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1.
Pacific white shrimp, Litopenaeus vannamei, exhibit a remarkable ability to tolerate low‐salinity environments, facilitating its culture far from coastal areas using various production systems at salinities less than 15 g/L. Recirculating aquaculture systems (RAS) and biofloc systems are usually operated using reconstituted sea salt (RSS), which is a considerable financial burden to commercial producers due to its higher price. Current study was carried out with the objective of testing the efficacy of a low‐cost salt solution to replace expensive RSS to grow shrimp under laboratory conditions. Low‐cost salt mixture (LCSM) was formulated to yield sodium, potassium, calcium and magnesium concentrations closely comparable to that of diluted seawater using agriculture grade sodium chloride, magnesium chloride, magnesium sulphate, potassium oxide, calcium chloride and sodium bicarbonate. Growth trials were conducted at three different salinities of 3, 6 and 15 g/L, incrementally replacing RSS with LCSM (0, 2.5, 25, 50, 75 and 100%) at four replicates per treatment. Twenty juvenile shrimp were reared for 42 days in 150 L polyethylene tanks. Ionic profile of water, ionic profile and osmolality of shrimp haemolymph were determined to justify growth and survival data through analysing ionic variations and osmoregulatory capacity of shrimp. At the conclusion, no significant differences were observed in survival, growth, osmoregulation and levels of cations in shrimp haemolymph between RSS and LCSM treatments at all salinities examined. Results reflect the potential use of LCSM to replace RSS which could be an excellent solution to bring down the cost of production in inland shrimp aquaculture.  相似文献   

2.
We evaluated the performance of whiteleg shrimp Penaeus vannamei (Boone, 1931) in response to different stocking densities and acclimation periods. Shrimp postlarvae were acclimated from seawater (30 g L?1) to low‐salinity well water (<1.0 g L?1) at a constant hourly reduction rate of 40, 60, 80 and 100 h. After acclimation to low‐salinity well water, postlarvae from each acclimation time treatment were stocked in three replicate tanks at densities of 50, 100, 150 or 200 shrimps m?2 for 12 weeks of growth. Salinity averaged <1.0 g L?1 for each growth study. The different treatments resulted in significant differences in both the final body weight and the survival rate (SR). Shrimp acclimated for 100 h showed substantially improved survival (83%) relative to shrimp acclimated for shorter periods. Shrimp yields for all cultured periods ranged from 0.32 kg m?2 in tanks stocked at 50 m?2 to 1.14 kg m?2 in tanks stocked at 200 m?2. We conclude that whiteleg shrimp can be successfully grown in low‐salinity well water, and that the growth, production output and SRs are significantly higher when shrimp are acclimated for longer periods.  相似文献   

3.
Shrimp farming at low salinity is a trend that will continue to grow globally. Performance of Litopenaeus vannamei postlarvae in the nursery at different salinities with a biofloc technology (BFT) system needs to be explored further, as the nursery is currently used as a transitional stage between the hatchery and grow-out ponds. Hence, this study evaluated the effect of seven salinity levels (2, 4, 8, 12, 16, 25, and 35 ‰) on the performance of L. vannamei postlarvae reared with a BFT system and zero-water exchange at 2000 org/m3. Additionally, this study evaluated the water quality of all salinity treatments. After 28 days of culture, the findings showed that, under biofloc conditions, salinity affected the performance of some variables of water quality in some cases, but only the combination of a high nitrite-N concentration (>4 mg/l) and low salinity (2 and 4 ‰) caused up to 100 % shrimp mortality in the first 2 weeks. In the rest of the treatments (8, 12, 16, 25, and 35  ‰), shrimp survival was >72 %. Shrimp mortality was affected by salinity, especially when it decreased from 35–25–16 to 12 and 8 ‰. The organisms reared at low salinities presented lower final weights and specific growth rate than those reared at higher salinities. An inverse relationship was shown between the ion concentration and the final weight of shrimp.  相似文献   

