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1.
The growth performance and stress response in striped knifejaw, Oplegnathus fasciatus (body weight 100–300 g) reared under four photoperiods (6L:6D, 12L:12D, 16L:8D and 24L:0D) were investigated. Fish were fed a commercial diet to apparent satiation, two times a day for 8 weeks. A trial of acute handling and confinement stress was also carried out to investigate the stress-induced levels of different stress indicators in O. fasciatus. Blood was also collected from undisturbed fish which was considered as control. Although there were no significant differences in weight gain, specific growth rate (SGR) and feed conversion efficiency (FCE) in fish exposed to 6L:6D, 16L:8D and 24L:0D photoperiods, all parameters in these photoperiods were significantly higher than those of 12L:12D photoperiod (P < 0.05). There was no significant difference in protein retention efficiency (PRE) between fish exposed to 16L:8D and 24L:0D photoperiods, but PRE in both photoperiods was significantly higher than that of 12L:12D photoperiod.Acute stress significantly increased the plasma levels of cortisol (110.3 ng ml− 1) and glucose (195.4 mg dl− 1), and decreased plasma levels of total protein (0.8 g dl− 1); however, all parameters were returned back to the levels indistinguishable from those of control, undisturbed fish within 24 h. The levels of cortisol, glucose and total protein in fish exposed to different photoperiods during the study were far from the stress-induced levels (P < 0.05). The results demonstrated that the growth performance of O. fasciatus reared from 100 to 300 g can be stimulated significantly by using the manipulated photoperiods where feeding time may be playing an important role to increase food intake and feed conversion efficiency. It also revealed that the artificial photoperiods did not cause significant stress response in fish.  相似文献   

2.
We held juvenile big-headed turtles, Platysternon megacephalum, from eastern China, at temperatures from 20 to 29.4 °C to determine effects on feeding, growth and food conversion. Food intake increased significantly from 20 to 22.4 °C, remained high until 27.1 °C, and then decreased dramatically at 29.4 °C. Digestive efficiency for energy decreased as temperature increased, whereas the digestive efficiency of protein increased from 20 to 25 °C, and decreased at higher temperatures. The relationships between specific growth rate (SGR), food conversion coefficient (Cc) and temperature (T) were curvilinear, and could be described by quadratic equations: SGR = −0.01 T2 + 0.47 T − 5.24 and Cc = −0.37 T2 + 17.20 T − 181.85. Maximum growth was estimated to occur at 23.9 °C, with 90% of the maximum being achieved within the range of 21.9–25.8 °C; maximal food conversion occurred at 23.2 °C, with a 90% range from 21.0 to 25.4 °C. The temperature range (22–25 °C) found to promote best growth and food conversion in juvenile P. megacephalum is lower than for many other freshwater turtles. Temperatures of 22–25 °C are recommended for use in culture of this species to maximize growth and food conversion.  相似文献   

