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1.
A series of four trials were conducted on inland saline groundwater of 58 g L?1 diluted to lower salinities up to 10 g L?1 and later manipulating its ionic concentrations to enhance the survival and growth of Penaeus monodon postlarvae (PL). In the first experiment, the survival of PL was tested at several salinities (10, 20, 30, 40, 50 and 58 g L?1), and the survival of PL was studied in comparison with natural sea water of similar salinities. Complete mortality of PL was observed at all salinity levels within 144 h. Longest survival for 96 h followed by 72 h was found at 10 and 20 g L?1 salinity respectively. In the second experiment, survival of PL was tested at 10–20 g L?1 salinity at different concentrations of calcium varying between 100 and 300 mg L?1. The survival of PL could be increased to 7 days at 12.5 g L?1 salinity by reducing the calcium level to 200 from 921.8 mg L?1 with magnesium and potassium levels of 208.5 and 30.03 mg L?1 respectively. In the third experiment, the survival of PL could be further enhanced to 18 days at the same salinity by increasing the magnesium level from 208.5 to 400 mg L?1 with potassium held at 30.03 mg L?1. Survival and growth of PL in inland saline water of 12.5 g L?1 salinity similar to performance in sea water of the same salinity was achieved by increasing the potassium concentration from 30.03 to 200 mg L?1 with calcium and magnesium levels of 199.5 and 199.4 mg L?1 respectively.  相似文献   

2.
Salinity tolerance and growth of Japanese flounder Paralichthys olivaceus at different developmental stages were evaluated, including newly hatched larvae (nhl), yolk sac larvae (ysl), oil droplet larvae (odl), post oil droplet larvae (podl), premetamorphic larvae (preml) and prometamorphic larvae (proml), at 11 salinities from 5 to 55 g L?1 for 96 h. The ontogenesis during the early life of P. olivaceus was investigated under hatchery salinity 35 g L?1. The results showed that suitable salinities for nhl, ysl, odl, podl, preml and proml larvae were 10 to 25 g L?1, 10 to 30 g L?1, 20 to 30 g L?1, 30 g L?1, 10 to 30 g L?1, 15 g L?1, respectively, demonstrating an ontogenetic variation of salinity tolerance. The salinity tolerance of nhl, ysl, preml was higher than that of odl, podl and proml. The ysl and preml larvae displayed wide salinity tolerances. The present findings demonstrate that the suitable salinity for larviculture of P. olivaceus is 20–25 g L?1 before the depletion of oil droplet; after that, higher salinity (30 g L?1) should be ensured for the post‐oil droplet larvae; the premetamorphic larvae can be cultured at a wide salinity range (10–30 g L?1), and the metamorphosed larvae should be reared at salinity about 15 g L?1.  相似文献   

3.
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   

4.
Survival of marble goby larvae fed either Rhodovulum sulfidophilum, a phototrophic bacterium cultured from palm oil mill effluent (pPB), or microalgae ( Nannochloropsis sp.) was evaluated at two salinities. Larvae directly fed pPB had survival of 0–29% at 5 g L?1 salinity and 0–19% at 10 g L?1 salinity, whereas larvae directly fed microalgae suffered complete mortality after 20 days of culture at both salinities. However, larvae indirectly fed pPB or microalgae, i.e. via rotifers (Days 1–30) and Artemia nauplii (Days 21–30) cultured solely from pPB or microalgae, showed improved survival of 35–55% or 44–49% at 5 g L?1 salinity respectively. In all experiments, fish larvae reared at 5 g L?1 salinity showed significantly higher (P < 0.01) mean survival than those reared at 10 g L?1 salinity. The survival of larvae fed the bacterial‐based diet was higher compared with microalgal diet used in previous studies. The pPB had higher total polyunsaturated fatty acids and docosahexaenoic acid (DHA) than the microalgae, which had very high eicosapentaenoic acid (EPA). Larvae with very high ratios of DHA/EPA (>11) or/and ARA (arachidonic acid)/EPA (>5), attributable to their given diet, however suffered the highest mortality.  相似文献   

