Pelagic fish vision
It is important to understand that you are encased in the light from the sun, passing though the atmosphere and falling on the land and the surface of the sea. When you look up at the sky, on a clear day the sky, or rather the atmosphere is blue, and that indicates that our atmosphere is, like oceanic water, a blue filter. The light that falls on the ocean is filtered by the Ozone layer and the atmosphere over many kilometres, filtering and attenuating the various light wavelengths until the predominant colour is blue.
The atmosphere also collects and holds water vapour in the form of clouds, which are really just water droplets which refract the coloured photons, like little prisms, and produce white light. So the clouds are white. Often the water droplets are large, and absorb the light photons and the greater the absorption the darker the colour, ie storm and rain clouds. The darker the clouds the greater the light attenuation and the lesser the amount of light which falls onto the ocean surface. But looking down on the clouds, regardless of the type, the colour is white.
Those things that affect you, the night/day cycle, the seasonal changes, the variations in the weather conditions, winds, storms, rain whatever, all affect the passage of light into the oceans, rivers and lakes. The fish, their vision and their day to day activities are affected by the same things that affect us.
In the rivers there are variations relating to bank vegetation, which is varied by sun angle, seasonal growth, wind movement etc. If you understand that, and can modify your fishing to accommodate these changes you are more than halfway there.
Light is modified as it passes through the atmosphere depending on latitude, time of day or sun angle, and cloud cover all of which produce large variations in the amount of light that falls on the surface of the sea. Rain causes surface distortion and wind causes surface waves which move in relation to the direction and force of the wind.
Climate Change and Small Pelagic Fish
Book (Cambridge University Press)
This tuna is hungry2004-05-09 14:06:24 by Bruce_
Tunas are migratory pelagic fishes inhabiting all the world's oceans from temperate to equatorial regions. Although most tunas are spawned in tropical waters, general biological characteristics and habitat ranges of the adults vary among species. Although all tuna species have extreme habitat ranges from the Equator to temperate regions, it is convenient to classify species on the basis of their temperature preference as tropical tunas (skipjack, Katsuwonus pelamis and yellowfin, Thunnus albacares), subtropical tunas (bigeye, Thunnus obesus and albacore, Thunnus alalunga) and temperate tunas (northern and southern bluefin, Thunnus thynnus and T. maccoyii). Tagging studies have shown that all major species of tunas are capable of large-scale movements (>
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Bottom temperature and salinity of the North Sea during the International Young Fish Survey 1983 (C.M)
Book (International Council for the Exploration of the Sea, Pelagic Fish Committee)