3.
Aquafeed production faces global issues related to availability of feed ingredients. Feed manufacturers require greater flexibility in order to develop nutritional and cost-effective formulations that take into account nutrient content and availability of ingredients. The search for appropriate ingredients requires detailed screening of their potential nutritional value and variability at the industrial level. In vitro digestion of feedstuffs by enzymes extracted from the target species has been correlated with apparent protein digestibility (APD) in fish and shrimp species. The present study verified the relationship between APD and in vitro degree of protein hydrolysis (DH) with Litopenaeus vannamei hepatopancreas enzymes in several different ingredients (n = 26): blood meals, casein, corn gluten meal, crab meal, distiller's dried grains with solubles, feather meal, fish meals, gelatin, krill meals, poultry by-product meal, soybean meals, squid meals and wheat gluten. The relationship between APD and DH was further verified in diets formulated with these ingredients at 30% inclusion into a reference diet. APD was determined in vivo (30.1 ± 0.5 °C, 32.2 ± 0.4‰) with juvenile L. vannamei (9 to 12 g) after placement of test ingredients into a reference diet (35 g kg− 1 CP; 8.03 g kg− 1 lipid; 2.01 kcal g− 1) with chromic oxide as the inert marker. In vitro DH was assessed in ingredients and diets with standardized hepatopancreas enzymes extracted from pond-reared shrimp. The DH of ingredients was determined under different assay conditions to check for the most suitable in vitro protocol for APD prediction: different batches of enzyme extracts (HPf5 or HPf6), temperatures (25 or 30 °C) and enzyme activity (azocasein): crude protein ratios (4 U: 80 mg CP or 4 U: 40 mg CP). DH was not affected by ingredient proximate composition. APD was significantly correlated to DH in regressions considering either ingredients or diets. The relationships between APD and DH of the ingredients could be suitably adjusted to a Rational Function (y = (a + bx)/(1 + cx + dx2), n = 26. Best in vitro APD predictions were obtained at 25 °C, 4 U: 80 mg CP both for ingredients (R2 = 0.86; P = 0.001) and test diets (R2 = 0.96; P = 0.007). The regression model including all 26 ingredients generated higher prediction residuals (i.e., predicted APD − determined APD) for corn gluten meal, feather meal, poultry by-product meal and krill flour. The remaining test ingredients presented mean prediction residuals of 3.5 points. A model including only ingredients with APD > 80% showed higher prediction precision (R2 = 0.98; P = 0.000004; n = 20) with average residual of 1.8 points. Predictive models including only ingredients from the same origin (e.g., marine-based, R2 = 0.98; P = 0.033) also displayed low residuals. Since in vitro techniques have been usually validated through regressions against in vivo APD, the DH predictive capacity may depend on the consistency of the in vivo methodology. Regressions between APD and DH suggested a close relationship between peptide bond breakage by hepatopancreas digestive proteases and the apparent nitrogen assimilation in shrimp, and this may be a useful tool to provide rapid nutritional information.  相似文献   

4.
The effect of density on growth in body mass (BM) and total length (TL) of Caiman latirostris hatchlings raised in small pens (area 0.36 m2), for 3 months, was investigated. Twelve animals from each of three clutches were randomly distributed (1, 2 or 3 individuals) to two replicates at low rearing density (LRD: 0.12 m2/individual), medium rearing density (MRD: 0.06 m2/individual) and high rearing density (HRD: 0.04 m2/individual. Growth at LRD [BM: 150.75 ± 43.83 g (SE); TL: 11.58 ± 0.93 cm] and MRD (BM: 141.96 ± 22.55 g; TL: 8.38 ± 1.26 cm) was significantly more than at HRD (BM: 57.19 ± 14.38 g; TL: 4.61 ± 0.89 cm; p < 0.001). Density is important to achieving optimal growth and maintaining the well-being of C. latirostris in commercial ranching programs.  相似文献   

5.
Immunolocalization by using rabbit polyclonal antibody against APGWamide demonstrated that there was APGWamide immunoreactivity (APGW-ir) in the varicosed nerve fibers in the capsule, connective tissue and trabeculae of the testis whereas there was no APGW-ir in the ovary of sexually mature broodstocks of Haliotis asinina. In vivo bioassay, by injecting APGWamide into foot muscle of mature males and females (age over 24 months), showed that most males (87.50%) injected with 200 μl of 10− 3 M APGWamide (170 μg APGWamide/animal) could be induced to spermiate whereas fewer males (43.75%) injected with 200 μl of 10− 6 M APGWamide (0.17 μg APGWamide/animal) could spermiate. Following injection with 10− 3 M, 53% of males spawned within 3 to 4 h, while the remaining males spawned within 2 to 3 h. The former tended to release more sperm at the range of 1.04 to 2 × 109, and the latter at the range 3.62 × 107 to 2.07 × 108 cells, respectively, and that the sperm of the former group appeared to be more motile. Following the injection of 10− 6 M, all inducible males spawned within 2–3 h, and 43% of spawned males have sperm around 2 × 109, while 57% have fewer sperm number ranging from 2.75 × 107 to 9.94 × 108 cells. In contrast to males, none of the mature females with ripen ovary could be induced to ovulate. These data suggest that APGWamide is an important signaling molecule that plays a role in the male reproductive process that could be used to induce spermiation.  相似文献   

