Ok, I'll be honest, when I hear or read about someone discussing grass beds, I think of grass that grows above the water line. BUt I know from watching some fishing shows, that a lot of these grass beds are beneath the surface. So, my question is this: I have a low end Humminbird sonar unit (factory model with a Tracker boat a few years old)  and every now and then it will show the bottom with thin lines that rise up form the bottom. Is this underwater grass? How do I know and how can I find out? I know these areas can be productive but unless i actually see them I don't know how to find them. Little help on this one? Thanks        :-?

Does your sonar have varying shades of gray to it? If so and the color is lighter than dark black it is either grass or wood. If it doesnt you could always run a treble hook down and see what you come up with.  Sometimes you can tell if there is grass by looking to see if there is any contrast in color on the water. Sometimes the water has a dark patch where grass is.

It does have shades of gray, but quite frankly I don't trust it. Of course, I could run a treble down there (why didn't I think of that??) but the last time i noticed it (which was when I really started thinking about it) was when I was motoring to a new spot, just before taking off. It was in about ten feet of water near a bank.

Generally speaking, most "grasses" are emergent weeds and not submergent plants.

For example, torpedograss and panicgrass both grow in wet soil or very shallow water,

but most of the plant is above the water. Maidencane is a grassy weed, but it too

is an emergent weed. Most of the submergent plants do not consist of grass blades

but sport compound foliage that resembles an underwater forest of trees,

nothing like grass. The only exception that comes to mind is eelgrass (valisneria),

but the blades are 1" wide and 4-ft long.

Submergent vegetation can be seen on any high-end depth sounder,

but exactly how it appears depends on many things:

1. Whether the sonar monitor is LCD, CRT, Digital or Graph.

2. The depth of the water, and how high the "gain" is set (sensitivity).

3. What species of plant (sparse or dense).

4. Whether or not the unit has a 'Grayline' feature.

Weeds such as cabbage, cabomba and hydrilla will typically produce light-colored,

nebulous clouds that indicate the presence and height of the weedbed. In addition,

the 'Grayline' itself will be exceedingly slender or non-existent, because plant life is soft

and absorbs the lion's share of the signal.

Roger

Tie on a deep running crankbait and see if you dig up some grass.

To go with Chris's suggestion: a Carolina rig will also tell you.

If it's the Humminbird 2000 that came on most Trackers a while back, you're outta luck. It's fair for finding bottom. You really need to upgrade a long way. Look around at surrounding dry land. Most aquatic plants like some mud to grow in, so if the terrain has soil then there should be some mud on the lake bottom. You won't find much on rocky bottoms. It's already been suggested to scrape bottom or tops of weeds with a bait, but you can also learn to feel the grinding vibration of line on hydrilla, or a mushy line loading on coontail.

A better sonar with good resolution will sure make things easier for you. Go for 480x480 pixels or higher, and color is much better for evaluating what's on screen. Weeds show up brown for me at my usual colorline setting, while wood is tan to faint yellow. Fish are red, algae on tree limbs is blue.

Jim

A new sonar is what I've been looking in to. I just need to bite the bullet and get one. I KNOW it would make everything better--right now, anything the Humminbird picks up looks like a fish. Yet I don't catch 'em--anyhoo, thanks.

not knowing the quality of your d.f. or the settings,most will at least show you a difference from the bottom.hydrilla,millfoil, and the likes will show up as a spike on you screen.if your not sure run a bait with trebles down and see if yiou pull up weed(grass).as far as a fishfinder finding fish that you can target and catch ,in most instances its not going to happen.true, in deeper water points that show fish relating to structure you may be able to fish for fish your seeing,but mostly its a area locating device that tells you it has the right ingredients to hold fish.those that have yrs. of experience w/ electronics can decipher what there seeing much better than the avg. angler

Cruising around by sonar doesn't show up fish very often, I agree, the main point being to locate places we know bass like, mostly just something different. But once over a suspect spot, zoom to bottom or wherever you suspect fish. A good sonar will show up fish arches if the boat is moving at troll speed, but quality arches only happen directly under the transducer. Whatever depth they show at isn't normally their actual depth, but distance of fish from transducer. The only true depth is bottom directly plumb down. That gets a little tricky trying to figure out how deep a fish arch really is. Adjusting Colorline (Lowrance), sensitivity level, etc will do a good job separating fish from weeds, excellent job separating them from bottom, especially hard bottom. While parked still, if fish are on the move vertically, as when chasing baitfish, instead of arches you will see lines grow across the screen. If multiple fish, you get multiple lines, quite often straight lines on an angle indicating rise & fall of fish. That's the holy grail to watch for, indicating active fish feeding.

Jim