GnRHa‐induced Multiple Spawns and Volition Spawning of Captive Spotted Rose Snapper,Lutjanus guttatus,at Mazatlan,Mexico

Sexual maturation and induced spawning treatments were carried out with captive spotted rose snapper, Lutjanus guttatus. A total of 3013 × 10⁶ eggs (64.7% were floating) were produced from eight treated females in 42 spawns induced with GnRHa implants during the course of the present study. GnRHa ethylene‐vinyl acetate copolymer effective doses were 204 ± 11 µg/kg in June 2005, and 224 ± 13 µg/kg in July 2005. General fertilization was 50.9 ± 34.5% and 12–14 h after spawning, viability of floating eggs was 90.4 ± 12.4%. Mean incubation period at 29–31 C was 18–20 h, and mean hatching was 94.4 ± 8.2% (73–100%). Newly hatched larvae were 2.18 ± 0.15 mm in total length (TL). One month after the last hormone experiment, previously GnRHa‐treated and untreated fish began spawning voluntarily. Hormone‐treated breeders had higher fecundity than untreated fish, producing 72.5 million eggs versus 13.9 million eggs for the untreated fish, over the following 11 mo. Combined data of volitional spawning for total egg fertilization, viability, hatching, and larval TL were 77.7 ± 1.8%, 90.3 ± 1.3%, 87.9 ± 2%, and 2.50 ± 0.12 mm, respectively. These results can ensure the sustainability of a commercial hatchery.     

Hormone-induced ovulation, natural spawning and larviculture of Brazilian flounder Paralichthys orbignyanus (Valenciennes, 1839)

Mature Brazilian flounders Paralichthys orbignyanus were captured in coastal southern Brazil and their reproduction in captivity was studied. Brazilian flounder will spawn naturally in captivity when the water temperature is around 23 °C and 14 h of light is provided daily. Females were induced for ovulation and hand stripping using human chorionic gonadotropin, luteinizing hormone‐releasing hormone analogue or carp pituitary extract. There was no need to inject males, as running milt was observed during the spawning season. Fertilization and hatching rates were above 80% independent of the hormone used. Notochord length at hatching was 2.18±0.07 mm for larvae hatching from naturally spawned eggs. Larvae were reared in salt water (30–35 g L^?1) at 24 °C and under continuous illumination. Larviculture was with green water (Tetraselmis tetrathele 50 × 10⁴ cells mL^?1). Rotifers (10–20 ind mL^?1) were offered as first food 3 days after hatching and gradually replaced by Artemia nauplii (0.5–10 ind mL^?1). Larvae settled to the bottom 20 days after hatching and completed metamorphosis within a week after that. The total length for newly metamorphosed juveniles was 12.9±2.2 mm and the mean survival was 44.8%. The results demonstrate the feasibility of producing Brazilian flounder fingerlings for stock enhancement or grow‐out purposes.     

Captive Breeding of Endangered Ompok pabda with Ovatide

The Pabdah catfish, Ompok pabda, was successfully spawned with the synthetic hormone Ovatide at two different doses (0.4 and 0.6 ml/kg of body weight of female). The latency period was 9–10 h at 0.6 ml compared to 10–12 h at 0.4 ml kg^?1 of body weight. All the females spawned successfully. Average rate of fertilization (75.5 %) and hatching (60.5%) was higher with a dose of 0.6 ml kg^?1, while lower fertilization (65.1%) and hatching rate (45%) were observed at 0.3 ml kg^?1 of body weight. Fecundity ranged from 80–130 eggs gm^?1 body weight of female. Eggs hatched between 12–14 h after spawning at a water temperature 28°–32°C. The mean egg diameter was 0.95 ± 0.15 mm.     