6.
The successful culture of the east coast rock lobster Panulirus homarus rubellus is reliant, among other factors, on the provision of optimal water quality for growth and survival. This study investigated the effect of temperature over a range of 9.7 °C (18.9 ± 0.7 °C to 28.6 ± 1.5 °C) on the growth and survival of juvenile (40.4 ± 9 mm CL; 63.64 ± 12.05 g) P. h. rubellus fed a diet of fresh mussel flesh. Specific growth rate (SGR) was significantly different between temperatures (p = 0.01), with the highest values recorded for the 24 and 28 °C treatments. There was no significant difference in moult increment (MI) between temperatures in terms of both an increase in weight (p = 0.83) and carapace length (p = 0.54). Intermoult period (IMP) differed significantly between temperatures (p = 0.0015) with mean IMP lowest at 24 °C, although not significantly different from the means of the 26 and 28 °C treatments. IMP was highest at 19 and 21 °C. Apparent feed intake was significantly different between treatments (p < 0.0001) and exhibited a strong positive correlation with increasing temperature (y = − 1.67 + 0.16x ; r2 = 0.81). Food conversion ratio (FCR) differed significantly between temperatures (p = 0.02) with 24 °C exhibiting the most efficient FCR. Results indicate that efficient growout of juvenile P. h. rubellus, in terms of both growth and food conversion efficiency, is obtainable at 24 °C.  相似文献   

7.
A possible factor behind the successful use of polychaetes for prawn broodstock diet was investigated. Some steroid hormones in polychaetes have been suspected as being a potential component for prawn reproductive system development. Progesterone (P4) and 17-alpha hydroxyprogesterone (17α-OHP4) were extracted from polychaetes (Perinereis sp.) and female Penaeus monodon broodstock at various maturation stages. Concentration of both hormones was determined using RIA or HPLC. Immature natural polychaetes (2 months old) displayed the highest level of P4 and 17α-OHP4 compared to more mature ones (4, 6 and 8 months old polychaetes) (47.48 ± 6.70 ng P4/mg Protein and 143.74 ± 28.70 ng 17α-OHP4/mg Protein) whereas opposite results were received with cultured polychaetes in which a reverse relationship between P4 and its derivative with polychaete maturation was obtained. Diverse concentrations of both hormones may be linked with other factors such as types of polychaetes, habitats, seasons, and feed intakes. Twenty-four hours in vitro incubation of prawn previtellogenic oocytes with P4 or 17α-OHP4 extracted from polychaetes or with synthetic hormones, significantly increased percentages of vitellogenic oocytes and oocytes with cortical rod compared to the control with no hormones. P4 was more effective in enhancing the final maturation of oocytes while 17α-OHP4 had more effects on vitellogenic oocytes. Synthetic steroid hormones at equal hormone concentrations produced similar results to steroid hormones extracted from natural polychaetes.  相似文献   

8.
The relative contributions of live Artemia metanauplii and an inert diet for growth of Senegalese sole larvae and postlarvae were assessed through the analysis of carbon stable isotopes ratios (δ13C) in both diets and whole larval tissue. Larvae were reared on four dietary regimes: 100% live prey (rotifers and Artemia), 100% inert formulated diet and two co-feeding regimes of 70:30 and 30:70 ratios of Artemia and inert diet, respectively. Larvae from the live food regime and both co-feeding regimes showed a steep increase in δ13C from 10 days after hatching (DAH) as a result of the onset and continuation of Artemia consumption. From 12 DAH fish larvae from all the regimes showed significant isotopic differences as their δ13C increased to final asymptotic values of − 15.1, − 15.6 and − 16.3‰ in the live food, 70:30 and 30:70 regimes, respectively. Carbon turnover rates in larvae from both live food and co-feeding regimes were relatively high (0.071 to 0.116 d− 1) but more than 90% of the observed change in fish tissue isotopic values was accounted for by the retention of carbon in new tissue growth. A two-source, one-isotope mixing model was applied to estimate the nutritional contribution of Artemia and inert diet to postlarvae growth in the co-feeding regimes. At 23 DAH, the relative contribution of live and inert diets to tissue growth in larvae was respectively, 88 and 12% for the 70:30 co-feeding regime and 73 and 27% for the 30:70 co-feeding regime. At 17 DAH, the estimated proportion of tissue carbon derived from the inert diet was higher at 23 and 38% for the 70:30 and 30:70 regimes, respectively. The results suggest that co-feeding regimes in Solea senegalensis larvae may be adjusted to meet ontogenetic changes in the capacity for larvae to utilise inert diets. The contrasting levels of carbon isotope discrimination between diet and tissue in larvae reared on either 100% live feed or 100% inert diet indicate relatively poor utilization of nutrients from the inert diet. The use of isotopic discrimination factors as potential indicators of the digestive physiological performance of a consuming organism in regards to its diet is discussed.  相似文献   

