Pond Boss Forums INTRO Questions & Observations Mouth Gape of a LMB

Well I am not sure anyone posted anything on this yet. But Saturday my son caught a 17 inch 2.6 pound LMB and the gape on it was 2.75 inches from inside to inside of mouth. That reading is from side to side not top to bottom. Here are 2 pics of the fish. 1 is in mid jump!

RC

RC51 - Great! thanks for remembering to measure the mouth size of a largemouth bass. I will see the information gets to the right location.

No problem Bill. Glad to help out!

RC

What is the correct gape measurement for LMB or any other fish?

There is no correct or standard gape measurement. Every bass and fish of a specific size will have a gape measurement close to the average for that species and body length. Note there will be a little variation of width (+/- 15%) based on natural species variation for that species. Note most of variation or differences will be in the technique used to measure width by each person. Once we get numerous measurements the trend will be evident.

So --- all you pondmeisters and anglers get to angling and catch some fish, any fish, and measure the width of its open mouth held open usually by pinching it lower jaw. Report back here and we will tabulate all the data, and put it in the archives. Gape measurements will provide pond managers an idea of how big a food item each fish can eat. With these great informative data, Once again we will be the best pond and fish management forum on the web!. RC provides good advice in the next post for making measurements .

Keep in mind like I said up above that measurement I took was from inside to inside of it's mouth not outside to outside. IMO inside to inside is what really maters when it comes to fish eating ability. I know that sounds simple but I caught myself at first taking the measurement outside to outside casue it's just natural to put the tape on the outside edge and read over. Just FYI.

RC

Bill and others, won't the gape of an overweight fish be smaller than expected? I suppose enough data points will cover this, but I caught a 4 lber yesterday that I thought had a very small mouth. I did not measure the length but I would guess it at 120+ rw.

FWIW

LMB
Length: 13.25"
Weight: 1.3 lb
Gape: 1 7/8" top to bottom, 1 7/8" side to side (inside measurements)

I'll try to include a photo next time

It sure seems to me that yes, fat bass look like they have smaller heads. Skinny bass look like they have bigger heads.

RC51 way to go on the really cool pic of the bass airborne.

Question: ".won't the gape of an overweight fish be smaller than expected?"" You will see some variation in the mouth gape of individual fish species. The amount of variation is part of the data set for each species. The average or normal is what is most important to get general ideas about what that fish species can eat. IMO on average, overweight fish are not the average but the exception in most ponds. In reality based on how most ponds are managed, older bass are probably more often underweight than overweight.

When taking gape measurements you can include the fish's weight but it is not necessary. The total body length with mouth width is more important than weight IMO.

HSB caught tonight:

Length: 16"
Gape top to bottom: 1 3/4"
Gape side to side: 1 5/8"
Weight 2.2 lbs

No pic again, dangit!

My buddy caught this yesterday, biggest LMB to date out of my pond at 3.5 lb.

The HSB are approaching 2 lb with the biggest one at 2.2 lb so far with the BG growing nicely as well.

Pretty exciting times for 19 months after stocking!

Length: 18"
Inside gape top to bottom: 3"
Inside gape side to side: 2 7/8"



It's highly likely the LMB shown was one of about 10 that I bucket-stocked from 8-2012, before I knew any better, although none were over 2 lb.

I caught 3 LMB today that were in the measurable catagory (that is unless you want even 6" LMB measured, and if so I can do that) I have a number of culls in a cage.

15" long Male 2 1/4" horizontal gape
19" long Female 3" horizontal gape
19" long Female 3" horizontal gape

14 inch HSB yesterday - vertical gape ~1.75".

Measurements for 4"-6" LMB are very welcome here. We would like to have a full data set for all sizes of LMB & HSB. Take a ruler along when you go fishing.

Bill,
We caught several LMB at our farm this past weekend. Here is the data I collected:

7 1/2 inch LMB 1 1/4 gape
7 1/4 inch LMB 1 inch gape
9 1/4 inch LMB 5.5 oz 1 1/2 inch gape
17.5 inch LMB 3LB 2oz 3.125 inch gape
17.75 inch LMB 3lb 7oz 3.5 inch gape
18 inch LMB 3lb 11 oz 3.5 inch gape

The first three are from last years' spawn, the other three are two or three years old.

Thanks Highflyer for helping. Any other anglers willing to help us??? I had to go catch some LMB for pictures for an upcoming article. Here is the gape of 3 of the bass I caught.
6.25" LMB Gape 0.88" (22.5mm)
9.1" LMB Gape 1.45" (37.0mm)
10.0" LMB Gape 1.57" (40.0mm)

Highflyer's data is close to my measurements.

Bill,
I will have a few guys over in a few weeks and I am sure we will get you more data. BTW, I did take pictures of all the LMB including the gape, let me know if you would like any of those photos.

Were the dial calipers digital or electronic?

Caught tonight:

12.5" LMB gape 1.625"
12" LMB gape 1.75"
11.5" LMB gape 1.5"
11.5" LMB gape 1.625"
11" LMB gape 1.5"
10.5" LMB gape 1.5"

Interesting with smaller fish having larger gape!

They were measured on the cutting board, not with a dial caliper but still very accurate measurements

Thanks guys for all the great data collection. We will have a very beneficial data set with all your help.

Some of the variation in measuring the gape can be in the amount of stretch of the jaw and how the fish is held. Numerous variables can enter the measurement gathering 'picture'. Generally a smaller fish does not have a larger gape assuming each is the same species. When that happens, I question my technique and I re-measure. There is some natural variation of sizes (lengths-widths) among the same species. I'm not saying it is impossible, just doubtful or questionable. It does make evolutionary sense that an individual with a slightly bigger mouth has a competitive, predatory advantage.

A fish that is growing extra fast may have a slightly smaller head & mouth as evidenced by those here that are raising "football" shaped fish. Also a bass with low RW or is stunted may have a slightly over sized mouth compared to the body length? Basically we are looking for averages or trends for the species.

Fished for a few minutes this morning. Didn't catch any braggers. Measured two LMB.

Both had identical #'s across the board:

L: 14.25"
W: 1lb 3oz
G: 2 3/8" horizontal

Both were females. Had just a small small amount of roe inside. A little light on RW.

Hey Ross - thanks for contributing some bass length and mouth measurements. We will get some good data with guys like you helping.

Bill, sorry I had not referenced back to this thread recently and knew you wanted smaller bass measurements as well. I caught several 6"-10" fish that I just tossed back w/o measuring.

9" LMB 1 1/8" mouth gape.

First one I have caught since fingerlings were placed Sept 2, 2013. Did not weigh it, but it looked fat and healthy.