First paragraph: Culturing fish requires that the animals be confined in some controllable volume such as a pond, raceway, net pen, or tank. An important goal with the culturing system is to provide the fish a satisfactory culture environment so that growth and conversion of feed is as efficient as possible. Choice of the culture system is partly dependent upon the species of fish being cultured. Salmonids require very high water quality in comparison with carp and catfish, which have less-stringent water-quality requirements. The largest-scale production systems in the world have generally been constrained to ponds. As an example, the U.S. catfish industry produces 200 million kg per year from pond systems that consist of units that are typically between 2.5 to 5 ha in a rectangular shape. Raceway construction typifies the production systems used to produce salmonids, and in particular trout, and in both Europe and the United States the majority of production occurs for these species in raceways. Tanks, round, hexagonal, or octagonal, are commonly used for a variety of species, but generally for smaller scales of production. This trend is changing, however, with some of the largest farms concentrating on the use of tank structures. The advantage of tank culture is that it lends itself to easy maintenance because tanks can be designed to be relatively self-cleaning of fish waste and uneaten feed. For indoor fish farms, tank culture is by far the most dominant method of culture. In Norway, all juvenile salmon are produced in tanks using a range of tank sizes from 3 to 15 m in diameter and up to 4 m in depth. Recent advances in indoor culture technology indicate that indoor fish farming and tank culture may become the standard of the future, particularly in the United States, where environmental considerations and constraints may force tank culture in which waste streams can be controlled. Net pens are used mainly for larger fish and on sites that have good natural water currents. Net pens are generally considered cheaper per unit of fish-carrying capacity than land-based units. Most of the adult salmon production in the world uses net-pen culture systems. Each of these culture-system types is discussed in the following sections. A key factor in selecting the appropriate culture system is the scale of operation intended. Small-scale operations of 12,000 to 20,000 kg per year often are economically competitive only because of local market opportunities and the use of family (subsidized 245 or noncosted) labor [1, 2, 3]. Sedgwich [1] found that 20,000 kg of trout production was the smallest farm that could provide a viable income if fish production were the sole source of income. Intermediate-sized operations do not appear to offer much advantage.
Nile tilapia Oreochromis niloticus (L.) held in timed-pulse feeding chambers, were provided with algal-rich water dominated by either green algae (Scenedesmus, Ankistrodesmus, Chlorella and Tetraedron) or cyanobacteria (Microcystis) to determine the effect of temperature and phytoplankton concentration on filtration rates. Green algae and cyanobacteria filtration rates were measured as suspended particulate organic carbon (POC) kg−1 wet fish weight h−1. Ivlev's filter-feeding model described the relationships between filtration rates and suspended POC concentration of green algae and cyanobacteria. Filtration rates of both green algae and cyanobacteria increased linearly as water temperature increased from 17 °C to 32 °C and were significantly higher in the warm-water regime (26–32 °C) than in the cool-water regime (17–23 °C). Filtration rates at 95% saturation POC (FR95) in green algal and cyanobacterial waters were 700 mg C kg−1 h−1 and 851 mg C kg−1 h−1 in the warm-water regime and 369 mg C kg−1 h−1 and 439 mg C kg−1 h−1 in the cool-water regime respectively. The FR95 in warm water were achieved at lower POC concentrations than in cool water.
Abstract A commercial micropulverized 50% crude protein diet for penaeid culture was studied for biochemical oxygen demand and to assess its effect upon water quality in the hatchery and raceway environment. The feed was separated into 13 sizes ranging from 250 μm to 2 mm in diameter. The first order reaction rate constant (k) increased with decreasing particle size. The micropulverized feed was highly biologically reactive and the rate constant (k) varied from 0.1 to 0.24 day ‐1 , depending on the particle size. The ultimate BOD was 660 mg/g. The goal of this research was to predict the impact of this feed in relation to varying particle size upon the oxygen and ammonia dynamics of the water. This information will enable shrimp hatchery managers to more effectively assess the water quality impact and water replacement schemes when using artificial micropulverized feeds.
A generalized ecologic model of a fertilized warm-water aquaculture pond is under development. The model is intended to represent the pond ecosystem and its response to external stimuli. The major physical, chemical and biological processes and parameters are included in the model. A total of 19 state variables are included in the model (dissolved oxygen, alkalinity, pH, ammonia, phytoplankton, etc.). The model is formulated as a system of mass balance equations. The equations include stimulatory and inhibitory effects of environmental parameters on processes taking place in the pond. The equations may be solved for the entire growth period and diurnal as well as seasonal fluctuations may be identified. The ultimate objective of the model is to predict the fish biomass that can be produced in a pond under a given set of environmental conditions.
Globally, aquaculture continues to grow in importance. Equally important is the need to intensify all forms of modern agriculture, in particular, aquaculture. Internationally, aquaculture poses a potential threat to public freshwater and saline water resources. Aquaculture systems and practices are needed that offer potential to reduce or completely eliminate water and waste discharge to the environment. Tilapia co-culture offers great potential as a technique to intensity and improves existing aquaculture production, while simultaneously providing a pathway to recover, recycle, and reuse wasted aquaculture nitrogen and phosphorus discharges as valuable by-product foods, feeds, and fuels. Tilapia co-culture also continues to play an integral role in the ongoing development of The Partitioned Aquaculture System (PAS), The Controlled Eutrophication Process (CEP), emerging zero-discharge marine shrimp production system designs, and aquaculture live food production systems.
ABSTRACT Large‐scale algal culture remains an attractive concept primarily because of the enormous potential productivity that such systems offer. However, the problem of harvesting microalgae remains a major obstacle. This paper examines the usefulness of using brine shrimp culture as a technique for harvesting microalgae and converting to protein and lipid. Specifically a mathematical model which describes brine shrimp growth and conversion efficiency is presented. The usefulness of this model is illustrated by solving for the required brine shrimp biomass needed for conversion of a constant rate of production of single‐celled marine diatoms. The model is further used to demonstrate that the most useful design of such a conversion system is that of a two‐stage system in which the first stage consists of a reactor, or reactors, of young animals operating at low algal cell removal efficiencies followed by a number of reactors of increasing age groups operating in parallel flow arrangement. This arrangement permits a high overall rate of continuous cell removal.