4.
Techniques for head starting or nursing postlarvae (PL) has received considerable attention with regards to nursery protocols, yet there is little data pertaining to the effects of nursery period on the final growout of shrimp to marketable size. This study was performed to investigate the influence of nursery duration on survival and growth of Litopenaeus vannamei during subsequent pond culture. For this research, a single population of high health PL were received from a commercial hatchery and held in a tank for acclimation, quantification, and distribution to nursery tanks or ponds. Treatments included direct stocking of 10-d-old postlarvae (PL10) into production ponds as well as the nursing of PL in a covered greenhouse nursery system for an additional 10 or 20 d. After nursing, the PL were harvested, quantified, and transferred to growout ponds. All ponds were stocked at a density of 35 PL/m2 and maintained under standardized conditions. Shrimp were fed with a 35% protein shrimp feed, twice daily during the 112-d growth trial. Ponds were aerated as needed using a maximum of 19 hp/ha to maintain adequate dissolved oxygen (DO > 3.0). No statistical differences (P >0.05) were found in survival, yield, or growth between treatments. At harvest, survivals during growout were generally higher in ponds with nursed shrimp (77% for PL20 and 79% for PL30) than in ponds receiving PL10 shrimp (67%). Yields were similar between treatments, ranging from 3,525 for direct stocked shrimp to 3,747 kg/ha for those that were nursed for 10 d. Although growth rates of PL under pond conditions will be faster than that of a nursery system, results suggest that a nursery period of at least 10 d helps improve survival during pond production and promotes better size uniformity. Shrimp nursed for 20 d showed little improvement in survival over shrimp nursed for 10 d but did result in a more uniform size of shrimp at harvest.  相似文献   

5.
Intensive Culture Potential of Penaeus vannamei   总被引：3，自引：0，他引：3  
Tank and pond rearing studies were conducted to assess the potential for intensive culture of Penaeus vannamei in South Carolina. Postlarvae were stocked in intensive nursery tanks at 500/ m2. Growth and survival were compared for shrimp reared in control fiberglass tanks and in tanks with artificial substrates (fiberglass screen). Addition of substrate improved survival (82% versus 58%), but not growth. Juvenile shrimp (mean weight, 1.3 g) from the nursery trial were stocked into 6 m diameter tanks at densities of 10, 20 and 40/m2. Growth rate was inversely related to stocking density, with mean sizes of 33.9, 32.5, and 26.7 g attained at the low, medium, and high densities respectively after 168 days. At harvest, standing crop biomass averaged 225.6, 442.0, and 685.4 g/m2 for the three densities. To further test the intensive culture potential, two 0.1 ha ponds were stocked with hatchery-reared postlarvae at densities of approximately 40 and 45/m2. The ponds were managed intensively using paddlewheel aerators and water exchange averaging 16–17%/day. The ponds were harvested after 138 and 169 days and yielded 6,010 kg/ha of 16.7 g (mean weight) shrimp and 7,503 kg/ha of 17.9 g shrimp, respectively. Average production was 6,757 kg/ha with a food conversion of 2.51. These data suggest good potential for intensive pond culture of P. vannamei in South Carolina and other areas of the continental United States.  相似文献   

6.
This study was designed to determine the production characteristics of the Pacific white shrimp, Litopenaeus vannamei, stocked into grow‐out ponds at three different sizes and ages. To meet this goal, three groups of postlarvae (PL) were obtained. The first group was placed in a nursery system for 21 d (N21), the second for 14 d (N14), and the third was stocked directly into ponds (DS). Shrimp from each nursery treatment (three tanks per treatment) were pooled and then subdivided for stocking into four replicate 0.1 ha ponds per treatment, another four ponds were stocked directly (DS) with PL8. All 12 ponds were stocked on the same day at a density of approximately 35 PL/m2, and cultured over a 16‐wk period and then drain harvested. After harvest, mean average weights (15.4, 16.9, and 14.9 g), survivals (63, 62, and 64%), FCRs (2.7, 2.5, and 2.7), and average yields (3592, 4005, and 3374 kg/ha) were determined for N21, N14, and DS, respectively. No significant (P > 0.05) differences were observed among treatments. Regardless of nursing time, nursed juveniles did not differ significantly in production characteristics from shrimp stocked directly from the hatchery.  相似文献   

