Parental genetic effects evaluation of growth-related traits of red common carp in China

Reciprocal differences have been observed widely for given traits in fish breeding programs, but maternal and paternal effects and heritable extranuclear genetic effects have often been omitted in the evaluation of genetic variance. In this study, we have applied a mixed genetic model to conduct a complete diallel cross using three varieties of red common carp (Cyprinus carpio L.), namely, C. carpio. var. singuonensis, C. carpio var. wuyuanensis and C. carpio var. color. Parental and direct (additive and dominance) genetic effects for growth-related traits at 8 and 20 months post-hatch were analyzed. At 8 months post-hatch, only significant additive and dominance variances were observed, while maternal and paternal variances were low and non-significant in the traits evaluated: body weight, total length, standard length, pre-dorsal height, pre-dorsal width, caudal peduncle length, and caudal peduncle height. At 20 months post-hatch, with the exception of significant additive and/or dominance variances, maternal variances were significant for the traits of body weight, pre-dorsal height, pre-dorsal width, and caudal peduncle height, and the paternal variance was significant only for total length. The maternal effects in the common carp had greater genetic influence on offspring than the paternal effects. Female C. carpio var. wuyuanensis were more suitable as brooders than males, but both female and male C. carpio var. color can be used as brooders according to breeding programs of improved traits. Cyprinus carpio var. singuonensis was the worst brooder of the three varieties of common carp evaluated.     

Additive, dominance genetic effects for growth-related traits in common carp, Cyprinus carpio L.

Additive, dominance genetic effects were analysed for body weight (BW) and seven morphometric traits from three variants of red common carp, Cyprinus carpio var. singuonensis, C. carpio var. wuyuanensis and C. carpio var. color, based on a diallel cross‐mating design by using the additive–dominance genetic model. The results indicated that at 8 months of age (juvenile stage), the traits of pre‐dorsal height (PDH), pre‐dorsal width (PDW) and caudal peduncle height (CPH) were mainly controlled by additive effects; the traits of BW, total length (TL), standard length (SL), head length (HL) and caudal peduncle length (CPL) were mainly controlled by dominance effects. The narrow‐sense heritabilities of all traits ranged from 0.000 to 0.556; however, the broad‐sense heritabilities ranged from 0.453 to 0.775. At 20 months of age (adult stage), the traits of TL, SL, PDH and CPL were mainly controlled by additive effects, whereas the traits of BW, PDW, HL and CPH were mainly controlled by dominance effects. The narrow‐sense heritabilities of all traits ranged from 0.000 to 0.710; the broad‐sense heritabilities ranged from 0.629 to 0.934. Through the genetic merit prediction from three parents, it was found that the additive and dominance effects of C. carpio var. color could increase the BW and body length in their progeny, but these two genetic effects of C. carpio var. singuonensis and C. carpio var. wuyuanensis could decrease BW in their progeny. The genetic effects of C. carpio var. wuyuanensis could reduce total length, SL and caudal peduncle length, but increase body height in their progeny.     

红鲤生长性状的上位性遗传效应分析

运用加性-显性-上位性遗传模型及其分析方法,研究了兴国红鲤(Cyprinus carpiovar.singuonensis)、荷包红鲤(C.carpiovar.wuyuanensis)和瓯江彩鲤(C.carpiovar.color)的双列杂交子二代F2的体质量和10个形态性状(全长、体长、体高、体宽、头长、吻长、眼径、眼间距、尾柄长和尾柄高)的上位性遗传效应。结果表明,除体高外,其余性状均存在不同程度的加性×加性上位性方差,其中体质量、全长、体长、头长、吻长和尾柄长的加性×加性上位性方差达显著水平(P<0.05);这10项性状的上位性方差占总遗传变异量的百分率为:体质量11.4%、全长22.6%、体长14.0%、体宽8.3%,头长24.2%、吻长17.5%、眼径12.9%、眼间距23.1%、尾柄长5.4%和尾柄高20.1%;通过3种红鲤亲本的遗传育种效应预测发现,瓯江彩鲤的加性和上位性效应能显著增加后代的体质量、全长和体长,而兴国红鲤和荷包红鲤的加性和上位性效应能显著降低后代的体质量、全长和体长。上位性遗传效应在鱼类数量性状的遗传育种中具有较重要作用。[中国水产科学,2006,13(4):573-578]     

