Effects of different feeding regimes on ovarian maturation and spawning of pond-reared giant tiger prawn in Thailand

Large pond-reared Penaeus monodon were used in three maturation and spawning trials lasting 60 days. One group of prawns was fed a fresh diet only; a second group was supplied a fresh diet combined with a formulated pelleted diet; a third group of prawns received the formulated diet only. Total maturation (N = 66 and 55) and spawning events (N = 63 and 48) were much greater for prawns receiving only the fresh diet, and the combined fresh with formulated diets, respectively. Prawns receiving only the formulated diet matured only 12 times, and spawned 11 times. Prawns fed a fresh diet produced significantly more eggs than those given a formulated diet alone. No significant differences were seen in eggs produced per spawning event, % fertilization, % hatch or % metamorphosis from egg to protozoea. Female prawns exhibited greater mortality than did males, while females on the fresh diet only had greater mortality than did other females, presumably due to greater handling and other stress factors. Female prawns on a combined diet had lower mortality than other females. The formulated diet used is suitable for supplementation, but not as a sole maturation food.     

Sperm Quality of Pond-Reared and Wild-Caught Penaeus monodon in Thailand1

Sperm quality, as determined by visual examination and by reaction with “egg-water” was not significantly different (P > 0.05) for sperm obtained by electro-ejaculation from ablated or non-ablated pond-reared Penaeus monodon. Nor was sperm quality different between pond-reared and wild-caught prawns. Normal sperm, determined by appearance, ranged from 17.1 to 21.0%, while reactive sperm ranged from 1.5 to 3.0%. There were, however, significant correlations (P < 0.01) between spermatophore weight and prawn weight (r= 0.73, N= 434). Male prawns weighing 4150 g produced on average spermatophores weighing 22.7 mg and containing 0.8 million sperm, while prawns weighing 61-90 g produced on average spermatophores weighing 56.6 mg with 2.5 million sperm. Ablation did not increase spermatophore size or sperm quality, although it significantly increased mortality of ablated males. Male prawns could be re-ejaculated at about weekly intervals with no change in sperm quality. Wild-caught female prawns artificially inseminated with spermatophores from electro-ejaculated males produced normal spawns with 51% average egg fertilization, and 41% nauplii hatch success. Nauplii hatch success following spawning increased from >60% for newly inseminated females to near zero after 30 days post-insemination, indicating spermatophore depletion and/or deteriorated sperm quality during spermatophore storage in the thelycum. The findings of the present study indicate that electro-ejaculation and artificial insemination are relatively simple and practical methods for improving captive reproduction performance of closed-thelycum prawns such as P. monodon, and that pond-reared and wild-caught males produced sperm of similar quality.     

Reproductive Performance of Different Sized Wild and Pond-reared Penaeus paulensis Females

The present study analyzes the reproductive performance of three size classes of wild (average weight of 46.5, 55.0, and 63.2 g) and three size classes of pond-reared (18.4, 21.3, and 25.1 g) Penaeus paulensis females. Unilaterally eyestalk ablated females were placed for 70 d in 3.6 m diameter tanks at 6 individuals/m² and a 1.2:1 female-male ratio. Number of spawns, eggs, nauplii, fertilization and hatching rates were recorded every second day. The length of unfed protozoea I larvae was also recorded. Larger broodstock shrimp tended to suffer higher mortality rates. Smaller, pond-reared females started spawning at 28.2 ± 4.1 g. The number of eggs and nauplii per spawning event were not significantly different between experimental groups (P > 0.05), but due to their higher spawning frequency, small wild females (46.5 ± 3.7 g) outperformed medium (55.0 ± 1.8 g) and large ones (63.2 ± 7.0 g). No relationship between protozoea length and spawner size was found. Optimum size for the maturation of wild P. paulensis females was estimated to be from 30 to 60 g. It is suggested that the use of this size range can potentially enhance nauplii production of P. paulensis .     

