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1.
The consumption of electricity and propane for producing larvae and postlarvae of the whiteleg shrimp (Litopenaeus vannamei) was examined in a commercial shrimp hatchery on the Baja California Peninsula of Mexico. Between January and August 2005, 6 × 106 postlarvae (average age PL16) were produced from 1.43 × 109 nauplii. During that production period, the hatchery used 2.48 × 109 kcal of fossil fuel energy (30% for electricity, 70% for liquid propane), which was equivalent to 16% of the operating costs. Electricity was used mainly for larval and postlarval rearing (36% and 10%) and microalgae culture (27%). During this production period, 1.47 × 109 kcal of propane were consumed for heating daily more than 600 m3 seawater daily. Of that total, 33% was used for broodstock maintenance, 65% for larvae culturing, and 2% for postlarvae rearing. With increasing costs for shipping postlarvae to the mainland Mexican coastal areas (15% of operating costs) and the need to remain competitive with hatcheries in the coastal areas of Sonora and Sinaloa, alternative energy sources to reduce overall operational costs in hatcheries of Baja California Sur are discussed.  相似文献   

2.
Abstract

This paper presents a study of operating costs in shrimp hatcheries. Size effects are presented for fixed, variable, unitary, and marginal costs. Cost structures by functional production department and by cost‐category are discussed for a hypothetical 100‐million postlarvae/month hatchery in an industrialized country, and compared to those of a hatchery in a developing country. Health management issues, mainly measures commonly used to manage bacterial diseases, and their economic impact are discussed, focusing on the trade off between survival rates and sanitation down‐time.

Salaries and benefits represent the largest cost‐component (37%) for hatcheries in industrialized countries, while feeds and operating supplies constitute the most important costs in developing countries (60%). The need to import hatchery feeds and other operating supplies into developing countries works against savings from lower labor costs typical of developing countries.

Total fixed costs depend on the size of a hatchery and are constant for all possible levels of output. Average fixed cost per unit (thousand postlarvae) can be reduced by producing high postlarval outputs. Hatcheries in areas with seasonal shrimp crops face the challenge of covering fixed costs with revenue from a short production season. Hatcheries with large fixed costs can operate in a cost‐efficient manner only by producing high levels of output. Average total cost and average variable cost curves follow a U‐shaped curve, in which costs first decline as output increases, then reach a minimum, and finally increase as output increases above a point of diminishing returns.

In hatcheries total costs are independent of larval survival, but lower output resulting from low survival increases unit costs. This effect is more pronounced at lower levels of output. Bacterial diseases decrease survival rates and increase unit costs.  相似文献   

3.
The hypothesis that intraspecific competition affects survival and growth during the culture and harvest at extensive/semi-intensive Penaeus vannamei shrimp ponds was evaluated. Thus, the effect of stocking density on the biomass, shrimp average weight, survival, and economic performance during the culture (133 days) and at the harvest of the P. vannamei shrimp was investigated in 400 m2 earthen ponds. In order to reduce the likelihood of infectious diseases, shrimp received preventive health treatments (probiotics and β-1,3/1,6-glucans) during all culture phases. In this way, the effect of density on the intraspecific competition for space/food was isolated. Ponds stocked at 6, 9, and 12 shrimp m?2 showed competition-dependent growth. Ponds stocked at 12 shrimp m?2 presented a mortality (12 %) between days 76 and 99. Competition, and accordingly individual growth reduction, could have begun at day 76 at a density of 5 shrimp m?2. Survival was significantly higher at 6 shrimp m?2 (84.2 ± 6.2 %) compared with the 12 shrimp m?2 (64.8 ± 12.4 %) treatment, while no significant differences in yield were observed between both treatments. Ponds stocked at 3 and 6 shrimp m?2 presented the best benefit–cost rates. The optimal shrimp density during the experimental culture was 5 shrimp m?2. Given the experimental conditions and considering the fraction of density-independent mortality observed, the optimum stocking density was found to be 6 shrimp m?2.  相似文献   