Performance of common carp,Cyprinus carpio L. and Nile tilapia,Oreochromis niloticus (L.) in integrated rice–fish culture in Bangladesh

Irrigated rice fields have enormous potential for expanding the aquaculture production in rice producing countries. Two field experiments were carried out at the Bangladesh Agricultural University, Mymensingh, to optimize the productivity of integrated rice–fish systems using Nile tilapia, Oreochromis niloticus (L.), and common carp, Cyprinus carpio L. Both experiments were laid out in a randomized complete block design with three replicates per treatment and regular rice monoculture as control. In the first trial, carp and tilapia were tested in single culture and in mixed culture with supplementary feeding at 2× maintenance level. The highest fish yield was obtained in the carp/tilapia mixed culture (586 ± 125 kg ha^− 1), followed by tilapia alone (540 ± 65 kg ha^− 1), and carp alone (257 ± 95 kg ha^− 1). Carp had significantly lower yield than the other two fish groups (p < 0.05) due to high mortality and inefficient feed utilization. As the carp/tilapia combination performed the best in the first experiment, it was tested with different inputs in the second trial, i.e. regular urea fertilization and two different feeding levels. The feeding levels were: continuous feeding at 2× maintenance level (feed level I) and a declining feeding schedule from 4× to 2× maintenance level (feed level II). The highest fish yield was obtained in feed level II (935 ± 29 kg ha^− 1), followed by feed level I (776 ± 22 kg ha^− 1), and the non-fed group (515 ± 85 kg ha^− 1). Yield differences between the treatments were significant at p < 0.05. Rice yields showed controversial effects between the rice–fish treatments and were dependent on the inputs provided. The highest rice production (4.2 t ha^− 1) was obtained from rice–fish plots with regular urea fertilization. Various significant effects of fish on water quality parameters were observed. Fish decreased the dissolved oxygen (DO) and pH value compared to rice only, especially when supplementary feed was provided. Moreover, fish stimulated the growth of phytoplankton and increased chlorophyll-a concentration. In conclusion, carp/tilapia mixed culture with supplementary feeding was found to be optimal for maximizing the output from rice–fish culture.     

A novel 79‐bp insertion/deletion polymorphism in 3′‐flanking region of IGF‐I gene is associated with growth‐related traits in common carp (Cyprinus carpio L.)

Insulin‐like growth factor‐I (IGF‐I) participates in the modulation of the cellular development, differentiation and proliferation in various vertebrate tissues. Therefore, variations in IGF‐I gene are good candidates as growth regulators. In this study, a novel 79‐bp insertion/deletion (I/D) polymorphism was identified in 3′‐flanking region of IGF‐I gene by polymerase chain reaction (PCR) and sequencing approaches in common carp Cyprinus carpio. To gain insight into the association of the 79‐bp I/D polymorphism with growth‐related traits, a total of 747 individuals from Heilongjiang carp Cyprinus cario haematopterus (YL) (n = 263), selective line of German mirror carp Cyprinus carpio L. mirror (JL) (n = 229), and cold‐resistance line of Hebao red carp Cyprinus carpio var. wuyuanensis (HL) (n = 255) were genotyped. The DD genotype of the polymorphism was significantly associated with higher body length (135), body weight (325, 385, and 445 days), net weight (445 days) and lower overwintering body loss rate in JL. In addition, in pooled population (YL+JL+HL), fish with DD genotype also showed significantly higher body weight (445 days) and net weight (445 days) than those with II genotype. Taken together, these results suggest that the novel polymorphism in IGF‐I gene could be considered as a potential genetic marker for selection of growth performance in common carp.     

Practical applications of low-pressure hydrocyclone (LPH) for feed waste and fecal solid removal in a recirculating aquaculture system

