Man's avarice has started harming even the existence of tuna fish.
Though tuna used to be seen in almost all the oceans of the world, commercial fishing has risen to such alarming levels that the population of tuna fish is reduced drastically.
Especially, the populations of popular varieties like bluefin, albacore and yellowfin tuna are getting reduced.
So getting these varieties of tuna is becoming more and more difficult.
The migration patterns of these varieties of tuna fish are also changing rapidly, posing a challenge to tuna hunters.
But if you learn the right techniques and plan your tuna fishing perfectly, you can succeed in getting a great catch.
Mostly, eight species of tuna fish are there including albacore, yellowfin, blackfin, southern blue fin, bigeye, pacific blue fin, northern blue fin and long tail tuna.
You have several other species also.
Tuna are called warm-blooded fish and their color varies from pink to dark red.
Such color variation is due to a protein molecule called myoglobin and this molecule binds oxygen in the blood.
Due to this binding of oxygen in the blood, muscular activity is allowed and the body temperature of the tuna fish is raised above that of water.
That is the reason for finding tuna in warm and cool waters and also at different depths of water.
Another aspect of tuna fish is that they like to live where the water current is quite strong.
This is because they need a good flow of water over their gills so that they will be able to extract a good amount of oxygen for living comfortably.
Wherever you see strong currents of water, there is always a possibility of finding a good catch of tuna in that place.
Tuna fish also like to live in clean and blue ocean waters.
Some of the species of the tuna like the yellowfin tuna fish like to live and swim along with herds of dolphins and other fish species.
During night hours, they live close to the surface but during day time, they prefer to remain in the depths of water.
If you learn to differentiate between sea temperatures, you can easily find out where you can get a good catch of these tuna.
In general, temperature breaks in ocean waters happen when cold water and warm water converge.
These can lead to differences of huge degrees.
Such areas of convergence will be frequented by baitfish, tuna, billfish and sharks.
This is due to the fact that almost all fish types like warm waters but they may like to cross over to the line of cold water so that they can feed off plankton that live in cold water.
You can observe that yellowfin tuna like to live near floating objects like grass, debris, etc.
that support bait fish.
You will find them only beyond 10 miles away from the shores.
They are called messy feeders and so churned water, terns or shearwaters feed on the left-overs.
If you see circling and feeding birds on the surface of water, you can construe that tuna fish may be available close by.
Albacore species of tuna usually preys upon smaller schooling fish such as sardines and anchovy, and also squid but albacore is eaten voraciously by billfish and sharks.