4.
The cultural practices used to produce fingerling walleye, Stizostedion vitreum, in drainable earthen ponds are described for a state fish hatchery in Nebraska and two federal hatcheries in North Dakota. The ponds were filled 1 to 7 days before D2-D4 (Dl=the day of hatch) walleye fry were stocked. At one hatchery, ponds were sometimes double-cropped, first for production of northern pike, Esoxlucius. The two federal hatcheries fertilized ponds with ground alfalfa hay or pellets, while the standard practice at the Nebraska hatchery was not to fertilize walleye ponds, because of concern that fertilization would result in weed problems and oxygen depletion. One hatchery seeded the ponds with rye grass in the fall. Two of the hatcheries regularly used herbicides to prevent the stranding of fingerlings during harvest and their mortality caused by entangment with net algae, Hydrodicton. When used, herbicide treatment was applied before ponds were filled (AquazineTM) or as needed during the culture interval (AquazineTM) or copper sulfate). Harvesting was done after 24 to 58 days; the extreme range represented variation among hatcheries; the variation among ponds at a given hatchery ranged from 4 to 10 days. Harvest occurred when fingerlings were 25 to 50 mm total length and weighed 1,500-5,440 fish/kg. Harvests ranged from 11,933 to 308,537 fingerlings/ha. Survival ranged from 3 to 104% of the estimated number of fry stocked.  相似文献   

5.
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   

6.
Seasonal timing of transportation and acclimation of juvenile Chinook salmon (Oncorhynchus tshawytscha) between hatcheries may affect osmoregulation and survival. We investigated the duration of time fish need to acclimate to hatchery conditions prior to being presented with a saltwater challenge. We monitored acute survival and osmoregulatory ability following a 24-h saltwater challenge of fish previously transported to a hatchery at various times throughout the year compared to fish reared at that hatchery. Fish that underwent a saltwater challenge 3 weeks after transport had significantly reduced osmoregulatory performance and increased mortality compared to fish allowed an acclimation period of 2 months.  相似文献   

7.
The effect of supplementing dehydrated seaweed Ulva clathrata (20 g/kg) in the squid fraction of a formulated fresh diet on the reproductive performance of Litopenaeus vannamei broodstock was evaluated in two commercial hatcheries (A and B). The origin of broodstock, use of ablation on females, tank/culture conditions (for maturation, spawning, and larval rearing) were different between hatcheries. Daily mortality was higher (p < .01) for females in the control group compared to Ulva‐fed group of hatchery A, where females were ablated. No differences in mortality were found for unablated females in hatchery B, or with males from either hatchery. In hatchery A, broodstock fed Ulva produced more eggs (an increase in +5% compared to control, p < .05) and nauplii per female (+18%, p < .01). In hatchery B, broodstock fed Ulva produced significantly more eggs (+26%, p < .05) and nauplii per day (+33%, p < .05). In hatcheries A and B, eggs from broodstock fed Ulva had increased hatching rates (+13 and +7%, respectively, p < .001 in both cases). The number of spawns per day had a tendency to be higher in broodstock fed Ulva in both hatcheries, but the difference did not reach statistical significance (+14% for hatchery A and +20% for hatchery B). Dehydrated U. clathrata appears therefore as a functional additive in L. vannamei maturation diets that enhances the reproductive performance at commercial scale, regardless of the management conditions.  相似文献   