5.
First‐feeding halibut larvae (245‐day degrees; 40 days post hatch), reared at 34 g L?1 salinity and 7°C, were subjected to handling and allowed to recover in a range of salinities (0–34 g L?1) and at 10°C. Survival of the unfed larvae was determined daily for 18 days. Mortality rates approached 0 after 4 days in all treatments and presumed starvation‐induced mortality started at about 11 days post handling. By 20 days post treatments, all larvae had died. Salinities in the range of 10–20 g L?1 produced significantly (anova , P<0.01) higher initial survival (71–95%) than salinities above 20 g L?1 (24–48%) or below 10 g L?1 (0–19%) and this survival pattern changed little in unfed larvae for the first 10 days following the stressor. For example, 24 hour post handling, survival of halibut was improved from 28.7±16.5% (mean±standard error, n=3) at 34.0 g L?1 to 95.2±4.8% at 13 g L?1. A second‐order polynomial regression of 4‐day post‐handling survival data (y=?0.002x 2+0.0603x+0.0699, r2=0.3936) predicted a maximum survival at 15.1 g L?1 salinity. These results have important implications for halibut aquaculture and research when handling of larvae is unavoidable. For practical applications, we recommend reducing salinity of receiving waters to 15–20 g L?1 with a slow (3–4 days) reacclimation to ambient conditions.  相似文献   

6.
Larval stages of the Pacific white shrimp, Litopenaeus vannamei (Boone) were fed standard live diets of mixed microalgae from the first to the third protozoea (PZ1 to PZ3), followed by Artemia nauplii until post‐larvae 1 (PL1). Trypsin enzyme activity for each larval stage was determined using N‐α‐p‐toluenesulphonyl‐l ‐arginine methyl ester (TAME) as a substrate. Results were expressed as enzyme content to assess ontogenetic changes during larval development. Tissue trypsin content (IU µg?1 DW for each larval stage) was significantly highest at the PZ1 stage and declined through subsequent stages to PL1. This contrasts with previously observed patterns of trypsin development in Litopenaeus setiferus (Linnaeus) and other penaeid genera, which exhibit a peak in trypsin activity at the third protozoea/first mysis (PZ3/M1) larval stage. Litopenaeus vannamei larvae transferred to a diet of Artemia at the beginning of the second protozoea (PZ2) stage were significantly heavier on reaching the first mysis stage (M1) than those fed algae, while survival was not significantly different between treatments. At both PZ2 and PZ3 stages, trypsin content in larvae feeding on Artemia was significantly lower than in those feeding on algae. The rapid decline in trypsin content from PZ1 and the flexible enzyme response from PZ2 suggest that L. vannamei is physiologically adapted to transfer to a more carnivorous diet during the mid‐protozoeal stages.  相似文献   

7.
Despite the importance of certain highly unsaturated fatty acids in osmotic regulation, few studies have been addressed to determine the essential fatty acid requirements for a given species cultured under different salinities. As Galaxias maculatus is a diadromic species, the present study aimed to determine the effect of salinity on the optimum dietary EPA/docosahexaenoic (DHA) ratio for survival and growth during the larval stages. Larvae were fed for 20 days with rotifers containing two different EPA/DHA ratios (low: 0.64 and high: 2.18) at three different salinities (0, 10 and 15 g L?1). The results of this study showed a marked effect of water salinity on larval dietary lipid utilization in G. maculatus larvae. These results suggested that G. maculatus larvae reared at higher salinities may have a higher dietary requirement for DHA, whereas larvae reared at 0‰ showed higher requirements for EPA. The overall results of the present study indicate that even small changes in salinity can determine the optimum dietary EPA/DHA ratio and the quantitative essential fatty requirements of fish. This may have important repercussions and affect the rearing performance of G. maculatus cultured under different salinities.  相似文献   

8.
Temperature and salinity are two factors known to influence the growth potential and survival of the Pacific white shrimp, Litopenaeus vannamei, acclimated to low salinity waters. In west Alabama, farmers suspect low water temperatures at stocking, in conjunction with low salinity and suboptimal ionic profiles, might be responsible for reduced survival and production at harvest. To determine the influence of temperature and salinity on post‐larval (PL) L. vannamei, a series of bioassays were conducted at the E.W. Shell Fisheries Research Station in Auburn, Alabama and Claude Peteet Mariculture Center in Gulf Shores, Alabama. PL L. vannamei of ages 11, 13, and 20 (PL11, PL13, and PL20) were acclimated down to salinities of 12, 4, 2, 1, 0.5, and 0.2 ppt at different temperatures ranging from 17.6 to 24.0 C. During the acclimation bioassays survivals were assessed at 24 and 48 h. PL survival of the three age groups examined were significantly reduced at salinities of 1, 0.5, and 0.2 ppt. These results correspond well to those reported at higher temperatures confirming that across the tested temperature range salinity endpoint was the driving factor in determining survival and that suboptimal temperatures had a minimal influence on survival.  相似文献   