Larval and post‐larval growth,spat production and off‐bottom cultivation of the smooth venus clam Chionista fluctifraga

Harvesting practices of the clam Chionista fluctifraga show a decline in commercial size and densities, but no strategies have been developed to maintain clam beds. Aquaculture represents an alternative for preserving this resource. Adult clams from commercial grounds were used as broodstock. Conditioning, induction of spawning, cultivation of larvae, settlement of eyed larvae and nursing of postlarvae were performed in the hatchery for producing spat. Larvae and postlarvae were used to measure increase in shell height and data were fitted to exponential growth models. Spat were placed in floating trays and maintained in off‐bottom cultivation for 9 months. Samples of clams and tissues were collected monthly to measure absolute growth, shell height increase and a condition index. Larvae, postlarvae and juveniles showed exponential growth patterns. Mean shell height increased about 0.030 mm day^?1 during larval and post‐larval stages and 0.049 mm day^?1 during field cultivation. Pediveligers (height 215 ± 83 μm) entered metamorphosis at days 9–13 after fertilization, and postlarvae reached 3011.7 ± 325.5 μm (height) at day 60. After field cultivation, survival was about 95%; juvenile shell height was 20.6 ± 2.2 mm, and total weight was 5.3 ± 0.7 g. Growth rates were superior to natural conditions and the condition index was high throughout the study. Our results show that spat of C. fluctifraga can be produced in the hatchery, and that field production can be maintained in off‐bottom trays until reaching commercial size. Aquaculture activities for this species need to be established and evaluated.     

Spawning behaviour,early development and first feeding of the bluestriped angelfish [Chaetodontoplus septentrionalis (Temminck & Schlegel, 1844)] in captivity

Successful natural spawning of Chaetodontoplus septentrionalis in captivity from 19 March to 11 May, 2008 is described for the first time. A single male dominates a harem of two females, spawning with each at dusk, from 10 min before to 20 min after sunset. Each female laid an average 119 × 10³ eggs during the spawning period. Fertilized eggs were spherical, buoyant and had a diameter of 0.83 ± 0.02 mm (mean ± SD). Embryonic development lasted 15–18 h at 28.1 °C. Newly hatched larvae were 1.60 ± 0.07 mm in total length (TL) with 27 myomeres. Larvae completed yolk absorption within 3 days post hatching (ph) at 3.01 ± 0.08 mm TL. Ten days ph, the larvae had attained 3.95 ± 0.12 mm TL. Larvae were fed either 100% s‐type rotifers (Brachionus rotundiformis), 100% copepods (Microsetella sp.), a combination of the two (50%:50%) or without live feed (starved control) to determine the effect of live feed on the survival rate. The survival was significantly (P<0.001) higher in larvae fed a combination of diet than the others. These results indicate that C. septentrionalis is a potential species for captive breeding programs and the use of a combination of diet (s‐type rotifers and copepods) may be a suitable first food for the larvae.     

Production and storage of sperm from the black sea bass Centropristis striata L

Black sea bass Centropristis striata L. are protogynous hermaphrodites that develop and spawn as females before changing sex to male. Since all fish eventually become males, determining the relationship between sperm production, sperm quality and seasonal changes in plasma levels of testosterone (T) and 11‐ketotestosterone (11‐KT) could be useful for identifying appropriate males to maintain as broodstock. Milt and blood samples were collected three times during an 8‐week spawning season. Milt volume (3.5±0.76 mL kg^?1), sperm density (3.2 × 10⁸± 0.31 cells mL^?1), sperm production [11 × 10⁸±3.4 cells kg^?1 body weight (BW)] and sperm motility (80±0.6%) were at their highest during the first sampling interval and coincided with the highest 11‐KT levels (1.0± 0.11 ng mL^?1). All of the sperm indices decreased to their lowest levels during the final 3 weeks of the study. Sperm viability was highly correlated (adjusted R²=0.84) with sperm motility. Sperm cryopreserved in modified Mounib's extender (MME) had the highest post‐thaw motility compared with two other extenders. Post‐thaw motility of sperm cryopreserved in MME was not different from fresh after 90 days of storage. There was no difference in fertilization rates between fresh (69±2.4%) and post‐thaw (67±4.1%) sperm samples taken from the same male or among males. These results demonstrate that the quality of black sea bass spermatozoa is higher earlier in the spawning season and that acceptable post‐thaw fertilization rates can be obtained from cryopreserved sperm.     

