I will tell you from my own experience, that I will no longer sex another species, the yellow perch, based on the appearance of the urogenital openings. Two springs ago post spawn, I had about 100 yellow perch 8 to 11 inches I got back from two of the high schools that overwinter them indoors for me in systems I set up for them.
Anyway about 20 were textbook as far as female urogenital openings and I planted them in the female only perch pond. The rest were very iffy so they went into a cage.
Fast forward this year and I have YOY yellow perch in the pond. Apparently at least one of those fish was a male.
If I was to give advice to anyone sexing a species that does not show definitive sexual dimorphism, that would be to only sex a fish by the presence of sex products, i.e., milt when the fish is gently squeezed during spawning time, or a definite plumpness due to enlarged ovaries. Using a catheter tube if the fish appears to be a female to extract eggs would be a good idea.
If in doubt keep it out should be your motto if you are striving to have a monosex pond.
Perhaps the accuracy of my sexing was compromised in my pond due to the young age of the perch? (1 +)
Last edited by Cecil Baird1; 07/24/1510:41 PM.
If pigs could fly bacon would be harder to come by and there would be a lot of damaged trees.
Thus the use of the word "likely" in my picture descriptions. I'll be the first to say there is some overlap in general characteristics between male and female RES. The urogenital opening appears to be the most consistent difference that I am seeing along with other general stuff, one really needs to look at the whole fish to get a good picture. I plan on putting this to the fillet knife test next spring to see how accurate this really is.
In general male RES have wider and more brightly colored margins on their ear tabs, slightly longer pelvic fins, and the urogenital opening is roughly the same size as the anal opening.
In general female RES have a narrow and much more dull colored margins on the ear tab, slightly shorter pelvic fins, and a much larger urogenital opening size relative to the anal opening.
I have seen both what I would consider male and female RES to have brightly colored bellies, and creamy colored bellies. I would not use that as a sexual differentiation characteristic.
On the length of the pelvic fins, in general with what I believe are males the pelvic fins will completely cover the urogenital opening most of the time when laid flat against the body. With females the pelvic fins will not completely cover the urogenital opening when laid flat against the body most of the time. Body condition will affect how the pelvic fins appear when laid flat against the body and should always be considered. This did play a role in what I needed to do in order to get pictures of the urogenital openings, some I had to spread the pelvic fins apart, others I didn't.
There might be a biological reason for the slight differences in pelvic fin length based on sex.
I can see where longer pelvic fins in males might aid in fanning the milt onto eggs as the are being deposited. I can see where slightly shorter female pelvic fins would be less likely to damage or touch the eggs as they are being deposited.
I haven't caught many BG this year but a cursory look at the pelvic fin lengths in the few that I have caught also appears to be sexually differentiated as well.
Next time you are BG fishing lay the pelvic fins flat against the body, male pelvic fins should come very close to touching the anal fin, females well short of touching the anal fin. Also note whether not the belly appears to be full, empty, or somewhere in between as this will affect how close the pelvic fin comes to touching the anal fin, it's all about the difference in "the gap".
Catching RES has been far a few between lately but I did catch this likely female tonight. Is she gravid or just a pellet hog? This one was caught on a pellet.
I had a big one pop off last night that I never got to look at, not sure how big it was but it fought a lot harder than the 9-3/4" RES pictured from last night. It could have been a SMB but it didn't fight like a SMB.
I do have a large year class of 6" RES but all of my RES have become difficult to catch lately which correlates to a very large GSH hatch in my pond this year.
Wish I could tell the little 2" ones. Some of the 3" fingerlings I caught in the minnow trap could see a tiny dot on the ear flap. All I am catching in the traps right now are smaller and I can't tell the RES from the CNBG.
In my pre-sediment pond (20x40') I put 4, 5-6" RES in there early summer from the sediment pond and one male went right on a nest. Trapping lots of 1" somethings out of there now, but can't tell if they are RES or CNBG that swam upstream from the sediment pond last high water event. Sure wish I could tell what I am getting. Kind of wish I had not put the CNBG in the sediment pond and just the RES, then I would have known.
One interesting note on colored portion of the ear tabs, that area is very thin and is easily subject to getting damaged. When I occasionally see the RES in my aquarium being aggressive with each other they do nip at the cheeks and ear tab but I don't see this behavior very often. I wonder if the presence of another sunfish such as BG might result in more damage from nipping at the ear tab, at this time I do not have any other type of sunfish in my pond. The fish pictured above appears to have some damage to the colored portion on one side making it look thin and lighter orange like one would expect with a female RES. Is it a female? or a male who has been repeatedly picked on by a more dominant male?
It could be an immature male that has been pushed around (delayed maturity). But if you have males that length and condition with delayed maturity then you have a world class RES fishery.
I do have steep banks and very limited spawning areas in my pond, when the water level was down this winter 3+ ft I could only find a total of 5 beds/depressions around the entire pond.
Caught yesterday in about a foot of water a couple feet from bank. Came from my sediment pond stocked as fingerling last fall.
Wish the second picture was better but the little bugger was doing his best to squirm and spike me. Moved this one to the pre-sediment pond where I saw a male and female spawning a few days ago.
Thanks Eric! These are mostly pellet fed fish that were caught on pellets. I have quite a few RES and SMB taking (non-hydrated) pellets off the surface every night.
All of my RES have been difficult to catch ever since this years hatch started reaching a 1" size or better. From late May until mid July I saw newly hatched fry along the banks each an every week, water temps have been very favorable for spawning this year.
.gif)