9.
The aim of this study was to evaluate the growth and survival of pacu, Piaractus mesopotamicus, larvae reared in different salinities and to determine the Artemia nauplii life span in freshwater and in saline water. First feeding 5‐d‐old pacu larvae were reared in freshwater or at 2, 4, 6, 8, 10, 12, and 14 ppt salinities. The larvae were reared in 1.5‐L aquaria at a density of 10 larvae/L with three replicates per treatment. After 10 d of rearing, significant differences (P < 0.05) were observed for growth and survival. Larval growth was higher at 2 and 4 ppt, and survival at 2 ppt was 100%. In freshwater and at 4, 6 and 8 ppt, the survival was 91.1, 93.3, 73.3, and 39.9%, respectively. At higher salinities, there was 100% mortality after 2 h (12 and 14 ppt) and 8 h (10 ppt) of exposure. The slightly saline water of at least 2 ppt increased the Artemia nauplii life span compared to the life span in freshwater. Later, in a second trial, 5‐d‐old pacu larvae were reared in freshwater and at 2 and 4 ppt salinities during the first 5 or 10 d of active feeding, and then the fish were transferred to freshwater. At the end of 15 d, larval growth was lower in freshwater (42 mg) than in treatments 2 and 4 ppt (59–63 mg). The abrupt transfer of fish from freshwater to slightly saline water and the return to freshwater did not affect the survival rates (89–97%). The larvae were able to adapt to these saline environments and handle abrupt changes in salt concentration. We concluded that salinity concentration of 2 ppt can be used for pacu larval rearing, allowing the Artemia nauplii lifetime to last longer and cause faster fish growth.  相似文献   

10.
Larvae of two caridean shrimp species, Macrobrachium rosenbergii (De Man) and Palaemon elegans Rathke, were fed live and artificial diets. P. elegans larvae fed exclusively live Artemia salina (15 nauplii mL?1) developed into first postlarval stage (PL1) within 12 days at a temperature of 25°C and salinity 32.5 g L?1. Their survival and mean total length at this stage were 88.5% and 6.7 mm respectively. M. rosenbergii larvae fed on 15 Artemia mL?1 started to metamorphose into PLl within 24 days at 29–30°C and 12 g L?1. Attempts to completely replace live Artemia for rearing P. elegans during early stages failed, and only a partial replacement was achieved for the larvae of both species. P. elegans larvae survived (49%) solely on a microgranulated diet (Frippak PL diet) from stage zoea (Z) 4–5 to PL1. Similarly, a microencapsulated diet (Frippak CD3) also sustained M. rosenbergii larvae from Z5–6 to PL1 with a 28% survival. Development of the larvae of both species was retarded by 2–3 days and their survivals were lower than those fed on the live diet. The inability of the early larvae of these caridean species to survive on artificial diets is attributed to their undeveloped guts and limited enzymatic capabilities. Trypsin activity in the larvae was determined for all larval stages. It was found that the highest trypsin activity, at stage Z4–5 in P. elegans and at stage Z5–6 in M. rosenbergii, coincides with a rapid increase in the volume of the hepatopancreas and the formation of the filter apparatus. These morphological changes in the gut structure appear to enable the larvae to utilize artificial diets after stage Z5–6. Low larval trypsin activities may be compensated by the easily digestible content of their live prey during early larval stages (Z1–Z4/5) and by longer gastroevacuation time (GET) and almost fully developed guts during later stages.  相似文献   

