Pond Boss Forums FISH & FISHING Fly Fishing & Other Fish Species Mouth Gape of HSB

Is there any information on this? I'm looking and I can't find anything. I'm curious what the max gape of the mouth is based on the length of the fish.

It's not anywhere near the size of LMB.

I know it's not the same fish but we would catch Stripers in Raccoon Reservoir on slow trolled 6"-7" BG. IIRC we didn't catch one less than 12# on BG that size.

I'm curious for a few reasons, but I'd like to compare it to a SMB.

That's a big HSB though.

I'm not sure the mouth gape of HSB is published in the literature. ewest may be able to help us with this info in the literature. We have enough members here that we could do a data accumulation here on the forum for mouth gape of various sizes of HSB. I think the gape of HSB is smaller than that for SMB. As I recall the mouth gape of SMB is not "all that" smaller than for the same length of LMB. It would be a good idea if we compiled this information in the Archives for HSB, SMB and LMB. How about you doing some fishing and measuring to help us???? Please?

For those with ponds, lets go out and catch a fish and measure the fish's total length and the width across its full open mouth. Do not try to stretch the moth open to get extra width. Just hold the mouth open and measure across the opening. When we have numerous measurements this thread can go into the Archives about HSB information. Duplicate measurements are good and give us an idea of the natural variability. Thanks for fishing, measuring and contributing.

Here is my contribution for this project:
HSB Gape Information
Total length then Gape Width.
5.5" gape 0.59" (15mm)
9.75" gape 0.94" (24mm)
13.5" gape 1.1" (28mm)
19.0" gape 1.73" (44mm)
22.0" gape 2.1" (55mm)

Here are some data that I have for SMBass.
Total Lgn Gape Width
5.5" gape 0.71" (18mm)
9.5" gape 1.1" (28mm)
13.5" gape 1.57" (40mm)
17.0" gape 2.3" (58mm)

Here are some of my data for LMBass
Lgn Gape Width

5.5" Gape 0.83" (21mm)
9.5" gape 1.5" (39mm)
12.75" gape 2.0" (51mm)
17.0" gape 3.9" (100mm)

I will gladly contribute once I catch a few. Let me ask my next question though (to clarify for myself).

Is the distance across the same as the top to bottom measurement? Would that even matter?

It is different and it would matter, exactly how much I don't know. HSB are definitely the most gape restricted of the "bass" though. Since, we're at it, how about walleye gape since it seems to be a more and more commonly stocked predator into ponds these days... Bill, you happen to have that info handy as well? I know, CC have also been researched on mouth gape. I think Theo Gallus did a lot of work on that. I think crappies have a bigger gape than HSB do. I sure know a 15" crappie sure has a giant mouth! I honestly think a GSF has a bigger mouth than a HSB of the same size...

Great start to a nice research project!
I took the liberty of dividing gape by length and found that your very small samples are quite constant within a species and definitely show a trend.

HSB avg gape/length=0.094
SMB avg gape/length=0.124
LMB avg gape/length=0.174

So, HSB may be roughly half the gape width per body length as LMB.

Furthermore, I ran across the paper below which has info from Ohio research.

You can add two points for HSB: 22/220mm and 32/335mm.
Those yield gape/length=0.100 and 0.096. (min for smaller class cited as 190mm elsewhere in paper) The published data are in line with Bill's data.

Transactions of the American Fisheries Society, Vol. 127, No. 1, 1998, pp. 84-94.
http://kb.osu.edu/dspace/bitstream/handl....pdf?sequence=1
we estimated the largest prey that predators could consume by comparing gizzard shad body depth to hybrid striped bass mouth width. Hybrid striped bass efficiently consumed prey that were at their morphological limits of consumption. For hybrid striped bass shorter than 250 mm, the largest potential prey size was 80 mm (body depth = 22 mm), whereas for hybrid striped bass of 310-360 mm, the largest potential prey size was 120 mm (body depth = 32 mm). Regressing capture efficiency against the proportion of the maximum gape for each prey, we found no relationship for either predator size (linear regression, F = 0.07, df = 1, 8; P = 0.80 for large hybrid striped bass; F = 0.30, df = 1, 12; P = 0.60 for small hybrid striped bass). Consequently, hybrid striped bass in the laboratory can consume prey whose limiting dimension equals their maximum gape without reducing capture efficiency.

In general, the SMB will have a larger gape than the HSB.

Wow great data right here. Truly an eye opener to see a 12.75" LMB with the same gape as a 22" HSB. Demonstrates why HSB and SMB are not nearly as effective managing BG populations

At least for smaller individuals of SMB, HSB, and LMB in my measurements, the difference between the horizontal gape and vertical gape is the vertical gape is about 2mm less than the horizontal. I do have some gape information for other species but let's get this bass mouth gape data accumulated first. Hopefully you members can do some fishing and get us some bass length - mouth measurements. Just about every member has one of these three bass species in their pond. Get out there and catch us a bass for our mouth gape study. Let's fill in the gaps of our data set!

Bill,

Maybe this is another post all together, but how much gape would be needed to eat say... BG at 3" 5" 7"? Maybe say the same for YP? This could be other extremely useful information to a lot of us.

