The open ocean

Offshore Fishing

Fishing the deep-water areas on the edges of ocean currents or the blue-water shelves for big-game pelagic species, particularly billfish and tuna

Oligotrophic Lake

A lake which is generally surrounded by infertile or sterile land, releasing very few nutrients into the water. Also often referred to as trout lakes.

Operculum

This is  the bony support structure that provides a cover for the gills. Involved in respiration and feeding

Outriggers

Poles that extend out from a boat to enable several lines to be fished, without tangling.

Optimum Yield

The recreational harvest level for a species that achieves the greatest overall benefits including economic, social and biological considerations.

Oxbow

A small lake or channel to the side of a river formed when the main river meanders and cuts through a point of land and then rejoins itself downstream, creating an island that separates the two sections of water.

Oxygen Level of Water

The measured concentration of oxygen in water. Different fish species require different oxygen levels. Knowing the oxygen levels of lakes at different depths may help anglers to find fish. For example, oxygen dissolved in water is measured in parts per million (ppm). 8 to 9 ppm is considered ideal for bass.

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