11.
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   

12.
The southern flounder, Paralichthys lethostigma, is an important commercial and recreational marine flatfish that inhabits estuaries and shelf waters in the south Atlantic, from North Carolina through the Gulf coasts, with the exception of south Florida. Because juvenile and adult fish are highly euryhaline, it is a prime candidate for aquaculture. Methods for captive spawning of southern flounder are well developed; however, information on optimal culture requirements of the early larval stages is required for reliable mass production of juveniles.To determine the optimal photoperiod and salinity conditions for culture from hatching to day 15 post-hatching (d15ph), embryos were stocked into black 15-l tanks (75 l−1) under four photoperiods (24L:0D, 18L:6D, 12L:12D, and 6L:18D) and two salinities (25 and 34 ppt) in a 4×2 factorial design. Temperature was 18 °C, light intensity was 150 lx, and aeration was 50 ml min−1. Significant (P<0.05) effects of photoperiod and salinity on growth (notochord length, wet and dry weights) were obtained. Growth increased with increasing photoperiod and salinity and was significantly greater at 24L and 18L than at 12L or 6L, and at 34 than at 25 ppt. On d11ph and d15ph, significant interactive effects between photoperiod and salinity on growth (wet and dry weights) were also evident. Growth of larvae reared at 25 ppt increased with increasing photoperiod to a maximum at 24L, while growth of larvae at 34 ppt reached a plateau at 18L. While there were no significant photoperiod effects on these parameters, larval survival, body water percentage, and larval osmolality on d15ph were significantly higher at 34 than at 25 ppt (41% vs. 16% survival; 322 vs. 288 mosM kg−1; and 84% vs. 76% water, respectively), suggesting stress and nonadaptation to 25 ppt, a salinity more nearly isoosmotic than full-strength seawater. Since larvae from both salinity treatments were neutrally or positively buoyant at 34 ppt, but negatively buoyant at 25 ppt, larvae reared at 25 ppt probably allocated energy to maintain vertical positioning, compromising growth and survival.The results demonstrate that growth and survival of early-stage southern flounder larvae are maximized under long photoperiods of 18–24L and in full-strength seawater. Longer photoperiods probably extend the time larvae have for feeding, while full-strength seawater salinity optimizes buoyancy and vertical positioning, conserving energy. The results show that early larval stage southern flounder larvae are not entirely euryhaline, which involves not only the ability to osmoregulate, but to conserve energy under reduced buoyancy. This is consistent with suboptimal vs. maximal growth of larvae reared at 25 and 34 ppt, respectively, under 18L (i.e., photoperiod×salinity interaction). This is also consistent with other reports that tolerance to lower salinities in these euryhaline flatfish increases post-metamorphosis when transition from a pelagic to benthic existence alleviates the need to counteract reduced buoyancy.  相似文献   

13.
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   

14.
The activity of the enzyme Na+,K+-ATPase and morphological changes of gill chloride cells in grouper, Epinephelus coioides larvae and juveniles were determined 6–48 h after abrupt transfer from ambient rearing conditions (30–32 ppt, 26.5–30 °C) to different salinity (8, 18, 32, 40 ppt) and temperature (25, 30 °C) combinations. Na+,K+-ATPase activity in day 20 larvae did not change at salinities 8–32 ppt. Activity decreased significantly (P <0.01) after exposure to 40 ppt at 25–30 °C, which was accompanied by an increase (P <0.05) in density and fractional area of chloride cells. Enzyme activity in 40 ppt did not reach a stable level and larvae failed to recover from an osmotic imbalance that produced a low survival at 25 °C and death of all larvae at 30 °C. Enzyme activity and chloride cell morphology in day 40 groupers did not change in 8–40 ppt at 25 °C and 8–32 ppt at 30 °C. A significant decrease and a subsequent increase in Na+,K+-ATPase activity in 40 ppt at 30 °C was associated with the increase in chloride cell density resulting in an increased fractional area but a decreased cell size. Enzyme activity and chloride cells of day 60 grouper were unaffected by abrupt transfer to test salinities and temperatures. These results demonstrate that grouper larvae and juveniles are efficient osmoregulators over a wide range of salinities. Salinity adaptation showed an ontogenetic shift as the larvae grew and reached the juvenile stage. This development of tolerance limits may reflect their response to actual conditions existing in the natural environment.  相似文献   

