Results of comparative growing test of all-female and bisexual population in two-year-old common carp (Cyprinus carpio L.)

The aim of this study was to verify whetherall-female carp populations grow faster thanbisexual ones. All-female mirror and scalypopulations were obtained by crossingmasculinizated females (neomales) of Northernmirror carp (M72) with regular females of M72and scaly Ropsa carp (ROP) purebreds,respectively. All-female and bisexual progenyof both mirror and scaly carps were rearedseparately for one year. However, controlgroups of a distinct phenotype of scalinesswere put in ponds with tested fish to make anadjustment for fish weight, which could becaused by environmental influence. Nodifferences were found after eight weeks ofrearing between all-female and bisexualpopulations, but, all-female mirror carppopulation (M72) gained 29.7% more weight(P < 0.0001) by the end of the first year thanthe bisexual (68.5 g ± 15.8 against 52.8 g± 13.9; mean ± S.D., respectively).Before beginning the second growing season,each group was marked and stocked together intriplicate ponds. Corrected weight after secondgrowing season (P < 0.0062) was 9.9% higher inall-female mirror carps (395.9 g ± 98.6)compared to the bisexual (360.2 g ± 89.0).No significant differences were found incorrected weights between scaly all-female andbisexual crossbreds (522.4 g ± 102.4 and518.3 g ± 95.8, respectively). Nodifferences in survival of all-female andbisexual populations were observed.     

Amino acid composition of edible parts of three-year-old experimental scaly crossbreds of common carp (Cyprinus carpio, Linnaeus 1758)

The aim of this study was to compare the amino acid (AA) composition of edible parts of three experimental groups of carp, i.e. a pure line of Přerov scaly carp (PS), a hybrid line of Přerov scaly carp and Northern mirror carp (PS × M72), and a hybrid line of Přerov scaly carp and Ropsha scaly carp (PS × ROP), with the quality of the edible parts of control hybrids of Hungarian and Northern mirror carp (M2 × M72) in harvest size (K₃). A comparison between the controls (M2 × M72) and experimental carp (PS, PS × M72, PS × ROP) showed that their muscle tissues contained the same amounts of 10 AA [essential amino acids (EAA): Thr, Val, Leu, Phe, Lys, His; non‐essential amino acids (NEAA): Asp, Gly, Ala, Tyr] of the 16 AA determined. Glu, Asp, Lys and Leu were the AA with the highest muscle concentrations. The total EAA_sum and NEAA_sum contents in the fastest‐growing PS × ROP hybrid, in spite of specific differences found (P<0.05: Arg, Met; P<0.01: Pro), were practically identical to those found in the control group of M2 × M72 mirror carp. PS × ROP hybrid female and male muscle tissues differed (P<0.05) only in Met and Ala levels. Hard roes of experimental female carp (PS, PS × M72, PS × ROP) contained the largest quantities of Glu and Val, and that of control female carp (M2 × M72) the largest quantities of Glu and Gly. Hard roes of PS × ROP hybrids contained the largest quantities (P<0.01) of EAA_sum (52.44±0.19%). Compared with hard roes, soft roes from all groups of carp contained more EAA_sum (PS × ROP: 55.03±0.26%). The two most abundant AA in soft roes were Lys and Arg. The most abundant AA in the hepatopancreas in all carp groups were Glu, Asp, Leu and Arg. Hepatopancreas EAA_sum levels in experimental carp (PS, PS × M72, PS × ROP) were significantly (P<0.05) lower than those in controls (M2 × M72).     

Evaluation of growth and dressing out parameters of experimental scaly crossbreds in 3-year-old common carp (Cyprinus carpio, Linnaeus 1758)

Performance tests of the Pr?erov Scaly Carp (PS), two crossbreds (PS × M72 and PS × ROP) and an internal control group (M2 × M72) were designed to assess their production and dressing out parameters at harvest size for their potential commercial utilization. The fastest growth rate (standard length (SL): 405±21.91 mm, P<0.01) and the highest final live weight (FLW: 2015.70±323.92 g, P<0.01) were recorded in the PS × ROP hybrid. The SL values in this group of carp were 12.5%, 19.12% and 11.57% higher (P<0.01) than those at M2 × M72, PS and PS × M72, respectively, and the FLW values were 21.57%, 62.83% and 24.37% higher (P<0.01) compared with M2 × M72, PS and PS × M72 hybrids respectively. Growth rate parameters of PS × M72 hybrid and control group M2 × M72 were practically identical. The lowest growth rate potential and FLW were recorded in the PS group (P<0.01). The highest (P<0.01) dressing out parameters were found in the control group of mirror carp M2 × M72 with a dressing percentage of 65.64±2.11%. There were practically no differences in this parameter between scaly carp groups (PS: 61.79±2.82%, PS × M72: 61.51±1.72%, PS × ROP: 63.60±1.96%). This study shows evidence for faster somatic growth and bigger final weight in the hybrid line PS × ROP of 3‐year‐old common carp compared with the pure line PS and the crossbreed PS × M72.     