Reproductive Performance of Macrobrachium rosenbergii Females in Captivity

Abstract.— The breeding frequency, fecundity, egg hatchability, larval output and viability of pond-reared, mature Macrobrachium rosenbergii females were individually followed up during 180 d. Sexually mature prawns were maintained under controlled laboratory conditions (28.7 C and 12-h light/d) in a 190-L freshwater recirculation system and fed a formulated diet. Ovarian development, moulting and spawning events were checked daily. At least six consecutive moults were recorded for each of the 18 females. The duration of the intermoult period averaged 27.5 d and was not affected by ovarian development or spawning, but intermoult periods followed by spawning had significantly lower growth rates. From a total of 126 moulting events recorded, egg laying successfully followed 76 (60.3%) of them. The number of eggs per spawn (NES) varied from 26,587 to 74,775 for females weighing 20.0 to 55.8 g. The relationship between NES and female size (W; in g) was found to be NES = 484 + 1454W ( r ²= 0.74). Results suggest that the number of viable larvae produced per egg clutch may be increased by in vitro incubation, as the losses of eggs, which usually occur under in vivo incubation, are prevented. The present study illustrates that under adequate and stable rearing conditions, M. rosenbergii females are able to spawn up to five times during 180 d, in comparison to three to five times per year as reported for wild prawn populations.     

Tissue Lipid Content and Fatty Acid Composition of Penaeus monodon Fabricius Broodstock from the Wild

Tissues (hepatopancreas, muscle, gonad) of wild Penacus mordon females with ovaries in different stages of development and males were analyzed for Upid content and fatty acid composition. Hepatopancreatic tissue had the highest mean levels of lipid at 15.72–25.20% in females and averaged 46.20 ± 1.53% in males. Levels of Lipid in the muscle were low with no marked variation throughout the maturation s-es. Ovarian lipid levels increased significantly at stage II (early maturing ovaries) and remained high through stage IV (fully mature ovaries). Peak lipid level was found at stage III (late maturing ovaries) and coincided with a decline in hepatopancreas lipid. Ovarian and hepatopancreatic lipids declined drastically in spent females. Profiles of fatty acid in the tissues consistently showed the presence of PUFA 204n-6, 20:5n-3 and 22611-3, with high levels in the polar lipid fraction of vitellogenic ovaries. These values were reflected in the male testis and spawned eggs. The finding suggest storage and utilization of lipids for maturation and spawning processes and that the phospholipids were mainly responsible for increases in ovarian lipids. The type of fatty acids present in maturing prawn ovaries is indicative of their importance in reproductive physiology.     

Observations on growth, sexual maturity and spawning performance of pond-reared Penaeus merguiensis

This 12‐month preliminary study investigated the development of sexual characters, primary sexual maturity, ovarian maturity and spawning performance of pond‐reared Penaeus merguiensis in relation to culture conditions in south‐east Queensland, Australia. Post‐larvae of P. merguiensis were produced and cultured in two 60‐m³ tanks during the first 14 weeks. Before winter, they were harvested and stocked in three different overwintering facilities: a 200‐m² covered pond, two 60‐m³ outdoor tanks and a 15‐m³ indoor, recirculated tank at a stocking density of 10 individuals m^?2. The development of sexual characters was found to be similar to that reported previously in wild P. merguiensis. Males matured at younger ages and smaller sizes than females. Overall, the average size at primary sexual maturity of pond‐reared P. merguiensis was 23.1 mm carapace length for males (possessed spermatophores) and 29.3 mm for females (being impregnated). Water temperature and the availability of natural food strongly influenced prawn growth, maturity rate and their subsequent spawning performance. Growth, maturity rate and spawning performance of prawns in the covered pond were significantly higher than in the other overwintering facilities. Prawns started mating at 6–7 months, reached full ovarian maturation and spawned as early as about 8 (peaked at 9–11) months from hatching, producing high fecundity and viable larvae. There was a strong relationship (P < 0.001) between prawn size and fecundity. The results of this study suggest a potential for using pond‐reared broodstock P. merguiensis for hatchery production and for domestication or selective breeding programmes.     

