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1.
A need to improve larval rearing techniques led to the development of protocols for catecholamine‐induced settlement of flat oyster, Ostrea angasi, larvae. To further refine these techniques and optimize settlement percentages, the influence of salinity or temperature on development of O. angasi larvae was assessed using epinephrine‐induced metamorphosis. Larvae were reared between salinities of 15–35 and temperatures between 14.5 and 31°C. The greatest percentage survival, growth, development occurred when larvae were reared between 26 and 29°C and between salinities of 30 and 35. Larvae reared outside this salinity and temperature range exhibited reduced growth, survival and/or delayed development. Short‐term (1 h) reduction in larval rearing temperature from 26°C to 23.5°C significantly increased larval metamorphosis without affecting larval survival. Short‐term (1 h) increase in larval rearing temperature from 26°C to 29 and 31°C decreased larval survival and metamorphosis. To ensure repeatability in outcomes, tests showed that larvae sourced from different estuaries did not vary significantly in their metamorphic response to short‐term temperature manipulation and epinephrine‐induced metamorphosis.  相似文献   

2.
The effect of photoperiod on survival and growth of cultured young soles (Solea solea) was investigated from hatching to the age of three months, at 18° C. Two experiments were performed, comparing days with 12, 18 and 24 h light. The fishes were reared in 60 1 tanks, conical ones before metamorphosis, square ones with a sandy bottom from metamorphosis to the age of three months. They were fed on live food organisms for 1 month, on frozen flesh of the bivalve Laevicardium crassum for the two other ones.During the larval period, no significant difference was recorded in the survival rate but a better growth was obtained with 18 and 24 h light, suggesting a predominant diurnal feeding. From metamorphosis to the age of three months (mean weight: 1 g) no significant effect of the photoperiod on the survival and growth of the juveniles could be demonstrated.  相似文献   

3.
The tolerance of postlarval Macrobrachium rosenbergii to gradual and rapid increases in salinity was determined. Mortalities occurred at salinities around 25‰ and increased rapidly at levels ≥30‰ in both cases. However, acclimation substantially increased survival time at 35‰.Freezing point depressions of blood were measured from laboratory-reared M. rosenbergii postlarvae and juveniles exposed to various salinities from fresh water to approximately 35‰. The blood concentration was hyperosmotic to the medium at salinities from fresh water to about 17–18‰ and hypoosmotic at higher salinities. Postlarvae maintained a nearly constant blood concentration (freezing point depression = ?0.89 ± 0.13°C) over a wide range of external salinities (fresh water to about 27–30‰). The animals' osmoregulatory mechanisms failed at salinities ≥30‰, and thereafter the blood concentration paralleled that of the medium. The blood concentrations of juvenile shrimp grown for 5 months at salinities from fresh water to about 15‰ (freezing point depression = ?0.88 ± 0.07°C) closely resembled those of postlarvae.The osmoregulatory performance of young M. rosenbergii is generally similar to that of other brackishwater animals, but in their ability to hyperosmoregulate effectively in fresh water they more closely resemble fresh water species. It is suggested that M. rosenbergii may be able to conserve salt in dilute media by producing blood-hypoosmotic urine.An interesting stress symptom often preceded death of postlarvae in high salinities. The animals changed gradually from nearly transparent to opaque white and then died, usually within a day or so.  相似文献   

4.
Larvae and early postlarvae of the ocean quahog, Arctica islandica, were reared under experimental hatchery conditions. Mature eggs were stripped from ripe adults and exposed to a dilute solution of ammonium hydroxide for various lengths of time prior to addition of stripped sperm. The larval clams were reared through settlement and metamorphosis using the Wells-Glancy (centrifuged, incubated seawater) method of algal culture and/or modifications of standard hatchery techniques developed by Loosanoff and Davis. Experimental cultures were maintained at various temperatures ranging from 8.5° to 14.5°C. At temperatures of approximately 13°C, the minimum time to settlement was 32 days, while settlement was not observed in a culture maintained between 8.5° and 10.0°C until approximately 55 days after fertilization. Larval growth rates were significantly lower in the culture maintained at 8.5–10.0°C than in cultures maintained at 11.0–14.5°C. An optical micrograph sequence of larval stages from the straight-hinge stage through metamorphosis is presented to facilitate identification of Arctica islandica specimens isolated from plankton samples. While various workers have reported exceedingly low growth rates of juvenile and adult Arctica, growth rates of larval Arctica appear to be fairly “typical” of rates encountered within the class Bivalvia.  相似文献   

