Congratulations on your expectant male, sir!
It certainly sounds like your gravid male is exhibiting typical "broody" behavior, so he may well be getting close. Pregnant ponies may become increasingly shy and reclusive. Gravid males may go off their feed as the delivery date approaches, missing meals or even going into hiding. When birth is imminent, he will become agitated and distressed and his respiration will increase markedly.
You may also be able to observe some interesting changes in the male’s brood pouch when he is ready to pop. For example, as the pregnancy progresses, the male’s pouch darkens due to the proliferation of epithelial and connective tissue and the placenta-like changes taking place in the wall of the marsupium, and the pouch gradually swells and expands according to the number of young developing within. The latter is not always a reliable indicator, however. Inexperienced couples often spill eggs during the exchange and a male’s first few broods are often inordinately small. The brood pouch of a male that is carrying only a few fetal fry is hardly any larger than normal, and hobbyists have often been surprised by unexpected births under such circumstances.
As you know, Seagazer, the brood pouch enfolds, protects, aerates, osmoregulates, and nourishes the developing embryos as the male undergoes a true pregnancy (Vincent, 1990). The volume of the pouch normally increases dramatically as the pregnancy progresses. A male that is carrying a significant number of young becomes very rotund so that only a very thin layer of epithelium and connective tissue separates the interior of the pouch from the outside world by the time birth is imminent (Vincent, 1990).
The fully developed young emerge from their individual compartments and shake loose into the lumen of the pouch prior to birth (Vincent, 1990). They become very active toward the end of the pregnancy and can sometimes be seen wriggling about through the membrane of the swollen brood pouch at this time. This appears to be every bit as uncomfortable as it sounds, since expecting males become agitated and distressed as the big moment approaches. They experience definite labor pains when birth is imminent, evident as a series of powerful contractions, and soon begin pumping in time with these birth spasms in order to forcibly eject the fry from their pouches. Labor usually begins well after dark in the early morning hours (Vincent, 1990). The distraught male may pump and thrust vigorously for hours before finally ejecting the first of the newborns (Vincent, 1990). The fry are expelled singly or in ones and twos at first, but are soon spewing forth in bunches and bursts of a half dozen or more.
Delivering a large brood this way is hard work, and the exhausted male will pause periodically to recover from his exertions, gathering his strength until he is caught in the throes of another round of contractions. In some cases, it takes 2-3 days for the entire brood to be delivered in this manner.
No matter how often I see a male giving birth, it never ceases to amaze me. Watching the fry erupt into existence that way is an incredible sight. They are perfect miniature replicas of their parents, able to fend for themselves from the first. It seems a brutal beginning, a ruthlessly rude awakening, to be violently thrust into the world in such an abrupt fashion, but the newborns hit the water swimming without missing a stroke. It’s a thrill to be witnessing such a miracle of nature and always leaves me awed and exhilarated!
In seahorses, a hormone known as fish isotocin, which is the equivalent of oxytocin in mammals, triggers parturition or giving birth (Vincent, 1990). Thus anything that stimulates excess secretion of isotocin can result in premature births, whereas anything which decreases or delays the secretion of isotocin can postpone delivery and prolong a pregnancy abnormally.
So there’s not really much a hobbyist can do to hurry things along when a stallion appears to be experiencing an extended pregnancy. Make sure his mate is present (i.e., don’t isolate the male in a paternity tank), maintain optimum water quality, keep the water temperature in the comfort zone, keep your dissolved oxygen levels high, and keep the aquarium as stress-free as possible. It sounds like you’ve already done all of that, Seagazer, so there’s not much else you can do but relax, give your pregnant male plenty of peace and quiet, and let nature take its course.
Best of luck with all your seahorses, Seagazer! Here’s hoping your gravid male delivers a healthy brood of newborns very soon.