量和草鱼凝血时间进行折线回归分析表明:草鱼幼鱼饲料中维生素K3适宜的含量为1.9mg/kg。     

Growth of the fan mussel Pinna nobilis (Linnaeus, 1758) (Mollusca: Bivalvia) in experimental cages in the South Adriatic Sea

Juveniles of the fan mussel Pinna nobilis were collected in Mali Ston Bay from October to December 2006. Cages with juveniles were placed at three depths: 1, 3 and 5 m. At the end of a 2‐year growth period at 1 m depths, the average length was 244.1 ± 22.9 mm, at 3 m depths, specimens averaged 244.0 ± 25.3 mm, and at 5 m depths, the average length was 231.1 ± 22.5 mm. The average monthly growth of shell length for the total experimental period was 8.7 ± 5.3, 8.4 ± 4.5 and 7.6 ± 4.4 mm, at 1, 3 and 5 m depths respectively.