In this work, the practical application of a low-pressure hydrocyclone was examined for feed waste and fecal solid removal for common carp (27 ± 3.1 g, average ± SD) and Nile tilapia (33 ± 3.4 g, average ± SD) in a recirculating aquaculture system. The dimensions of the low-pressure hydrocyclone included an inflow diameter of 30 mm, a cylinder length of 575 mm, an overflow diameter of 60 mm, an underflow diameter of 50 mm, a cylinder diameter of 335 mm and a cone angle of 68°. The different operating conditions tested were inflow rates of 400, 600, 800 and 1000 ml s⁻¹, and underflow rates of 25%, 25%, 20% and 10% of the inflow rates, respectively. Feed waste totals of 4.1 to 4.8% and 3.6 to 4.0% of the feed intake were produced by the common carp and Nile tilapia, respectively. The maximum separation efficiency (Et) for the feed waste from the common carp was 71% at an inflow rate of 600 ml s⁻¹ with an underflow rate of 25% of the inflow rate. The maximum separation efficiency for the feed waste from the tilapia was 59% at an inflow rate of 400 ml s⁻¹ with an underflow rate of 25% of the inflow rate. The fecal solid production estimated from the digestibility was 37.9% and 35.7% of the feed intake for the common carp and Nile tilapia, respectively. The maximum separation efficiency for the feces from the common carp was 60% for an inflow rate of 600 ml s⁻¹ and an underflow rate of 25% of the inflow rate. The maximum separation efficiency for the tilapia feces was 63% at an inflow of 400 ml s⁻¹ with an underflow rate of 25% of the inflow rate. The low-pressure hydrocyclone can be adopted for prefiltration and/or post-filtration for the removal of various sized solids. Furthermore, the solids separated from the underflow can be easily removed for further processing.     

Age and growth estimates of the sharptail mola,Masturus lanceolatus,in waters of eastern Taiwan

The sharptail mola, Masturus lanceolatus, is one of the largest teleost fishes in the world, and can be found in warm temperate and tropical regions worldwide. The increase of sharptail mola catch in the eastern Taiwan in recent years stimulated a concern that increasing exploitation of this species might lead to a decline of the stock. However, biological information of this species is very limited. Hence, this study provides the first information on age and growth of this species in the waters off eastern Taiwan based on 265 specimens (105 females and 160 males) collected from January 2003 to November 2006 at the Nanfanao and Hualien fish markets, eastern Taiwan. The relationships between whole weight (W) and standard length were expressed as: W = 9.98 × 10^?4 SL^2.45 (n = 105, p < 0.01) for females, and W = 3.33 × 10^?4 SL^2.68 (n = 160, p < 0.01) for males. Based on the MIR analysis, growth band pairs (including translucent and opaque bands) in vertebrae formed once a year and were counted up to 23 and 16 for females and males, respectively. Three growth functions, the von Bertalanffy (VBGF), Robertson, and Gompertz, were used to model the observed length at age data. The VBGF had the best fit and predicted an asymptotic length (L_∞) = 262.5 cm SL, growth coefficient (k) = 0.046 yr^?1, age at zero length (t₀) = ?3.350 yr (n = 80, p < 0.01) for females, and L_∞ = 231.0 cm SL, k = 0.059 yr^?1, t₀ = ?1.852 yr (n = 135, p < 0.01) for males. The longevities were estimated to be 105 and 82 yr based on the VBGF for females and males, respectively.     

The effects of food and the sum of effective temperature on the embryonic development of the seahorse,Hippocampus kuda Bleeker

The effect of different food (live Acetes spp., live Mysis spp., frozen Mysis spp., and mixed food of 50% live Acetes spp. and 50% frozen Mysis spp.) on gonad development of seahorses, Hippocampus kuda Bleeker, was evaluated in this experiment. The developmental durations of testes and ovary of seahorses were significantly different among the four experimental treatments. The live Acetes spp. treatment presented the shortest developmental durations to stage V, which were 87.6 ± 3.84 days and 89.2 ± 3.71 days, respectively, for ovary and testes. The frozen Mysis spp. treatment had the longest developmental durations (F_3,15 = 13.284, P < 0.05). The relationship between developmental duration of the ovary and gonad developmental stages could be formulated: Y₁ = 12.04x + 24.36 (r² = 0.9722, n = 16, P < 0.05). The gonadosomatic index (GSI) of parent seahorses among the four treatments differed significantly (F_3,15 = 18.364, P < 0.05). The standard GSI of seahorses fed live Acetes spp. was 15.64 ± 1.65%, which was the highest. Feeding live food had a significant effect on the fecundity and spawning of seahorses. The fecundity and spawning number of the live Acetes spp. treatment were 598 ± 45.49 and 552 ± 49.19 individuals, respectively, which were dramatically higher than those of frozen treatment (F_3,19 = 34.152, P < 0.05). Live food also had a similar effect on the fertilization and hatching rate during the embryonic development of seahorses (F_3,19 = 11.386, P < 0.05). Food treatment could also induce an indirect effect on survival rate of juveniles through gonadal and embryonic development of the parents (F_3,15 = 14.519, P < 0.05). In this experiment, the mortality within parent seahorses in the frozen Mysis spp. treatment was the highest (15.1 ± 6.55%), and the survival of juveniles was the highest in the live Acetes spp. treatment (90.4 ± 2.26% at 10 days). In conclusion, feeding live Acetes spp. significantly benefited the gonadal and embryonic development of H. kuda.The effect of temperature (22 °C, 24 °C, 26 °C, 28 °C, 30 °C and 32 °C) on the hatching time of H. kuda was also studied. We demonstrated that the higher the temperature, the shorter the hatching time, as well as the higher the hatching speed. The relationship between hatching time and temperature could be expressed: T = − 39.337 t + 677.75 (r² = 0.9755, n = 30, P < 0.05). In this finding, we provided the sum of effective temperature (SET) and threshold temperature of embryonic development of H. kuda (14066.9 °C h^− 1 and 13.7 °C, respectively). This new information on the effect of feeding type and culture temperature is beneficial for the commercial rearing and breeding industry of this species.     

