What are hydrographic maps and how can you use them?
Photo credit www.noaa.gov
Hydrographic maps are a valuable source of information above and below water. The details vary a lot, but if a tackle store has a hydrographic map or a map of a lake, you’ll be boating and fishing, pick one up and study it.
Over water, these maps or nautical charts contain information such as the shape of the coastline and the position of boat ramps, bays, points and any dams. A hydrographic map also gives the scale. It’s important to have a good idea of how far it is from point A to point B.
But perhaps just as valuable is the information that an underwater hydrographic map can provide in the form of contour lines. As you learn to read a nautical chart for fishing, look for lines in the water that trace the shoreline. Contour lines that are widely spaced indicate a gradual slope or a similar depth. Closely spaced contour lines are locations with steeper slopes, ridges or slopes.
Why is that important?
This information about depth and how it changes can help you find fish. Deeper sections are a source of cooler water during the summer heat and can remain weed-free as no sunlight hits the ground. Large flat areas can be spawning areas in spring. An area with a steep slope can be a source of buoyancy or current movement that hungry fish know they often carry food. You may be able to find canals that can act as fish highways for some parts of the year as fish move to or from spawning areas.
Hydrographic maps can help you find underwater humps, rock piles, and other places where the ground is changing. These transition areas often attract fish. When renewing your fishing license, see if you can find hydrographic maps of lakes or rivers in your area. It can help make the excursion a success.
Andy is an outdoor writer (http://www.justkeepreeling.com/) and stressed-out dad has contributed over 380 blogs to takemefishing.org since 2011. Born in Florida but raised on the banks of farm ponds in Oklahoma, he now hunts pike, small bass and steelhead in Pennsylvania. After graduating with a degree in zoology from OSU, he worked in fish hatcheries and as a fisheries research technician at OSU, in the US state of Iowa and the US state of Michigan.