8.
In animal breeding programs, selection coupled with a narrow genetic base can cause high levels of inbreeding to occur rapidly (in one or two generations). Although the effects of inbreeding have been studied extensively in terrestrial animals and to a lesser extent in aquaculture species, little is known about the effects of inbreeding on penaeid shrimp. The objective of this study was to investigate the effects of inbreeding on hatchery and growout performance of the Pacific white shrimp, Penaeus vannamei. The experiment was conducted over 2 yr, and data from two successive generations (G2 and G3) of inbred (sibling–sibling mating) and outbred families were analyzed. There were 11 inbred and 12 outbred families in G2 and 9 inbred and 10 outbred families in G3. Inbreeding coefficients (F) for outbred and inbred families were 0.00 and 0.25, respectively, for G2 and 0.00 and 0.375, respectively, for G3. Growth rates for outbreds and inbreds were similar in both G2 and G3. Hatch rate for inbred families was 33.1% lower than for outbred families in G2 and 47.1% lower in G3. Inbreeding depression (IBD) (relative change in phenotype per 0.1 increase in F) ± 95% CI for hatch rate was ?12.3 ± 10.1%. Hatchery survival for inbred families was 31.4% lower than for outbred families in G2 and 38.8% lower in G3. IBD for hatchery survival was ?11.0 ± 5.7%. Growout survival was 1.9% lower for inbred families than for outbred families in G2 and 19.6% lower in G3. IBD for growout survival was ?3.8 ± 2.9%. There was also a significant linear relationship between IBD estimates for survival traits and mean outbred survival. At high outbred survival, IBD was low (e.g., growout survival in G2), but IBD appeared to become more severe when outbred survival was lower. This suggests that stress (related to environment and/or life stage) may worsen IBD for survival traits. Results also indicate that moderate to high levels of inbreeding (>10%) should be avoided in commercial shrimp hatcheries because the cumulative effect of IBD on hatch rate and hatchery survival will significantly reduce postlarvae production. Thus, IBD can be significant enough to justify the use of inbreeding as a germplasm protection strategy (under certain scenarios) for genetic improvement programs.  相似文献   

9.
Rapid in vitro methods for measuring digestibility may be useful in analysing aqua feeds if the extent and limits of their application are clearly defined. The pH‐stat protein digestibility routine with shrimp hepatopancreas enzymes was previously related to apparent protein digestibility with juvenile Litopenaeus vannamei fed diets containing different protein ingredients. The potential of the method to predict culture performance of shrimp fed six commercial feeds (T3, T4, T5, T6, T7 and T8) with 350 g kg?1 declared crude‐protein content was assessed. The consistency of results obtained using hepatopancreas enzyme extracts from either pond or clear water‐raised shrimp was further verified in terms of reproducibility and possible diet history effects upon in vitro outputs. Shrimps were previously acclimated and then maintained over 56 days (initial mean weight 3.28 g) on each diet in 500‐L tanks at 114 ind m?2, clear water closed system with continuous renewal and mechanical filtering (50 μm), with four replicates per treatment. Feeds were offered four times daily (six days a week) delivered in trays at feeding rates ranging from 4.0% to 7.0% of stocked shrimp biomass. Feed was accessible to shrimp 4 h daily for 1‐h feeding period after which uneaten feed was recovered. Growth and survival were determined every 14 days from a sample of 16 individuals per tank. Water quality was monitored daily (pH, temperature and salinity) and managed by water back flushing filter cleaning every 7–10 days. Feeds were analysed for crude protein, gross energy, amino acids and pepsin digestibility. In vitro pH‐stat degree of protein hydrolysis (DH%) was determined for each feed using hepatopancreas enzyme extracts from experimental (clear water) or pond‐raised shrimp. Feeds resulted in significant differences in shrimp performance (P < 0.05) as seen by the differences in growth rates (0.56–0.98 g week?1), final weight and feed conversion ratio (FCR). Shrimp performance and in vitro DH% with pond‐raised shrimp enzymes showed significant correlation (P < 0.05) for yield (R2 = 0.72), growth rates (R2 = 0.72–0.80) and FCR (R2 = ?0.67). Other feed attributes (protein : energy ratio, amino acids, true protein, non‐protein nitrogen contents and in vitro pepsin digestibility) showed none or limited correlation with shrimp culture performance. Additional correlations were found between growth rates and methionine (R2 = 0.73), FCR and histidine (R2 = ?0.60), and DH% and methionine or methionine+cystine feed contents (R2 = 0.67–0.92). pH‐stat assays with shrimp enzymes generated reproducible DH% results with either pond (CV ≤ 6.5%) or clear water (CV ≤ 8.5%) hepatopancreas enzyme sources. Moreover, correlations between shrimp growth rates and feed DH% were significant regardless of the enzyme origin (pond or clear water‐raised shrimp) and showed consistent R2 values. Results suggest the feasibility of using standardized hepatopancreas enzyme extracts for in vitro protein digestibility.  相似文献   