When the fish start biting again, I can take data points for LMB and SMB from my pond. There may be a handful of HSB in there, (I think I've seen some swimming around) but none have ever been caught. I stocked 25 of them 2 years ago, but thought I had a complete kill of the stockers right after stocking.

Not trying to be argumentative here... Ran across a paper on LMB feeding kinematics. They define gape as the vertical distance from the tip of lower jaw to tip of upper jaw... kinda on an angle with lower jaw further forward. They do have a plot of their gape vs length (Fig 5) They were primarily evaluating kinematics of the capture, not size capacity.
The Journal of Experimental Biology 198, 419–433 (1995)
http://jeb.biologists.org/content/198/2/419.full.pdf

Here is a short post by esshup on HSB gape.

http://forums.pondboss.com/ubbthreads.ph...true#Post343110

Esshup data July '13:
HSB was 18.25" long, and weighed 3.18# Mouth gape was pretty round, and measured 2"

A few different LMB were measured; here one that was of comparable length, albet 3/4" shorter. 17.5" long, and weighed 3.0# Gape was more oval shape, 2 5/8" high by 3" wide.

Now here is a very nice paper.
http://www.seafwa.org/resource/dynamic/private/PDF/Hill-47-56.pdf
They do use width and not height for gape.

It indicates that for LMB, gape width = 0.14*Length - 5.59
where dimensions are in mm.
For a 17" fish (largest in their survey), that predicts GW=2.16" which is a .127 ratio.
That is more inline with our SMB data above. They cite the LMB as being from SE FL. Are FL bass different?

Given the results of this study, a peacock cichlid can eat deep-bodied prey of about 30% of its own total length and largemouth bass can eat slightly longer prey (i.e., about 35% of its own length).

For example, a 400-mm TL largemouth bass can eat a 132-mm TL spotted tilapia whereas a 400-mm TL peacock cichlid can eat a
116-mm TL spotted tilapia.

This also seems useful:
BD=body depth (how tall)
TL=total length
both in mm

Bluegill BD=0.46*TL–8.88
Largemouth bass BD=0.25*TL–3.38
Redear sunfish BD=0.40*TL–6.23

Spotted tilapia BD=0.39*TL–0.84

Still can't find a free online copy of the seminal paper by Johnson & Post (Transactions of American Fish Society 1996) that started this...

Another paper with gape info for LMB. Their point is the pharyngeal gape is smaller and they think that limits prey capture.
http://fishlab.ucdavis.edu/W%26REBF95.pdf
When you do gape/length, they run .18-.19 around 230mm length, 9". They say these data are for FL LMB.

ewest has access to some good literature in Journals. Let's see what he can provide. Once we know the gape size of various lengths of bass we can do some measuring of prey body depth - height of BG, GSF, Shiners, shad, YP, HBG, etc and create a large very useful data set. We can do our own study and get a good data set if we get enough member participation. Bruce Condello catches a lot of fish and Big fish. He can be a big help with this body length - gape size study. Numerous members catch lots of their pond fish and will be able to contribute some good information. Several duplicate measurements for for the same length of bass is good because it provides variation - variety - diversity. All you members can become amateur fishery biologists.

Hey now... I don't mind being a test subject... But biologist? I'll leave that for the smart people.

Is anyone catching HSB or LMB to help with our study of mouth gape for various sizes of these fish?. Don't forget to take along a pen paper and ruler next time you go fishing.

ruler? for pharyngeal gape I wonder if one of those fancy micrometers that measure the inside diameter of a pipe might be a really handy tool to have in the tackle box

I don't normally target bass, but in the interest of science I will see what I can come up with. Provided I can leave the bluegills alone for awhile.

I combined the Hill etal paper above with another I found..
http://nlc1.nlc.state.ne.us/epubs/U1500/T004-2008.pdf
which is a MS thesis from Nebraska. He sampled 2 NE lakes.

Plus a paper from Ball State on Yellow Perch from Lake Michigan.
http://cms.bsu.edu/-/media/WWW/DepartmentalContent/Biology/pdfs/GapeLimitationYEP.pdf



First LMB is the Hill paper. Next 6 lines are the NE MS thesis, and then the last two YP are the BSU work.

FYI, the sample size for the HSB was 168 fish, so a nice population from two lakes.
I'm struggling to believe the YP data though it was 284 fish. They have a very narrow mouth for body length. But I can see no other way to interpret their paper. As I am sending BSU tuition money for my daughter, I may well call one of the authors and inquire.

But, I'm pleased to find some reasonable census measurements for gape!

And of course, we want to know how our anecdotal data compares..
Looks like we have fish with big mouths. Perhaps small carefully managed BOW vs public?

I fished the pond today, specifically to measure gape. Here's some data points for you.

All gape measurements are horizontal gape.

YP Male 11" 1.2" 3 fish
10" 1.0" 4 fish
9.5" 9.9" - 1.0" 2 fish

YP Female 12" 1.2" 1 fish
11 3/4" 1.2" 1 fish
11" 1.0"-1.1" 9 fish
9.5" .9" 1 fish

SMB 11" 1.5" 1 fish
11" 1.3" 3 fish
10" 1.2" 1 fish





I have some LMB that I caught and tossed in a cage, and I can net 'em and measure them. Most were 7"-8" but one was around 17".