In the United Kingdom, the growing population of ornamental fish is estimated to be over 144 million – more than double the human population (OATA, 2003).
Keeping marine ornamental fish is the latest in the trend of fish keeping and consequently still relatively small, nevertheless, the hobby is expanding rapidly (Mills, 2001).
The vast majority of exotic marine ornamental fish are imported into the United Kingdom via a strictly and responsibly regulated network of wholesalers that makes up to marine ornamental trade industry.
It is believed that in the United Kingdom 300,000 ornamental fish are imported annually, costing ? 400,000 per tonne at import (OATA, 2003).
Worldwide, harvesting of marine ornamental fish accounts for only a small fraction of the sea-fish catch. The total number of marine ornamental fish imports is estimated to be 10 million, weighing between 70 – 100 tonnes. This is a mere drop in the ocean when compared to the 100 million tonnes of fish that are caught for human consumption and the 17 million tonnes that are caught and tossed back into the ocean as waste (OATA, 2003).
To the marine ornamental fish enthusiast, the ecological and educational benefits of fish keeping are clear: Responsibly regulated importing and exporting of environmentally sound ornamental fish help to raise the profile and understanding of marine life and the marine environment in general. Moe (1993) summarises some of the moral implications of keeping marine organisms in captivity by saying that as long as we use the living resource of the sea for food and fishing, sustenance and enjoyment, keeping a marine aquarium will be a source of knowledge, achievement and personal satisfaction. Ornamental Fish Production Alasdair M. Weddell Today, however, tank-bred fish provide the marine ornamental fish enthusiast with an alternative to wild-caught fish. Aside from the obvious absence much of the ecological considerations, tank-bred species offer the marine ornamental fish enthusiast organisms that are very often better suited to captive conditions than their wild-caught counterparts.
Due to advances in aquaculture and water filtration technology, many popular ornamental species of marine organisms can be successfully, commercially produced in a synthetic environment. The marine fish hatchery at Tropical Marine Centre Ltd in Hertfordshire raises animals in a mixture of borehole water, raised from 60 metres underground, and synthetic sea salt. Using its own designed and built range of water filtration equipment – spawning pairs of ornamental fish produce commercial quantities of offspring in an environmentally stable, controlled environment (TMC, 2004).
The hatchery at Tropical Marine Centre Ltd is one of a growing number of recirculation filtration systems, or closed systems (Walker & Whitaker, 2001), that give the ornamental fishproducers new levels of control over the chemical and biological parameters of the production environment. Hatchery systems, and recirculation systems in general, must employ three type of filtration to manage water quality: mechanical, biological and chemical filtration. In mechanical filtration, suspended particles such as uneaten food and faeces are physically removed (Walker & Whitaker, 2001).
In a small-scale hatchery, this is achieved using cartridge or bag filters that simply allow water to pass through while the filter retains particulate waste. Biological filters exploit the metabolic properties of certain bacteria to breakdown metabolites such as ammonia and nitrite. The bacteria are encouraged to grow on carrier media such as plastic rings or oolitic sand and gravel. The carrier media is incorporated into the filtration system as an under-gravel filter, trickle tower (Walker & Whitaker, 2001) or fluidisedsand tower.
Control of pathogens in a hatchery is an important aspect of water management and treating water under ultraviolet light is an effective way of limiting the numbers of harmful organisms. Chemical filtration refers to the removal of dissolved organic (Walker & Whitaker, 2001) and other undesirable chemical compounds. In the marine fish hatchery, this is important in maintaining a stable environment and eliminating toxic compounds that can affect production. 3 Ornamental Fish Production