7.
This study evaluated the zootechnical performance and enzymatic activity of Litopenaeus vannamei reared at different feeding frequencies during the nursery phase in biofloc system. The experiment consisted of four treatments, corresponding to the feeding frequencies of one, two, three and four times a day. Twelve‐day postlarvae (PL12) were stocked in 12 circular tanks at a density of 3,000/m2 for 35 days. These tanks were connected to a recirculation system supplied by a matrix tank where biofloc management was carried out. Water quality remained within acceptable limits for the species over the experiment. Food frequencies had no influence on survival (88.5–92.7%) and feed conversion ratio (1.5–1.7), but the final mean weight (0.43–0.56 g) was significantly higher in shrimp fed three times a day. This fact is probably associated with amylase (14.58 U/mg) and trypsin (23.84 U/mg) activities, as well as the significant increase of chymotrypsin (11.74 U/mg) and lipase (1.27 U/mg) in shrimp of this treatment at the end of culture period. Feeding three times a day provided the highest enzymatic activity and the best zootechnical performance of L. vannamei during the nursery phase in biofloc system.  相似文献   

8.
Litopenaeus vannamei (Boone) grown in ponds are exposed to salinities of less than 5 g L?1 during inland shrimp culture or to more than 40 g L?1 from evaporation and reduced water exchange in dry, hot climates. However, dietary requirements for shrimp grown in low or high salinities are not well defined, particularly for fatty acids. Feeding shrimp postlarvae with highly unsaturated fatty acids (HUFA) enhances tolerance to acute exposure to low salinity, as a result of better nutritional status, or/and specific effects of HUFA on membrane function and osmoregulation mechanisms. This study analysed the effect of HUFA supplementation (3% vs. 34%) on L. vannamei juveniles reared for 21 days at low (5 g L?1), medium (30 g L?1) and high salinities (50 g L?1). Juveniles grown at 5 g L?1 had lower survival compared with controls (30 g L?1) or shrimp grown at 50 g L?1, but no significant effect on survival was observed as a result of HUFA enrichment. In contrast, growth was significantly lower for shrimp grown at 50 g L?1, but this effect was compensated by the HUFA‐enriched diet. Osmotic pressure in haemolymph was affected by salinity, but not by HUFA enrichment. Shrimp fed HUFA‐enriched diets had significantly higher levels of eicosapentaenoic acid and docosahexaenoic acid in hepatopancreas and gills. These results demonstrate that growth at high salinities is enhanced with diets containing high HUFA levels, but that HUFA‐enriched diets have no effect on shrimp reared at low salinities.  相似文献   

9.
Biofloc (consortium of diverse microorganisms associated to suspending substrates) was developed from waste of shrimp Litopenaeus vannamei postlarvae culture under low salinity (5 g L?1) to provide an additional nutritious biomass and reduce fishmeal inclusion in feeds in a 28‐day indoor shrimp nursery trial conducted in 15 experimental containers (250 L stocked at 600 org m?3). Four experimental diets (isoproteic and isocaloric) containing different percentage of fishmeal: 0%, 10%, 20% and 30% substituted by vegetable meal mix (corn, sorghum and wheat) were formulated and elaborated. A control treatment consisted of a commercial feed. The main water quality parameters were monitored, and no significant differences were found among treatments. The growth and survival were similar among treatments. In general, digestive enzymatic activities showed differences being greater in the biofloc system compared with clear water. It was concluded that low‐salinity shrimp nursery could be successfully developed with minimum inclusion of fishmeal in feeds, without significant effect on production response. The adjustment of C : N ratio allowed the increase of microbial biomass in the bioflocs, which contributed to maintain good water quality, provide live food and enhance digestive enzymatic activity of cultured organisms.  相似文献   

