Glück Auf is loosely translated as "good luck to us all".

Sunday, January 27, 2013

Survey Study of and Stocking Densities for Tilapia-Shrimp Polycultures 10NSR3

Source: Oregon State University

Ecological Basis for Tilapia-Shrimp Polyculture In nature, tilapia are omnivores. Young tilapia graze on algal and bacteria films scraping most hard surfaces with tongue and teeth. As they grow they also become effective filter feeders of phytoplankton and predators of zooplankton. Larger tilapia are less effective filter feeders but begin to graze heavily on macrophytic algae and aquatic plants. In extensive farming situations, tilapia filter feed on algae, prey of zooplankton and scrape films from any hard surfaces in the pond. In intensive farms, most nutrition is derived from pelleted feeds, although fish will continue to spend time scraping algal and bacterial films from all surfaces.

In nature, shrimp feed first on phytoplankton and then zooplankton during larval stages. As juveniles and adults they are omnivores and detritovores. Their natural behavior is to search the bottom substrates for decaying plant and animal material. They also constantly pick up sand grains and pieces of organic matter and graze off the algae and bacteria, drop the grain or particle and go onto the next item. In farmed settings shrimp feed on pellets and natural productivity in the pond. Research by Samocha et al. (1998), has demonstrated that shrimp can be reared in systems with little water exchange, taking advantage of the natural abilities of shrimp to thrive in conditions with high bacterial loading so long as dissolved oxygen levels and other water quality factors are maintained.

There are several variations on tilapia-shrimp polyculture: simultaneous, sequential, and crop rotation. In the simultaneous instance the fish and shrimp are grown together in a pond or raceway, in the sequential case the water is moved from one growing unit to another, and the crop rotation alternates tilapia and shrimp. There appear to be distinct advantages with each of these systems.

No comments:

Post a Comment

Comment Guidelines: Please be respectful of others at all times. Pretend like this is a competition to see who can be the most mature and the most intelligent. And remember, you have the right to remain silent. I will not delete your posts just because you are embarrassed that your comments make you look like an idiot. Others may or may not treat you with the same respect you have treated them. And finally, thanks for reading and thanks for your comments!