9.
The tropical calanoid copepod Acartia sinjiensis has good potential for mass culture as live feed for reef fish larvae. The present study was conducted to evaluate the effects of photoperiod on various parameters related to A. sinjiensis productivity in culture.Five photoperiods of Light:Dark = 0:24; 6:18; 12:12; 18:6 and 24:0h were setup. Daily egg production of individual females under each photoperiod was monitored for 8 consecutive days. The females were randomly selected daily from stock cultures kept under respective photoperiods and discarded after experiment. The results showed a clear trend of increasing egg production with longer illumination period. Under constant darkness, acclimatization was evident as egg output increased steadily over the 8 day period. Statistics showed that photoperiod significantly (p < 0.005) affected mean daily egg production, with the highest egg output recorded at 18L:6D and 24L:0D (17.6 ± 1.7 and 17.6 ± 1.8 eggs/female/day respectively), which were significantly higher than all other treatments. Photoperiod also significantly affected 48 h egg hatching success (p < 0.005), a trend of increased hatching success with longer light phase was demonstrated. The highest hatching rate (87.2 ± 1.4%) was recorded at 24L:0D, which was significantly higher than the 0L:24D and 6L:18D treatments but not significantly different from the second highest (85.3 ± 2.6%) hatching rate of 18L:6D treatment.Photoperiod was further confirmed to significantly (p < 0.005) affected naupliar and copepodite development with accelerated development observed with increased illumination period of photoperiods. Mean development time from egg to adult was the shortest at 6.00 ± 0.33 days under constant light (24L:0D), followed by 6.24 ± 0.24 days at 18L:6D, both were significantly shorter than that of 0L:24D and 6L:18D treatments although no significantly difference was detected between themselves. Adult life expectancy was also found significantly (p < 0.005) affected by photoperiod with the shortest adult life span recorded under constant light (24L:0D) (9.4 ± 0.4 days), which was significantly shorter than all other photoperiods tested. Adult sex ratio was the only parameter tested that was not significantly affected by photoperiod, a skewed sex ratio in favor of female was found across all photoperiod treatments.Based on results of current study, it is recommended that a photoperiod of 18L:6D being adopted for A. sinjiensis culture to maximize its productivity for aquaculture hatcheries.  相似文献   

10.
The main biological characteristics for black scabbardfish in the Canary Islands waters were established, focusing on its reproductive behaviour and strategy and its growth pattern. The sex proportion differs significantly from the 1:1 ratio, being clearly unbalanced towards the females. The sex ratio according to depth clearly shows the presence of male and female individuals in all the studied layers, thus sex segregation does not happen according to depth. The Canaries can be considered to be a reproduction site for A. carbo, since samples showing all stages of maturity have been observed. The gonadosomatic index (GSI) showed that the mean values were higher in the third and fourth quarters of the year. The index values clearly allow the differentiation of the individuals in resting or in spent (II and V) stages from individuals in ripe or in ripe and running stages, indicating that index levels higher than 2 are typical of maturation followed by spawning process. Up to twelve marks, assumed to be annuli, were visible in the sampled otoliths. Three to five years old were the dominant age classes and only 7.7% of fish were 7 years old or older. Age estimates ranged between 2 and 8 years for males and between 2 and 12 years for females. Estimated growth parameters were: L∞ = 1477 ± 18.73 mm; k = 0.200 ± 0.016 year−1; and t0 = −4.58 ± 0.413 year. Biological aspects of the black scabbardfish suggest that this species has a generalist life-history strategy.  相似文献   