5.
Hydrated eggs obtained from a female milkfish, Chanos chanos, were artificially fertilized with the milt collected from a male injected with acetone-dried pituitaries of salmon. The fertilized eggs (1.1–1.25 mm in diameter) developed normally in seawater in basins and petri dishes at a salinity of 30–34‰, and successfully hatched in 25–28.5 hours at a temperature of 26.4–29.9°C. The yolk was completely absorbed in about 2.5 days and during this period many postlarvae died. A few larvae were reared up to 5 days but all died on the 6th day. Attempts were made to feed the postlarvae with freshly hatched trochophore larvae of oysters obtained from eggs artificially fertilized in the laboratory.  相似文献   

6.
The aim of the present study was to investigate the effects of different salinities (0‰, 6‰ and 12‰) and temperatures (23, 27 and 31 °C) on the food consumption, growth, blood biochemistry and haematocrit of Goldfish. After 45 days of exposure to different salinities and temperatures, Goldfish showed a good adaptation to these salinities and temperatures in terms of blood biochemistry (glucose and triglyceride) and haematocrit. Salinities (0‰ and 6‰) and temperatures (23 and 27 °C) did not affect the weight gain, specific growth rate, final biomass and feed conversion rates, but these parameters were significant (P<0.05) at 12‰ salinity and 31 °C temperature. Plasma total protein levels decreased with the increase in salinity (P<0.05), while they were independent of temperature. In conclusion, Carassius auratus, a freshwater stenohaline fish, showed good growth in saline waters with maximum 12‰ salinity and 31 °C temperature.  相似文献   

7.
Response surface methodology (RSM) in concert with central composite experimental design was firstly applied to optimize the culture condition for larval Genetically Improved Farmed Tilapia (GIFT) tilapia. Larvae were reared at different water temperature (16–37 °C) and salinity (0–20 ‰) for 35 days. Results showed that the linear and quadratic effects of temperature and salinity on specific growth rate (SGR), survival and hepatic HAMP-1 mRNA levels were statistically significant (P < 0.05). The interacting effects of temperature and salinity on SGR and survival were significant (P < 0.05), but the interaction on the levels of hepatic HAMP-1 and c-type lysozyme mRNA was not significant (P > 0.05). A significant increase in the levels of c-type lysozyme mRNA was observed as salinity increases; the quadratic effects of salinity were insignificant (P > 0.05). The regression equations of SGR, survival, the levels of hepatic HAMP-1 and c-type lysozyme mRNA toward the two factors of interest were established using multiple regression analysis, with the coefficients of determination being 0.980, 0.982, 0.968, and 0.949, respectively (P < 0.01). Based on RSM, the optimal temperature/salinity combination was obtained at 28.2 °C/6.8 ‰ of which the greatest SGR (10.08 % day?1) and survival (91.34 %) were simultaneously attained. Adequately increasing salinity would improve growth, survival, and innate immune function in larval GIFT tilapia.  相似文献   

