Vent Checking

Often, there is some question about the sex of even fully matured plecos. This does not work for all species, but can be a very good guide for those species which seem to defy the common odontode and shape methods. It is not always easy, and does take some practice to notice what is being looked for, but in time and with a bit of experience it does get easier.

I am trying to add photos to this article, and will be updating as I get better pics. Those attached at the moment just happen to be the best I have at this time. Hopefully, that will change as I develop better photography skills.

mvent
Male vent
fvent
Female vent
And a Side-by-Side
Comparison
The first step for this to work is to have a sizeable group of mature fish. The reason for the group is that you really need to compare closely for each species to see a difference. Once a group is together, you can use the odontodes and shape to separate obvious males and females into separate clear bottom containers. I use convalescent homes, which are traditionally used for bagging fish in shops, so it is easier to see the vent once the fish are separated.

At this point, you can begin comparing the separated fish. If the fish are not mature, all the vents will look like males. One thing that I have noticed is that even males which are not conditioned properly will look unusually shaped. If not conditioned properly, there will be an obvious rod shape just anterior of the vent regardless of the fish's sex. This makes it very difficult, if not impossible, to proceed beyond this point. If the fish are mature, and well conditioned, it should be obvious at this point which are which. Males will have a very small almost pin-point "V" shaped vent. Females, on the other hand, will have a more blob shaped "0" shaped vent. Depending on how conditioned the fish are, females may also have a noticeable bulge in the area around the vent. This is caused by an impending spawn putting pressure on that area. I hope this helps to answer at least a few questions, and I will get more photos up as soon as I have good ones.