Fishfinder For Anchoring

[thinwater]

I've done lots of UT at work.


a. Calibration will shift. What you think it means today will be different in a year.


b. Depth will make a difference, mostly because of beam spread.


c. You really need to dive. Otherwise you are guessing.


d. Because the beam is a cone, remember that a fuzzy return can mean EITHER a soft bottom or a rough bottom (returns from an angle).


You really need to go look at the bottom and compare MANY times.

[deblen]

Originally Posted by JPA Cate

A comment about kelp: In some areas where it is shown on charts, it has gone away. Whether it is cleared out by storms, or disease, I do not know. But it is something that we have encountered. Some places where it once was thick, now is much less, and a few years ago, was less still. It is as if something cleared it from the areas and it may be re-establishing itself...maybe a natural cycle, maybe due to something else. Since you are in an area where kelp is known to grow, kelp is a likely phenomenon, if the bottom will support it. Usually takes rock, like deblen said. Maybe always takes rock, I am not certain.

Ann

Kelps are a favourite food of sea urchins. In our area,urchins are harvested for their roe. Sea urchins will move into a kelp bed & denude it in a short time & then move on. The bed will grow back in time.

Kelps & rockweeds do not have roots. They have holdfasts which attach to rocks or other heavy objects. These anchors are required for kelp type plants. The plants themselves feed by absorbing nutrients from the water via the plant itself.
There are floating plants such as the sargassums which do not require being anchored.
Then there are the "grass" type plants which will root like a normal plant & grow in "soft" (muddy) bottom.


Cheers Ann / Len

[deblen]

Originally Posted by thinwater

I've done lots of UT at work.


a. Calibration will shift. What you think it means today will be different in a year.


b. Depth will make a difference, mostly because of beam spread.


c. You really need to dive. Otherwise you are guessing.


d. Because the beam is a cone, remember that a fuzzy return can mean EITHER a soft bottom or a rough bottom (returns from an angle).


You really need to go look at the bottom and compare MANY times.

Yes-I won't disagree with your conclusions.
My experience comes from 30+ yrs. servicing & learning from commercial fishermen & includes a fair amount of time on the water with them.
It is amazing how the more experienced fishermen can tell bottom composition from their fishfinders. Of course,they have the proof of what the actual bottom is when they haul back their drags or other gear.

As with most things,experience is a mighty teacher.
Len