Maturation and spawning performance of pond-reared Penaeus merguiensis in different combinations of temperature, light intensity and photoperiod

The combined effects of temperature (23 and 27 °C), light intensity (1100 and 2 lux or ≈ 21.5 and 0.04 μEinst m^?2 s respectively) and photoperiod (10 h light/14 h dark and 14 h light/10 h dark) on ovarian maturation and spawning performance of ablated pond‐reared Penaeus merguiensis were investigated in a 51‐day experiment. The results showed that temperature was the most influential factor, followed by light intensity, whereas the effect of photoperiod was minor. As the maturation process progressed, the effects of temperature and light intensity became stronger while that of photoperiod became less significant. Temperature significantly affected all the reproductive parameters assessed. Prawns in the 27 °C treatments outperformed those in the 23 °C treatments (P < 0.05). The effect of light intensity was found to have a significant effect (P < 0.05) only on the proportion of spawners (prawns that spawned) and spawning rate. More prawns spawned at a higher rate under dim light (2 lux) than under strong light (1100 lux). Photoperiod affected only the proportion of prawns reaching stage III of ovarian development (P < 0.05). There were interactions between temperature and light intensity affecting the proportion of prawns reaching stage III and, although not significantly, the proportion of spawners (P = 0.177), fecundity (P = 0.134) and survival (P = 0.061). Overall, it is recommended that a combination of 27 °C, 2 lux and 10 h light/14 h dark is suitable for the maturation of pond‐reared P. merguiensis. There were indications that temperature can be used to control the rate of ovarian maturation. Also, it is possible to increase light intensity up to 1100 lux in P. merguiensis hatcheries if prawns are ablated.     

Spawning Characteristics of the South African Mudcrab Scylla serrata (Forskål) in Captivity

Scylla serrata is a potential aquaculture species in Southern Africa. Information about its reproductive biology is required as a prerequisite to establishing hatchery technology. Adult female S. serrata were caught in the Umlalazi estuary on the subtropical east coast of South Africa and kept in captivity to observe and record spawning characteristics. Data collected included crab size and mass, time in captivity prior to spawning, fecundity per batch, relative fecundity, individual egg mass and size, size of zoea 1 larvae, incubation time, and hatch success rate. Of the 119 crabs kept in captivity 83% spawned in the maturation system– most within 40 d of capture. The crabs were highly fecund (mean relative fecundity per batch = 10,655 ± 4,069 eggs/g female) and the majority of the batches hatched within 288 h (12 d) at 27 C. Spawning in captivity occurred throughout the year, with a peak in late winter/early spring. This differs slightly from records of ovarian maturity stages of the crabs in the wild. A pattern of synchronous spawning was recorded where the females were observed to extrude their eggs in groups, commonly within 3 d of one another, separated by long periods of inactivity, suggesting an exogenous spawning cue. A total of 1,374,488 zoea larvae were obtained per kg of female per month. This means that if sufficient mature females can be caught from the wild, these could be used for stocking hatchery operations. The crabs were easy to maintain, mature, and spawn in captivity. This will facilitate future domestication which will eventually reduce the need for wild caught broodstock. The spawning characteristics of South African 5. serrata At in well with those observed for the genus throughout its distribution implying that ecological and fisheries management could be similar.     

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.     

Embryonic development of Ganga river prawn Macrobrachium gangeticum (Bate)

Macrobrachium gangeticum (Bate) are commercially valuable prawns that are broadly distributed in the Ganga river that flows from northern to eastern India. We studied embryonic development from cleavage (blastomeres), segmentation, formation of optic vesicle, eye pigment development to larva formation, as these data are largely unknown in this species. We conducted this study using mature M. gangeticum broodstock placed in freshwater tanks. Just after spawning, females were kept in separate aerated tanks, where fecundity was estimated from the total number of eggs. Thereafter, egg samples from berried females were used to study their embryonic stages. The correlation coefficient between size and prawn weight, egg weight, egg number, body weight and egg mass of different sizes of prawns was analysed. Our results show that an increase in prawn size led to an increase in egg weight and egg number while decreases in body weight:egg mass ratio was noticed. Further results indicate that an increase in prawn weight had a positive impact on egg weight and egg number. The embryo development stages were used in this study as a tool to evaluate the development process of the prawn in a hatchery environment.     

