When thinking of endangered species, most people will automatically imagine the large mammals: giant panda bear, rhinoceros, tiger or elephant. However, there are hundreds of smaller species who find themselves on the endangered list. The task of preserving these species and increasing their numbers sufficiently to remove them from the endangered species list falls to citizens; and fish hatcheries would seem to be one such method to achieve this.
The International Union for Conservation of Nature (IUCN) has a red list which categorizes species depending on the global level extinction risk. This list is far from complete, however, and assessments are ongoing. According to the IUCN only 5 percent of the species on the red list are marine species, making this a highly under-represented group. In addition to this, species in the freshwater ecosystems are used for human livelihood, making this the most threatened group. Overfishing, pollution and a change in the environment, such as dams or a decrease in water, all threaten the numbers of fish in the affected populations. Thus fish are a commonly overlooked, but threatened, taxon that needs to be preserved.
The aim of fish hatcheries in aiding endangered species is to breed individuals in a controlled environment for release into the wild in order to increase the number of individuals in the natural population. Hatcheries can be used either for only one specific type of fish or for a number of various species all together. There are two types of programs with very different focuses. An augmentation program seeks to increase the natural population for commercial use. The hatchery fish are not intended for integration into the wild population, and generally the fish that are reared in the hatchery become the brood stock for the next generation, although straying does occur. Breeding fish in these hatcheries uses a limited genetic pool, which creates a genetic drift from the wild population and limits the genetic variance of the captive bred population in comparison with the wild population. Interbreeding these two populations decreases the genetic diversity, which threatens the productivity and adaptability of the natural population. Studies have shown that hatchery-bred fish produce less offspring than their naturally occurring counterparts. Additionally, fish bred in a hatchery are adapted for the hatchery environment and are less suited to survival in the wild. This reduces the fitness of the population as a whole.
Programs that are focused specifically on conservation are more beneficial to endangered species. These programs use adults from both the natural population and hatchery origins. The juveniles are kept in an acclimation facility before they are released into the wild population to continue their life cycle in conjunction with the wild population. These hatcheries are focused on the long-term increase in the numbers and the fitness of the fish instead of the short-term boost in numbers. There is a constant need for monitoring of the genetic and ecological impact of the program to ensure that the hatchery-bred fish do not replace the natural fish.
The research is still ongoing, and more is being learned about the impact of fish hatcheries on the natural population and what can be done to minimize the negative effects. With an increase in the awareness of the effects of hatcheries on the natural population, more steps can be taken to reduce this impact and the conservation efforts will improve. Although hatcheries are beneficial for endangered species, it is unwise to eliminate all other options of survival and rely solely on fish hatcheries to ward off extinction for every endangered species.