Conditioning of the European flat oyster (Ostrea edulis,Linnaeus 1758): effect of food ration

To establish a reliable protocol for the broodstock conditioning of the oyster Ostrea edulis (Linnaeus 1758) in hatcheries is important to obtain the best number of viable larvae all year even outside the natural season for maturation and spawning. Hatchery production of bivalves depends on their initial gonadal maturation state, which is linked to season and several other factors, such as temperature, daylight, salinity and food supply. Ration and diet composition are important in broodstock conditioning because food availability affects fecundity and gametogenic development. In this work, the effect of food ration on O. edulis conditioning was studied in autumn and winter. The results of this study showed that the broodstock conditioned with a food ration of 6% and 9% produces the highest number of larvae in autumn and winter. These food rations produced rapid gonadal development and larval release in a short period with a similar larval production. The oysters conditioned with a food ration of 3% delayed larval release and produced a significantly lower number of larvae in autumn. In the 9% ration treatment, the percentages of mortality were significantly higher in both autumn and winter. Thus, a 6% food ration is likely to be the most suitable for flat oyster conditioning combined with a gradient of temperature (14–18°C) and a gradient of daylight (8–16 h).     

Spawning Frequency Analysis of Wild and Pond-Reared Pacific White Shrimp Penaeus vannamei Broodstock under Large-Scale Hatchery Conditions

Second generation Penaeus vannamei broodstack, pond-reared and wild populations, were compared for spawning frequency and several variables associated with reproductive performance. For this purpose, 470 pond-reared and 237 wild-caught individually tagged females were stocked with males of the same origin in ten maturation tanks in a commercial hatchery, and several productivity variables were recorded over time. Results of the analysis indicate that wild shrimp had higher mating and spawning frequencies compared to pond-reared broodstock. The number of nauplii per spawn was higher for wild shrimp, but fertilization and hatching rates were higher for pond-reared spawners. A larger proportion of nonmating females were found in pond-reared shrimp; whereas, wild females had a higher potential for multiple matings. The spawn quality (fertilization and hatching rates, percentage of viable spawns, and number of nauplii) in consecutive matings did not decline substantially. The present study indicates that selection of females with multiple spawning capabilities can be an important commercial strategy to improve nauplii production over the short term. Pond-reared broodstock can be an adequate source for applying this strategy because of their year-round availability and an overall acceptable reproductive performance.     

Broodstock conditioning of the Portuguese oyster (Crassostrea angulata,Lamarck, 1819): influence of different diets

The Portuguese oyster Crassostrea angulata shows great potential in oyster farming. The conservation of pure populations of this species is important for production diversification and biodiversity preservation. In this way, the zootechnological development for seed hatchery production is extremely important. Broodstock conditioning is a key step in the process of rearing bivalves in a hatchery. Many factors regulate the reproductive cycle, being food one of the most important ones. To evaluate the effect of different diets on C. angulata reproductive performance, broodstock were conditioned with different food regimes formulated fundamentally by flagellates (Diet 1 – Pavlova lutheri and Isochrysis galbana clone T‐ISO; Diet 2 – P. lutheri, T‐ISO and Skeletonema costatum) and constituted fundamentally by diatoms (Diet 3 – S. costatum and Chaetoceros calcitrans; Diet 4 – P. lutheri, S. costatum and C. calcitrans). During conditioning, samples of oysters were collected to evaluate condition index, gonadal development and biochemical composition. At the end of the conditioning period, oysters were induced to spawn to evaluate reproductive output (fecundity, fertilization rate and D‐larvae development). The diets had an impact on the gametogenesis process, energy storage and reproductive output performance, being the best results those obtained in broodstock fed with the diatoms‐predominant diets. However, those fed with diets majority flagellates had an unsuccessful performance. Holistic approaches incorporating all results in this study reveal and reinforce the idea that the diatom species used presented the nutritional requirements to C. angulata broodstock, being essential in the conditioning phase.     