15.
Abstract.— Salinity tolerance limits during the ontogenetic development of Farfantepenaeus paulensis postlarvae (PL) were determined at different temperatures. Initially, PL 10, 20, 30, 40, 60 and 80 maintained in 30 ppt (parts per thousand) salinity, 22‐25 C, were directly transferred to 15 combinations of salinity (2, 5, 10, 20 and 30 ppt) and temperature (15, 20 and 30 C) for 96 h. Irrespective of age or salinity, higher survival rates were registered at 25 C. PL 10 suffered high mortality, especially at low salinities combined with low (15 C) or high (30 C) temperatures. From PL 20 to PL 40, an increase in survival was observed in all combinations. For PL 60 and 80, tolerance to low salinity was reduced, suggesting that PL have a maximum age by which they are able to develop adaptability to low salinities. In general, the effect of temperature contributed more significantly to mortality in PL 10 and PL 30, but its influence decreased afterwards. From PL 40, salinity becomes the main factor determining mortality. In order to examine the effects of acclimation to salinity on the tolerance limits, a second set of experiments was performed with PL 5, 10, 15 and 25 acclimated to 2, 5, 10, 20 and 30 ppt, 25 C, over a 5‐d period. Postlarvae were then transferred to different salinity levels (2, 5, 10, 20 and 30 ppt) and kept for 96 h. High mortality of PL 10 occurred after direct transfer from high to intermediate/low salinity levels. Although the acclimation to salinity increased survival, it was still poor. An increase in the salinity tolerance was observed from PL 15 to 30, even with no acclimation. Results indicate that PL 10 do not have a fully developed osmoregulatory capacity to cope with low and/or abrupt changes of salinity. It is recommended that non‐acclimated PL 10 should only be released in environments with salinity at or above 20 ppt. If acclimation is carried out, PL may be released in salinities above 10 ppt. The release of PL 10 in salinities below 5 ppt may result in mortality rates of up to 70%. The best age for the release of non‐acclimated F. paulensis PL in environments with low and/ or wide fluctuations of salinity would he PL 15‐30.  相似文献   

16.
The nitrite toxicity was estimated in juveniles of L. vannamei. The 24, 48, 72 and 96 h LC50 of nitrite‐N on juveniles were 8.1, 7.9, 6.8 and 5.7 mg L?1 at 0.6 g L?1; 14.4, 9.6 8.3 and 7.0 mg L?1 at 1.0 g L?1; 19.4, 15.4, 13.4 and 12.4 mg L?1 at 2.0 g L?1 of salinity respectively. The tolerance of juveniles to nitrite decreased at 96 h of exposure by 18.6% and 54.0%, when salinity declined from 1.0 to 0.6 g L?1 and from 2.0 to 0.6 g L?1 respectively. The safe concentrations at salinities of 0.6, 1.0 and 2.0 g L?1 were 0.28, 0.35 and 0.62 mg L?1 nitrite‐N respectively. The relationship between LC50 (mg L?1), salinity (S) (g L?1) and exposure time (T) (h) was LC50 = 8.4688 + 5.6764S – 0.0762T for salinities from 0.6 to 2.0 g L?1 and for exposure times from 24 to 96 h; the relationship between survival (%) and nitrite‐N concentration (C) for salinity of 0.6–2.0 g L?1, nitrite‐N concentrations of 0–40 mg L?1 and exposure times from 0 to 96 h was as follows: survival (%) = 0.8442 + 0.1909S – 0.0038T – 0.0277C + 0.0008ST + 0.0001CT–0.0029SC, and the tentative equation for predicting the 96‐h LC50 to salinities from 0.6 to 35 g L?1 in L. vannamei juveniles (3.9–4.4 g) was 96‐h LC50 = 0.2127 S2 + 1.558S + 5.9868. For nitrite toxicity, it is shown that a small change in salinity of waters from 2.0 to 0.6 g L?1 is more critical for L. vannamei than when wider differences in salinity occur in brackish and marine waters (15–35 g L?1).  相似文献   

17.
The present study evaluated various sodium and potassium concentrations in hatchery water to determine which proportions would be optimal for Macrobrachium rosenbergii larviculture. Using a closed RAS system (60‐L), experiments were conducted in two stages. In the first stage, larval quality parameters were compared among triplicate treatments of sodium (2000, 3000, 4000 and 5000 mg L?1) and potassium (100, 150, 200 and 250 mg L?1). During the second stage, these same parameters were compared from interactions of the two best concentrations determined in the first stage. Initial larval density was fixed at 100 larvae L?1 and larval quality parameters such as larval stage index (LSI), larval condition index (LCI), larvae dry weight, survival (%), LC50‐24 h for formalin stress and time of the first postlarvae (PL) appearance were measured. Results showed that during the early larval period time LSI, LCI and survival parameters were affected only by potassium and the interaction with sodium was not significant. At a later period of the larval development, interactions between both sodium and potassium were measurable for LSI (P < 0.05) while the interactions on LCI and survival were not significant. Measurable differences among the combined treatments 4000 mg L?1 sodium and 150 mg L?1 potassium resulted in the best performance for M. rosenbergii larviculture. This concentration also provided the highest final survival to PL metamorphosis (40.6 ± 2.5%) which was at least 10% higher than the other treatments.  相似文献   

