A stochastic bioeconomic model was used to estimate the production cost and risk factors affecting economic performance of juvenile redclaw crayfish, Cherax quadricarinatus, commercial nursery ...production, in a farm located in Baja California Sur, Mexico. At harvest, the biological submodel showed there is 95% confidence to obtain an average weight of 19.98 g, with 126,341/ha surviving organisms, representing 84% survival. Biomass was 2.5 t/ha, with a feed conversion ratio (FCR) of 0.98, reflecting the efficient adaptation of the species to culture conditions. The economic submodel showed that at Day 90, there is 95% confidence that the cost of producing a preadult will be US$0.090 or US$4.55/kg. With increasing demand and worldwide sale prices of US$9/kg, there is a potential market for 20–30 g redclaw reared in intensive lined ponds. Sensitivity analyses showed that the regression coefficients from a second‐order polynomial used for calculation of FCR associated with time (a2 and a1) were the most important parameters influencing the production cost. Mortality rate and parameters used to calculate individual weight also had considerable influence on production cost. The bioeconomic analysis contributes significantly to establishing the economic viability of the intensive three‐phase production system.
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.
The potential for commercial Australian redclaw crayfish culture is considered very significate. However, information on maximization of pond carrying capacity that provides consistent production of ...commercial sizes is limited. A stochastic model was used to study the dynamics of commercial male redclaw production in 2500 m2 gravel-lined ponds with continuous aeration, when reared at 1, 2, 4, and 6 pre-adults m−2. After 119 days, the individual weight ranged from 80.9 to 90.5 g, survival averaged 74.0%, yields varied from 0.68 to 3.2 ton ha−1, depending on density, and the feed conversion ratio fell within the 0.75–0.87 range, indicating good production performance of male redclaw when compared with other reports. Three commercial whole-body size ranges were considered for evaluation: 40–60, 61–90 and over 90 g. The commercial category including males weighing 90 g or more was the most productive in terms of biomass, followed by the groups integrated by 61–90 and 40–60 g individuals. Production distributions inferred using the stochastic model resulted in mean yields approximating the crops in the database, with differences ranging from 0.9–7.1% and coefficient of variation values from 0.03 (1 m−2) to 0.81 (6 m−2) indicating higher uncertainty in the expected production at the highest density. The random variability of the 40–60 category and mean individual weight during rearing were the main factors affecting yields. We conclude that it is feasible to produce up to 3.2 ton ha−1 male redclaw crayfish in gravel-lined ponds, and that the stochastic model is useful for redclaw production analysis, establishing the relationships among commercial categories from a dynamic perspective, and to identify and assess production variability.
•The manuscript presents production results obtained in a commercial farm cultivating all male redclaw in gravel-lined ponds.•Weight and growth rate showed inverse correlations with stocking rate but not survival. Low FCRs indicate high efficiency.•Total and commercial yields significantly increased with density. Maximum carrying capacity for the system was determined.•The stochastic model was useful for production analysis, establishing dynamic relationships for commercial size categories.
ABSTRACT In this work, we studied the digestibility, growth, blood chemistry, and enzyme activity of Nile tilapia (Oreochromis niloticus) juveniles (0.95±0.18 g) using different animal (fish silage ...meal, whey meal, bovine blood meal, and red crab meal) and plant (extruded bean, extruded chickpea meal, coconut paste, Jatropha curcas meal, and chickpea meal) dietary byproducts. Nine isocaloric diets (321.92±9.10 kcal g−1) were evaluated for 60 days. The highest digestibility of crude protein values for animal and plant sources were obtained for the whey (93.6) and extruded bean meal (90.5) diets, respectively. The final body weight was higher for the red crab and extruded chickpea meal diets, meanwhile the fish silage and red crab byproducts obtained the highest protein efficiency ratio. Hematocrit was similar among the diets of each byproduct source and presented correlation with growth parameters. The highest glucose, cholesterol, and triglyceride values were obtained for fish silage (138.0, 260.5, and 389.0 mg dL−1, respectively) and whey meal (174.5, 242.3, and 284.0 mg dL−1, respectively) groups. A positive correlation was found between the digestibility of crude protein of ingredients and chymotrypsin activity. Oreochromis niloticus is able to better utilize fish silage, whey, extruded bean, and extruded chickpea byproducts, adjusting its digestive physiology. Such ingredients can be used for formulating cheaper and efficient tilapia diets.
A dynamic stock model was used to predict biomass of shrimp
Litopenaeus vannamei when affected by white spot disease. A database prepared from records of intensive commercial farms in Mexico was used ...for estimating model parameters for summer and winter production cycles. Parameters were analyzed in relation to stocking density, pond size, and mean values of water quality variables measured during the cycles. Significant results from correlation analysis indicated that final weight of shrimp was positively correlated with mean pond water temperature and dissolved oxygen, but inversely correlated with salinity. When temperature and oxygen increased or salinity decreased, mortality from the disease diminished. Early mortality occurred when water temperature increased, oxygen decreased, or large ponds were used. Stocking density did not affect production parameters. Simple linear regression showed that differences in management of aeration affected oxygen levels. Oxygen concentration and aeration were important factors determining the magnitude of mortality from disease and the time when it occurred. Diminished mortality occurred later in the culture period with higher aeration or early start of aeration. Multiple regression analysis was used to predict model parameters as a function of water quality and management variables. Simple regression analysis and an equivalence test indicated that biomass at harvest was adequately predicted by the stock model and multiple regression coefficients. Predicting shrimp production indicated that raising aeration from 9000 to 14
000 horsepower per hour per hectare (Hp
h
ha
−
1
) increased biomass at harvest from 6610 to 8750
kg
ha
−
1
(32%). On the other hand, starting aeration at the beginning of the culture cycle resulted in 8360
kg
ha
−
1
, while starting after 5
weeks yielded 6840
kg
ha
−
1
representing a reduction of 18%. Management of aeration in small ponds is recommended as an approach to reducing mortality from white spot disease.