Progress Toward Year-round Spawning of Southern Flounder Broodstock by Manipulation of Photoperiod and Temperature

Reliable methods have been developed for controlled spawning of captive southern flounder, Paralichthys lethostigma, broodstock during their natural winter (December–February) spawning season. From 1999 to 2004, we evaluated the effects of manipulation of photoperiod and temperature on both advance and delay spawning to produce viable embryos throughout the year. Wild‐caught adult broodstock were held in 4.8‐ to 7.0‐m³ controlled‐environment tanks at a sex ratio of approximately 12 females to 4 males. Broodstock were subjected to different artificial photothermal conditioning regimes: extended winter (EW), accelerated (A‐10‐, A‐6‐, A‐4.5‐, and A‐3.8‐mo regimes), and delayed (D‐16‐ and D‐14‐mo regimes), with gradual and abrupt transitions, respectively, from long to short daylengths. Under an EW cycle, fish were exposed to constant short daylengths (10 L: 14 D) after the winter solstice in January. Eighty‐seven natural spawnings from December to April produced 18.3 × 10⁶ eggs, with 20.9% hatching successfully (i.e., overall egg viability). Under an A‐10‐mo cycle, rate of decrease in daylength was accelerated after the summer solstice in July, to reach winter conditions in October. Seven induced spawning trials from October to November produced 897 × 10³ eggs, with 40.4% viability. Under an A‐6‐mo cycle, rate of change of photoperiod was accelerated after the winter solstice in January, to reach winter conditions in July. Three induced spawning trials in July produced 550 × 10³ eggs, with 14.7% viability. Under an A‐4.5‐mo cycle, broodstock exposed to EW from January through April were exposed to an accelerated cycle to reach winter conditions by October. Four induced spawning trials from September to November produced 729 × 10³ eggs, with 28.7% viability. Under an A‐3.8‐mo cycle, broodstock exposed to EW conditions from January through April were exposed to an accelerated cycle to reach winter conditions by September. Five induced spawning trials from September to November produced 510 × 10³ eggs, with 45.9% viability. Under a D‐16‐mo cycle, fish were exposed to a decelerated decline in photoperiod after the summer solstice in July, to reach winter conditions in May, when atretic females were observed. Under a D‐14‐mo cycle, fish were exposed to constant summer conditions from December through mid‐June and then to an abrupt decline in photoperiod to winter conditions in late June. Six induced spawning trials from September to November produced 763 × 10³ eggs, with 13.0% viability. Production of viable embryos was greatest during the extended winter because of abundant natural spawnings. While successful natural spawnings were rare during the fall or summer, viable embryos were produced through induced spawnings during all seasons of the year, with no significant (P > 0.05) differences in egg viability. Extended winter conditions prolonged spawning from 3 to 5 mo. Accelerated (3.8–10 mo) regimes were effective in producing viable embryos from summer through fall, but a minimum of 5 mo was required to complete gonadal recrudescence. While constant long daylengths after the summer solstice delayed gonadal recrudescence, with spawning obtained 2.5 mo after an abrupt reduction to short daylengths, a decelerated decline in photoperiod did not. Artificial control of daylength enabled precise control of gonadal recrudescence and year‐round spawning in southern flounder without adverse effects on the quality of eggs and larvae and will improve availability of seedstock for commercial aquaculturists.     

Comparison of spawning induction techniques on <Emphasis Type="Italic">Paracentrotus lividus</Emphasis> (Echinodermata: Echinoidea) broodstock

The performance of different and expedite spawning induction methods was compared on samples of both mature wild and captive Paracentrotus lividus sea urchin populations. Thermal, saline and mechanical shocks, emersion during different periods of time, addition of con-specific gametes and different KCl concentrations were tested. Percentage of spawned sea urchins, mean number of released eggs, percentage of males that released more than 200 million spermatozoa, and survival after 5 days were the variables analysed. Results indicate that both thermal and saline shocks were ineffective methods to trigger spawning. Mechanical shock and addition of con-specific gametes were able to promote spawning but with a reduced number of released gametes. Emersion for a period of 3 h induced spawning with 100% broodstock survival but longer periods up to 12 h, although increasing the number of spawners can cause significant broodstock mortality. An injection of 1-mL intra-peristomial KCl was an expedite method to obtain P. lividus gametes, but high mortalities were always recorded and was related with excessive KCl concentrations. When there is need for a small number of gametes, the mechanical shock technique can be considered since led to 100% survival. When large spawnings are required, the emersion procedure can be a viable method, but further investigation must be carried out to assess the best time period to obtain broodstock full survival.     