Hormonally Induced Spawning, Embryonic Development, and Larval Rearing of the Southern Temperate Banded Morwong, Cheilodactylus spectabilis

Banded morwong (Cheilodactylus spectabilis) are of interest for marine finfish aquaculture in temperate southern Australia. To improve their ovulatory response, adult females were implanted during the autumn spawning season with slow‐release pellets containing 0–400 μg luteinizing‐hormone‐releasing hormone analogue (LHRHa)/kg body weight within 24 h of capture from the wild. Compared to the sham control group, animals treated with LHRHa produced significantly more eggs on each day after implantation for the following 7 d (91 ± 39 and 290 ± 38 mL) and a higher proportion ovulated (8/12 and 27/27). Of fish treated with LHRHa, 93% ovulated 2 d after implantation and 79% ovulated three times at 2‐d intervals, whereas control animals showed no cyclicity of ovulation and few ovulated more than once. Egg production was highest at the first ovulation after LHRHa treatment and declined at subsequent ovulations. In a second experiment investigating the range 100–400 μg LHRHa, there was no effect of dose rate on ovulation parameters, which additionally examined implantation either immediately after capture or after a 5‐d delay. Compared to immediate implantation, a delay resulted in a lower proportion of animals that could be stripped after implantation (100 and 50%, respectively) and the volume of eggs was lower (135 ± 15 and 107 ± 10 mL). The egg quality was poor following delayed implantation, resulting in no fertilization after artificial insemination compared with immediate implantation in which fertilization and hatch rates were higher for eggs collected on Day 2 after implantation (79 ± 8% and 58 ± 9%) than on Day 4 (23 ± 7% and 15 ± 6%). Thus, it is important to implant animals as soon as possible after capture to ensure optimum egg quality. Good‐quality eggs were buoyant and spherical and had a diameter of 1050 ± 25 μm with a single pigmented oil droplet of 190 ± 9 μm. When a separate large batch of eggs collected 2 d after implantation with 100 μg LHRHa was inseminated and cultured at 18 C, larvae hatched after 63 ± 2 h at a standard length of 2.6 ± 0.4 mm. Newly hatched larvae were buoyant and transparent with only a few melanophores, eyes were nonpigmented and jaws were nonfunctional. By the fourth day, jaws were functional and eyes were fully pigmented. Utilization of the endogenous yolk and oil was completed by Day 6, and swimming commenced with exogenous feeding. Larvae, initially fed lipid‐enriched rotifers followed by Artemia, reached 8.9 ± 0.7 mm length on Day 55, after which they metamorphosed to the postlarval paperfish stage of development, 22 ± 0.9 mm on Day 100, and 43 ± 1.0 mm at 6 mo of age. The results show that treatment of wild‐caught females with slow‐release pellets containing LHRHa is effective for the production of eggs for hatchery rearing.     

Fertilization by refrigerator stored sperm of the Indian major carp, Labeo calbasu (Hamilton, 1822)

This study reports on the spermatological properties, and on the development of a protocol for refrigerator storage (4°C) of Labeo calbasu (Hamilton, 1822) sperm for artificial breeding. Volume, motility, concentration and pH of the freshly collected sperm were 2.21 ± 0.53 (μL g^?1 of fish weight) (mean ± SD), 95 ± 1 (%), 1.93 ± 0.44 × 10⁹ (cells mL^?1) and 7.56 ± 0.17 respectively. Sperm activation was evaluated at different osmolalities of NaCl solution, and motility ceased completely when osmolality of the extender was ≥287 mOsmol kg^?1. Sperm retained motility for 24, 72 and 108 h, after refrigerator storage when sperm were undiluted, suspended in Alsever's solution and suspended in Alsever's solution containing 5% methanol respectively. Fertilization rate of fresh eggs with sperm stored at 4°C in Alsever's solution and Alsever's solution containing 5% methanol was 77% and 60% with a hatching rate of 60% and 43% respectively. The fertilization and hatching success of the stored sperm suggests potential to use refrigeration for transporting genetic material to hatcheries for artificial breeding of L. calbasu in Bangladesh.     