10.
The effect of low salinity on survival and growth of the Pacific white shrimp Litopenaeus vannamei was examined in the laboratory due to the interest of raising shrimp inland at low salinities. In three separate experiments, individual L. vannamei postlarvae (∼ 0.1 g) were cultured at salinities of either 0.5, 1, 1.5, 2, or 3 ppt ( N = 5 or 10/treatment) for 18 to 40 d at 30 C in individual 360-mL containers. In each experiment controls of 0 and 30 ppt were run. There was no postlarval survival at salinities < 2 ppt. Survival was significantly different ( P < 0.01) at 2 ppt (20%) compared to 30 ppt (80%). Growth was also significantly different ( P < 0.01) at 2 and 3 ppt compared to 30 ppt (416%, 475%, and 670%, respectively). A fourth experiment compared juveniles (∼ 8 g) and postlarvae (∼ 0.05 and 0.35 g). Shrimp were cultured at salinities of 0, 2, 4, and 30 ppt for 40 d at 25 C, in individual 360-mL and 6-L containers ( N = 7/treatment). There was no postlarval survival at < 2 ppt. Postlarval survival at 4 ppt (86%) was not significantly different (P > 0.05) from 30 ppt (100%). Juveniles exhibited better survival at lower salinities (100% at 2 ppt) than 0.05 and 0.35 g postlarvae (29% and 14% respectively, at 2 ppt). The effects of salinity on growth varied with sizdage. Final growth of 0.05 g postlarvae at 2 ppt (693%) was significantly less ( P < 0.01) than at 4 ppt (1085%) and 30 ppt (1064%). Growth of 0.35 g postlarvae was significantly less ( P < 0.01) for 4 ppt (175%) than for 30 ppt (264%). There was no growth data for juveniles (8 g). It appears from these experiments that the culture of L. vannamei poses risks when performed in salinities less than 2 ppt.  相似文献   

11.
Nursery production may be enhanced by the addition of artificial substrate to increase the surface area upon which shrimp graze and to serve as refuge. The objective of this study was to assess the effects of the artificial substrate, AquaMatsTM, on the performance of postlarval Pacific white shrimp Litopenaeus vannamei stocked at three densities. Eighteen 230-L tanks were stocked with 10-d postlarvae (mean weight < 0.01 g). Six treatments were evaluated and consisted of shrimp stocked at three densities (778 shrimp/m2, 1,167 shrimp/ m2, and 1,556 shrimp/m2) with and without access to artificial substrate. Shrimp in all treatments received a commercial diet ad libitum . After 6 wk, shrimp were harvested from each nursery tank, counted, and batch weighed. Mean final weight, survival, production, feed conversion ratio, and water quality parameters were analyzed by 2-way ANOVA. There were highly significant ( P < 0.001) density and substrate effects on final weight, but there was no significant interaction effect. Final weight was 26.0, 17.4, and 34.5% greater in treatments with substrate than without substrate when stocked at 778, 1,167, and 1,556 shrimp/m2, respectively. There was no significant density, substrate, or interaction effect on survival or water quality. Mean survival was ± 89.1% for all treatments. Increased shrimp growth in the presence of added substrate was likely due to the availability of attached particulate organic matter on the AquaMatsTM that served as an additional food source. Results from this study indicate that artificial substrate can be used to mitigate the potential negative effects of high stocking density on growth of L. vannamei in nursery systems.  相似文献   

12.
Growth, immunological and physiological parameters of white shrimp Litopenaeus vannamei reared at different salinity levels (1, 10, 15, 25 and 35 g/L) at stocking density of 214 shrimp/m3 were examined at 1, 30 and 63 days. Results showed that the total haemocyte count (THC) of shrimp decreased with time at all salinity levels, indicating a potential reduction in the resistance of shrimp against pathogens, since a low value of THC indicates a perturbation of the immune system. Glucose and protein values observed in the haemolymph throughout the study indicate that shrimp adapted well to low salinities (1, 10 and 15 g/L). Although of those shrimp reared at 10 g/L only 83.3% survived, at this salinity, shrimp depicted a higher glucose concentration in haemolymph at the beginning and end of the study.  相似文献   

13.
The production of Litopenaeus vannamei was analysed when affected by the acute hepatopancreatic necrosis disease using a dynamic stock model and primary data of seven production cycles from a shrimp farm in Mexico from 2013 to 2016. Significant results (p < .05) of the correlation analysis indicated that during those years mortalities by the disease were more severe when water salinity was high and productivity was low. Significant results from ANOVA showed that throughout the period, disease severity and salinity diminished while pond productivity initially declined but subsequently improved. Significant results from regression analyses conducted for each production cycle also indicated the importance of salinity and productivity on disease severity and showed that early mortality by the disease occurred in ponds with warmer water. Within the observed range of water quality parameters, increases of 1 cm in water transparency and 1 g/L in salinity resulted in increments within 0.17%–0.25% and 1.7%–3.1% in shrimp mortality by the disease. When increases of 1°C in water temperature were recorded, outbreaks occurred 0.2–1.57 weeks earlier. In conclusion, the disease strongly determines the dynamics of shrimp production, and the role of salinity, productivity and temperature is worthy of further delving.  相似文献   