11.
The compatibility of olive barb, Puntius sarana (Hamilton) with major carps was studied in grow-out carp polyculture system for one year in a set of nine earthen ponds of 0.08 ha each. Three different species combinations evaluated were Control: catla (Catla catla Ham.), silver carp (Hypophthalmichthys molitrix Valenciennes), rohu (Labeo rohita Hamilton) and mrigal (Cirrhinus mrigala Hamilton) at 0.5:0.5:1:1; T1: catla, silver carp, rohu and olive barb at 0.5:0.5:1:1 and T2: catla, silver carp, mrigal and olive barb at 0.5:0.5:1:1 at combined density of 7500 fingerlings/ha. While survival levels of the carps did not differ significantly in treatments (P > 0.05), silver carp recorded highest survival levels (94–96%) followed by olive barb (87–90%), mrigal (72–74%), rohu (72–73%) and catla (67–69%). The specific growth rate (SGR) and average harvested body weight (ABW) of catla and silver carp did not differ significantly among the treatments revealing their competition with mrigal or olive barb to be minimum. In absence of rohu in T2, both mrigal and olive barb showed higher SGR and ABW revealing minimal competition between these two species, while their lower performance in presence of rohu in Control and T1 indicated inter-specific competition with the latter. Such olive barb–rohu inter-specific competition, however, failed to yield significant effect on growth of rohu as revealed from its non-significant SGR difference in presence and absence of olive barb. The lower FCR (2.54 ± 0.06) and higher treatment biomass production (3418.4 ± 95.0 kg ha− 1 year− 1) in T1 with rohu–olive barb combination compared to T2 with mrigal–olive barb (2.84 ± 0.11; 3155.1 ± 104.7 kg ha− 1 year− 1) indicated feasibility and advantage of culturing rohu with olive barb rather than mrigal in carp polyculture. Further, similar biomass production in Control and T1 also indicated feasibility of replacing mrigal with olive barb in the grow-out carp polyculture system.  相似文献   

12.
The effects of 5 mg/L of dissolved manganese on juvenile mulloway at salinities of 5, 15 and 45 ppt were determined by comparing their survival, growth and blood plasma and organ chemistry with those of fish grown at the same salinities without manganese addition. Survival of mulloway at 45 ppt in the presence of 5 mg/L of manganese (73 ± 13%) was significantly lower than all other treatments, which achieved 100% survival. Those fish grown in water without manganese exhibited rapid growth, which was not affected by salinity (SGR = 4.05 ± 0.29%/day). Those fish grown at 5 ppt and 45 ppt in the presence of manganese lost weight over the 2-week trial (SGR − 0.17 ± 0.42 and − 0.44 ± 0.83%/day, respectively), whilst those at 15 ppt gained some weight (SGR 1.70 ± 0.20%/day). Manganese accumulated in the gills, liver and muscle of the fish and significant differences in blood plasma chemistry were observed. Blood plasma sodium and chloride of fish exposed to manganese were significantly elevated in hyperosmotic salinity (45 ppt) and depressed at hyposmotic salinity (5 ppt) compared with unexposed fish at the same salinity; consistent with manganese causing apoptosis or necrosis to chloride cells. We did not, however, observe any gill epithelial damage under light microscopy. Blood plasma potassium was significantly elevated at all salinities in the presence of manganese and liver potassium and glycogen reduced. These findings are consistent with manganese interfering with carbohydrate metabolism.  相似文献   