The effects of sperm–egg ratios on polyspermy in the blood clam,Tegillarca granosa

Polyspermy in Tegillarca granosa, which leads to failure or abnormal development of early embryos, appears to be directly related to varying sperm–egg ratios. We investigated the correlation between sperm–egg ratios and conditions of embryonic development by setting six strict sperm–egg ratios and subsequently scoring fertilization rate, abnormal rate, rates of trochophore and D‐shaped larvae. When sperm–egg ratios rose from 2 × 10²:1 to 1 × 10³:1, D‐shaped larvae rate dropped significantly from 78.8 ± 13.3% to 47.8 ± 14.9% (analysis of variance, P< 0.05), and to 3.6 ± 2.8% in the 2 × 10⁴:1 group. Using fluorescence microscope observation, polyspermy rates rose from 2.6 ± 0.8% to 72.9 ± 4.8% with increases in sperm–egg ratios. Sperm–egg ratios were therefore correlated with polyspermy rate, which seriously affected larval survival. Under the premise of higher fertilization rate, the sperm–egg ratios of ≤2 × 10²:1 appeared to be more beneficial for embryonic development of T. granosa.     

Influence of gamete density,salinity and temperature on the normal embryonic development of the mangrove oyster Crassostrea rhizophorae Guilding, 1828

Laboratory experiments were undertaken to determine the optimal environmental conditions and some of the other factors concerned in the development of Crassostrea rhizophorae embryos.Critical variables such as the number of spermatozoa per ovocyte during fertilization, the time of fertilization after gamete liberation, egg density, temperature and salinity were related to the proportion of normal D-larvae of C. rhizophorae in the resulting broods.The highest proportion of normal D-larvae was obtained at concentrations of 500–5000 spermatozoa/ovocyte, under conditions of 25‰ salinity at 25 ± 1°C. The optimal density of eggs, for the production of normal D-larvae, was 10⁴?4 × 10⁴ ovocytes/l. If fertilization was delayed for more than 45 min after liberation of spermatozoa the proportion of normal D-larvae was greatly reduced. The experiments demonstrated that the temperature for developing embryos should be below 30°C. At 20 and 25°C there was a high proportion of normal D-larvae 24 h after fertilization. The ideal salinity for embryonic development in C. rhizophorae was 25–37‰. Below a salinity of 16‰, less than 2.5% of the D-larvae were normal.     

Estimation of sperm concentration of wild and reconditioned brown trout, Salmo trutta L.

Sperm concentrations were assessed for milt samples taken from three stocks of brown trout, Salmo trutta L., (wild resident trout, and reconditioned and seareared sea trout) using direct counts, spermatocrit and an optical density of 1:1000 dilutions. There were significant linear relationships between spermatocrit and absorbance, and both spermatocrit and absorbance with sperm concentration. The results gave sperm concentrations from 2.2 × 10⁹ mL^?1 to 26 × 10⁹ mL^?1. Mean concentrations differed significantly between stocks; the reconditioned males had a mean concentration of 9.1 × 10⁹ mL^?1, sea-reared males 18.0 × 10⁹ mL^?1 and 8.0 × 10⁹ mL^?1 in 1994 and 1995, respectively, and wild resident males 13.3 × 10⁹ mL^?1. Sperm concentrations from all three stocks of trout were negatively correlated with length, and therefore, age. It was indicated that sufficient milt was being produced to achieve good rates of fertilization, although some of the larger trout did have low sperm counts, suggesting that fertilizing ability may decrease with male size or age within any one stock.     

Changes of sperm morphology,volume, density,and motility parameters in northern pike during the spawning period

