Grow-out Systems Research Articles

Disease Problems Affecting Cultured Penaeid Shrimp in India.

Some of the major disease problems affecting cultured shrimp (Penaeus monodon, the major species and P.indicus) in India are presented. In hatcheries, mortalities due to Vibrio infection are common. A high incidence of occlusion bodies indicative of monodon baculovirus (MBV) has been found in larvae obtained from various hatcheries. However mortalities due to MBV infections are observed only occasionally. In the growout systems, white spot syndrome is the major problem causing serious mortalities. Parasitic diseases are aproblem in badly managed ponds and in shrimp infected by viruses.

Trade Disputes and Productivity Gains: The Curse of Farmed Salmon Production?

Trade Disputes and Productivity Gains: The Curse of Farmed Salmon Production?

Optimal stocking and harvesting of size-structured farmed fish: A multi-period linear programming approach

In this paper, a new approach to the production planning problem in fish farms is developed. Production planning problems include: the determination of the optimal number of fry to transfer into the grow-out system, the estimation of population growth and production costs, and the determination of the optimal harvesting schedule in order to maximise profits from the operation. Fish growth has been modelled as a series of transitions through different size-classes. The probability of an individual belonging to a certain size-class at a given future time can then be estimated. Both the growth model and the minimum feed requirements of fish can be determined as linear functions of fish growth. A multi-period linear programming model was then developed to optimise the number of fry and number of harvested individuals from various size-classes, that maximises the net present value of the fish stock.

Empirical investigations on growth of post-smolt Atlantic salmon ( Salmo salar L.) in land-based farms. Evidence of a photoperiodic influence

The growth rates of post-smolt Atlantic salmon ( Salmo salar L.) at four commercial and two experimental-scale land-based farms in southern Norway were estimated. These farms are among the first land-based salmon grow-out systems that are operated in Norway. The fish were reared in various sized circular tanks, and neither feeding regimes, water quality nor stocking densities were considered to have limited growth rate at any time during the study. A seasonal variation in growth rate was evident at all the study farms. Growth rate in fish subjected to natural daylight was depressed during the autumn and winter. Conversely, no such growth depression in winter was determined at the farm using a continuous light regime. The relationship between growth rate and possible explanatory variables (fish size, water temperature and photoperiod) was analysed and quantified using multiple regression analysis. The results demonstrated clearly that growth in post-smolts in land-based farms was strongly influenced by photoperiod. This commercial-scale work confirms results from experimental studies reported by several authors.

Preliminary Observations on Oyster Pearl Net Cultivation in Coastal Georgia

This work reports on survivorship and growth rates attained by a transplanted northern stock of Crassostrea virginica (x̄ = 15 mm) tested at various densities in pearl nets in sheltered and exposed sites in coastal Georgia (October 1985 - August 1986). Monthly growth increments ranged from 4.5 to 5.1 mm (shell height). One hundred oysters per net was the optimum stocking density. One hundred percent mortality was suffered at both sites during June - August (probably due to Perkinsus marinus). Current growth rates indicate a growth to market size time of 18 months or less for 15 mm seed grown in pearl nets. However, pearl net cultivation is shown to have serious drawbacks as an oyster grow-out system for coastal Georgia and alternative systems are discussed.

The Sheepshead Minnow Cyprinodon variegatus—A Major Pest in Experimental Mariculture of the Gulf Killifish Fundulus grandis

AbstractIn an experimental Fundulus grundis hatch and growout system at the Cedar Bayou Mariculture Laboratory, egg‐to‐harvested‐fry survival rate of F. grundis was inversely related to percentage of Cyprinodon variegatus fry present (P < 0.05). Competition for food and space was noted in growout ponds, and high mortalities of F. grundis fry and adults occurred in mixed holding containers as a result of the agonistic behavior of C. variegutus. The hardiness and aggressiveness of the sheepshead minnow, its ability to enter water supplies as small prolarvae, its early sexual maturity, and rapid increase in ponds make it a significant pest in mariculture.Control measures for C. variegutus include screening incoming water; hand‐sorting contaminated broodstock and fry; and draining, drying, and refilling infested ponds to allow drought‐resistant eggs to hatch, then draining and drying again.

A 13C/12C Tracer Study of the Utilization of Presented Feed by a Commercially Important Shrimp Penaeus vannamei in a Pond Growout System1

AbstractA study of added feed utilization by pond grown shrimp was done using seven feeds with different 13C/12C ratios, as expressed by δ13C. The pond shrimp did not track the δ13C value of the feed to the extent that tank grown shrimp did. For the seven pond experiments the δ13C data indicate that the added feed supplied between 23 and 47% of the growth carbon. This implies that between 53 and 77% of the growth is due to the grazing on pond biota. It is suggested that this experimental approach can be used to evaluate the relative contribution of presented dried feeds versus natural productivity in ponds as an aid to developing pond management strategies and optimum feeds.

Fish bioenergetics and growth in aquaculture ponds: I. Individual fish model development

A dynamic model of fish bioenergetics and growth at the organismal level under controlled environments was developed as a tool to study, evaluate, and improve the management of fishpond grow-out system. The model incorporated five key variables, namely body size temperature, dissolved oxygen, unioinized ammonia and amount of food, and 17 growth parameters which defined the species of fish used. Parameters were estimated for channel catfish. Fish growth was more sensitive to changes in food consumption parameters than to changes in metabolic parameters. Within either the food consumption component or the metabolic component, fish growth was more sensitive to changes in temperature parameters than to changes in parameters for body size, dissolved oxygen or unionized ammonia. The model may be reparameterized to represent different species of fish in different environments and provides a common ground for theoretical, laboratory and field studies. It also provides a means by which research activities of several groups can be coordinated toward achievement of a common goal.

Optimization and Partial Characterization of a Putative Probiotic Bacterium Antagonistic to Vibrios in Shrimp Larval Rearing System

Organic aquaculture utilizing probiotics for disease control and bioremediation has gained global acceptance in recent years. A preliminary study was conducted to isolate indigenous bacteria antagonistic to pathogenic vibrios as putative probiotics for shrimp hatcheries and grow-out systems. These efforts resulted in the isolation of a Gram-positive bacilli after screening thirty one water samples, collected from the coastal areas of the Bay of Bengal. This probiont, identified as Bacillus licheniformis exhibited vibriocidal activity in vitro against 60% of the Vibrio species isolated from the same water samples based on broad spectrum antagonistic and hydrolytic properties. In this study, we looked into the effects of pH, temperature, salinity, surfactants (Triton X114, Tween 80 and SDS) and EDTA on the vibriocidal property of the cell-free supernatant of the probiotic and observed that the antagonistic property was refractory to the surfactants used. The optimum activity of the cell-free supernatant was observed at 30°C, below and above which there was a marked decline in the inhibition. Neutral and alkaline pH ranges favored the antagonistic property while it was negligible at acidic ranges. The metal chelator EDTA nullified the antagonistic property at 0.01 mM concentration, the lowest tested, indicating the presence of a metal active group in the active fraction. The study suggests the potential of the selected bacterial isolate as a putative, antagonistic probiotic useful in the aquaculture systems of the tropics considering its broad antagonistic activity, higher activity in the neutral and alkaline pH and optimum activity at 30°C. Efforts are underway to purify and characterize the antagonistic compound in the cell-free supernatant. Key words: Probiotic; vibrios; Bacillus; shrimp; cell-free supernatant DOI: 10.3329/dujps.v9i1.7426 Dhaka Univ. J. Pharm. Sci. 9(1): 23-29 2010 (June)