10.
Cannibalism is one of the main causes of mortality in the culture of the mud crab Scylla paramamosain, particularly in the early post‐larval and juvenile stages when the densities of hatchery‐reared crabs may be very high before stocking into ponds or release into the wild for stock enhancement. In a series of experiments investigating cannibalism mitigation, the influence of stocking density, the effectiveness of sand substrate, brick and shell shelters and feed type were compared in culture of crabs from instar 1 for short nursery periods of 15–30 days. Inclusion of brick and shell shelters significantly increased survival over sand substrate alone. However, inclusion of shelters did not affect growth rates. In scaled‐up nursery production in lined‐ponds, with shelters, live Artemia biomass and fresh chopped shrimp or tilapia were found to be equally effective feeds for juvenile crabs stocked at a density of 70 m−2 from instar 1 and grown for 30 days [52–66% survival, 21.6–24.6 mm carapace width (CW)]. In an extended nursery period for a further 30 days, crabs of 22 mm CW, stocked at 30 m−2 in the same ponds, attained a final size of 34.5–36.2 mm CW with a survival of 64.3–67.0% using the same feeds.  相似文献   

11.
This study investigated razor clam Ensis arcuatus culture from larval rearing to commercial size to assess it's aquaculture potential. Broodstock was spawned several times in hatchery facilities to demonstrate that larval availability is not a constraint for hatchery production. Larval culture lasted 20 days, showing an average survival of 14.35%. The razor clam seed reached a size of 28.5 mm at 4 months. Seed culture is feasible; however, it is constrained by the fact that razor clams need to be buried. Higher survival was observed when culturing razor clam seed with a substrate (82–83%), irrespective of the substrate grain size, while containers held without a substrate showed a significantly lower survival (56.5%). We showed that it is possible to rear E. arcuatus juveniles in bottles, with survival as high as 94–95% being achieved. The length increase of the hatchery‐produced E. arcuatus over 600 days was described by the equation Ln L=4.5+(?141.17/t), where L is length in mm and t is time in days. On‐growing showed adequate survival rates and it took 2–3 years to reach commercial size.  相似文献   

12.
The feasibility of substituting soybean meal for fishmeal diets for juvenile white shrimp Litopenaeus schmitti (0.35±0.01 g) was evaluated, and an adequate substitution level was determined. Five diets were evaluated using 46%, 59%, 75%, 88% and 100% substitution levels. Pellet water stability was significantly affected by dietary soybean content (P<0.05). Increased soybean content produced lower pellet stability, ranging from a dry matter loss of 14–22% after a 2‐h immersion, and 20–33% after an 8‐h immersion. After 52 days, significant differences (P<0.05) were found in shrimp weight, feed conversion ratio and protein efficiency ratio. The values were 0.64–1.06 g, 2.8–7.9 and 0.45–1.21, respectively, for the three measurements. Overall, better results were obtained with diets where soybean meal was substituted for fishmeal up to 75%. The 100% soybean meal diet resulted in poor growth performance of shrimp. Survival rates were acceptable for all treatments (90% or higher) and no significant differences were found in survival between treatments. Regression analysis using the broken‐line methodology indicated that 76.5±2% is an optimum soybean substitution level in diets that contained fishmeal and soybean as the major protein sources for grow‐out of juvenile white shrimp.  相似文献   