Sexually mature males (BW?=?1600?±?150 g and TL?=?235?±?30 mm) of northern pike (Esox lucius L.) were randomly selected from a pond to record changes in their sperm quality parameters (spermatozoa morphology, sperm volume, density, and motility parameters) during the spawning season. The morphological and motility parameters changed significantly during the reproductive season with following trends. Only, head width was not changed during the spawning season. The longest spermatozoa and its flagellar length were found at the middle of spawning period (TL?=?38.24?±?0.37 μm and 35.14?±?0.26 μm) and shortest at the beginning of spawning period (TL?=?34.81?±?0.29 μm and 32.53?±?0.18 μm). Other morphological characters were always the lowest at the beginning of spawning period. Sperm volume was changed from 0.33?±?0.3 ml in February, 0.43?±?0.2 ml in March to 0.24?±?0.1 ml in April, and density from 16.2?±?0.2?×?109 spermatozoa ml^?1 in February, 19.4?±?0.2?×?109 spermatozoa ml^?1 in March to 4.8?±?0.2?×?109 spermatozoa ml^?1 in April. Same sperm velocity was observed in all spawning terms at 10 and 20 s after activation. Higher velocity was found at 30 and 40 s after activation in sperm collected at the middle and the end of spawning period. Significantly, higher percentage of motile sperm was observed at 20, 30, and 40 s after activation in sperm sampled at the end of spawning period. This study supports the hypothesis that longer spermatozoa swim faster.     

Live transportation of Macrobrachium rosenbergii (De Man) in chilled sawdust

Three cooling rates of 1.26±0.09°C h^?1 within 8 h (slow, T₁), 2.52±0.18°C h^?1 within 4 h (moderate, T₂) and 5.04±0.36°C h^?1 within 2 h (fast, T₃) were tested to cold‐anaesthetize farm raised Macrobrachium rosenbergii (De Man) (45–52 g) in each case from 25°C down to 15±1°C in a refrigerated chilling tank, provided with aeration. The cold‐anaesthetized prawns subjected to each chilling rate were packed in an insulated cardboard box (triplicate) between two layers of moist and chilled (2–3°C) sawdust, and kept inside a chilled storage cabinet at 15±1°C, for set durations of 6, 9, 12, 15 and 18 h. Survival was determined by revitalizing the prawns in aerated water with an initial temperature of 20°C, which was raised to 29±1°C within 3 h. The experiment was repeated using berried females acclimated to brackishwater of 12 g L^?1 salinity and the percentage survival recorded after live storage for durations ranging from 6 to 24 h at intervals of 3 h. Statistically valid safe durations for obtaining 100% survival of the cold anaesthetized and live stored prawns were determined using probit analysis at the three chilling rates tested, and were found to be 7.39, 6.98 and 4.54 h in the case of adult prawns, and 7.87, 8.17 and 6.43 h for berried females for T₁, T₂ and T₃ respectively. For practical purposes, the durations that yielded 95% survival rates were computed to be 16.47, 12.14 and 8.35 h in the case of adult prawns and 18.49, 19.02 and 11.11 h for berried females for T₁, T₂, and T₃ respectively. The berried prawns revitalized after live storage were incubated in tanks and the zoea larvae reared up to postlarvae (PL‐5), and compared against a control. No significant difference was found in larval hatch fecundity, survival rate and the production of PL L^?1 between the treatment and control, indicating that the method of cold anaesthetization and live storage of berried prawns could be used for successful transportation of broodstock.     

The Scale‐up of Spotted Rose Snapper,Lutjanus guttatus,Larval Rearing at Mazatlan,Mexico

The scale‐up of spotted rose snapper, Lutjanus guttatus, larval rearing is described. Fertilized eggs (480,000) were obtained from a 1‐d harvest of a natural spawning captive broodstock acclimatized for 1 yr and 6 mo in two fiberglass tanks (18 m³). Fourteen hours after spawning, 89.6% of the collected eggs were floating, of which 96.2% were transparent with live embryos. Incubation at 25–26 C lasted 21 h, with 90.2 ± 2.1% hatching percentage of normal larvae. The percentage of viable larvae at 48 h after hatching was 79.7 ± 1.9%. Initial stocking density was 10.4 ± 1.0 larvae/L 2 days after hatching (d.p.h.). A total of 22,600 juveniles (1256 ± 170 juveniles/m³) were harvested from six 3‐m³ cylindrical fiberglass tanks. Average survival was 12.1 ± 1.1%. Final mean length and weight were 5.5 ± 0.05 cm and 2.24 ± 0.04 g, respectively. Growth expressed in total length was TL = 2.1476e^0.0543t (R² = 0.9911). Final mean biomass and condition factor were 2.8 kg/m³, 12.3% and 1.346. General length‐weight ratio was W = 0.05460 LT^2.2306.     