8.
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.  相似文献   

9.
The upper incipient lethal temperatures of the freshwater mullet, Rhinomugil corsula, acclimated to 15, 20, 25, 30 and 35°C in fresh water, were 32.4, 34.1, 36.0, 36.2 and 36.5°C respectively, and the corresponding lower lethal temperatures were 10.5, 11.5, 13.2, 15.8 and 19.5°C. The mullet has a total tolerance (area of thermal polygon) of 569°C with an upper and lower thermal tolerance of 253 and 316°C2. Likewise, the total resistance of the mullet was 391°C2, with upper and lower resistance zones of 181 and 210°C respectively. The upper critical temperatures of swimming inhibition of R. corsula (17.2 cm; acclimation 30°C), determined in a swimming tunnel, were 35.2, 34.6 and 34.2 for water current velocities of 38, 62 and 77 cm s?1 respectively. The corresponding lower critical temperatures were 26.2, 27.5 and 28.1°C. These results indicated the stenothermal nature of the mullet by comparison with other fishes, e.g. Tilapia mossambica.In tests on the influence of ambient salinity on thermal resistance, R. corsula survived longest at 7‰ (iso-osmotic salinity). At salinities above and below this point, survival times were shorter at any lethal temperature. In a tentative scheme for quantification of stress due to temperature and salinity at death (after acclimation to 30°C and tested at 37°C), the hypo-osmotic and hyper-osmotic stress were estimated to be 50 and 31% of the thermal stress (100%) respectively.  相似文献   

10.
Physiological responses of pink abalone Haliotis corrugata were determined under different temperature and salinity conditions. Oxygen consumption rate was not affected by temperature and salinity. Ammonium excretion of pink abalone was inversely related to salinity. The O:N ratio indicated that abalone maintained in lower salinities had an interval of 4.9–7.7, which is indicative of a protein‐dominated metabolism, whereas the O:N in 35‰ was 28.8–35.5 for both temperatures, suggesting that carbohydrates were used as energy substrate. Haemolymph osmolality of abalone exposed to 20 and 24 °C was slightly hyperiso‐osmoconformic in salinity ranges of 20–35‰. The results of this study suggested that for optimized culture, pink abalone should be cultivated at 24 °C at a salinity of 35‰.  相似文献   

11.
The ideal water conditions for maximizing the performance of the nursery culture of glass eels harvested from the wild for aquaculture need to be determined for the New Zealand shortfin (Anguilla australis) and longfin (Anguilla dieffenbachii) eels. This study determined the survival and growth of glass eels reared under different temperature and salinity conditions in the laboratory. The growth and survival of shortfin and longfin glass eels reared in salt water (35‰) maintained at 25 °C was examined over 84 days from capture. The mean specific growth rate (SGR) was higher in shortfin [2.30±0.29% body weight (b.w.) day?1] than longfin glass eels (1.52±0.06% b.w. day?1), and survival was also higher in shortfin (76.0±4.16%) than for longfin glass eels (28.7±6.36%). A second experiment identified the effect of salinity (0, 17.5‰ and 35‰) and temperature (17.5 and 26.5 °C) on the acclimation, growth performance and survival of shortfin and longfin glass eels over a period of 84 days from capture. There was no incidence of mortality for either shortfin or longfin glass eels reared across all salinity treatments (0‰, 17.5‰ and 35‰) at 26.5 °C, while survival of shortfin and longfin glass eels reared at 17.5 °C was the highest in 17.5‰, followed by 35‰ and 0‰ treatments. Both temperature and salinity affected the SGR of shortfin glass eels, with the highest SGR observed for shortfin glass eels reared in 0‰ water maintained at 26.5 °C. In longfin glass eels, salinity alone had an effect on the SGR, with the highest SGR observed in glass eels reared in 0‰ water regardless of the water temperature (17.5 and 26.5 °C). In addition, the adaptability of glass eels to salinity was evaluated from the development and the physiological responses of gill chloride cell (CC) morphology. The number and size of CCs increased significantly with increasing salinity in both shortfin and longfin eels.  相似文献   

12.
The Monaco shrimp Lysmata seticaudata (Risso, 1816) is a marine ornamental species whose ecology and biology, as well as its larval culture has previously been addressed. The objective of the study was to predict and improve productivity of this species rearing protocol through modelling. The models developed intend to help aquaculturists to maximize survival to postlarva, decrease larval duration and increase synchronism of metamorphosis and newly metamorphosed postlarvae size by manipulating temperature, diet, first feeding period and stocking density.The models developed allow us to conclude that the L. seticaudata rearing protocol productivity can be improved by raising larvae at a density of 40 larvae L− 1 and fed newly hatched Artemia nauplii since hatching to zoea V, and with Algamac 2000™ enriched Artemia metanauplii from zoea V to metamorphosis to postlarvae.By providing more productive protocols to aquaculturists, destructive practices and wild collection may be reduced.  相似文献   