18.
The brown shrimp, Farfantepenaeus californiensis (Holmes), is a species native to north‐west Mexico, where its culture potential is presently being addressed. Because of the climatic conditions prevailing in the region, salinities over 40 g L?1 is a commonly encountered problem. In the present study, the effect of salinity on the growth and mortality of juvenile F. californiensis is described. The change in short‐term routine metabolism at different salinities was also evaluated in order to define the adaptive capacity of the shrimp and to provide insight into the changes in the pathways of energy distribution. Groups of shrimp were exposed to increasing salinity (25, 35, 45 and 55 g L?1), and growth and survival rates after 75 days were determined in duplicate 1.8‐m3 tanks for each salinity level. Significant differences were found in final weight, growth rate and mortality of shrimp as a result of salinity level. Final mean shrimp weights at increasing salinity levels were 10.0, 9.4, 8.6 and 7.8 g. Corresponding mortality was 24.4%, 15.1%, 33.6% and 55.7%. Oxygen consumption was found to depend significantly on salinity and was equivalent to 0.0027, 0.0037, 0.0043 and 0.0053 mg g?1 min?1 respectively for the increasing salinities. The increased rate of oxygen consumption at high salinities reflects the response of the organism to osmoregulatory and ionic imbalances. Increased energy requirements to fulfil basic metabolic function as salinity increased resulted in a reduction in the energy that could be diverted to growth. Consequently, the culture of the brown shrimp at salinities over 35 g L?1 would probably result in reduced yields.  相似文献   

19.
In this study, we tested the lower salinity tolerance of juvenile shrimps (Litopenaeus vannamei) at a relatively low temperature (20 °C). In the first of two laboratory experiments, we first abruptly transferred shrimps (6.91 ± 0.05 g wet weight, mean ± SE) from the rearing salinity (35 000 mg L?1) to salinities of 5000, 15 000, 25 000, 35 000 (control) and 40 000 mg L?1 at 20 °C. The survival of L. vannamei juvenile was not affected by salinities from 15 000 to 40 000 mg L?1 during the 96‐h exposure periods. Shrimps exposed to 5000 mg L?1 were significantly affected by salinity, with a survival of 12.5% after 96 h. The 24‐, 48‐ and 96‐h lethal salinity for 50% (LS50) were 7020, 8510 and 9540 mg L?1 respectively. In the second experiment, shrimps (5.47 ± 0.09 g wet weight, mean ± SE) were acclimatized to the different salinity levels (5000, 15 000, 25 000, 35 000 and 40 000 mg L?1) and then maintained for 30 days at 20 °C. Results showed that the survival was significantly lower at 5000 mg L?1 than at other salinity levels, but the final wet weight under 5000 mg L?1 treatment was significantly higher than those under other treatments (P<0.05). Feed intake (FI) of shrimp under 5000 mg L?1 was significantly lower than those of shrimp under 150 00–40 000 mg L?1; food conversion efficiency (FCE), however, showed a contrasting change (P<0.05). Furthermore, salinity significantly influenced the oxygen consumption rates, ammonia‐N excretion rates and the O/N ratio of test shrimps (P<0.05). The results obtained in our work provide evidence that L. vannamei juveniles have limited capacity to tolerate salinities <10 000 mg L?1 at a relatively low temperature (20 °C). Results also show that L. vannamei juvenile can recover from the abrupt salinity change between 15 000 and 40 000 mg L?1 within 24 h.  相似文献   

20.
High larval mortalities during rearing of gilthead bream, Sparus auratus L., led to experiments on the influence of salinity and temperature on eggs and yolk-sac larvae. Test salinities ranged from 5 to 70 ppt for eggs and from 15 to 45 ppt for larvae; experimental temperatures were 18–20°C for eggs and 18, 23 and 26°C for larvae. Spawning conditions were 18–20°C and 33–35 ppt salinity; the yolk-sac larvae were chosen from hatches obtained under similar conditions (18°C and 35 ppt salinity). For eggs the optimum survival range was found to be 30–50 ppt at 18°C and 15–60 ppt at 23°C, while that for yolk-sac larvae was 15–25 ppt at all three temperatures. Choosing normal development (no dorsal curvature) as the decisive criterion, the optimum salinity range for egg incubation was reduced to 30–40 ppt at 18°C and to 35–45 ppt at 23°C, while that for the yolk-sac stage remained 15–25 ppt at all test temperatures. Egg incubation was most successful at salinity-temperature combinations close to those during spawning, whereas salinity had to be reduced by at least 10 ppt for yolk-sac larvae.  相似文献   

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