Ocean currents and gamefishing
by Rocky Carosi
Ocean currents are nature's highways and food chain providers of the open seas. Off Tasmania, East Coast gamefisherman await the arrival from the North - the East Australian current carrying the complete marine food chain and gamefish.
In offshore fishing, blue is beautiful, and this is often the colour sought for big fish in many places, including Tasmania. The best gamefishing can often be in the cooler water - not all gamefish come from the blue water.
At times, for many reasons, the action comes in green and brown water, but whatever the colour, the dominating effect of the currents is known to successful fishermen.
The current temperature and flow over the sea bed, coastal configurations, continental shelf and deeper canyons and drop-offs trigger the concentrations of microscopic plant and animal life that start the food chain. Currents trigger upwellings of the deep ocean water with its concentration of nutrient-rich decaying and dead organisms brought to the surface. This concentration of minerals and salts stimulates the growth of plant plankton which is the start of the food chain that nurtures the microscopic animals that are the base of predatory life in the ocean.
The current edges are most productive. The currents and counter currents become ocean drifts as they weaken or are wind-driven. All have names.
Their direction is guided by that of the prevailing winds, the rotation of the earth and the shape of the coastline.
Southern Hemisphere currents circle anti-clockwise.
Even though currents often appear to be streams running along the coast, in reality they meander in pools and eddies surrounded by the circling edge of the current. These pools and eddies are important to offshore recreational and commercial fisherman who look for current and temperature edges.
The edges are a guide to where to fish and are clearly shown on satellite photographs of the ocean surface. The currents are the hunting ground as well as the moving home of the gamefish, many of the fish wander with the currents.
Research of tagged gamefish and sharks shows that many species pass or congregate in the same area at approximately the same time and conditions each year.
The currents vary in temperature, speed and direction from season to season. In some seasons, fingers of differing water temperature will push into the water along the coast. These fingers have the benefit of providing temperature edges but can have the disadvantage of pushing cool water in close to the coast and moving warm water further offshore out of range of sport fishermen.
Tasmania's East Coast is only just reached by the East Australian current and the distance it travels south varies each year. Sometimes the leading edge will stop off Bicheno or, in years of a strong push, will continue south past Tasman Island. Unseasonal strong, cold offshore winds will also push the current further from shore or cool the top layer keeping the warm water and fish down deeper.
Wherever you gamefish, the important rule stays the same - current edges and temperature differences should not be ignored.
When you do find a current edge, and this can be by sight - either a rip, flat water or a change in colour - concentrate on this area. Troll across it whilst keeping watch on the fish finder for changes in water temperature.
Known reefs are also perfect places to look and for many gamefishers this is the first place they visit.