13.
Low feed consumption has been suggested as a major impediment for the development of effective formulated diets for spiny lobsters. To seek an explanation for the low feed consumption, this study compared the feed consumption, appetite revival, foregut evacuation and fecal production of different sizes of spiny lobster Jasus edwardsii juveniles fed a fresh natural diet (i.e. mussel flesh) and a dry formulated diet. In addition, the effect of feeding frequency was determined by feeding juvenile lobsters the same ration of formulated diet at different time intervals. i.e., same ration delivered 3 week− 1, 1 day− 1, 2 day− 1, 5 day− 1 and 5 night− 1. Lobster (10–15 g) growth and feed consumption (1.15% BW day− 1) was maximized when receiving a single ration daily of the formulated diet. A slow appetite revival (AR > 18 h) on the formulated diet was consistent with the negative effect of increasing feeding frequency on growth and consumption. In addition, there appeared to be no major advantage in dry matter intake by providing the nutrient dense dry formulated diet to Jasus edwardsii. Lobsters fed fresh mussel flesh (79.8% moisture) consumed similar levels of dry matter as those lobsters fed the dry formulated feed (7.3% moisture). This appears to be due to high moisture gain and expansion of the dry feed in the lobster foregut. Foregut evacuation lasted 10 h for the two diets but a delay in initial foregut evacuation and processing of the formulated diet was evident, and may have negatively affected feed consumption, appetite revival and dry matter digestibility (61.2%) of the dry formulated diet compared to the mussel flesh diet (89.2%). Appetite revival on mussel flesh was almost complete by 12 h after a satiation ration and was governed primarily by the rate of foregut evacuation. Differences in the timing of foregut evacuation and fecal production between the two diets suggested that a greater proportion of the formulated diet entered the midgut directly.The results indicate that J. edwardsii cannot achieve high levels of feed consumption on formulated diets because gut throughput is reduced due to a small foregut capacity, expansion of the feed post-ingestion, lengthy foregut filling time (1–2 h) and clearance time (10 h), combined with slow gut throughput time (34–42 h) and appetite revival (> 18 h). A slow appetite revival and difficulties in processing and digestion of formulated diets appear as major issues to be resolved to improve the performance of formulated diets required for the commercial aquaculture of J. edwardsii and possibly other spiny lobsters.  相似文献   

14.
This study investigated the effect of different light intensities on feeding, growth and survival of early stage leopard coral grouper Plectropomus leopardus larvae. Four different light intensities (0, 500, 1000 and 3000 lx) were used and larvae were kept under constant light conditions from 0 day after hatching (DAH) to 5 DAH. The larvae were fed a small S-type of Thai strain rotifers at a density of 20 individuals/mL from 2 DAH. The number of rotifers in larval digestive organ and total length of larvae were examined at 3 h intervals between 04:00 and 22:00 h on 3 DAH, and thereafter at 6 h intervals until the end of the experiment (5 DAH). Four experimental trials of the larval rearing were repeated using by 60 kL mass-scale rearing tanks. The results indicate that coral grouper larvae are visual feeders and their food intake increases with increasing light intensity. Food intake of larvae reared at 3000 lx was significantly higher than those reared at 0–1000 lx on 3 DAH despite being the first-feeding day (P < 0.01). On 4 DAH, total length of larvae reared at 3000 lx was significantly larger than those reared at the lower light intensities (0, 500 and 1000 lx), and thereafter light intensity significantly influenced larval feeding and growth until the end of the experiment. Survival on 5 DAH did not show a significant difference between light intensities, but survival rate at 3000 lx and 1000 lx had a tendency to be higher than those reared at the lower light intensities (0 and 500 lx). In contrast, larvae reared at 0 lx exhibited stagnant and/or negative growth. These results indicate that light intensity is significantly the factor affecting larval feeding, growth, and survival in coral grouper larvae under the rearing conditions.  相似文献   