池塘养殖斑节对虾生长、发育与性成熟

为了解不同养殖条件下斑节对虾的生长、外生殖器发育、性腺发育及性成熟之间的关系,对其养殖进行跟踪调查研究.结果显示:①斑节对虾雌雄外生殖器官发育和头胸甲长呈线性关系;②不同养殖环境条件下,斑节对虾性成熟生物学最小型个体无显著差异.雄性精荚出现的生物学最小型个体为头胸甲长3.1 cm,体长11.1 cm,体质量20.0 g;雄性性成熟个体的头胸甲长3.7 cm,体长13.0 cm,体质量37.0 g.池养雌性斑节对虾的性成熟生物学最小型个体以纳精囊的发育完全(可与雄虾交配)为标志,其最小性成熟个体的头胸甲长4.3 cm、体长15.1 cm、体质量53.0 g,雌性性成熟个体为头胸甲长5.0 cm,体长17.0 cm,体质量75.0 g以上;③池塘养殖斑节对虾性成熟与日龄和养殖环境相关.鱼塭雄虾精荚出现的最早时间为日龄120 d前后,其性成熟日龄约为160 d;池塘养殖雄虾精荚出现的最早时间为日龄150 d前后,其性成熟日龄约为260 d.鱼媪雌虾最早交配发生在日龄165 d前后,性成熟日龄205～236 d,池养雌虾最早交配发生在日龄240～ 280 d,性成熟日龄295～360 d以上.     

Effects of silvering state on induced maturation and spawning in wild female Japanese eel <Emphasis Type="Italic">Anguilla japonica</Emphasis>

ABSTRACT:   The effects of silvering state of wild female Japanese eels Anguilla japonica on the success of induced maturation and the following spawning were examined. Thirty-eight females, collected in Mikawa Bay, were divided into four stages based on their silvering state: yellow (Y1), late-yellow (Y2), silver (S1) and late silver eels (S2). Despite injections of salmon pituitary extract (SPE) through the standard technique, Y1 and Y2 eels did not respond to the treatment with undeveloped gonad (gonad-somatic index [GSI]: 0.3–0.9), and all these females died by 5 weeks, probably due to an abnormal physiological condition. Most S1 (81%) and S2 eels (100%) matured completely (GSI: 17.8–51.4), and finally spawned successfully (69% for S1, 89% for S2). S2 eels fully matured with oocytes of over 750 μm in diameter by significantly smaller number of injections of SPE (5–6 times) than the case of S1 eels (6–8 times). The amount of eggs released by S2 eels (0.65 ± 0.11 g/fish per body weight [BW]) was significantly larger than those by S1 eels (0.54 ± 0.09 g/fish per BW). There was no difference in fertilization and hatching rates between eggs released by S1 eels and those of S2 eels. These results indicate that the success of induced maturation and spawning in wild female Japanese eels depends on their silvering state, and matured eggs can be obtained efficiently through the use of S2 eels rather than other stages.     

Temporal Variation in Egg and Larval Productivity of Eyestalk Ablated Spawners of the Prawn Penaeus monodon from Cook Bay, Australia

This paper reports on the variability in spawner performance and viability of the eggs and larvae of Penueus monodon from a single geographical region (Cook Bay, Australia). Data is presented from seven separate experiments spawning eyestalk ablated P. monodon conducted between Sep tember 1992 and July 1994. These experiments used 200 spawners from which 290 spawns were assayed. Total egg and larval (Nauplius, and ha,) production values per prawn were calculated and were significantly different ( P < 0.05) between experiments. Spawner weight and number of spawns per prawn also varied significantly between experiments and, although these factors afiected egg and larval productivity, they accounted for only a small percentage of the observed variability. The cause of this variation is unknown but it may be due to differences in the age of the spawners and to seasonal environmental effects. The variation in reproductive success of wildcaught spawners probably reflects differences in overall condition of the spawners and/or their nutritional status at different times. Understanding the causes of variation in productivity is important if hatcheries are to improve the reliability of supply of larvae for the prawn farming industry.     