Mass culture of fairy shrimp Streptocephalus proboscideus (Crustacea – Anostraca) and its use in larviculture of the Persian sturgeon, Acipenser persicus

This study was conducted with cysts of Streptocephalus proboscideus obtained from the University of Gent‐Belgium. The cysts were hatched in Environmental Protection Agency (EPA) medium. The nauplii were reared at the Sturgeon Research Institute using a pure culture of Scenedesmus obliquus alga supplied at a density of 5 × 10³ cell mL⁻¹ that gradually increased to 1 × 10⁴, 5 × 10⁴ and 1 × 10⁵ cell mL⁻¹ with the growth of the nauplii. The nauplii attained sexual maturity and started producing cysts in 8 days and yielded a mean cyst number of 220±40 female⁻¹ brood⁻¹ cysts. These cysts were used in the larviculture of Persian sturgeon, Acipenser persicus (Borodin). Forty‐three larvae of Persian sturgeon (mean weight: 15.4±1.1 mg; mean length: 27.1±2.7 mm) with roughly absorbed yolk sacs were stocked in three aquaria and fed S. proboscideus nauplii at 8‐h intervals. By the end of the experiment (day 5), the mean weight and length of Persian sturgeon larvae were 51.4±13.3 mg and 20.7±1.4 mm respectively.     

Storage of common carp, Cyprinus carpio L., eggs for short durations

In this study, a short-term storage of pre-activated eggs of the Japanese ornamental (koi) carp, Cyprinus carpio L., at three different temperature regimes is reported. Koi eggs were stored at low temperatures (6-9^oC), at variable or high temperatures (12-31C) and at moderate-stable temperatures (20-24.5^oC). Survival of the developing embryos was examined at the first and the second day post-activation, and in hatch-out larvae. Survival was calculated for each treatment by linear regression Y = a-bX (P± 0.01), except for eggs incubated at temperature of about 20 C(P > 0.1).The specific mortality index (b/a 100), as a ratio between the mortality rate (b) and the fertilization rate (a), indicated that the highest mortality is associated with the high and unstable storage temperatures, while the lowest mortality is with the moderate and stable storage temperatures. Eggs can be stored at moderate and stable temperatures for a maximal duration of 6h, yielding survival of hatch-out larvae higher than 50%. In two trials, fertilization potency of sperm stored in a domestic refrigerator (5-9^oC) for 5h, was compared with freshly stripped sperm and no differences in fertilization rates were found between the two treatments.     

Effects of three cold weather event simulations on early life stages of Southern Flounder (Paralichthys lethostigma)

ABSTRACT

To determine the minimum age/size at which Southern Flounder, Paralichthys lethostigma, can safely be moved to outdoor rearing facilities in Texas, we examined survival of simulated temperature drops in two distinct life stages: premetamorphic larvae and two size classes of postmetamorphic juveniles (small = 9.8 ± 0.3 mm in TL; large = 19.7 ± 0.6 mm). Temperature was lowered by ?0.33°C/h to 4°C, 7°C, or 10°C, held for 48 h and then raised at +0.33°C/h back to normal rearing temperature. Fish were monitored daily for survival. Larger postmetamorphic flounder had high survival for all temperature treatments (89%–100% survival), whereas both premetamorphic larvae and smaller postmetamorphic juveniles had low survival (<30%) for all temperature treatments.     

Some properties of bream Abramis brama L. sperm and its cryopreservation

Concentration and motility of spermatozoa, total protein content and its electrophoretic profile, glucose content, activity of aspartate aminotransferase (AspAT) and acid phosphatase (AcP) were assessed in 18 samples of semen from common bream Abramis brama L. males, which were hormonally stimulated to spermiation. Also, milt pooled from four donors was cryopreserved as pellets in vapours of liquid nitrogen (?80 °C) using four extenders (each with or without the addition of hen egg yolk). Mean spermatozoa concentration was 11.68 × 10⁹ mL^?1, and mean spermatozoa motility was about 60%. Protein content in seminal plasma was 2.08 mg mL^?1; both PAGE and SDS–PAGE showed considerable heterogeneity of protein fractions. Mean glucose content was over 11 mg%. AspAT and AcP activities were detected in both seminal plasma and spermatozoa extracts. As calculated to 1 × 10⁹ spermatozoa, AcP and AspAT activities were almost sixfold and 46-fold higher in spermatozoa than in seminal plasma respectively. In the best variant, cryopreservation attempts resulted in 66.6% of eyed embryos (compared with control fertilization) obtained after fertilization of eggs with cryopreserved semen.     