Spawning per recruit analysis of the pelagic thresher shark,Alopias pelagicus,in the eastern Taiwan waters

The pelagic thresher shark, Alopias pelagicus, is a cosmopolitan species and abundant in Taiwan waters. Some of its biological information has been documented yet its population dynamics are poorly known. The purpose of this study is to assess the pelagic thresher shark stock status in the eastern Taiwan waters. The whole weights (W) of 51,748 individuals of the pelagic thresher shark landed at Nanfanao and Chengkung fish markets, eastern Taiwan from 1990 to 2004 were converted to precaudal length (PCL) based on the W–PCL relationship (W = 2.25 × 10⁻⁴ × PCL^2.533, n = 2165). The sexes combined VBGE L_t = 189.5 × (1 − e^{−0.10(t+6.47)}) was used to estimate the age for each length group. Total mortality rates (Z) obtained with length-converted catch curves ranged from 0.208 to 0.277 year⁻¹. Natural mortality rate (M) estimated from Hoenig method was 0.132 year⁻¹, and exploitation rate (E) ranged from 0.069 to 0.127 for 1990–2004. Annual abundance was estimated to range from 97,551 in 2000 to 153,331 in 2003 from virtual population analysis, and the highest fishing mortality occurred in ages 8–18 years. There were four different scenarios being simulated in this study. Scenario 1 indicated that spawning per recruit (SPR) ranged from 23.07% in 2001 to 47.71% in 1990 with a mean of 36.41% for the period of 1990–2004. The mean SPR of pelagic thresher for 1990–2004 was below the BRP of SPR = 35% in scenarios 2–4 suggesting that this stock was slightly overexploited. Therefore, to ensure sustainable utilization of this stock, reduction of fishing effort and close monitoring on A. pelagicus are needed.     

Use of stochastic models to estimate the growth of the Port Jackson shark,Heterodontus portusjacksoni,off eastern Victoria,Australia

Three stochastic models were used to describe the growth of Heterodontus portusjacksoni off eastern Victoria, Australia. The models are based on a reparametrization of the von Bertalanffy growth model to take account of length-at-age heterogeneity, and incorporate random variation of the von Bertalanffy growth coefficient (k), using three different probability distribution functions (pdfs): Weibull, gamma and log-normal. They were fitted to the lengths of 179 specimens (79 females and 100 males), and associated age estimates obtained by counting growth bands in the inner trunk dentine layer of the dorsal-fin spines. The species is relatively long-lived (maximum estimated age of 35 years for females and 28 years for males) and slow growing, but has rapid growth during the early stages of life. All the models provided similar growth parameters and length-at-age quantiles. However, Kullbac?s information mean indicated that the stochastic model assuming a log-normal distribution fitted the length-at-age data better for both females (L∞ = 1337, E(k) = 0.059, t₀ = 5.294) and males (L∞ = 1125, E(k) = 0.075, t₀ = 4.944) than the models assuming other distributions. The χ² likelihood ratio test indicated that females and males grow differently.     