13.
The performance of hatchery‐reared juveniles either in aquaculture grow‐out systems or stock enhancement is likely to be dependent on a range of factors during the hatchery phase of production. With recent progress in the development of hatchery systems for the mud crabs Scylla spp., there is growing interest in evaluation of the quality of hatchery‐reared juveniles relative to wild seed crabs as currently used in aquaculture. Hatchery‐reared and wild‐collected Scylla paramamosain juveniles were stocked either together in ponds or separately. All crabs were tagged with microwire‐coded tags, so that origin could be determined in the mixed groups. Preliminary validation demonstrated that tagging did not affect survival or growth, with a tag retention of 94%. After 106 days of culture, there was no significant difference in survival at harvest between the two sources of crabs. The wild juvenile crabs had a significantly higher initial weight:carapace width (CW) ratio compared with those from the hatchery, indicating a difference in condition. However, where crabs were stocked separately, the hatchery‐reared animals exhibited significantly faster growth than those collected from the wild, both in terms of specific growth rate and CW increase per month. However, in the mixed ponds, where there was competition with wild crabs, there was no significant difference in growth rate between crabs from the two sources. Overall, the results demonstrate that the growth performance of hatchery‐reared S. paramamosain can at least equal that of wild‐collected seed crabs in ponds culture.  相似文献   

14.
Abstract

Construction and operating costs for three common snook (Centropomus undecimalis) hatcheries in Florida, USA, are illustrated. Hypothetical capacities and targets of the three hatcheries (Scenarios I, II and III respectively) were 615, 000 juveniles (8 ‐ 10 g in weight) for stock enhancement, and 1, 275, 000 and 3, 000, 000 juveniles (1‐g in weight) for commercial grow‐out. Estimated production costs were lower than for many marine finfish species. The 20‐year mean costs per 1, 000 juveniles were estimated to be $324, $215, and $159, for hatcheries I, II, and III respectively, and the initial capital investments were $731, 660, $1, 162, 460, and $1, 896, 0301, respectively. Major cost items of annual production were labor (22 ‐ 33%), supplies (14 ‐ 20%), fixed costs (15 ‐ 17%), and interest (13 ‐ 15%). The most profitable hatchery was the 3 million 1‐g juvenile hatchery due to the hatchery size effect, with a net present value (NPV) of $1, 760, 000, an internal rate of return (ERR) of 81%, a payback period of 3.6 years, and a profitability index of $2.86 for every dollar invested. Possible cost reductions to increase financial profitability were discussed.  相似文献   

15.
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   

16.
Abstract

Apart from penaeid shrimp culture, crab farming and fattening and other several diversified aquaculture practices are now emerging as viable ventures in India. About 11 types of crab products are being exported from India with an average unit value realization of US$ 3.73 kg?1, pinpointing its importance in the foreign exchange earnings. An economic evaluation of mud crab culture, fattening and fattening with composite culture of shrimp/finfish has been attempted in this paper. The major operating cost was that of seed and it was higher for crab fattening (87% of the total operating cost). Feed costs were very low compared to that of shrimp farming. Annual profit obtained was US$ 22812.5 ha?1 year?1 for culture and US$ 30820.8 ha?1 year?1 for fattening. Economic indicators such as net profit, rate of return, pay back period and breakeven price indicate that crab fattening/culture is much more profitable than any other coastal aquaculture operations currently in practice, provided hatchery production is established in the country to ensure adequate supply of mud crab seeds.  相似文献   

17.
The freshwater African catfish Clarias gariepinus is carnivorous and cannibalistic even during the larval and juvenile stages and this behavior causes economic losses in aquaculture. This study examined for the first time the effect of salinity on cannibalism, survival, and growth of African catfish larvae in the hatchery. Larvae (4 days old, median 7.8 mm TL, 2.8 mg BW) of the African catfish were reared for 21 days at nominal salinity 0, 1, 2, 3, 4, 5, 6, and 7 ppt. After 21 days, they grew to 10–39 mm (median 22 mm) and 10–490 mg (median 90 mg), with no significant difference by salinity treatments. Survival ratios were similarly low (24–31%) at 0, 1, 3, and 7 ppt and significantly higher (49–55%) at 2, 4, 5, and 6 ppt. Cannibalism was significantly lower, 15–30% at 4–6 ppt, than the 40–50% at 0–3 and 7 ppt. Size variation was lower at 4–6 ppt and higher at 0–3 and 7 ppt. We recommend hatchery rearing of African catfish at the optimum low salinity of 4–6 ppt rather than in full fresh water at least up to 21 days. This rearing method fosters larval welfare and improves hatchery production.  相似文献   