Oogenesis and relevant changes in egg quality of abalone Haliotis discus hannai during a single spawning season

Oogenesis of abalone Haliotis discus hannai was examined histologically during a single spawning season using broodstock of various maturation conditions, which were controlled by effective accumulative temperature (EAT). The quality of eggs spawned was determined in relation to oogenesis. For histological examinations, three to five females were sacrificed at 300, 600, 850, 1050, and 1150 °C days EAT, without induction of artificial spawning. Other females were successfully induced to spawn at 700 °C days EAT and were reared following spawning. Three of these females were then sacrificed every 200 °C days EAT until 1300 °C days EAT. Gonad histology showed that two oocyte cohorts matured in H. discus hannai ovaries during a single spawning season. One mature oocyte cohort could be spawned in multiple times. The second oocyte cohort started developing after the first oocyte cohort had been spawned or reabsorbed, and became fully mature 400 °C days EAT after the first cohort was depleted. For egg quality measurements, three to five females were successfully induced to spawn at 850, 1050, 1150, 1900, and 2350 °C days EAT (Experiment 1). Three females were induced to spawn twice, at 700 and 1500 °C days EAT, resulting in two batches of eggs from the same individuals (Experiment 2). Total lipid and protein content of eggs were measured and were greater in eggs from the second cohort than in eggs from the first cohort. No carbohydrates were detected in eggs and there was no difference in cytoplasm volume between the two cohorts. In hatcheries producing H. discus hannai, it is important to increase post-larval starvation tolerance by increasing the quality of eggs, to yield higher and more consistent survival. The results of this study suggest that H. discus hannai hatcheries should use eggs from the second oocyte cohort, which are of higher quality, rather than eggs from the first oocyte cohort.     

Characterization and comparison of variations in reproductive performance of Chitralada strain Nile tilapia, Oreochromis niloticus (L.)

In an attempt to better understand and characterize the variability in the female reproduction of individual Thai‐Chitralada strains of Nile tilapia, Oreochromis niloticus (L.), tagged mature females (n=68) from a single population were monitored in a hapa‐in‐pond system over a 12‐month experimental period. Spawn female⁻¹, eggs female⁻¹ day⁻¹, eggs kg female⁻¹ day⁻¹, day spawn⁻¹ and weight (g) at first spawning of individual females were determined from the regular weekly sampling of weight (g) and eggs per spawn. For analysis, the females were grouped into two, high spawning (HSF) and low spawning frequency (LSF) classes based on their spawning frequency (SF) record. Moreover, nested under these two classes were two groups each based on growth rate, i.e., high frequency – large size (HL), high frequency – small size (HS), low frequency – large size (LL) and low frequency – small size (LS). There was no difference in eggs spawn⁻¹ among all females. The HSF group produced 68% and 361% more eggs female⁻¹ day⁻¹ than the population mean and LSF group respectively. Eggs female⁻¹ day⁻¹ and spawn female⁻¹ remained high in the HSF group and low in the LSF group throughout the 12‐month experimental period. This suggests that individual female spawning activity is consistent within a population in a common environment. The inter‐spawn interval increased with age in all four groups, and day spawn⁻¹ was shorter by 130% in HSF females compared with day spawn⁻¹ in LSF. The HSF group also spawned more successively (≥3), while the LSF group of females had fewer successive spawns (≤2). Body weight (g) had no influence on the number of eggs produced. The study indicates that separating frequently spawning females could be used as an important strategy to improve commercial seed production of Nile tilapia.     