13.
Eggs of raised gilthead bream, Sparus aurata (L.), were incubated to hatching at various temperatures ranging from 7.7°C to 26.3°C. For four stages of development, the relationship between temperature and incubation time is given. Time from fertilization to hatching varies from 135 h at 11°C to 40 h at 21.3°C. In our experiments no egg hatched below 11°C or above 22°C. The highest hatching rate and the lowest rate of larval abnormalities were both observed at 14.5°C which is also the spawning temperature.  相似文献   

14.
Larvae of the yellow crab, Cancer anthonyi Rathbun, were reared through five zoeal stages and one megalops stage in the laboratory. Total larval development times were 33 and 45 days at 22°C and 18°C, respectively. Survival rates to the first crab instar, for larvae reared in recirculating systems on a diet of Artemia nauplii, were 26% at 22°C and 17% at 18°C. Although no larvae reared in glass containers at 22°C survived past the first zoeal stage, 11% of those in similar containers at 18°C reached the first crab instar. Bacterial infections were associated with most observed mortalities. Antibiotics failed to increase the survival rates of larvae reared in glass containers.Juvenile crabs were reared in individual containers and in communal aquaria through 14 crab instars. Although instar durations were shorter at 22°C than at 18°C, mean carapace widths were significantly greater at the lower temperature. Crabs in communal aquaria at 22°C were larger than corresponding crabs at the same temperature in individual containers. Crabs reared in aquaria at 22°C reached the twelfth instar with a mean size of 90.3 mm, 195 days after hatching. Sexually mature thirteenth stage laboratory-reared crabs were mated and their offspring were reared through the ninth crab stage.  相似文献   

15.
The combined effects of temperature and salinity on larval survival and development of the mud crab, Scylla serrata, were investigated in the laboratory. Newly hatched larvae were reared under 20 °C temperature and salinity combinations (i.e. combinations of four temperatures 25, 28, 31, 34 °C with five salinities 15, 20, 25, 30, 35 g L−1). The results showed that temperature and salinity as well as the interaction of the two parameters significantly affected the survival of zoeal larvae. Salinity at 15 g L−1 resulted in no larval survival to the first crab stage, suggesting that the lower salinity tolerance limit for mud crab larvae lies somewhere between salinity 15 and 20 g L−1. However, within the salinity range of 20–35 g L−1, no significant effects on survival of zoeal larvae were detected (P>0.05). The combined effects of temperature and salinity on larval survival were also evident as at low salinities, both high and low temperature led to mass mortality of newly hatched larvae (e.g. 34 °C/15 g L−1, 34 °C/20 g L−1 and 25 °C/15 g L−1 combinations). In contrast, the low temperature and high salinity combination of 25 °C/35 g L−1 resulted in one of the highest survival to the megalopal stage. It was also shown that at optimal 28 °C, larvae could withstand broader salinity conditions. Temperature, salinity and their interaction also significantly affected larval development. At 34 °C, the mean larval development time to megalopa under different salinity conditions ranged from 13.5 to 18.5 days. It increased to between 20.6 and 22.6 days at 25 °C. The effects of salinity on larval development were demonstrated by the fact that for all the temperatures tested, the fastest mean development to megalopa was always recorded at the salinity of 25 g L−1. However, a different trend of salinity effects was shown for megalopae as their duration consistently increased with an increase in salinity from 20 to 35 g L−1. In summary, S. serrata larvae tolerate a broad range of salinity and temperature conditions. Rearing temperature 25–30 °C and salinity 20–35 g L−1 generally result in reasonable survival. However, from an aquaculture point of view, a higher temperature range of 28–30 °C and a salinity range of 20–30 g L−1 are recommended as it shortens the culture cycle.  相似文献   