Influence of different microalgal diets on gonadal development of the carpet shell clam <Emphasis Type="Italic">Ruditapes decussatus</Emphasis> broodstock

Studies considering broodstock conditioning of Ruditapes decussatus mostly used flagellates and diatoms for feeding, mainly Isochrysis galbana and Chaetoceros calcitrans, respectively. The present study evaluated the effect of different microalgal diets on gonadic maturation of R. decussatus including three microalgae species (C. calcitrans, Tetraselmis suecica, and Nannochloropsis oculata) which were used to prepare six diets: three monospecific and three bispecific mixed diets at a proportion of 1:1. Clams were daily fed at a ratio of 1% dry weight of algae/live weight of clam and unfed treatment was used as control. Results showed that clams fed C. calcitrans alone or mixed with T. suecica attained earlier full maturity with the highest response to spawning induction (after 34 conditioning days) and largest proportion in the partial spawning phase for both, followed by T. suecica alone after 48 days. In contrast, N. oculata alone or mixed diets demonstrated poor performance for gonadal maturation. Unfed treatment did not show any sign of maturation. The results indicated that T. suecica has high conditioning potential like C. calcitrans and their mixture gave the highest benefit. Therefore, T. suecica can be recommended for R. decussatus broodstock conditioning.     

Broodstock management and egg production of milkfish, Chanos chanos Forsskal

Abstract. The milkfish, Chanos chanos Forsskal, industry in the Philippines suffers from a limited supply of wild fry. The demand for milkfish fry has spurred research in artificial propagation to supplement the natural seed supply. Spontaneous maturation and spawning of milkfish beginning at 5 years of rearing in floating net cages or concrete tanks coupled with improved egg collection technique have increased daily egg collection to a maximum of 3 million eggs and provided adequate volumes of eggs for mass fry production. Annual egg collection and number of spawnings were markedly higher in cage-reared stocks older than 9 years old than stocks less than 9 years old. Egg collection of tank-reared stocks were comparable to those collected in cages. As feed constitutes a major portion of the operating expenses for establishing and maintaining milkfish broodstock, further studies must be geared towards defining optimum dietary requirements and ration size for gonadal maturation and spawning. Also environmental manipulation studies must be conducted for year-round spawning. Developments in these areas should ensure the production of maximum numbers of high quality eggs and fry year-round.     

Oocyte and embryo quality in Crassostrea gigas (Portuguese strain) during a spawning period in Algarve,South Portugal

Egg quality is one of the most important factors determining larval viability. The study of oocytes released by `wild' broodstock will contribute to the definition of quality criteria applied to hatcheries as well as being an indicator of the oyster reproduction potential and aquaculture ongrowing systems. The aim of this study was to determine the relationship between condition of Crassostrea gigas spp. angulata (Portuguese strain) from `wild' broodstock (condition index, gonadal maturity and number of oocyte released), oocyte biochemistry and hatching rate of eggs during the spring/summer of 1995. Stages of gonadal maturity and condition index indicated that natural spawning of this species occurred between April and August with the highest spawning intensity occurring in June. Analyses demonstrated that C. gigas oocyte organic matter consist of 44–74 % proteins, 16–38 % lipids and 7–12 % carbohydrates. A significant relationship was observed between some biochemical parameters – organic matter and lipid content – and broodstock condition index and hatching rate. It seems that these two oocyte parameters (organic matter and total lipids) could be used to define quality of oocyte and thus larval viability. The oocyte protein content was also found to be associated with broodstock and larval quality. In summary, these data are a contribution to the knowledge of the reproductive cycle of oysters in Europe and may be useful in improving hatchery management of this species.     

Broodstock Condition and Egg Quality in Tiger Prawn, Penaeus monodon, Resulting from Feeding Bioencapsulated Live Prey

This study was motivated by the need to find a solution to poor egg quality and the resulting mass mortality of hatchery-produced larvae of the tiger prawn, Penaeus monodon. The approach adopted sought to improve the broodstock condition and determine its effect on egg quality using rates of fertilization, hatching and metamorphosis. Broodstock specimens were given four separate dietary treatments (D1–D4), all of which comprised squid and trash fish plus supplements. D2, D3 and D4 were supplemented with bloodworm, bioencapsulated bloodworm and a commercial broodstock diet, respectively. Tricalcic phosphate (Ca₃(PO₄)₂) was used to enrich the live bloodworm. The bioencapsulated ration performed better than regular bloodworm and other diets. This was evident from the bioencapsulation results which showed the highest rate of hatching, survival of nauplii and larvae metamorphosing into zoea stage.     

Egg Quality in Wild and Broodstock Cod Gadus morhua L.