18.
We calculated the recapture rates for Chinese shrimp Fenneropenaeus chinensis following hatchery release in Jiaozhou Bay and Bohai Bay in 2012 based on parentage identification using simple sequence repeat (SSR) markers. The results and process were as follows: In total, 3 × 105 postlarval Chinese shrimp (inner marker), comprising six full-sib families, were released into Jiaozhou Bay with a hatchery release of approximately 9 × 107 same-sized stock in the spring. Eight shrimp (inner marker) were identified from 2,507 recapture catches in the autumn, with information about eight SSR loci available by using Cervus 3.0. Similarly, another six full-sib families, comprising 2.04 × 105 postlarvae, were released into Bohai Bay with a hatchery release of approximately 1.6 × 108 same-sized Chinese shrimp of postlarval stock, and four shrimp were identified from 3,232 recapture catches in the autumn. Furthermore, we calculated the number of released stock in the recapture catches, i.e., 2,400 and 3,137 in Jiaozhou Bay and Bohai Bay, respectively. Combined with statistics for Chinese shrimp resources during the autumn fishing season, we calculated that the recapture rates for Jiaozhou Bay and Bohai Bay were 2.70 and 2.59 %, respectively, being slightly lower but more precise compared with results obtained using traditional methods (2.81 and 2.67 %).  相似文献   

19.
Two trials were conducted to evaluate the growth, survival and hepatopancreas histology of the Argentine red shrimp Pleoticus muelleri (Bate, 1888) fed different levels of vitamin E and butylated hydroxytoluene (BHT) in a semipurified diet. The diets contained 0, 100, 600 or 1500 mg vitamin E kg?1 and 16 mg BHT kg?1 diet (trial 1) and 0, 1250, 1500, 1750 or 2000 mg vitamin E kg?1 diet, squid mantle and vitamin‐free diet as a control (trial 2). After 30 days (trial 1), survival ranged between 43% and 64%, and the percentage weight gain of the shrimp varied from 22% to 31% with no significant differences among treatments (P<0.05). After 40 days (trial 2), survival of shrimp fed the diet with no vitamin E and squid mantle was significantly lower (62%) than the other treatment (86–90%). Shrimp fed diets containing vitamin E from 1250 to 1750 mg kg?1 exhibited increased weight gain (34–65%); however, a significant difference was observed for shrimp fed the diet containing 2000 mg kg?1. Histological results yielded differences among treatments. In shrimp fed 1750 mg kg?1 of vitamin E, the functional morphology of the organ was normal, with abundant secretion in the tubules. Signs of malnourishment such as cellular and nuclear retraction, desquamation of cells and hipertrofia, were evident in the hepatopancreas of shrimp fed the other diets. The results indicate that optimal vitamin E requirement for P. muelleri under the present experimental conditions appears to be approximately 1750 mg vitamin E kg?1 diet.  相似文献   

20.
Strategies to reduce operating costs at an expanding shrimp hatchery in NW Mexico are presented for a period covering 3 years (2004–2006). The hatchery increased its greenhouse-type larval rearing halls from three (50 tanks, total water volume 996 m3) in 2004, to five (70 tanks, water volume 1,396 m3) in 2005, and to seven (94 tanks, total water volume 1,876 m3) in 2006. Production increased from 400 million postlarvae in 2004 to 579 million in 2005 to 760 million in 2006, but operating costs increased only 6% during this period and the unit cost for postlarvae was 44% lower. Administration expenses were the highest variable cost, but restructuring the company reduced them from 35% in 2004, to 29 in 2005 and to 21% in 2006. Feed was the second largest variable cost, reduced from 44 to 36 to 31 through improved feeding practices, changes in feed composition, and bulk purchases of commercial feeds. Costs for propane and the workforce increased, in part from higher consumption and additional staff and higher salaries to retain the trained workforce. Competition will continue to lower the market price for shrimp postlarvae, forcing hatcheries into a permanent improvement process. Increasing costs for energy will require investments in energy-saving technologies. Improved sanitation and strict bio-security procedures will increase the survival rate, thereby reducing unit costs still further.  相似文献   

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