Quantitative trait loci (QTL) associated with growth rate trait in common carp (Cyprinus carpio)

Growth rate is one of the important economic traits in aquaculture species that is influenced by quantitative trait loci (QTLs). Recently published complete genetic map of common carp (Cyprinus carpio) with 307 markers (including 109 SSR, 31 EST-SSR and 167 SNP markers) was used to determine the number and position of QTLs effecting body weight (BW) and growth rate. Ten-, 11- and 12-month-old individuals of common carp were measured, and seven QTLs were detected in three linkage groups (LG1, LG6 and LG20); three were significant QTLs (qBW2-6, qBW3-6 and qBW3-20, P < 0.001), and four were suggestive QTLs (qBW1-1, qBW1-6, qBW2-20 and qBW3-1, P < 0.01). The three significant QTLs related to BW2 and BW3 were in LG6 and LG20 and covered 18 and 41 cM, respectively. The explained variances of qBW2-6, qBW3-6 and qBW3-20 were 34.4, 32.1 and 33.4 %, respectively. The four suggestive QTLs affecting BW1, BW2 and BW3 were in LG1, LG6 and LG20 and had variances that ranged from 17.9 to 26.7 %. The similarity of the QTL intervals for BW1, BW2 and BW3 in LG6 suggested that these genes may affect growth continuously during the early stage of growth and may be important for growth. The identification of QTLs for growth rate and BW in C. carpio will lead to a better understanding of the factors that influence these traits at a genetic level and will promote the growth to higher production through marker-assisted breeding.     

Seasonal Differences in Growth Performance of Four Strains of Common Carp,Cyprinus carpio in India

To assess strain related differences in growth performance and growth patterns under the same culture environment, four strains of common carp, two each of the scale carp, Cyprinus carpio var. communis (Chinese big-belly carp and long bodied carp) and mirror carp, C. carpio var. specularis (scattered carp and linear carp) were communally stocked in three fertilized earthen ponds of 0.14 ha each at 5,000 fish ha^?1 in the ratio of 1:1:1:1 during an 11-month (February to December) culture cycle. Chinese big-belly carp grew larger than other groups, among which there were no significant differences. Scale carp strains performed relatively better than mirror carp at higher temperatures and then essentially stopped growing as temperatures declined into winter. The strains of mirror carp, on the other hand continued growing well later into the cold season.     

3个鲤群体杂交后代生长性状的灰色关联及复合杂交后代的体重预测分析

为了更好地了解和利用杂种优势,并在此基础上期望从可能产生的多个复合杂交组合中寻找可能的优良组合。实验通过建立回归模型、方差组分剖分、灰色关联度、比较不同方法的预测效果对建鲤、黄河鲤、黑龙江野鲤3个鲤群体双列杂交F₁代杂种优势的利用进行了分析。结果表明,(1) 未考虑PIT标记和考虑PIT标记时所测性状对体重影响作用不同。结合灰色关联度分析表明,2个时期的体长(体长和标记体长)对体重均有影响；(2) 不同组合、组合内家系间以及初始体重和雌性的互作固定效应显著；(3) 3种不同预测方法的分析表明,组合Hyj,Hjy和JJh可在复合育种时优先考虑。实验结果表明,杂交F₁代体重与初始体重和性别(尤其是雌性)的互作、标记体长对体重的影响要在实际育种中引起足够的重视；复合杂交可提高杂种优势的利用率。     

Movement patterns and growth estimates of big skate (Raja binoculata) based on tag-recapture data

From 2003 through 2006, 18,180 big skate (Raja binoculata) were tagged in three regions in British Columbia, Canada: northern Hecate Strait, Queen Charlotte Sound and the west coast of Vancouver Island. To date, this is the largest tagging program conducted for skates or rays worldwide. As of December 31, 2008, 7% of the tagged fish (n = 1238) have been recaptured through the commercial fisheries. Generally, 75% of the recaptured fish were recaptured within 21 km of the tagging location. Long-range movements (up to 2340 km) were undertaken by a small percentage (1.5%) of the recaptured fish. Tagged big skate were recaptured in waters off of Oregon, Washington, throughout the Gulf of Alaska and the Bering Sea. The majority of big skate recaptured outside of Canadian waters were female (83%, n = 15), of which 80% (n = 12) were likely immature at release. Three methods of estimating growth parameters were employed and produced varying results. The Gulland and Holt method was not able to produce growth parameter estimates. The GROTAG method for combined sexes produced von Bertalanffy growth curve parameters L_∞ (294.7 cm), K (0.05) and t₀ (?1.44) that were similar to published estimates for British Columbia big skates. The von Bertalanffy growth curve parameters produced by Fabens method for combined sexes were L_∞ = 168.6 cm, K = 0.16 and t₀ = ?0.81.     