15.
The present research investigated the effect of carbon/nitrogen ratio (C/N ratio) control in ponds with or without substrate addition for periphyton development on production of giant freshwater prawn. C/N ratios of 10, 15 and 20 were investigated in 40 m− 2 ponds stocked with 2 prawn juveniles (5.023 ± 0.02 g) m− 2 with or without added substrates for periphyton development. The various treatment combinations of C/N ratio and periphyton substrate addition are abbreviated as ‘CN10’, ‘CN15’, ‘CN20’, ‘CN10 + P’, ‘CN15 + P’ and ‘CN20 + P’, P representing periphyton substrate. A locally formulated and prepared feed containing 30% crude protein with C/N ratio10 was applied. Tapioca starch was used as carbohydrate source for manipulating C/N ratio and applied to the water column separately from the feed. Increasing the C/N ratio from 10 to 20 reduced (P < 0.001) the total ammonia-nitrogen (TAN), nitrite–nitrogen (NO2–N) and nitrate–nitrogen (NO3–N) in water column and total Kjeldahl nitrogen (TKN) in sediment. The addition of substrates only influenced the NO2–N concentration in the water column (P < 0.001). Increasing the C/N ratio raised the total heterotrophic bacterial (THB) population in the water column, sediment and periphyton (P < 0.001). It also increased the dry matter (DM), ash free dry matter (AFDM), and chlorophyll a content of periphyton (P < 0.001). The lowest specific growth rate (SGR), the highest food conversion ratio (FCR), and the lowest protein efficiency ratio (PER) were recorded in treatment CN10 (P < 0.05). The addition of substrates did not influence size at harvest (P > 0.05) but improved the survival from 62.8 to 72% (P < 0.001). Increasing the C/N ratio from 10 to 20 increased the net yield by 40% and addition of substrate increased the net yield by 23%. The combination of C/N ratio control and substrate addition increased the net yield by 75% from 309 (CN10) to 540 (CN20 + P) kg ha− 1 (120 days)− 1. This 75% higher production concurred with (1) a lower inorganic nitrogen content in the water column, (2) a higher THB abundance supplying additional single cell protein to augment the prawn production, and (3) an improved periphyton productivity and quality.  相似文献   

16.
This paper evaluates the resource and energy requirements of six different types of land-based, hatchery production systems located in the U.S. Pacific Northwest: flow-through with a gravity water supply, flow-through with a pumped water supply, flow-through with pure oxygen, partial reuse system, partial reuse with heating, and a reuse system for the production of Atlantic salmon (Salmo salar) smolts. Key parameters used in the evaluation include direct energy, indirect energy, transportation energy, greenhouse gas emissions, and pollutant discharges.Power (electricity and natural gas) and feed energy accounted for the majority of the required energy for all the rearing option evaluated. The sum of the fixed capital and chemicals components accounted for less than 2–12% of the total energy budget for any rearing option. The energy efficiency (energy output/energy input) of the six options ranges from 0.97% for flow-through with pumped supply to 3.49% for the flow-through with gravity supply. The rearing options with the three highest energy efficiencies were flow-through with gravity supply (3.49%), partial reuse (2.75%), and reuse (2.64%).On a kg of smolt produced basis, the six rearing options showed a wide range in performance. The reuse system had the lowest water (2 m3 kg− 1) and land (0.13 m2 kg− 1) requirements and the third lowest total energy requirement (288 MJ kg− 1). The partial reuse system had the second lowest total power requirement (276 MJ kg− 1), a low land requirement (0.21 m2 kg− 1), and moderate water requirements (33 m3 kg− 1). The partial reuse with temperature control had the second highest total power requirement (657 MJ kg− 1) and land and water requirements similar to the partial reuse system without temperature control. The flow-through system with pumped water supply had the highest water (289 m3 kg− 1), land (2.19 m2 kg− 1), and energy requirements (786 MJ kg− 1) of any of the rearing options. By comparison, the flow-through system with gravity water supply had the lowest energy requirement (218 MJ kg− 1), a moderate land requirement (0.78 m2 kg− 1), and a high water requirement (214 m3 kg− 1). The ranking of the six rearing options based capital and operating costs are likely to be quite different from those based on energy, water, and greenhouse gas emissions.  相似文献   

17.
In five experiments, Atlantic salmon (Salmo salar L.) parr were found to grow better under conditions of rhythmically alternating water temperature (P<0.031), than control groups reared under stable temperature conditions. The daily temperature sums for the experimental and the control groups were carefully equalized and monitored in all five experiments. The experimental group was reared in a rhythmically alternating temperature regime, of 10.0 h of high temperature (16.0°C) and 10.0 h of low temperature (10.0°C), the temperature adjustments being made during the 2 h between the periods of fixed temperature. The control group were reared in a relatively stable temperature regime (13.00–13.98°C). The growth rate of the fish reared under the varying temperature conditions was higher (mean for all five experiments 1.96% day−1) than that for the salmon reared under stable conditions (1.85% day−1).  相似文献   

