Original environment rehabilitation manual 3.1
This article focuses on how fish can be bred in order to repair the environment to its original state.
 Determining indigenous species to an area
Due to the rise of Biodiversity projects, it is now possible to find a list of species indigenous to any location on earth. This allows anyone to determine whether a fish is indigenous or not (and thus need to be removed). Examples of a popular catalogue available online is the Encyclopedia of Life, and the Global Biodiversity Information Facility. Besides these international catalogues, local universities and governmental environment divisions also often have lists that may be used.
In practice, not all of the species that inhabit an area are not determined and thus it is not economically feasible nor recommended that all non-indigenous species are removed from the area you wish to repair. However, if certain species becomes a pest, and it is determined that they are non-inginious, it is advised that the species is eradicated fully. An aid in determining the species that has become a pest may be the DAISY, and the barcode of life
If your project is aimed at fish enhancement, then water quality parameters will need to be of a particular degree to allow this. Also, if the fish need coral or other benthic life for feeding purposes, the water quality needs to be hightened to allow the survival and propogation of these species as well (corals generally require higher water qualities, bentic lifeforms often do not require higher water qualities but may appreciate eg salinity levels that are closer towards their personal optimal range).
For fish, make sure dissolved oxygen (DO) levels can support fish and rarely, if ever, become hypoxic (low oxygen levels). Use Dissolved Oxygen (DO) Test Kit if you are in water you believe might be marginal. (See the glossary for information on DO test kit use). While there is no universally accepted threshold for dissolved oxygen, in most cases, water with less than about 3ppm (parts per million) of dissolved oxygen is considered hypoxic, and is too low for most fish species. Water with between 3-5ppm is marginal, and greater than 5ppm is normoxic, or normal.
Salinity is also important for many fish species especially estuarine fish. Salinity can be measured with a hydrometer (specific gravity meter) or refractometer. Specific minimum and maximum salinity reference levels very widely from species to species. Some species can tolerate water all the way from fresh (0ppm) to fully saline (?35ppm). Some can only tolerate a very narrow band of salinity. Be sure to study the requirements of the specific species you are trying to protect.
Temperature ranges and depth are also important to fish. Your local experts can assist in determining the particular conditions that your target species prefers. In many cases you will find ample scientific research on the subject. Consider investigating online databases such as Fishbase (www.fishbase.org) as a starting point for your research. In some cases, you may have to rely on the instincts of local experts. Fishing and diving groups are usually knowledgeable sources. You will probably learn that their may be other local conditions that play an important role in site suitability.
Toxicity is also an important factor, and not only toxicity to fish but toxins that can accumulate and build up in fish tissues making them dangerous for human consumption. If you are working in an area (either water column or sediments) that might contain heavy metals, red tides, PCBs, or suspected carcinogens you will need to test for their presence and consult local authorities about acceptable levels. Do not use base materials that contain toxic elements. It is beyond the scope of this manual to identify all the tests and potential toxins to be concerned about in your project so we suggest obtaining local experts.
If you have sufficient resources and expertise, Geographic Information Systems (GIS) analysis and remote sensing techniques to determine spatial and temporal distribution patterns may be useful. If the conditions are suitable for your target species, then the most important factor for rehabilitation of reef dwelling fish (and reef associated pelagic populations) is protective voice space and for fish that obtain significant dietary contributions from the fouling community, the surface area of hard substrate. This is a combination of the size and complexity of the artificial reef or base rock chosen and its layout on the sea floor. Contact the artificial reef manufacturer or local fishery scientists for information on how to choose the right sizes, layout and styles of artificial reefs or base rock for fishery enhancement purposes.
In general, if there are reef-associated fish on or near your site, more fish will be there once you add protective void space (via your base materials). ‘Fish only’ projects do not need to plant corals. In environments where corals can grow, they will recruit to the artificial substrate naturally over time, so it is best to focus project funding on protective void space creation. These projects are better classified as artificial reef or fisheries rehabilitation projects, as they usually don't focus on reef rehabilitation.
This information was Reef Ball's Draftguide document.