Testing of performance in common carp Cyprinus carpio L. under pond husbandry conditions I: top-crossing with Northern mirror carp

Performance tests of Northern mirror carp (M72) and three different crossbreds were conducted in semi‐intensive pond conditions from the larval stage up to market size. The aim of this study was to evaluate the possible utilization of new hybrid combinations (M72 × PL – Poho?elice mirror carp) and (M72 × Dor – Israeli mirror carp), and to compare them with a hybrid widely reared as a commercial product (M72 × M2 – Hungarian mirror carp) and with M72 purebred. The testing model was derived from similar studies carried out in the conditions of the Czech Republic, where an internal control of different scale cover is used to eliminate all non‐genetic effects. ancova revealed at market size significantly better growth in M72 × Dor (1 619±28.3 g; LS mean±SE) and M72 × PL (1475±29.8 g) compared with M72 (1278±26.3 g). Survival during the test of 3 years duration was significantly the best in the M72 × Dor hybrid as were the dressing out parameters measured at market size, even if these were significantly different only in proportion of fillets with skin (39.1±0.28%). Interestingly, the crossbred M72 × M2 commonly used by Czech fishermen showed for both, growth (1371±26.2 g) and survival, the lowest values among crossbreds and with regard to dressing out parameters mostly among all tested groups.     

Production of market-size European strain Atlantic salmon (Salmo salar) in land-based freshwater closed containment aquaculture systems

Interest in land-based farms using recirculating aquaculture systems (RAS) for market-size Atlantic salmon (Salmo salar) continues to grow, and several commercial facilities are already rearing fish. Performance data for commercially available mixed-sex, all-female, and triploid all-female Atlantic salmon reared to market-size in freshwater land-based facilities, however, are limited, particularly for European strain fish. Accordingly, eight groups of European-sourced Atlantic salmon (five groups of diploid mixed-sex, two groups of diploid all-female, and one group of triploid all-female fish) were reared from eyed egg to market-size in a semi-commercial scale land-based aquaculture systems over five separate production cycles to quantify performance metrics. Fish reached market-size (4−5 kg) in 24.7–26.3 months post-hatch. Fish were reared at a mean water temperature of 12.3–13.7 °C from first feeding to a mean size of 466–1265 g, then 13.3–15.1 °C during growout. On average, all-female groups grew faster than mixed-sex groups; however, environmental conditions and performance of individual cohorts varied. In a comingled production cycle, diploid all-female salmon grew faster than triploid counterparts. Early maturation rates ranged from 0 % to 67 %, with a mean maturation rate of 34 % for diploid mixed-sex fish and 67 % and 13 % for two diploid all-female groups, respectively. Triploid all-female Atlantic salmon did not mature. This research confirms biological and technological feasibility of growing Atlantic salmon to market-size in land-based systems but controlling early maturation of diploid salmon remained a challenge under the conditions utilized in these trials. This research provides important data inputs to optimize operational and financial projections for existing and potential land-based Atlantic salmon farms.     

Resistance of genetically different common carp, Cyprinus carpio L., families against experimental bacterial challenge with Aeromonas hydrophila

The objective of this study was to determine the differences in disease resistance against artificial infection with Aeromonas hydrophila between genetically different common carp families. Four strains differing in their origin and breeding history were selected from the live gene bank of common carp maintained at the Research Institute for Fisheries, Aquaculture and Irrigation (HAKI, Szarvas, Hungary) to establish families with wide genetic background: Szarvas 15 (15), an inbred mirror line; Tata (T) scaly noble carp; Duna (D), a Hungarian wild carp and Amur (A), an East Asian wild carp. A diallele mating structure was used to allow the assessment of genetic variation within and between the tested 96 families for a variety of traits. The existing technologies of fertilization and incubation of carp eggs, as well as larval and fingerling rearing had been modified because of the large number of baseline populations. Two challenge trials of the 96 families of carp with Aeromonas hydrophila were done. The 10 most resistant and 10 most susceptible families to A. hydrophila were identified from these two challenges. The crosses that produced the most resistant families were mainly those having parents from Tata and Szarvas 15 domesticated strains, while the most susceptible families were from the wild strains Duna and Amur.     