16.
Water salinity affects survival, growth and metamorphosis of anuran tadpoles. Hoplobatrachus rugulosus is considered not only as a freshwater amphibian but is also found in brackish wetlands. However, whether salinity change interferes with hatching, survival, body mass and development of H. rugulosus tadpoles is unknown. We found that salinity levels of <4‰ did not affect of survival or hatching of H. rugulosus eggs. At an early larval stage, tadpoles could tolerate up to 9‰ salinity for 96 h; however, body water content decreased when salinity was >5‰. After a 3‐week experiment, body weights of tadpoles exposed to 2‰ and 4‰ salinities were higher but that of the 6‰ group was lower compared with the 0‰ group. More than 90% of tadpoles exposed to 2‰ and 4‰ salinity showed complete metamorphosis. Salinity levels <4‰ promoted survival of tadpoles better than 0‰, whereas none of tadpoles in the 6‰ group became juvenile frogs in 50 days. Time taken to reach metamorphosis was shorter for 2‰ and 4‰ (47.22 ± 0.28 and 47.26 ± 0.33 days, respectively) than for 0‰ (49.31 ± 0.35 days). Juvenile frogs in the 2‰ group had greater body weight than the control. It could be concluded that salinity of <4‰ increased survival and body weight of H. rugulosus tadpoles, and shortened the time taken to reach metamorphosis.  相似文献   

17.
The effect of seasonal variation of environmental factors on daily shell growth rates (DGR) of postlarval Nodipecten nodosus was studied at the southern distribution limit of the species in Santa Catarina State, Brazil. Five deployments of hatchery produced postlarvae (initial shell height 0.5 mm) in the sea-based nursery were carried out from August 2000 to September 2001, and DGR and percent retrievals were recorded. Chlorophyll-a, seston, salinity, dissolved oxygen and turbidity were measured weekly, and temperature was recorded hourly. Additionally, DGR and retrievals were compared for postlarvae maintained simultaneously in the sea- and land-based nurseries (initial shell height 0.5 mm), and also for post-larvae deployed in the sea-based nursery at different initial sizes (0.29–1.1 mm). Mean DGR was significantly lower in late winter–early spring 2000 (0.045 mm day−1), intermediate in late winter–early spring 2001 (0.078 mm day−1) and significantly higher in the other seasons (late spring–early summer, 0.152 mm day−1; late summer–early autumn, 0.149 mm day−1 and late–autumn early winter, 0.130 mm day−1). Temperature was the best predictor of growth, which was least at temperatures below 20 °C. Growth rate was also minimal during a period of low salinity and high turbidity. Mean DGR was significantly higher in postlarvae deployed in the sea-based nursery than in those maintained in the land-based nursery. Loss of postlarvae in the sea-based nursery was initially higher in collectors transferred earlier to the sea (ca. 2–3 weeks post-set; shell height 0.5–0.8 mm), but percent retrievals were similar after postlarvae deployed to the sea ca. 4–5 weeks post-set (shell height 1.1 mm) were retrieved simultaneously with those deployed earlier. At retrieval, postlarvae deployed approximately 2 weeks post-set were larger than those deployed subsequently, but spat deployed 1 week post-set attained a similar size to those deployed 2 weeks post-set. A strategy to deploy postlarvae in the sea-based nursery at a size circa 0.5 mm is proposed as more advantageous than keeping them longer in land-based facilities. In southern Brazil, there is a wide window of opportunity to deploy post-larval scallops in the sea-based nursery in which growth is maximized, except when water temperatures drop below 20 °C.  相似文献   