14.
There is considerable interest in the culture of whiteleg shrimp (Litopenaeus vannamei) in inland low‐salinity water in Alabama and other states in the Sunbelt region of the US. However, the growing season is truncated as compared with tropical or subtropical areas where this species is typically cultured, and temperature is thought to be a major factor influencing shrimp production in the US. This study, conducted at Greene Prairie Aquafarm located in west‐central Alabama, considered water temperature patterns on a shrimp farm in different ponds and different years; and sought possible effects of bottom water temperature in ponds on variation in shrimp survival, growth and production. Water temperature at 1.2 m depth in 22 ponds and air temperature were monitored at 1‐hr intervals during the 2012, 2013, 2014 and 2015 growing seasons. Records of stocking rates, survival rates and production were provided by the farm owner. Correlation analysis and linear mixed model analysis of variance were used. Results showed that hourly water temperatures differed among ponds. The range of water temperature in each pond explained 41% of the variance in average final weight of shrimp harvested from each pond. In conclusion, the results suggest that variation in water temperature patterns has considerable influence on shrimp growth and survival in ponds.  相似文献   

15.
The use of artificial substratum consisting of poly‐β‐hydroxybutyrate (PHB)‐based biodegradable plastic for penaeid shrimp culture was investigated in the present study. The survival of postlarval tiger shrimp Penaeus monodon (30 ± 5 mg) provided with PHB substratum made out of PHB type DP9002 (Metabolix GmbH, Köln, Germany) was 88.7 ± 3.4% and this was significantly higher as compared to postlarvae provided conventional substratum consisting of polyvinylchloride (PVC) pipes (67.3 ± 6.5%). However, no significant weight improvement was observed for the postlarval tiger shrimp indicating that PHB could not be used as growth promoter. Nevertheless, a trend of improved robustness against adverse environmental conditions (lethal ammonium chloride concentration) and increased resistance to pathogenic Vibrio was observed in postlarval tiger shrimp provided with PHB substratum as compared to postlarvae provided with PVC substratum. Results indicate higher preference by postlarvae on PHB substratum over PVC substratum. Overall, this study indicates the potential of artificial substratum consisting of PHB‐based biodegradable plastic as replacement for conventional substratum consisting of PVC pipes in enhancing the survival of postlarval tiger shrimp and improving its performance against adverse environmental conditions and disease resistance.  相似文献   

16.
To improve feed management strategies for the semi‐intensive culture of Litopenaeus vannamei, outdoor tank and pond trials were conducted. In the tank trial, shrimp (35 shrimp/m2, n = 4) were offered feed for 6 weeks based on a standard feeding protocol (SFP, designed as T100) with five variations (T80:90:100, T90, T90:100, T100:110, T110) of this protocol produced by varying the feed inputs and expressing the treatments as a percentage. Results demonstrated no significant differences in survival rate and feed conversion ratio (FCR) among treatments. The mean final weight and final biomass in the treatments T100:110 and T110 were significantly higher than those in treatment T90 but were not different from the other treatments. In the pond trial, juvenile shrimp (28 shrimp/m2, n = 4) were stocked into twelve 0.1‐ha ponds over a 16‐week period. Three feeding protocols were evaluated including a SFP, a 10% reduction in the SFP (SFP:90), and a variable feed input (SFP:80:90:100), which included 80% SFP at week 4th–8th, 90% SFP from week 9th–12th and 100% SFP for week 12th–16th. There were no significant differences in growth performance and economic return among treatments. Based on previous studies, in which higher feed inputs were evaluated, and results of this study, it does not appear to be economically beneficial to use high feed inputs. Instead, feed input could be either applied at a standard ration to optimize growth and economic return or at restricted rations to reduce FCR (feed cost) albeit at the expense of some growth.  相似文献   