Problems concerning egg viability or egg quality have received increasing attention, in relation to cultivation as well as to the assessment of reproduction of wild fishes. One important aspect of this paper is to discuss the use of cell morphological characteristics as indicators of egg quality in cod. Early cellular malformation rates in egg batches show a positive correlation with their later egg and larval survival, and can be used as a rough prediction of normal development and mortality rates.
The natural mortality rate offish eggs is not well understood, and observed egg viability of captive cod is are discussed in relation to egg viability in the wild. Results from recent work indicated that approximately 10% of naturally spawned cod eggs from both wild fish (planktonic samples) and from a broodstock had abnormal cleavages at the 2–128 cell stage. Eggs with observed early abnormal cell-cleavage showed very poor survival and hatching rates. For broodstock cod, egg viability was highest during the peak of the spawning season.
The North Atlantic cod may provide a good model species for studies of egg viability variations in wild and captive individuals, as its reproductive biology is well studied. It is now documented that the egg production in cod is dependent on fish age, nutritional status, batch number, and stress factors.     

仿洄游培育美洲鲥亲本的性腺发育

为解决美洲鲥(Alosa sapidissima)人工培育亲本性腺发育不佳的问题,开展了美洲鲥亲本仿洄游的培育,研究观察了美洲鲥亲本卵巢和精巢不同发育阶段(II^V期)的形态特征及相关参数,确定了仿洄游培育美洲鲥亲本性腺初次发育的特征。结果显示:在美洲鲥仿洄游培育过程中,在卵巢、精巢发育前期(II期),雌雄亲本生长迅速;而性腺发育到III期后,雌雄亲本的生长滞缓,雌鱼亲本甚至出现负生长。仿洄游培育美洲鲥性腺初次发育(II^V期)过程中,雌雄亲本均有较高的肥满度,分别为1.55~2.07和1.56~1.71;卵巢发育Ⅴ期雌鱼亲本的肥满度(2.07)显著高于在卵巢II^IV期亲本(1.55~1.67);而雄鱼亲本肥满度在精巢发育各阶段(II^V期)均无显著性差异。仿洄游培育美洲鲥性腺发育良好,雌雄亲本的性腺指数均较高,性腺发育Ⅴ期雌雄亲本的性腺指数(GSI)分别为(26.10±6.46)(18.88~33.62)和(5.18±0.68)(4.49~6.11)。研究表明,仿洄游培育的水温(10.8~30.8℃)和盐度(1~15)的周年变化符合美洲鲥亲本性腺发育的要求。     

Variation in Reproductive Performance and Egg Quality Between Wild and Pond-Reared Indian White Shrimp,Fenneropenaeus indicus,Broodstock

ABSTRACT

The shrimp hatchery industry worldwide has placed immense interest on the production of closed-life cycle broodstock from farm stock. Unfortunately, majority of the studies have proven that pond-reared broodstock are inferior to their wild counterparts in terms of reproductive performance, spawn quality and post-hatching performance. In the present study, reproductive performance, egg, and nauplii quality of wild and pond-reared Indian white shrimp, Fenneropenaeus indicus, broodstock were analyzed. Biochemical analyses were done with egg and nauplii from both the sources, in an attempt to explain the difference in their performance. Results indicated better reproductive performance by wild females compared to pond-reared ones. The wild eggs contained higher total lipid, and vital HUFAs namely EPA (Eicosapentaenoic acid), DHA (Docosahexaenoic acid) and ARA (Arachidonic acid). However, one of the dominant PUFA, 18:2 (n-6) was high in pond broodstock eggs. Biochemical analysis also indicated that glucose, carotenoids, and triacylglycerol content were significantly higher (P < 0.001) in wild eggs. But, egg protein and triacylglycerol content did not record significant difference between the egg samples. The percentage viable nauplii, nauplii length and triacylglycerol content were all significantly higher (P < 0.05) with wild nauplii. This study proves the better nutritional profile of wild eggs and nauplii in terms of analyzed biochemical components. But, as our knowledge on specific nutrient requirement for successful reproductive performance and offspring quality is limited, the better performance of wild eggs could not be attributed to any single nutrient. Meanwhile, it could be presumed that all the deficient nutrients collectively contributed to the poor reproductive performance and spawn quality.     