The effect of two crude dietary protein (26% and 32% P) and two lipid levels (4.7% and 12% L) on gonadal development of female redclaw crayfish
Cherax quadricarinatus was determined. The ...gonadosomatic index (GSI), hepatosomatic index (HSI), biochemical composition of gonad and hepatopancreas, oocyte diameter and frequency of the developmental stage of oocytes were analysed. The GSI was significantly less using 26% P to 4.7% L. A significant interaction between P and L content was found for GSI. A significantly higher HSI value was obtained when L was 12%. P content in the hepatopancreas was significantly higher using 32% P and 4.7% L. The maximum L content in the hepatopancreas was obtained from the 32% P and 12% L diet. A significant interaction between P and L content was found for L content in the hepatopancreas. A higher frequency of post‐vitellogenic oocytes was obtained with diets containing 32% P. There was an interaction between dietary P and L level causing lipid accumulation in the hepatopancreas and changes in GSI. For an optimum 32% P, excess dietary lipid is bioaccumulated in the hepatopancreas, indicating that there is excess available energy. When the P and L levels are restricted, there is a limited gonad development, thus affecting overall reproduction in female
C. quadricarinatus.
ABSTRACT The objective of our study was to assess the apparent digestibility of plant ingredients in diets for juvenile (50 g) and adult (220 g) Nile tilapia (Oreochromis niloticus). Dietary dry ...matter and protein apparent digestibility coefficients of four plant-derived feedstuffs (chickpea, maize, high-quality maize protein, and beans) were tested. The beans diet had the lowest apparent digestibility coefficient of dry matter (ADCDM) (69.41%), while no significant differences were detected in ADCDM among the other diets; ADCDM was significantly higher in adults compared with juveniles (77.02 vs. 73.76%). Apparent dry matter digestibility coefficient of ingredients (ADCI) was significantly higher in the chickpea (70.48%) and high-quality protein maize (71.09%) ingredients, and lower in the beans (52.79%) ingredient. Apparent dry matter digestibility coefficient of ingredients was significantly higher in juveniles compared with adults (72.56 vs. 56.80%). The protein digestibility of diet (ADCCP) was significantly higher in the reference diet (93.68%), while the lowest corresponded to the maize (87.86%) and beans (87.29%) diets. Significantly lower apparent digestibility coefficient of protein (ADCICP ) was obtained with the high-quality maize protein (59.11%) and maize (49.48%) ingredients, while higher ADCICP was obtained with the chickpea and beans ingredients (71.31 and 63.89%, respectively). The apparent digestibility coefficient of ingredient crude protein ADCICP was significantly higher in juveniles compared with adults (67.35 vs. 53.46). Digestibility is generally higher in juveniles, and we recommend using chickpea as an ingredient in diets for Nile tilapia.
The objective of the present study was to establish the impact of monosex-female redclaw crayfish (Cherax quadricarinatus) culture in gravel-lined ponds, by using a stochastic approach to analyze ...production dynamics for the 40–60g, 61–90g and >90g commercial-size intervals. After growing female redclaw crayfish 17weeks in 2500m2 gravel-lined ponds stocked at 6femalesm−2, mean final weight was 80.53±0.70g, survival was 76.2±1.7% and FCR was 0.82±0.10. Overall, yields averaged 0.26tha−1, 2.12tha−1 and 0.99tha−1, respectively, for the 40–60g, 61–90g and >90g size intervals. This resulted in a mean total biomass of 3.39tha−1 and a commercial biomass of 3.3tha−1. Values of the coefficient of variation of total commercial biomass indicated a maximum certainty in production after 10weeks, when percentages of recruitment of the 40–60g and 61–90g size intervals were similar. The contribution of the >90g size interval was negligible, and the total composition of the commercial population was more homogeneous. The sensitivity analysis showed consistency of the simulation model. After 10weeks, variability of the commercial biomass is particularly influenced by the rate at which mean individual weight (wt.) changes from its initial value to its final value (k). In contrast, after 17weeks the variability of k was not relevant in determining the variance of commercial biomass, because the influence of k progressively diminishes as the final weight of crayfish is approached.
Results from the Monte Carlo simulation indicated that, when increasing sample size from one pond to 100 ponds, variability in production forecasts was reduced 89.8%.
The present study demonstrates the feasibility of monosex-female redclaw crayfish culture in gravel-lined ponds. It also shows that the stochastic approach used to analyze production dynamics for the 40–60g, 61–90g and >90g commercial-size intervals is an important tool to evaluate the impact of size classes on total production and commercial yields. According to our results, we recommend an initial stocking density of 6organismsm−2 for commercial monosex grow-out of females in gravel-lined ponds.
•Consistently low FCRs, high survival, high growth rates and commercial final weights for female redclaw crayfish.•Stochastic modeling of the commercial gravel-lined pond production of female redclaw crayfish.•Highest reported yields for female redclaw commercial cultivation.•To our knowledge, information of gravel-lined pond production of redclaw has not been reported in a scientific paper.
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