Comparisons of growth and economic performance among monosex and mixed-sex culture of red mud crab (Scylla olivacea Herbst, 1796) in bamboo pens in the tidal flats of mangrove forests, Bangladesh

An experiment was conducted in a randomized block design to compare growth and economic performance between monosex and mixed-sex culture of red mud crab ( Scylla olivacea Herbst, 1796) fed with trash fish at 5–10% body weight per day in the mangrove tidal flat at Burigoaliny Union of Satkhira District, Bangladesh. The experiment had three treatments in triplicate each: (a) all-male culture, (b) all-female culture and (c) mixed-sex culture. Crabs of 80–120 g in size were stocked at a density of 0.5 crab m⁻² and cultured for 100 days. Specific growth rates (SGRs) by weight and internal carapace width (ICW) in the all-male culture were significantly higher than those in the all-female culture ( P <0.05), while SGRs in the mixed-sex culture showed no significant differences from those in the all-male and all-female culture ( P >0.05). No significant differences in final mean body weight, ICW, daily weight gain, survival rate, gross and net yields were found among all the treatments ( P >0.05). The area of high water level with mangroves gave significantly better results in terms of feed conversion ratio, survival rate, gross and net yields than the area of low water level ( P >0.05). The experiment suggests that the all-female culture in the area of high water level with mangroves could be suitable in developing commercial pen culture of red mud crabs in Bangladesh.     

Growth testing of two breeds of common carp, Cyprinus carpio L. (Hungarian mirror and Třeboň scaly carp), in ponds with low and high stocking density

The growth of two breeds of common carp, Cyprinus carpio L., was tested in ponds under the climatic conditions of South Bohemia. T?eboň scaly carp (TR) and Hungarian mirror carp (M2) were kept in both low and high stocking densities during the second growing season and then stocked together for communal testing during the third growing season. Before the communal testing, the mean initial weights of fish from low‐ and high‐density stocks differed significantly (374.1 vs. 227.7 g for the TR breed and 766.7 vs. 317.3 g for the M2 breed respectively, P<0.01). After communal testing, mean weights of fish from low‐ and high‐density stocks gained 761.8 vs. 543.8 g for the TR breed and 1339.7 vs. 706.7 g for the M2 breed respectively. These observed weights were also significantly different (P<0.01). However, the test of corrected weight gain, i.e. gain not related to the initial weight of fish, revealed insignificant differences (P>0.01) between the weight gains after correction, i.e. the effect of different initial weights was successfully eliminated. These results seem to confirm the applicability of this method for the assessment of growth of purebred common carp under the climatic conditions of Central European fish farms.     

Effects of Stocking Density and Monosex Culture of Freshwater Prawn Macrobrachium rosenbergii on Growth and Production in Concrete Tanks in Saudi Arabia

Abstract This study was conducted to evaluate the effects of stocking density and monosex culture on growth, survival, yield and feed conversion ratio of freshwater prawn Macrobrachium rosenbergii in concrete tanks. Juvenile prawns with an average weight of 1.8 g were stocked into triplicate tanks at densities of 5, 10, 15 and 20 prawns/m², grown for 168 d and fed a 34% tilapia diet. Stocking density had significant effect on prawns. Final mean body weight decreased with the increasing density, being highest at 5 prawns/m² (29.6 9). and lowest at 20 prawns/m² (17.4 g). Total yield increased from 135 g/m² (1,350 kg/ha) at a density of 5 prawns/m² to 261 g/m² (2,610 kg/ha) at density 15/m^z to 245 g/m² (2,450 kg/ha) at 20/m^z. Feed conversion ratios were high and ranged from 3.7 (5 prawns/m²) to 5.6 (20 prawns/m²).
In monosex culture of freshwater prawns stocked in triplicate tanks at a density of 5 prawns/m² for 112 d, the all-male population had the best growth performance and feed conversion ratio, followed by the mixed-sex and all-female populations. The all-male population had 99% marketable prawns (>20 g) with an average yield of 159 g/m² (1,590 kg/ha); the mixed-sex population had 90% marketable prawns and the yield was 135 g/m^z (1,350 kg/ha); and the all-female population had 75% marketable prawns with an average yield of 108 g/m² (1,080 kgha).     