Broodstock Rearing and Controlled Reproduction of Reeves Shad Tenualosa reevesii

Reeves shad Tenualosa reevesii is one of China's best known anadromous fish, but is presently on the verge of extinction. There is an urgent need for conservation of this species through artificial reproduction and culture. In this study, shad broodstock were held in captivity then were induced to spawn with serial injections of luteinizing hormone-releasing hormone analogue (LHRHa) following GtH priming by implantations of 17-methytestosterone (T) combined with environmental manipulations. Induced maturation of 4, 5, and 6-year-old females reached 83.3%, 87.5%, and 100%, respectively, while fish in control treatments remained immature. During the gonadal development priming period, mean serum 17-estradiol levels in the T treatment were significantly higher than the LHRHa treatment and control fish. Gonadal development of females was suppressed when their mesenteric fat index was below 1.5% by April. The effective accumulating temperatures for female and male maturation were 3,995 ± 31.4 C/d and 2,278 ± 8.9 C/d, respectively. Two injections of LHRHa in combination with domperidone (DOM) and environmental regulations were effective in inducing ovulation. About 800,000 fertilized ova were obtained (fertilization 75%) in 1995, and 5,000 fry were hatched in 1996. These results are an important step to develop shad culture and save this endangered species.     

Effects of temperature and photoperiod on the conditioning of the flat oyster (Ostrea edulis L.) in autumn

The production of the flat oyster Ostrea edulis (L.) natural spat in Europe has decreased almost by 60% in the past ten years. Thus, the importance of the production of oyster spat in hatcheries is evident. One of the critical steps in hatchery production is broodstock conditioning, especially difficult in autumn, when gonadal development is in resting period. Conditioning is influence by temperature, photoperiod and nutrition. In this work, the effects of two temperature and three photoperiod regimes on the conditioning of O. edulis were studied for three years by stereological analyses and registering number and dates of spawning and larval yield. Temperature had a positive effect on the gonadal development of O. edulis during conditioning. The percentages of germinal cells in oysters conditioned with a gradient of temperature (14–18°C) were double compared to oysters conditioned at 15°C. Oysters conditioned with longer photoperiods showed higher percentages of germinal cells. There was no interaction between temperature and photoperiod. Spawning was observed in the oysters treated with daylight (8–16 h) ten weeks from the beginning of conditioning. Flat oysters conditioned with 8 h and 8–12 h of daylight delayed the first spawning for a month. Total larval production was higher in the oysters treated with the longest daylight gradient. Gonadal and gametogenic development was a non‐synchronic process and the spawning extended for around two months. A protocol for flat oyster broodstock conditioning in autumn by using both a gradient of temperature (14–18°C) and daylight (8–16 h) is proposed.     

Genetic structure and genetic relatedness of a hatchery stock of Senegal sole (Solea senegalensis) inferred by microsatellites

Solea senegalensis is a fish species in an early stage of domestication. A commercial hatchery in southern Spain experienced a dramatic failure in spawning and embryo survival, after incorporation into the broodstock of fish reared in their hatchery. To assess the impact of management on the stock quality, a population genetics study was made of adult broodstock present at this hatchery in 2000. The broodstock was composed of a group of fish of wild origin and two more groups from F₁ progeny. A set of eight microsatellite loci was used to compare genetic variability among the three groups and to establish the relationships between pairs of individuals within each group.Individuals from F₁ origin showed a substantial reduction in genetic variability when compared to those from the wild. There was a greater than 50% decrease in the number of alleles per locus corrected by sample size and 16% and 26% reductions in H_e values in the two F₁ groups, respectively. The degree of genetic relationship between individuals, evaluated by the relatedness estimator, rxy, and by graphical approaches, revealed a high proportion, almost 75%, of full-sibs and half-sibs in both F₁ groups, which might account for the reduction in overall variability. The high proportion of siblings also suggests a reproductive pattern in this stock in which few individuals breed successfully. This mating behaviour, along with factors inherent to selection and management systems, might be responsible for the negative effects on the reproductive capacity of the stock.     

The Effects of Stressful Broodstock Handling on Hormonal Profiles and Reproductive Performance of Rhamdia quelen (Quoy & Gaimard) Females

Abstract.— A stressful environment induces cortisol that might affect fish breeding and reproduction. In the present work, which aimed to mimic aquacultural conditions of the jundia (Rhamdia quelen) hatcheries in southern South America, females were submitted to normal or stressful handling and the effects of cortisol on serum levels of 17β‐estradiol (E2) and testosterone (T) were determined. In addition, the effect of stress on reproductive parameters such as eggs and swim‐up fry production was also measured. Eight females from a group submitted to stressful handling (SH) conditions and eight females from a group with normal handling (NH) conditions were captured for blood sampling at D 0 and at D 1, 10, 20, 30, and 40 of the experiment. A typical cortisol response was observed in the SH females group in that they presented higher cortisol level in contrast to the NH female group, in all days sampled, except at D 0. In the 10th and 20th d, the E2 levels were lower in SH females, but cortisol levels were higher, suggesting an effect of cortisol on E2 production and/or release. Stressful handling appeared to affect both the number and the quality of the gametes because a lower number of oocytes was stripped from SH females, and from SH fertilized eggs, a lower number of viable swim‐up fry was obtained to be transferred to earthen larviculture ponds. Taken together, the results indicated that stressful handling of broodstock impairs R. quelen reproduction.     