Low levels of cadmium exposure induce DNA damage and oxidative stress in the liver of Oujiang colored common carp <Emphasis Type="Italic">Cyprinus carpio</Emphasis> var. <Emphasis Type="Italic">color</Emphasis>

Cadmium (Cd) compounds are widely distributed toxic environmental and industrial pollutants, and they may bring danger to growth and development of aquatic organisms. In China, the Oujiang color common carp, Cyprinus carpio var. color, is a very important fish, from an economic point of view, and is well used for fish culture in paddy fields. The purpose of this study was to show the low concentrations of cadmium-induced oxidative stress response and DNA damage in the livers of Cyprinus carpio var. color. Superoxide dismutase (SOD), malondialdehyde (MDA), and glutathione (GSH) in liver were measured after exposure to Cd levels (0.41, 0.52, 0.69, 1.03 and 2.06 mg/L, respectively) for 7 days and compared with the control groups. DNA damage, including indicators of damage percentage, DNA tail length (TL) and DNA tail moment (TM) were also analyzed by comet assays. Results showed that MDA and GSH levels in all treatment groups increased significantly relative to the controls (P < 0.01). Treatment with Cd at concentration of 0.41 mg/L increased SOD activity, while treatment with Cd at concentrations >0.41 mg/L inhibited SOD activities. DNA damage percentage, TL and TM also significantly increased when the Cd level was >0.41 mg/L. Positive correlations were also found between DNA damage levels and MDA levels (r = 0.74 for DNA damage percentage, r = 0.83 for TL, r = 0.84 for TM; P < 0.01 for all) as well as between GSH and MDA levels (r = 0.77, P < 0.01). These results strongly suggested that Cd-induced DNA damage in the livers of Cyprinus carpio var. color was due to lipid peroxidation and oxidative stress.     

The effect of dietary bamboo charcoal supplementation on growth and serum biochemical parameters of juvenile common carp (Cyprinus carpio L.)

This study investigated the effect of dietary bamboo charcoal (BC) supplementation on the growth performance and health status of juvenile common carp (Cyprinus carpio L.). A 63‐day feeding trial was carried out wherein the carp were reared on diets containing increasing levels of BC (0%, 0.5%, 1%, 2% and 4%). Treatment with BC did not produce any obvious effect (p > .05) on the growth performance of the juvenile common carp and on the overall muscle fatty acid composition. However, significant improvements (p < .05) were reported on serum indicators such as alanine aminotransferase (ALT), aspartate aminotransferase (AST), total protein (TP), triglycerides (TG), total cholesterol (TC), high density lipoprotein (HDL) and glucose (GLU) with the 4% inclusion level producing the most beneficial effects without adversely affecting some of the indices that were not improved at this level. Improvements were further observed in the intestinal villus length and goblet cells numbers at 4% supplementation. Although some evidence of potential toxicity exists, the overall findings of this study suggest that supplementation of common carp diets with 4% BC has a potential to enhance serum biochemical indices, intestinal functions and fatty acid content in common carp. Furthermore, while no positive effects were observed on the growth performance and total muscle fatty acid composition, no adverse effects were reported on these parameters. Therefore, BC has the potential to be used as a feed additive in the diets of juvenile common carp to improve health status and intestinal function.     

