Fish is one of the most nutritious food available to man. With a large amount of protein and other macro nutrients, it is a reservoir of other micro nutrients too, which are needed by our bodies for good functioning and are not available from any other sources in adequate quantities. Apart from being a food source, it has medicinal properties embedded in its every form. Be it oil, flesh, eyes or any other organ or secretions, fish fulfil every need. Food being the prime necessity, fish is a respected source.
Since the times man has known, not only food, but fish has served as an object for recreation and commerce. Fish hunting and spear fishing has been famous since the times of great emperors. Along with tigers, great fishes were caught as a trophy to prove someone’s might. Today also, Mahaseers and Trouts are known to be very famous sport fishes. But due to human negligence and selfishness, they are not far from being highly endangered or extinct.
Commercially, various species of carps and catfishes are liked by people on their plates. Apart from these two, Tilapia, pomfrets, sardines, mackerels, tuna, shrimps, etc. and other species are very famous as food. Due to such increasing popularity and demand, we culture these fishes in our vicinities artificially. But with the increasing populations, this is not enough.
Man has used nature in its own ways which have surely upset it. With the increasing trade in this sector, several fishes are continuously torn apart from their habitats and brought in other new places to breed. This abrupt introduction of foreign members in a community disturbs the whole ecosystem. It has many adverse effects to the newly introduced species, native species, flora, other fauna as well as the physical environment. Following the Darwin’s theory of Natural Selection, every animal fights its chance to adapt in the ecosystem to survive and not be the weakest. This game of nature vanishes species because of human interference. Such species, those are newly introduced at a new place other than their own native grounds, are known as Alien/Invasive species. These organisms, whether or not introduced for human benefits, sooner or later, effects the native fauna and flora or the place adversely and disturbs its ecosystem.
Till yet, a large number of species of fishes are introduced in Indian grounds intentionally or unintentionally. For example, the Chinese carps from China were introduced in India due to their high fecundity, easy adaptability, fast growth, high tolerance range [Grass carp (Ctenopharyngodon idella) can survive the temperature range till 40˚C], as well as their high feed conversion efficiency (now measured as the protein assimilation efficiency). The 3 major species were introduced for food in Indian waters and as highly culturable fishes for food in aquaculture.
But if we take the example of the introduction of the Walking catfish (Clarias gariepinus) in the Ganges, it affected the growth of native species to a great extent as to adversely reduce the species richness of the said ecosystem.
In every field of fisheries, we see various alien species being introduced that are either beneficial or only commercially viable which effect the environment harshly upon multiplication. Similar invasions were seen in the ornamental, sport and other fields to improve the commercial values ignoring the disturbances imposed on the ecosystems.
Ornamental sector has seen emergence of exotic live bearer species becoming very famous in the commercial market. With their beauty and easy handling, they became the cherry on the top in the sector. We see fishes as egg layers only. This unique phenomenon of giving live births and also the different methods of parenting taken up by different parent fishes attract various enthusiasts in the industry. They give whatever price asked for them. These species give a new aura to the habitat of the aquarium adding to its aesthetic value. A little extra care doesn’t count ahead of the richness they bring to the table.
In a nutshell, Exotic fishes bring a new value to the industry, be it in taste, aroma, products, aesthetics or entertainment. They leave us no reason to regret. But behind all this glamour, we don’t see the destruction to our nature. The alien species introduced multiply rapidly if favourable conditions are provided or they die at the similar rate if they are unable to adapt. Both contain their negatives. These organisms fight for their survival mercilessly. In many instances, the accommodation of such species proved disastrous for our native ones. Many such went extinct from their own habitats. Multiplication of the invasive species led to over crowding and overfeeding in natural waters disturbing the whole flora and fauna of the place. Some are plankton feeders, some are herbivorous while some are carnivorous in nature. All combined, interfere in the balance made by nature at a particular habitat.
Due to the varying physical and geochemical conditions of the Earth, every place on the planet harbours its own unique species of organisms and also the pathogens that thrive on the hosts. Every time a new alien is introduced in an ecosystem, it brings its own set of diseases which are new to the natives. With the stress of new accommodations, feed and space competitions as well as new predators, diseases spread rapidly perishing many natives at once. These diseases soon enter the humans zoonotically, sometimes creating new strains and becoming stronger.
Today’s competitive world is dragging nature into its jaws. The race of being a highly biodiverse and commercially superior nation has turned every thing upside down. The organisms who don’t even know their value are put price tags on. Humans, too, follow the survival law of nature but to the extent of killing every organism on Earth. Food remains the foremost priority to survive but the entertainment sectors still remain fully commercial and disturb the cycle of nature. Relocating resources disturb the balance and some things just cannot be undone by being sustainable.