Broodstock diet with water and astaxanthin improve condition and egg output of brood fish and larval survival in Atlantic cod,Gadus morhua L.

Broodstock of Atlantic cod were fed with three diets; astaxanthin supplemented (100 ppm kg^?1) hydrated diet (30% water) (HWHAs), no additional astaxanthin supplemented (50 ppm kg^?1) hydrated diet (30% water) (HWLAs) and a control diet (50 ppm kg^?1 astaxanthin and 10% water). Throughout the spawning period, eggs were collected daily and fertilization success and proportion of embryos with normal cleavage were recorded. Larvae were reared using standard culture methods. Larval growth was recorded every 10 days and larval survival was recorded at 50 days post hatch. In general, broodstock fed with diets containing higher water content (HWHAs and HWLAs) and higher astaxanthin (HWHAs) had higher egg production and efficiency of egg output, lower egg incubation mortality and higher larval growth and survival. Broodstock fed with higher water content diets consumed less feed compared to control group. Also, broodstock fed with HWHAs and HWLAs recovered faster in terms of body condition than the control group. The egg bound mortality of female fish was significantly higher in control broodstock compared to broodstock fed with HWHAs and HWLAs. Broodstock fed with higher astaxanthin (HWHAs) had significantly higher fertilization success than other two groups however; no differences were found in proportion embryos with normal cleavage among different groups. Larval survival was significantly higher in HWHAs broodstock compared to other two groups. Our results showed that increased water content and astaxanthin levels in the diet could improve the condition and fecundity of Atlantic cod broodstock.     

太平洋鳕(Gadus macrocephalus)亲鱼驯化培育与早期发育特征

采捕山东威海外海黄海海域的太平洋鳕(Gadus macrocephalus)亲鱼进行驯化和培育,在人工条件下成功驯化存活野生亲鱼49尾,经短期促熟培育后,通过人工授精方式获得了多批次受精卵.对胚胎和早期仔鱼发育过程进行了观察,详细描述了从受精卵到早期仔鱼各发育时期的形态特征.结果显示,太平洋鳕成熟卵子为沉性卵,圆球形,卵径为0.9-1.1 mm,无油球.胚胎发育分为5个时期,分别为卵裂期、囊胚期、原肠胚期、神经胚期和器官形成期.在水温为9-10℃、盐度为27-29的海水中孵化,受精卵历时312 h 30 min孵化出膜.初孵仔鱼全长为(3.85±0.12) mm,6日龄仔鱼开口,肛门与外界相通,进入混合营养期.8日龄仔鱼卵黄囊消耗殆尽,开始进入外源性营养阶段.仔鱼开口饵料为轮虫(Rotifer),12日龄开始摄食卤虫(Artemia saline)无节幼体.6日龄仔鱼鳔原基形成,16日龄鳔充气成为亮泡状.12日龄仔鱼形成肠道第1个生理弯曲,22日龄仔鱼第2个肠道生理弯曲形成.研究结果可为太平洋鳕亲鱼驯化培育和苗种培育提供基础资料.     

Artificial Spawning of Tilapia Eggs1

A stripspawning methodology was evaluated for tilapia (oreochromid) species. This technique achieved an average hatching success of 68.6 ± 3.6% (N= 31). Female fecundity and spawning frequency were dependant on both genetical and husbandry factors. Egg yields for Oreochromis niloticus, O. mossambicus, and O. niloticus±O. mossambicus hybrids averaged 4.54, 10.86 and 10.36 eggs/g female/spawn, respectively. Female broodstock that were adapted to an intensive spawning regime exhibited a significant increase in fecundity. Additionally, egg survival was not affected by hydration for up to 15 minutes prior to fertilization. Results suggest that the strip spawning of tilapia species may be an efficient method of providing viable gametes for hatchery purposes.     

亲鱼脂类营养对鱼类生殖性能的影响

亲鱼饲料的营养质量是影响生殖性能的主要因素之一,目前的研究大多集中在脂类营养方面。本文主要综述了饲料脂类成分对亲鱼的产卵量、卵和仔鱼质量、胚胎发育、精卵的脂肪酸构成的影响,以及营养成分影响生殖性能的机制。