Application of the random amplified polymorphic DNA technique in a study of heterosis in common carp, Cyprinus carpio L.

Random amplified polymorphic DNA (RAPD) analysis was applied to three varieties of common carp, Cyprinus carpio L.: Xingguo red carp, German mirror carp and Russian mirror carp. Twenty-seven decamer primers pre-screened from 40 random primers were used to assay polymorphisms within and between the populations. One hundred and ninety-nine fragments were generated in the three populations; 155 of these fragments were polymorphic. The similarity indices and genetic distances within and between the three populations of carp were calculated. The results indicated that the highest value of similarity within populations was obtained for German mirror carp, and the genetic distance between Xingguo red carp and Russian mirror carp was the farthest. It can be presumed that the heterosis between Xingguo red carp and Russian mirror carp is the highest within these three populations.     

Effect of different types of descaling methods on shelf life of air-/vacuum-packaged common carp (<Emphasis Type="Italic">Cyprinus carpio</Emphasis> L.) fillets under refrigerated storage conditions

Microbiological quality, sensory attributes and consumer preferences of common carp (Cyprinus carpio L.) fillets descaled by four different methods under two storage conditions (air packed and vacuum packaged) and refrigerated storage conditions were studied. Farmed common carps (scaly and mirror), of marketable size (2.2 kg, 3 years old), were randomly divided into four experimental groups (n = 10), and filleted and fillets were processed by four descaling methods: without skin, without scales, undercut scales and mirror carp (without any other treatment). Microbiological analyses were determined by total viable counts (TVCs) in logarithm of colony-forming units per gram (log CFU/g), and sensory quality of fillets was classified by odour, flavour, after taste and consistency on storage days 0, 3, 6 and 9. Vacuum packaging conditions affected the growth of microbiota and extended the shelf life of fillets in all experimental groups. Microbial communities grew to between 3.19–3.90, 4.03–6.00 and 6.35–8.28 log CFU/g after 3, 6 and 9 days of storage, respectively, and fillets without skin showed the lowest TVC among all analysed groups throughout storage. Also sensory analyses showed that consistency and odour of carp fillets were influenced by packaging conditions as well as descaling methods. The survey on consumer preferences of carp found out that 58.9 % of customers preferred scaly carp with undercut scales and processed to fillets instead of mirror carp. The results of present study show that different types of descaling methods combined with air/vacuum packaging can significantly prolong the shelf life of carp fillets.     

Sex reversal in salmonid culture: Part III. The production and performance of all-female populations of brook trout

Oral administration of 17β-oestradiol at 20 mg/kg diet for a period from 0 to 60 days following “swim-up” resulted in the sex reversal of male brook trout and the production of essentially all-female populations. The gonads of these animals were indistinguishable from the ovaries of untreated fish.Oral administration of this hormone at the same concentration but for the period from 0 to 40 days resulted in a population which comprised 67% females, 21% males and 12% bisexual animals.Within the control group, the growth rate of males was significantly greater than that of females. Growth in the all-female stocks produced by dietary oestradiol administration (0–60 days) was significantly lower than that of the untreated population taken as a whole but was identical to that of the control females.The growth of brook trout during the first year was closely comparable to that of rainbow trout reared under identical conditions. During the second year, the growth of the rainbow trout exceeded that of the brook trout. At 19 months of age, all the animals in the control and oestradiol treated brook trout populations were fully mature; maturity in the rainbow trout was substantially confined to males.     

RAPD技术在鱼类杂种优势研究中的应用↑（*）

从４０个引物中筛选了２７个引物,对兴国红鲤、德国镜鲤和苏联镜鲤进行随机扩增多态ＤＮＡ分析,共得到１９９条带,其中１５５条带（占７７９％）具多态性。计算得出这３个群体内的相似系数分别为：兴国红鲤０．７２２,德国镜鲤０．８２７,苏联镜鲤０．７８７,表明群体内的遗传变异较大;群体间的遗传距离为：兴国红鲤与德国镜鲤０．０９２,兴国红鲤与苏联镜鲤０．１０５,德国镜鲤与苏联镜鲤０．０７７,表明群体间的亲缘关系相近。兴国红鲤与苏联镜鲤遗传距离最大,推断这２个品种间的杂种优势较强,与育种实践一致。     

