About the time my report on Lowrance's new down-scan imaging (DSI) units reached these pages, Humminbird announced a new series of down-scanning units with both its Down Imaging and traditional sonar technology built in.

You might remember me mentioning that the new high-definition, down-scanning sonar units scan thin slices of water from a slow-moving boat to produce their best photo-like images. That can make seeing fish difficult when deeper depth-range settings are selected or while the boat is sitting still.

The five new Humminbird DI models also include a conventional 2D sonar option that delivers fish readings that look the same as they always have at any boat speed or depth range setting. Humminbird's idea is to give you a reasonably priced unit that can deliver picture-like views of the underwater landscape as you ease over it, and then present a conventional sonar view, if needed, when you stop to work any fish or fishy-looking areas.

The 788ci HD DI Combo model includes GPS chart-plotting with an internal antenna, 5-inch color display, Ethernet connection, dual SD card slots and upgradable software. Stepping down to the 597ci HD DI Combo model eliminates the Ethernet port and one of the two card slots. The 596ci HD DI is the top sonar-only model with 5-inch color display. The 570 DI is a sonar-only unit with 5-inch monochrome display, and it also comes as the 570 DI Portable with rugged carrying case, a suction-cup transducer and a 7Ah battery and charger.

All the new Humminbird models, except the portable, ship with a newly designed, high-speed transducer. Speeds over 50 mph and depths over 250 feet have been verified with the new transducer and different variations or attachments allow for mounting it in-hull, through-hull, on the transom or attached to a trolling motor. Prices for the new DI models range between $299.99 and $799.99. For more information, visit humminbird.com or call 800-633-1468.

Garmin's new "echo" generation of units marks the company's return to the freshwater fishfinder market. The new sonar-only series offers a substantial increase in power output, an updated new look and HD-ID technology to improve overall performance.

The flagship of the new series is Garmin's echo 550c with an MSRP of $449. Its video-quality, 5-inch color screen tracks bottom to a depth of 1,900 feet and displays fish as crisp arches in 640-by-480 pixel detail. A 500-watt transmitter fires through a dual-frequency (200/77 kHz) transducer designed for optimum performance in both deep and shallow water. The new unit's transducer scans with a traditional cone angle providing up to 120 degrees of coverage.

Stepping down one notch buys you the echo 500c ($349.99). It includes all the power and features of the 550c, but comes with a 320-by-234 pixel color display.

The echo 300c ($219.99) is designed to suit fishermen on a budget who still want a color screen. It has a 3.5-inch, TFT display and 300 watts of transmitter power for a maximum depth reach of about 1,500 feet. It includes the same dual-frequency operation with up to 120 degrees of cone angle to see fish and targets well beyond the sides of your boat.

Garmin's echo series also includes three models with monochrome screens that display everything in eight levels of gray. The echo 200 ($159.99) has a 5-inch screen and 300 watts of power. It is dual-beam capable, and can track bottom depth down to 1,500 feet.

The echo 150 comes with an MSRP of $99.99, yet offers a 4-inch screen and pushes 200 watts of power through a dual-beam transducer that can reach as deep as 1,300 feet.

The least-expensive model in the series is the echo 100 ($79.99). It has a 4-inch screen and 100 watts of power for a maximum depth capability of 600 feet.

The echo 200, 300c, 500c and 550c models have Garmin's Smooth Scaling technology, which keeps you from losing sonar history as you change depth ranges. All models with 5-inch screens have a rewind function that lets you back up through your sonar history to look for things you may have missed. All echo series units come with a trolling motor transducer mount and a quick-release mounting bracket for the head unit that tilts and swivels. An optional flush-mounting kit is available for each model. For more information, visit garmin.com/onthewater, or call 913-397-8200.

Today's recreational sonar units, from entry-level to top-of-the-line models, deliver more performance per dollar than ever. Humminbird and Lowrance continue to compete with each other on almost a model by model/feature by feature basis while Garmin continues to go its own way down a more traditional fish-finding path. And it's good to see the company introducing significantly improved sounders that should interest freshwater fishermen and boaters.

The new units from all three companies are scheduled to hit dealers' shelves early in 2011.