The discoverer of the Titanic, Dr. Robert Ballard, famously referred to the deep sea as "much more alien than going to Mars or the moon." The deep sea is one of the largest virtually unexplored ecosystems on the planet; it is found at a depth of 1000 fathoms [1] and is subject to, among other factors, adverse changes in temperature, pressure and light penetration. Therefore, as expected, fish decline in abundance and species diversity. This trend is evident because, to survive the harsh conditions of the deep sea, fish require a series of specific adaptations. Allowing them to survive, feed and reproduce. The deep sea is one of the most hostile environments in the world to which a living organism is subjected. As you proceed from the surface (epipelagic zone) to the abyssopelagic zone near the ocean basin; environmental characteristics begin to change drastically. Light, pressure, oxygen, temperature and food are abiotic factors that have led to the fascinating adaptations of life in the deep sea. Pressure alone increases by 1 atmosphere for every 10 meters of depth, an astonishing rate. The temperature of the deep sea remains between 2-4°C, which is just another factor that inhabitants must overcome to survive, along with a reduced quantity and accessibility of essential factors such as oxygen, food and light[3]. From surface to 'water its maximum depth is the ocean of 11 km, and with this distance comes a great change in the physiological characteristics of fish as they try to survive the changing conditions. The bottom of the deep sea exists in darkness as little light penetrates through the surface. Therefore, most inhabitants must rely on their senses to survive. Fish need light to survive; they... they're half the paper... any environment except the deep sea fish had to evolve immensely just to survive. Works Cited[1] http://www.bbc.co.uk /nature/habitats/Deep_sea[2] http://www.seasky.org/deep-sea/ocean-layers.html[3] http:/ /marinebio.org/Oceans/Deep[4] http://www .suite101.com/content/adaptations-of-deep-sea-fish-a230044[][6] http://www.eoearth.org/article /Bathypelagic_zone?topic=49523[7] http://www.allthesea .com/Deep-Sea-Fish.html[8] http://www.suite101.com/content/adaptations-of-deep-sea-fish -a230044#ixzz17YRH7Amz[9] Extreme deep-sea and shallow-water habitats: affinities and adaptations by Franz Uiblein, Jorg Ott and Michael Stacowitsh 1996[10] http://www.marinebiology.org/fish.htm[11] Adapted from http://www.mbari.org/earth/mar_tech/EITS/ob_deep /od_back.html[12] http://sanctuarysimon.org/regional_sections/deepSea/overview.php