A stochastic approach for analysis of the influence of white spot disease, zootechnical parameters, water quality, and management factors on the variability of production of shrimp Litopenaeus vannamei cultivated under intensive commercial conditions

We investigated the variability of shrimp Litopenaeus vannamei production by incorporating stochastic elements into deterministic stock models and determined the contribution that white spot disease, zootechnical parameters, water quality, and alternative management strategies have on variability. The model was calibrated for intensive shrimp cultivation in the State of Nayarit, Mexico. Mean annual production increased as a consequence of improved management from 8000 kg ha⁻¹ to 22,000 kg ha⁻¹ when cultivation was not affected by the disease and from 3200 kg ha⁻¹ to 10,400 kg ha⁻¹ when the disease affected production. When simultaneously considering both cases, mean annual production increased from 6300 kg ha⁻¹ to 16,800 kg ha⁻¹. White spot disease was a major factor determining variability of production. Shrimp production was particularly sensitive to levels of dissolved oxygen when management was inadequate, while final weight and mortality rate of shrimp were more sensitive when management improved. Water temperature and salinity had intermediate importance, and mortality caused by the disease and the time when mortality occurred had intermediate or low relevance. Improving management increased shrimp production and diminished variability. The duration of cultivation and stocking density were the most important management variables controlling variability of production when cultivation was affected by the white spot disease. When the disease was not present, pond size and duration of cultivation were the main factors affecting production. Starting time of aeration had relatively lower importance in determining variability, while the stochastic values of dissolved oxygen, in contrast, became most important. These results call for studies on improving aeration management to reduce variability of dissolved oxygen in ponds.     

Evaluating partial harvesting strategies for whiteleg shrimp Litopenaeus (Penaeus) vannamei semi-intensive commercial production: profitability,uncertainty, and economic risk

Aquaculture International - A bioeconomic model and Monte Carlo simulation were used to analyze alternative management scenarios of partial harvesting schedules in semi-intensive shrimp...     

Implementation of an experimental nutrient film technique-type aquaponic system

Aquaponics has been considered as having great potential as an organic production method of aquatic organisms and vegetables, because the nutrient-rich water from aquatic organisms is utilized for plant growth. The essential elements of an aquaponic system consist of the following five: a tank to maintain aquatic organisms; a clarifier or sedimentation; a biofilter; a hydroponic component; and a sump pump. In this paper, we propose the design and implementation of a nutrient film technique-type aquaponic system, which does not include the sump pump. Aquaponic systems were tested during one production cycle of the Carolina cucumber (Cucumis sativus) and Parris Island lettuce (Lactuca sativa). The aquatic organism employed was tilapia (Oreochromis niloticus). Nine systems were utilized with the aquaponic technique, and the remaining three were utilized with only the hydroponic technique as controls in plant production. The proposed aquaponic system worked efficiently during the entire crop cycle without any problems or deficiencies from lack sump. No changes were made in the flow of water in the aquaponic system during the growing season. Tilapia survival was 97.2 ± 2.4 %. Specific growth and food conversion ratios were 4.95 and 0.99, respectively. In plant survival, there were no significant differences (p > 0.05) between both production techniques. In lettuce, foliar wet weight, foliar dry weight, and yield were higher (p < 0.05) in hydroponics. In cucumber, fruit number and yield were higher (p < 0.05) in the hydroponic system. Fruit length, width, and weight exhibited no differences (p > 0.05).