18.
The effects of dietary protein and energy level on spawning performance of Nile tilapia broodstock and hatchability of their eggs were studied. Nine diets containing three protein (30, 35 and 40%) and three energy (14.6, 16.7 and 18.8 MJ GE/kg) levels were prepared. The diets were fed to duplicate groups of broodfish (average weight of 60.5 ± 4.6 g for males and 39.4 ± 3.1 g for females) at 2–3% of their body weight, twice a day, for 150 days. At low protein level (30%), time to first spawning was significantly longer than at 35 and 40% protein levels, and increased with increasing dietary energy (decreasing protein-to-energy (P/E) ratio). At 35 and 40% protein levels, time to first spawning was not affected by dietary energy. Inter-spawning intervals (ISI) showed irregular patterns in relation to dietary protein and energy, however, at 40% protein the females tended to spawn at shorter intervals, regardless of dietary energy. Spawning performances, including total number of spawnings per tank, number of spawnings per female, absolute fecundity and average number of eggs per spawn, were all significantly lower (P < 0.05) at 30% CP than at higher protein levels. At all protein levels, increasing dietary energy from 14.6 to 18.8 MJ GE/kg (and decreasing P:E ratio) resulted in a significant decrease in fish fecundity. Egg size was not significantly affected by dietary protein and energy. At all energy levels, egg hatchability increased with increasing dietary protein levels (P < 0.05). Eggs produced from broodstock fed 30 and 35% CP, exhibited significantly lower hatchability (P < 0.05) and needed less time for hatching and yolk-sac absorption, and resulted in lower larval length than those fed a 40% protein diet. However, increasing energy level at each dietary protein level did not significantly affect these parameters. These results revealed that the best spawning performance of Nile tilapia broodstock reared in a recycling system was achieved at 40% dietary protein and 16.7 MJ GE/kg, with a P/E ratio of 23.6 g/MJ.  相似文献   

19.
Dermal spicules (or ‘ossicles’) of cultured sea cucumbers can be fluorescently marked with tetracycline and calcein for sea ranching and restocking but optimal immersion conditions are unknown. Lethal and non-lethal effects, and the efficacy of marking spicules in juvenile sandfish (Holothuria scabra), were examined under different immersion conditions. Fluorescence brightness and the proportion of marked spicules generally increased with concentration and duration of immersion. Frequency of burial (an indicator of stress) in sandfish increased with both fluorochromes at concentrations above 50 mg L− 1. Growth in the two weeks post-marking was unaffected at immersion concentrations of 50 and 100 mg L− 1 compared to controls, but appeared inhibited by immersion in solutions of 200 and 400 mg L− 1 of tetracycline or calcein. Sequential marking by tetracycline (yellow) and calcein (green), in either order, showed that calcein was deposited in a higher proportion of spicules. Three other fluorochromes with disparate colors, alizarin complexone, calcein blue and xylenol orange, also marked sandfish spicules and expanded the variety of dichromic combinations. Both tetracycline and calcein fluoresced more brightly when juveniles were marked at 26 or 30 °C than at 21 °C, and this low temperature appears also to reduce the proportion of spicules marked by tetracycline. Our findings show that seawater temperature should be regulated for ex situ immersion marking. The behavioral and biological sensitivities of sandfish demand care in administering the fluorochromes. Fluorochrome immersion at 100 mg L− 1 for 24 h at ≥26 °C provides a practical compromise between minimizing the fitness of released juveniles and ensuring the efficacy of the markers for studies on the growth and survival of sea cucumbers stocked in the wild.  相似文献   

20.
An experiment was conducted to evaluate the rearing performance of different larval stages for optimum growth and survival during fingerling production of Clarias batrachus with an aim to reduce the rearing time of the catfish larvae in a hatchery system. The larvae were reared for 5, 10 and 15 days before stocking them in the nursery tanks. No significant (P < 0.05) difference could be found in length increment at the end of first week of rearing. But the total length was reduced during rest three weeks in five days old larvae compared to that of other two higher age groups. In 5 days old larvae the reduced weight (P < 0.05) was observed during the entire rearing period. However, the specific growth rate (SGR) did not vary among the groups. The survival rate as well as total biomass was decreased while stocking five days old larvae for rearing, compared to that of other two age groups.  相似文献   

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