Effects of salinity on osmoregulation during the embryonic development of the bullseye puffer (Sphoeroides annulatus Jenyns 1842)

To evaluate the effect of salinity on the hatching rate, hatching time, survival percentage, osmoregulation pattern and the incidence of abnormalities in newly hatched larvae, embryos of Sphoeroides annulatus (Jenyns 1842) were exposed to 5, 12, 19, 26, 33, 35 and 40 psu. The hatching percentage (HP), survival percentage (PS), normal larvae (PN), deformed larvae (PD) and hatching time (HT) were significantly affected by salinity (P < 0.05). The embryos exposure to 5 psu caused that HP, PS, and PN had lower values (2.6 ± 0.32, 7.78 ± 0.88 and 70.37 ± 7.75% respectively), PD and HT had the highest values 26.67 ± 7.54% and 55.53 ± 0.59 h respectively. However, the survival of newly hatched larvae was not possible in 5 ups, though it was in 40 ups. Osmotic pressure (OP) remained constant in each salinity, whereas isosmotic points changed from 435.5 mOsm kg^?1 in 21 h post fertilization to 342.8 mOsm kg^?1 at 47 h post fertilization, obtaining a pattern of hyper‐osmoregulation at lower salinities and hypo‐osmoregulation in higher salinities. This study is the first carried out on embryos of this species; therefore, the obtained information is essential to improve strategies and growing conditions in their initial development.     

Effect of different chilling rates for cold anaesthetization of Penaeus monodon (Fabricius) on the survival, duration and sensory quality under live storage in chilled sawdust

The present work was carried out with a view of determining the chilling rates for cold anaesthetization and live storage of Penaeus monodon (Fabricius) in chilled sawdust, for live transportation. Three chilling rates of 1.38 ± 0.16 °C h^?1 within 8 h (slow), 2.76 ± 0.32 °C h^?1 within 4 h (moderate) and 5.52 ± 0.64 °C h^?1 within 2 h (fast) were tested to cold anaesthetize 144 farm‐raised P. monodon (22–25 g) in each chilling rate at 15 g L^?1 salinity, from 25 °C down to 14 ± 1 °C in plastic net boxes kept in a refrigerated chilling tank provided with aeration. Eight cold‐anaesthetized shrimps subjected to each chilling rate were packed in an insulated cardboard box (triplicate) between two layers of moist and chilled (2–3 °C) sawdust, and kept inside a chilled storage cabinet at 14 ± 1 °C for durations of 16, 20, 24, 28, 32 and 36 h. Survival was determined by revitalizing the shrimps in aerated water with an initial temperature of 20 °C, which was raised to 28 ± 1 °C at 2.7 °C h^?1 within 3 h. Statistically valid, safe durations for obtaining 100% survival were 22.9 ± 1.1, 19.1 ± 0.4 and 14.6 ± 1.1 h, using probit analysis at the slow, moderate and fast chilling rates respectively. The weight loss (1.5–8.8%) due to cold anaesthetization and subsequent revitalization of the packed shrimp was insignificant. Sensory evaluation showed significant improvement in general appearance, and also in colour as well as in flavour of the meat when compared with that of the freshly harvested dead shrimps. The texture as well as odour of the raw and cooked meat between treated and untreated shrimps was unaffected. The effects of chilling rates and shipping durations on sensory quality were insignificant. One hundred per cent survival was obtained for 24, 20 and 16 h for the slow, moderate and fast chilling rates respectively. Percentage survival of the shrimps at different durations was significantly different among the chilling rates, but pair‐wise comparison revealed that the slow and moderate chilling rates were identical. Hence, the moderate chilling rate, which took only 4 h, can be considered the optimum, though the choice of different chilling rates depends on the duration of live storage desired.