Effect of mussel bio-pumping on the drag on and flow around a mussel crop rope

Drag measurements are conducted to determine if inhalant and exhalant of fluid during mussel feeding has a detectable influence on the drag of a mussel-encrusted rope such as is commonly used in suspended aquaculture. The experiment is conducted using an artificial mussel crop rope constructed using the shells of Perna canaliculus, with 100 mussels (mean shell length 83.4 mm, S.D. 8.7 mm) attached over a length of 0.90 m. Fluid pumping from mussel feeding is simulated using inhalant and exhalant jets pumping at a rate of 7 L h^?1 per mussel. The mussel rope is towed at speeds between 0.05 and 0.4 m s^?1. No significant difference is found between drag with and without the mussels pumping indicating that assessments of the drag on or from mussel long-lines may safely neglect the effect of mussel feeding. We suggest using twice the mussel shell size to define mussel rope diameter which gives a drag coefficient of C_D ～1.0. A value of C_D ～1.3 is obtained if the projected area of the mussel rope is used. Particle tracking velocimetry (PTV) is also used on a similar but shorter crop rope (0.3 m length) in a recirculating flume which reveals that mussel pumping induces only small changes to mean velocity and turbulence distributions downstream of the rope. The wake of the crop rope is highly turbulent and dominated by shear instabilities formed in the free shear layer, similar to bluff body wakes. The sharp edges of the mussel shells provide many points for flow separation to occur. At typical ambient velocities, turbulent kinetic energy produced by the exhalant jets is small in comparison to that from flow around the crop rope.     

Successful reproduction of common carp Cyprinus carpio in irrigation waterways

Some key reproductive characters of invasive common carp, Cyprinus carpio L., were studied in an irrigation system of south‐eastern Australia. Spawning occurred on a variety of natural (i.e. submerged vegetation, plant debris and stones) and artificial substrates, and the presence of 0+ individuals was an indicator of spawning success. Compared with other C. carpio stocks worldwide, the lower minimum length at maturity reflected the higher water temperatures of the region, whereas the relatively lower mean pseudo‐gonadosomatic indices were attributed to less diverse food resources than those available in floodplain areas. The successful reproduction of feral C. carpio in irrigation waterways confirms its high adaptability and plasticity of traits and its classification into the phytolithophil guild, as opposed to the phytophil wild form. The findings of the present study should be given careful consideration in view of preventative measures for further spread of invasive C. carpio in similar waterways worldwide, but also for the enhancement of the species' fisheries in some man‐made reservoirs.     

Molecular cloning and expression analysis of common carp Cyprinus carpio tumor necrosis factor-α

Tumor necrosis factor (TNF) is a pleiotropic and potent inflammatory cytokine produced during inflammation. In this study, we cloned the tumor necrosis factor-?? (TNF??) complementary DNA (cDNA) gene from common carp Cyprinus carpio. The TNF??4 cDNA was 1318?bp in length and contained a 768-bp open reading frame, which putatively encoded 255 amino acids. The cloned sequences have several polymorphisms in the 3?? untranslated regions. The TNF?? putative protein retains the TNF?? family signature and consists of a four-exon, three-intron structure similar to other known TNF??4 genes. Aeromonas hydrophila Ahcs01 induced expression of TNF??4 in carp; differential expression was observed at different times. Our results indicate that TNF??4 is a central regulatory and effector cytokine of carp inflammatory and antimicrobial responses.     

Effects of different substrates on settlement and growth of pearl oyster (Pinctada maxima) larvae in hatcheries

Metamorphosis of pearl oyster Pinctada maxima pediveliger is affected by physical and chemical characteristics of the collectors. In the present study, we conducted four experiments to evaluate the effects of collector characteristics on the settlement and growth of hatchery-reared pearl oyster. In the first experiment, black, red, yellow, and white plastic sheets were used as collectors. Settlement of P. maxima larvae in black and red plastic sheets was significantly higher than that in yellow and white plastic sheets (P < 0.05). Mean shell length was not significantly different among the four colored sheets (P > 0.05). In the second experiment, pediveliger larvae were settled onto palm rope and polypropylene rope collectors. The number of spat in the palm rope collector was significantly higher than that of spat in the polypropylene rope collector (P < 0.05). Mean shell length was not significantly different between palm rope and polypropylene rope collectors (P > 0.05). In the third experiment, settlement and subsequent growth were compared between plastic sheets with and without biofilm. The number of spat in the plastic sheets with biofilm was significantly higher than that in the plastic sheets without biofilm (P < 0.05). Mean shell length after settlement were not significantly affected (P > 0.05). In the fourth experiment, pediveliger larvae were stored in tanks with (experimental group) and without collectors (control group). The settlement rate of larvae on the wall was not significantly different between the two groups(P > 0.05). The settlement rates of the larvae on the wall and collectors in the experimental group were significantly larger than those on the wall in the control group(P < 0.05). Mean shell length was not significantly different between the groups (P > 0.05). Our results suggest that appropriate selection of collector types, color, and conditioning can improve the settlement of P. maxima larvae in hatcheries.