散鳞镜鲤两个保种群体的遗传多样性

利用20个微卫星标记分析国内仅存的两个散鳞镜鲤（Cyprinus carpio）保种群体（SP、CJ）的遗传多样性。结果表明：共检测到147个等位基因,平均值为7.35,有效等位基因数（Ae）、期望杂合度（He）以及多态信息含量（PIC）的平均值分别为2.7828、0.6041和0.5386。SP群体的Ae、He以及PIC值分别为3.1126、0.6479和0.5948,大于CJ群体（2.4529、0.5602和0.4823）。在两个群体中,群体特有等位基因共53个,其中9个为低频等位基因。对20个引物在两个群体中等位基因的显著性分析表明：其中有16个引物可以作为区分两个群体的特异性分子标记。瓶颈效应分析结果显示：2个群体均经历了瓶颈效应。同胞率检测结果（SP 97.5%;CJ 96.7%）偏高说明群体内近交压力较大。哈迪-温伯格平衡检测表明：两个群体大部分位点偏离平衡并处于杂合子过剩状态。两个群体间的遗传距离（D）为0.5625,SP和CJ群体的个体均各聚为一支。群体间的遗传分化指数（Fst）为0.1138,Nm值为1.9462。该研究表明：散鳞镜鲤群体遗传多样性水平较高,其中SP群体的遗传多样性水平高于CJ群体,两群体处于中度遗传分化。     

Top-crossing with evaluation of slaughtering value in common carp (Cyprinus carpio L.) offspring

A three-year test of growth performance andoffspring survival from top-crossing of commoncarp hybrids in low altitude (350 m above thesea level, middle European climate) and in highaltitude (750 m above the sea level, middleEuropean climate) was terminated by assessmentof slaughtering value of edible parts in therespective strains. A recently establishedHungarian synthetic mirror carp strain (HSM)was chosen for testing as maternal strain. TheHSM, as well as wild Amur carp (AC), Ropshacarp (ROP) and Tata carp (TAT) were used aspaternal strains.The evidential strain*altitude interactioneffect was demonstrated as significant forweight of fish (0.0005), fillet without skin(0.0001), index of highbackedness (0.005),index of head length (0.0404),Fulton's coefficient (0.0497),index of widebackedness (0.0315) andgonadosomatic index (0.0082). The interactioneffect was demonstrated as insignificantbetween altitude*sex and betweenstrain*sex.The comparative test of analysis of variance(ANOVA) revealed significantly (P < 0.05)higher weight of fish after killing on lowaltitude (1611.6 g) than on high altitude(1090.3 g), but processed body yield andpercentage of fillet without skin was notsignificantly different (64.0 and 34.2 for lowaltitude, 64.2 and 33.4 for high altitude). Thepercentage of processed body weight andpercentage of fillet without skin in analysisboth altitudes were significantly better infemales (65.5 and 34.6%) than in males (62.5and 33.00%), respectively. The highestsignificant differences in weight of fish afterkilling were found between HSM (890.8 g) andHSM × AC (1283.3 g) in high altitude. In lowaltitude, it was between HSM (1527.2 g) andHSM × AC (1706.9 g) and HSM × ROP (1693.0 g).     

镜鲤两个繁殖群体的遗传结构和几种性状的基因型分析

利用扩增效果好、在群体中具有多态性的28个微卫星标记,检测国家换新良种场的镜鲤繁殖群体和黑龙江水产研究所松浦实验场的镜鲤繁殖群体的遗传组成,计算了两个群体的有效等位基因数,期望杂合度和多态信息含量等遗传参数,换新与松浦两个群体的有效等位基因数分别为2.874和3.102, 期望杂合度分别是0.565和0.603,多态信息含量分别是0.534和0.568;遗传结构分析研究结果表明这两个群体的多样性较高,信息含量丰富,具有进一步筛选出优良品种的遗传基础。但连锁不平衡分析表明这两个群体在较大的选择压力下,已严重偏离Hardy-Weniberg平衡,要保持群体的优良性状相关的遗传基础,应该在进一步的选种中注意增加群体的遗传多样性。也用28个基因座的不同基因型与换新208个亲本的体重值进行了连锁分析,得到12个与镜鲤体重相关的基因型,其中紧密相关的基因型3个;分析了一些严重偏离平衡的基因型,并分析了出现这种现象的可能原因,同时探讨了一些基因型与胚胎期致死或易感病基因连锁的可能性。为描述基因型偏离程度,创造了基因型偏离指数,并用其对群体中一些基因型出现的偏离现象进行了探讨。图1表2参19     