Reproduction of striped bass, Morone saxatilis (Walbaum), broodstock: monitoring maturation and hormonal induction of spawning

Abstract Levels of gonadal steroid hormones were quantified in an adult striped bass, Morone saxatilis (Walbaum), broodstock during their gametogenic cycle. Blood plasma concentrations of Estradiol (E₂) and testosterone in females, or 11-ketotestosterone(11-KT) and testosterone (T) in males, were used as indicators of maturation. In both sexes, hormone levels were low in summer but increased significantly by late October to intermediate levels which were then maintained until late January. They then increased again rapidly to maximum pre-spawning values attained in late February or March, and subsequently decreased during the spawning period (April and May) with an increased incidence of spent fish with low hormone levels. The changes in blood hormone concentrations coincided with annual changes in photoperiod and water temperature that may be useful landmarks for maturation in captive broodstock. Mature females were implanted with pellets containing a dose of approximately 20 μg/kg body weight of [D-Ala⁶-Pro⁹-Net]-LHRH (GnRHa) in a matrix of cholesterol (CH) and cellulose. In April, they had not yet begun final oocyte maturation (FOM) and were too immature for conventional induction of spawning by injection with human chorionic gonadotropin (hCG). In early April, females given two 95% CH (slow hormone-release) GnRHa pellets (95/95) or females given one 80% CH (fast hormone-release) GnRHa pellet and one 95% CH GnRHa pellet (80/95) spawned within 13 days treatment (n= 4) with good egg fertility (76 ± 7% of total) and hatch rates (62 ± 15% of fertile). Females given dual fast-release GnRHa pellets (80/80) or control (Sham) pellets did not spawn or show evidence of increased oocyte diameter or development. In late April, four of six females given the 80/95 GnRHa pellet combination spawned within 9 days. Three fish produced fertile eggs (54 ± 18%). one spawned overripe eggs, and the remaining two increased oocyte diameter and maturation. Three corresponding controls did not spawn, and two of these showed clear signs of atresia within 11 days. In early May, some females were undergoing early FOM and were mature enough to be spawned by hCG injection. Three were given a single 80% CH GnRHa pellet and spawned within 6 days of treatment to produce fertile eggs (44 ± 6%). Of two other females given dual 80% CH GnRHa pellets, one spawned infertile eggs and the other failed to spawn within 9 days. GnRHa implants show promise as a technique for inducing spawning of captive striped bass broodstock although the optimum hormone delivery systems, dosages and release rates should be verified for fish at specific maturational stages.     

Preliminary Studies of Artificial Spawning of Channel Catfish as Male-Female Pairs or All-Female Groups in Recirculating Systems

Abstract— Channel catfish Icralurus punctatus are commonly spawned for research purposes by pairing of a hormonally treated female with a male in flow-through aquaria. A technique that allows hormonal induction of ovulation in females without pairing would accelerate genetic improvement and production of hybrid catfish. Over a 3-yr period (1994, 1995, and 1996) we conducted a series of trials to demonstrate the potential for artificial spawning in recirculating systems, and in 1996 we included trials with grouped females in addition to male-female pairs. Females were induced to spawn with injection of synthetic leuteinizing hormone-releasing hormone, and those that ovulated were stripped and the eggs were artificially fertilized. During 1994 and 1995, all fish were spawned by pairing, and in 1996, half of the females were spawned by pairing and half were grouped in tanks without males. Spawning success (percent of females that produced eggs), latency (time between injection and ovulation), and percent fertilization were observed for the paired and grouped trials. Spawning success was 36% in 1994 (N= 36). 22% in 1995 (N= 54). 41% in 1996 (N= 27). and 58% for grouped females (N= 26). The latency period was 113 ± 69 h in 1994, 109 ± 57 h in 1995, 44 ± 8 h in 1996, and 50 ± 9 h for grouped females. Percent fertilization was 16 ± 26% for eggs stripped in 1994, 72 ± 25% in 1995, 43 ± 20% in 1996, and 16 ± 37% for grouped females. In 1995, water quality problems were associated with high mortality of females (24 of 44 females; 4 of 44 males). The metabolic demands of final oocyte maturation in combination with methemoglobinemia caused by high nitrite levels could account for the increased vulnerability of females. These trials indicate that with adequate biofiltration, artificial spawning is possible in recirculating systems and with females grouped rather than paired. Further research on hormone dosage and timing of egg stripping will increase the utility of grouped spawning of channel catfish.     

