What is lead core fishing line primarily used for?

Lead core fishing line is designed specifically to help anglers present their lures at greater depths in the water column. This type of fishing line has a core made of lead, which provides the weight needed to sink the line quickly and effectively. When using lead core line, an angler can achieve deeper fishing without the need for heavy weights or downriggers, allowing for more precise lure presentations at various depths.

The other options don't align with the purpose of lead core fishing line. Staying on the surface pertains more to lighter lines that facilitate top-water fishing, while fishing in shallow streams typically does not require the use of a weighted line like lead core. Additionally, while larger fish species may be targeted with lead core line, the line's primary function is depth management rather than size targeting.