松浦镜鲤与长丰鲢食用鱼混养试验

2012年5-10月,在面积为0.19hm2的试验池1中放养体质量160g的松浦镜鲤（Cyprinus carpio Songpu）117,700尾·hm^-2,混养体质量160g的长丰鲢（Hypophthalmichthys molitrix）春片、乌子头和鳙（Aristichthys no-bilis）夏花鱼种。在面积为0.19hm2的试验池2中放养体质量149.5g的松浦镜鲤3,450尾·hm^-2,只混养鲢和鳙夏花,采用常规饲养方法。2012年10月2日,试验池1平均每hm2产鱼21,025.5kg,其中松浦镜鲤平均全长34.3cm,体质量1425g,产量18,294.0kg;长丰鲢春片平均体质量674g,平均产量1,816.5kg,长丰鲢夏花平均全长18.6cm,体质量112.4g,平均产量592.5kg;鳙夏花平均全长达12.1cm,体质量39.9g,平均产量322.5kg。试验池2平均每hm2产鱼3,069.0kg,其中松浦镜鲤平均全长35.0cm,体质量1225g,平均产量2,766.0kg;鲢夏花平均全长达11.3cm,体质量24.9g,平均产量130.5kg;鳙夏花平均全长达11.1cm,体质量35.1g,平均产量172.5kg。试验表明,高密度养殖的松浦镜鲤产量显著高于密度低时,长丰鲢夏花的出池体质量是普通鲢的4.5倍,特殊生长率（6.27%·d^-1）是普通鲢（3.5%·d^-1）的1.79倍。文中还讨论了松浦镜鲤养殖池的水质和技术特点。     

Studies on fish heterosis with DNA fingerprinting

One Tilapia hybridization, Oreochromis aureus, (Steindachner) ♂ × Oreochromis niloticus, (Linnaeus) ♀, and two common carp, Cyprinus carpio, (Linnaeus) ♂, hybridizations, Russian mirror carp ♂ × Xingguo red carp ♀, and German mirror carp ♂ × Xingguo red carp ♀ were used to study the feasibility of predicting heterosis using genetic distance from DNA fingerprinting. The results indicated that highly polymorphic DNA fingerprints could be obtained with human minisatellite 33.6 as a probe on the studied varieties. The within‐population similarity indices of O. aureus, O. niloticus, Russian mirror carp, German mirror carp and Xingguo red carp were 0.785, 0.577, 0.432, 0.348 and 0.339 respectively. The similarity indices between F1 and their parents of three hybridization combinations were not significantly different (P > 0.05). There were larger genetic distances between two hybridization combinations, O. aureus♂ × O. niloticus♀ and Russian mirror carp ♂ × Xingguo red carp ♀, which showed heterosis in production and were extensively used in Chinese aquaculture. The genetic distance between O. aureus♂ and O. niloticus♀ was 0.338, and that between Russian mirror carp and Xingguo red carp was 0.344. However, the genetic distance between German mirror carp and Xingguo red carp was 0.129; this corresponded with the fact that their F1 generation did not show heterosis in the Chinese fish hybridization experiment. The study suggested that genetic distance could be used to predict fish heterosis.     

水库小网箱养鲤效果及其与密度的关系

在３５０、４００、４５０、５００尾／ｍ２的放养密度下,研究了小网箱养鲤效果。结果表明,小网箱放养密度对净产量有极显著的影响,最佳放养密度为４７３尾／ｍ２,随密度增加,出箱鲤鱼的平均体重和生长比速下降。与大网箱相比,小网箱在饲料系数、效益指数等方面具有显著优越性。     

Potential use of otolith microchemistry for field studies of temperature-dependent sex determination and gonadal degeneration in fish

This paper describes a novel approach to study the expression of temperature-related reproductive phenomena such as thermolabile sex determination (TSD) and heat-induced germ cell loss in wild fish populations. The proposed approach is based on the reconstruction of the past thermal history of individual fish through the microchemical analysis of the otoliths (mineralized structures responsible for the sense of balance). As an example, we outline the preliminary results of an investigation on the natural occurrence of TSD in pejerrey Odontesthes bonariensis, an atherinid fish in which all-female to all-male populations can be produced by experimental manipulation of the rearing temperature during the critical time of sex differentiation, from Lake Kasumigaura, Japan.