The feeding cycle of some fish is directly influenced by tidal movements. In most parts of the world fish that cling to coastal areas feed mainly on the flood tide when smaller organisms are washed in with warmer water in winter and with colder water in summer. There are times when fish feed on the tail end of the ebb tide and the start of the flood tide. This would account for the variation in a fish species' diet from one area to another at different times. What may seem indicative of a certain species' feeding habits in one location, may not be the same at another location just a short distance away.



When smaller organisms and small fish are washed in with a rising tide, bigger fish will follow and feed on them, leaving again when the food source runs out. Dusk and dawn are another of the variables. Large numbers of marine organisms, which the surface fish feed on, move up from the depths at night when the surface water cools. They migrate back to the depths as the sun rises, away from the warmer upper layers and the sun's rays.

Locality also dictates behaviour, not all places in the world have two tides, such as New Guinea. There are places that have one tide higher than the other and other places with mixed tides, sometimes several a day. With the moon exactly over the equator, these places have two tides of equal height and as the angle of the moon to the equator increases, the second tide disappears.

The feeding behaviour and habits of fish which depend on tides vary as much as the tides vary. There is some thought that the variations of the tidal flow confuse the fish. This is not so, if the food rides in with the tide, so will the fish. Uncertain tides may not fool the fish, but they certainly fool the angler. A truly tidal feeding species will feed at irregular intervals, due to the variance of tides and indeed, many fish can go for long periods of time without feeding at all.

An estuary with a rising tide is good news for fish, with organisms washing in from outside the estuary. So just after high tide, many fish move in from the ocean and from the upstream areas to feed in the estuaries on all the fresh organisms.

Currents within the ocean are just as important, especially the vertical and inclined currents which firstly carry cooler water up from the depths to the surface and divert warmer water to the cooler levels and secondly, they bring vast numbers of organisms to the continental shelf where fish can feed on them.

Surface currents are affected by wind and surges, whereas vertical currents react to temperature and salinity. Fish use these vertical currents as birds do the wind currents, rising and navigating to different depths during their migrations. Without these currents which carry plankton and other organisms, fish may not be so abundant around our coastal areas.

The importance of the upwelling currents bringing cooler water to the top and moving warmer water away also negates the need for temperature sensitive fish to remain within their temperature tolerance by following the water away from the coast and away from their natural feeding grounds.