17.
Low‐salinity waters of inland shrimp ponds in Nakhon Nayok, Chachoengsao, Prachin Buri, and Samut Sakhon Provinces of Thailand often had concentrations of potassium and magnesium below those expected for normal seawater diluted to the same salinity. However, in Samut Sakhon Province – where the sampling area was nearer the coast – ponds typically had higher concentrations of these two cations than did ponds in the other three provinces. Studies of inland, shrimp ponds at Banglane in Nakhon Pathom Province revealed that magnesium additions to maintain a target concentration near 100 mg/L resulted in greater (P < 0.05) shrimp survival, size, and production than obtained in control ponds. Although potassium additions to ponds (75 mg/L target concentration) did not improve shrimp survival or production, the control ponds had potassium concentration higher than those previously reported for ponds in Alabama where potassium treatment was highly beneficial to shrimp survival and production. A study conducted using laboratory, soil‐water systems with soil from one site did not remove potassium and magnesium from the water, while soil from two other sites removed potassium and magnesium from water – but at different rates.  相似文献   

18.
The objective of this study was to evaluate the production response of Litopenaeus vannamei fed with production diets containing increasing percentages (0, 4, 8, and 12%) of soy protein concentrate (SPC). The diets were commercially produced and evaluated in outdoor tanks and 0.1-ha production ponds. In the outdoor green water tank system, the four test diets and a commercial reference diets were offered to juvenile shrimp (1.0 g initial weight) reared over a 10-week period at a stocking density of 30 shrimp per tank. At the conclusion of the tank trial, there were differences in final weight (13.5–15.0) biomass (399 g–432 g), and FCR (1.17–1.28) with the reference diet generally producing significantly better results than the test diets albeit there were no significant differences among the SPC test diets. In addition, the test diets were evaluated in 0.1-ha ponds using four replicates per diet. Nursed juvenile shrimps (0.013 g initial weight) were stocked at 35 shrimp m−2 and were cultured under standardized pond production conditions for 18 weeks. At the conclusions, net yield (4,190–5,051 kg/ha), final mean weight (13.5–15.7 g), survival (86.7–93.3%), and FCR (1.3–1.59) were evaluated with no significant differences between dietary treatments. The results from this study demonstrated that SPC inclusion up to 12% SPC in soybean-based diet can be used in commercial feed formulations for L. vannamei without causing negative effect on growth, feed conversion, survival and net yield.  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.— Inland culture of Liropenaeus vannarnei in low salinity well waters is currently conducted on a small scale in a few areas in the U.S. To successfully rear shrimp in low salinity water, postlarvae (PL) must be transferred from high-salinity larval rearing systems to low-salinity growout conditions. To determine effective transfer methods, a series of experiments were conducted under controlled conditions to evaluate the influence of PL age, rate of acclimation, and salinity endpoint on 48 h survival of shrimp. Three age classes of L. vannurnei PL (10, 15, and 20-d) were acclimated from a salinity of 23 ppt to treatment endpoint salinities of 0, 1, 2, 4, 8, and 12 ppt. Survival of PL10 acclimated to 0, 1, or 2 ppt salinity was significantly lower than survival of PL acclimated to salinities of 4, 8, and 12 ppt. Survival of PL, and PL20 shrimp was only reduced for the 0 ppt salinity treatment, thus indicating a clear effect of age on salinity tolerance. The same age classes of PL were acclimated from 23 ppt to final salinity endpoints of I or 4 ppt at three different rates of salinity reduction: low, 19%/h; medium, 258/h, and high, 478/h. Survival was not significantly influenced by the acclimation rates for any of the three PL age classes. As in the fixed rate experiments, survival of the 10-d-old PL was significantly lower for shrimp acclimated to the 1 ppt endpoint compared to the 4 ppt endpoint. Under the reported conditions, age appears to influence PL tolerance to a salinity end-point. A 10-d-old PL can be acclimated to 4 ppt with good survival, whereas 15- and 20-d-old PL can be acclimated to a salinity of 1 ppt with good survivals.  相似文献   

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