Reproductive Performance of Pigmented and Albino Female Channel Catfish Induced to Spawn with HCG or Ovaprim

Reproductive performance of albino and pigmented channel catfish ( Ictalurus punctarus ) females was compared when spawning was induced with HCG (human chorionic gonadotropin) or Ovaprim ³ (domperidone and [d-Ala⁶, Pro⁹ NEt]-luteinizing hormone-releasing hormone). In 1985, only HCG was used to induce spawning. Albino females required more injections, had a longer latency period from time of first injection to spawning, and had lower spawning success (30%) than pigmented females (77%). No differences were observed between albino and pigmented females for time-of-day of spawning, number of eggs obtained by manual stripping, and number of eggs/kg body weight. In 1988, HCG, Ovaprim, and saline (control) were used to induce spawning. HCG induced spawning in 80% of albino and 71% of pigmented females. Ovaprim induced 67% of pigmented females to spawn, but only 2 of 5 albino females spawned. One of four pigmented females injected with saline spawned. Albino females yielded 40–50% fewer eggs/kg body weight than pigmented females. Other performance characteristics for albino and pigmented females were similar whether injected with HCG or Ovaprim. High temperatures encountered during the 1985 spawning season my have had a differential effect on albino and pigmented fish and may account for some differences in spawning success.     

Reproductive development, GnRHa-induced spawning and egg quality of wild meagre (Argyrosomus regius) acclimatised to captivity

The objective of the study was to acclimatise wild-caught meagre (Argyrosomus regius) to captivity to produce viable eggs for aquaculture production. Twelve meagre (3 males and 9 females, mean weight?=?20?±?7?kg) were caught and transported to a land-based facility on 26 October 2006. During, March to June 2007, all three males were spermiating and five of the nine females were in vitellogenesis with mean maximum oocyte diameter ≥550?μm. No spontaneous spawning was observed. Two hormone treatments, either a single injection of gonadotropin-releasing hormone agonist (GnRHa, 20?μg?kg(-1) for females and 10?μg?kg(-1) for males) or a slow-release implant loaded with the same GnRHa (50?μg?kg(-1) for females and 25?μg?kg(-1) for males), were used to induce spawning on three different dates on 26 March 2007, 4 May 2007 and 18 April 2008. From each spawning event, the following parameters were determined: fecundity, number of floating eggs, egg size, fertilisation and hatching success, unfed larval survival, and proximal composition and fatty acid profile of the eggs. In 2007, two females that were injected on 26 March and 4 May spawned a total of 5 times producing 9,019,300 floating eggs and a relative fecundity of 198,200 eggs?kg(-1) and two different females that were implanted on the same dates spawned 14 times producing 12,430,000 floating eggs and a relative fecundity of 276,200 eggs?kg(-1). In 2008, a pair that was implanted spawned five times producing a total of 10,211,900 floating eggs and a relative fecundity of 527,380 eggs?kg(-1). The latency period was 48-72?h. Parameters were compared between hormone treatments, date of hormone induction and parents determined by microsatellites. Percentage hatch and egg size were 70?±?0.3% and 0.99?±?0.02?mm, respectively, for GnRHa-implanted fish and were significantly higher (P?相似文献   

Reproductive periodicity of a Penaeus esculentus population near Low Islets,Queensland, Australia

Since a major expense in the aquaculture of prawns is the location of gravid females, an investigation into the spawning habits of a north Queensland population of P. esculentus was begun as part of a wider survey of the East coast penaeid populations. This 31-month survey revealed a period of high reproductive potential limited to the autumn for both the new season prawns just reaching sexual maturity and the remnants of the last season's prawn population. The autumn sexual maturation was followed by a quiescent period through early spring when maturation again proceeded to the spawning period in the following autumn. In fact, the new season prawns' rapid sexual and somatic growth in the autumn was repeated by both generations in the summer and early autumn during the 3-year study. The temporal coincidence of both sea temperature and rainfall patterns with both somatic and gonad growth was investigated.