Can I prevent this egg-binding problem?
In the past three months, I've lost three female crowntail Betta due to retained eggs. In all three instances, the breeding pair didn't complete the process. In the first, the pair got about halfway through it and suddenly seemed to lose interest, despite the fact that initially the female was still dropping eggs at random. Despite efforts to re-engage the pair or stimulate her to release, she retained them and the bulge around her ovipositor was quite pronounced. She sickened and died within 72 hours.
The other two females had to be removed from particularly aggressive males after having already released at least a portion of their eggs. Both females succumbed to infection within 72 hours. All three of them, at some point in their decline, discharged clumps of pus and bloody eggs.
Until January, I'd never experienced anything other than what you'd expect while spawning this notoriously aggressive species: torn fins, bite wounds, exhausted fish. They were all treated and fed back up in recovery tanks and none of them died.
In the cases of the females I'm writing about, I've tried aquarium salt, almond leaf extract, Epsom salt and methylene blue baths, Hydroplex, Kanaplex, Metronidazole. I even tried Melafix and Pimafix.
I am a responsible breeder with a very small operation, and I only supply a select, small list of independent clients. I need to be able to fix the aforementioned issue with my females should I encounter it again. Male Betta can be unpredictable, and these losses are all related to their behaviour, so it's a given that an incomplete spawn will occur again at some point.
I'm holding off introducing my next pairs because I'm not only discouraged but also a little afraid — I don't know how to handle this issue should it arise again.
Can anyone shed some light on this and possibly advise how to treat it?
ELLIE, VIA EMAIL
PETER SAYS: Dystocia (‘egg-binding’) is reported in a range of fish species, including Koi, zebrafish, and salmonids. The term has also been applied to livebearing fishes such as some sharks and rays that are experiencing problems giving birth in captivity. In some cases, as you have found, it can be fatal.
You are obviously an experienced fishkeeper, so no doubt will be aware that, generally, if a female fish fails to spawn, her retained eggs will eventually become reabsorbed, enabling this valuable material to be efficiently recycled, and this is perfectly normal. But sometimes this does not happen and the unshed ‘overripe’ eggs may begin to decay unnaturally, risking pathological damage to the reproductive tissues, internal infections and possibly death.
In cases of dystocia, the affected female may develop an abnormally enlarged abdomen — much larger than that of a healthy female ripe with eggs.
Several reasons have been put forward to explain why female fish develop dystocia. These risk factors include stress; excess body fat affecting the reproductive system
(i.e. obesity, perhaps due to fatty diets); small size of the female; presence of heavy metals in the water; internal infections, such as mycobacterial infections, that affect the tissues and organs of reproduction. To this list we can add factors that may inhibit egg-release by otherwise healthy females, such as absence of sexually mature males; incorrect water temperature; incorrect photoperiod; other incorrect environmental conditions. We might expect to see a higher risk of dystocia in species that are reluctant to breed in captivity, and the Kuhli loaches (Pangio spp.) come to mind here: rarely do these worm-like loaches breed in the home aquarium and clearly some ‘spawning trigger’ is lacking, even if both sexes are present and sexually mature.
Dystocia is widely reported in captive Zebra danios and we know that old age is a risk factor for dystocia in this species, hence zebrafish research laboratories avoid using old fish for breeding purposes.
You mention that your male Betta are very aggressive towards the females, so some of the deaths could be due, at least in part, to physical damage caused by the male. In the wild the females can decide when they want to enter the male’s bubble-nest territory in order to spawn. And they can flee beyond his territory boundary whenever they wish. But given the natural territory range of a wild Betta is cited at around 1m2, then the average aquarium is far too small for the female to retreat to a safe distance. It’s a similar problem with the captive breeding of other aggressive territorial fishes such
as cichlids. So, you could try experimenting with a much larger or longer breeding tank, offering plenty of hiding spaces, and see if that helps. Or maybe the fish have an internal Mycobacteria infection that’s affecting their reproductive tissues, causing problems with egg development and/or egg release? I’m really guessing here, but we know that Betta seem prone to mycobacterial diseases — and I hasten to add that this isn’t necessarily due to poor husbandry
— so it is perhaps worth considering and might possibly explain the expulsion of pus and bloody eggs that you describe.
As for treatment, this is challenging, particularly as we can’t be sure what’s causing the problem. Hormone injections (such as carp pituitary extract) have been used to stimulate egg-release but this practice is largely confined to food-fish aquaculture. And of course, if the eggs are deteriorating or the egg-tube is blocked, as may happen with dystocia, then hormones won’t have the desired effect. A technique known as ‘hand stripping’ where the female fish is gently massaged in the belly region in a repeated head-to-tail direction to expel the eggs, is practiced on large brood-stock fish such as carp, but performing hand stripping on a relatively tiny female Betta is likely to cause serious internal damage, suffering, and possibly death, no matter how gently performed, so I’d strongly advise against trying it — we must remind ourselves that fish can feel pain.
Maybe your first action might be to try spawning the fish in a very large tank, as suggested above. I know this is a far cry from the smaller tanks used to commercially propagate domestic Betta, but it could be a good starting point along the road to solving the problem.
I don’t think we can ever eliminate the risk of dystocia in fish, but hopefully this might provide a few pointers in resolving the issue.