18.
Grouper have to face varied environmental stressors as a result of drastic changes to water conditions during the storm season. We aimed to test the response of brown-marbled grouper to drastic and gradual changes in temperature and salinity to understand the grouper’s basic stress response. The results can improve the culture of grouper. Brown-marbled grouper, Epinephelus fuscoguttatus (6.2 ± 0.8 g) were examined for temperature and salinity tolerances at nine different environmental regimes (10, 20, and 33 ‰ combined with 20, 26 and 32 °C), in which the fish were subjected to both gradual and sudden changes in temperature and salinity. The critical thermal maximum (50 % CTMAX) and the upper incipient lethal temperature (UILT) were in the ranges of 35.9–38.3 and 32.7–36.5 °C, respectively. The critical thermal minimum (50 % CTMIN) and the lower incipient lethal temperature (LILT) were in the ranges of 9.8–12.2 and 14.9–22.3 °C, respectively. The critical salinity maximum (50 % CSMAX) and the upper incipient lethal salinity (UILS) were in the ranges of 67.0–75.5 and 54.2–64.8 ‰, respectively. Fish at temperature of 20 °C and a salinity of 33 ‰ tolerated temperatures as low as 10 °C when the temperature was gradually decreased. Fish acclimated at salinities of 10–33 ‰ and a temperature of 32 °C tolerated salinities of as high as 75–79 ‰. All fish survived from accumulating salinity after acute transfer to 20, 10, 5, and 3 ‰. But all fish died while transferred to 0 ‰. Relationships among the UILT, LILT, 50 % CTMAX, 50 % CTMIN, UILS, 50 % CSMAX, salinity, and temperature were examined. The grouper’s temperature and salinity tolerance elevated by increasing acclimation temperature and salinity. On the contrary, the grouper’s temperature and salinity tolerance degraded by decreasing acclimation temperature and salinity. The tolerance of temperature and salinity on grouper in gradual changes were higher than in drastic changes.  相似文献   

19.
Transport of post‐larvae shrimp used in aquaculture is an important element of successful cultivation because of the potential for stress during stocking procedures. To find optimum transport conditions, several bioassays were performed in the laboratory to evaluate survival of whiteleg shrimp Litopenaeus vannamei 5–30‐day‐old postlarvae under conditions similar to those encountered during transport from the hatchery to nursery and shrimp ponds. Postlarvae were exposed for 4 h to different temperatures and pH levels ammonia concentrations. Survival was significantly reduced after a 4 h exposure to pH 9 and was inversely related to temperature with or without 7 mg L?1 of ammonia. The 15‐ and 20‐day‐old postlarvae had higher survival rates than other ages. The lowest survival occurred in alkali conditions (pH 9), with 7 mg L?1ammonia at 30 and 32°C. To assure optimal survival of postlarvae during transfer from the hatchery to the nursery and shrimp ponds, we recommend temperatures below 28°C, pH no higher than 8, no ammonia and post‐larval age at least 15 days.  相似文献   

20.
ABSTRACT

Egg hatch, larval growth, and metamorphosis of southern flounder, Paralichthys lethostigma, were examined at 13, 17, 21, and 25°C in laboratory experiments. The experiments were separated into four developmental phases: (1) from fertilization until hatch; (2) from hatch until mouth opening; (3) from first feeding until the onset of metamorphosis; (4) from the onset until the completion of metamorphosis. Time to egg hatch were 109, 58, 39, 30 hours at 13, 17, 21, and 25°C, respectively. Size at hatch varied little among temperatures, while percent hatch was significantly higher at 17°C (P < 0.05). There was no significant difference in total length at mouth opening among temperatures (P > 0.05). However, those larvae raised at higher temperatures reached mouth opening earlier, as it took on average 7.4, 3.9, 2.8, and 2.2 days from hatch at 13, 17, 21, and 25°C, respectively. During phase three, the growth rate was optimal at 17°C, as growth rates were 0.046, 0.110, 0.106 and 0.096 mm/day at 13, 17, 21, and 25°C, respectively. Larvae in phase four completed metamorphosis sooner at higher temperatures than at lower temperatures. It took 26.4, 15.7, and 13.1 days to complete metamorphosis at 17, 21, and 25°C, respectively, while only 16% of those at 13 progressed to stage “G” within the 27 days that phase four encompassed. No difference in total length was found among treatments (P > 0.05) at the completion of metamorphosis, but fish in the 21 °C treatment had a significantly higher survival (P < 0.05). It can be concluded that southern flounder could be produced in the highest quantity and at the largest size by raising them at 17°C from fertilization until the onset of metamorphosis, and at 21 °C during metamorphosis.  相似文献   

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