The fish was sacred to the Greco-Roman mythology, where it held symbolic meaning of change and transformation. We see this in the myth of Aphrodite and Heros when they turned themselves into fish in order to escape from the ferocious Typhon.
In Christianity, the fish is a symbol of abundance and faith as observed in the Biblical story of fishes and loaves. There are also several Biblical references as Christ and his disciples being “fishers of men.” Here, man is represented as the transformational fish and the ocean is a symbol of the abyss of sin in which man finds himself.
Pagan traditions recognized the fish as a feminine symbol of fertility and an attribute of the Goddess. Water is a natural emblem of the flow of the Divine Mother principal, and as such, all creatures of the water (including fish) are aspects of the fertility and power of the female deity.
As an ancient Celtic symbol, the symbolic meaning of fish (salmon, specifically) dealt with knowledge, wisdom, inspiration and prophecy. Ancient Celts believed the salmon derived its wisdom from consuming the sacred hazel nuts from the well of knowledge (Segais). Further, they believed to eat the salmon would mean gaining the wisdom of the well too.
In ancient Eastern Indian mythology, the fish is a symbol of transformation and creation. This is observed in the ancient flood myth in which Vishnu transformed himself into a fish (Matsya) to save the world from a great flood. In this form, he guided king Manu’s boat (which contained the select few survivors & seeds of life to re-create the world after the flood subsided) to safety.
Ancient African creation myths tell of Mangala, the creator, planting seeds in the cosmic womb. From these seeds two fish erupted, and were set forth into the cosmos upon the waters of creation. We see from this myth the symbolic meaning of fish yet again deals with fertility and creativity by embodying a new phase of initial life.
In China, the fish is symbolic of unity and fidelity as it is noted that fish (particularly koi) often swim together in pairs. With this in mind, fish are often given as wedding gifts in the form of charms or figurines to present the newly-wed couple with an auspicious sign of fidelity and perfect union. They also represent fertility and abundance due to their ability to reproduce in speed and volume.
Furthermore, in Buddhism, the fish symbolizes happiness and freedom. Also the fish makes an appearance as one of the eight sacred symbols of the Buddha: 1) Conch, 2) Lotus, 3) Parasol, 4) Wheel, 5) Knot, 6) Pair of Golden Fish, 7) Banner of Victory, 8) Vase.
Lastly, in Norse and ancient European cultures, the fish had symbolic meanings of adaptability, determination, and the flow of life. It was observed by these cultures that fish often display enormous attributes of adaptability in the wild, and they adopted these characteristics for themselves. Salmon were commonly revered for their determination in their annual pilgrimage to their spawning grounds – the entire journey swum against the current.
I still think people were planted in poo pots by disgruntled alien clock punchers, seeded on the earth, and accidentally implanted with the attitudes of the 'planters'. 
