With its gothic color combo, the red tail shark is one stunning freshwater creature. It originated from one of the busiest rivers in Thailand, Chao Phraya, and the shallow streams leading up to it.
Up until 2011, the red tail shark was thought to be extinct. It’s still critically endangered in the wild, but abundant in pet stores, all thanks to captive breeding.
If you’re looking to breed them at home, you might wonder: Is my red tail shark male or female?
Keep scrolling to learn how to distinguish the sex of your fiery fish and whether it’s possible to reproduce them in your tank successfully.
The red tail shark isn’t the easiest fish to identify the sex of, especially when it’s young.
The species was nearly wiped out years ago, so we have limited knowledge about it compared to other freshwater fish.
The male and female species look almost identical in size, appearance, and coloration for the untrained eye. Not just that, but male and female red tails also have similar personalities.
With more similarities than differences, even aquatic experts struggle to tell them apart. Fortunately, there are a few telltale signs to spot the ladies and gentlemen of the tank.
Let’s look at the distinguishing physical characteristics of male and female red tail sharks.
The female red tail shark tends to be larger than its male counterpart. Known as reversed sexual size dimorphism (RSD), this phenomenon isn’t exclusive to this fish.
It’s quite common in many species of cultured fish. However, the size difference isn’t so extreme in red tails, so it’s not the most reliable way to tell the sexes apart.
Fun Fact: In aquaculture, you can masculinize or feminize a fish. Using hormonal treatment, you can make a batch of sexually undifferentiated fish develop into the desired gender.
The red tail shark has a spindle-like shape that widens in the middle and tapers at both ends. It resembles the fusiform body type of shark, hence its name.
Despite the similarity, the red tail isn’t a true shark, but a species of freshwater fish from the carp family.
A male red tail has a slimmer and more sleek build. As it reaches sexual maturity, it also develops a more pointed or slightly longer unpaired (dorsal) fin.
Meanwhile, a mature female is thicker-bodied. When it’s ready to reproduce, its stomach grows even plumper, carrying up to 40 eggs at a time.
3 – Coloration
Unfortunately, there isn’t much significant difference in the colors of the male and female red tails. Both have the same jet-black body and a vivid red or orange tail.
Although there might be slight variations in the intensity of coloration, it’s not always a clear indicator of sex.
Sometimes, the surest way you can tell the sex of a red tail is to wait until breeding season. The reproductive organs of male and female red tails become more pronounced, making it easier to tell them apart.
The male has a tiny tube-like structure near the anal fin. This fertilization tube will poke out of its body days or weeks before the female sprays eggs into the water.
The female, on the other hand, has a less prominent genital papilla. Just before spawning, it’ll protrude from its body.
Differences in the behavioral traits between male and female red tail sharks can be subtle. Most times, they’re not always present in individuals.
Red tails may chase other fish nonstop to show who’s boss, so you should put them last in community tanks. They’re timid as youngsters but become increasingly meaner as they grow.
The differences in the level of aggression aren’t a clear marker of gender. Surprisingly, red tails tend to either attack or leave alone particular species.
In the wild, red tail sharks likely live solitary lives and only ever brush with their kind during spawning season.
The general trend is that male red tails are more aggressive and more territorial than females and other males. To tone down this aggression, they need spacious tanks with plenty of vegetation and hiding pots.
Red tail sharks have distinct reproductive roles based on their sex. Simply put, females produce eggs, while males fertilize them.
Female red tail sharks don’t carry their young in their bodies, so they should have a suitable environment to deposit their eggs safely.
They’ll look for dark nooks and crevices to nest their eggs away from predators. Once they’ve laid their eggs, it’s up to the males to fertilize them externally.
During breeding, male red tail sharks exhibit courtship, like chasing and nipping, to encourage females to release their eggs.
Then, they’ll fertilize the eggs by releasing sperm from their specialized anal fin. Finally, the fertilized eggs will settle down until they hatch.
Unfortunately, breeding red tail sharks in private aquariums is rare and almost unheard of. These feisty fish can be intolerant toward one another, leading to aggression.
They’ll harass the weaker species to the point of exhaustion or death.
It may be tempting to try breeding red tails at home. However, we don’t recommend it because of the high likelihood of failure and potential harm to the fish.
Instead, it’s best to support conservation efforts. The responsibility of keeping the species from extinction falls on commercial farms, which use artificial hormones to induce breeding.
If you’re keen on trying to breed red tail sharks at home, we must warn you again it’s not that easy. They can be territorial toward one another, so prepare a large breeding tank with lots of hidden spaces for egg-laying.
Next, ensure you have the correct water parameters, so consider these tips:
- Use a submersible water heater to keep the water temperature at 79–82°F.
- Monitor the water temperature with an aquarium thermometer.
- Maintain the pH of the tank water around 6.7–7.5. Add peat moss if necessary to keep the acidity.
After you have the proper tank setup, keep a higher ratio of females to males, using the above guide to sex your red tails. Watch your fish closely for mating behavior.
If you get your red tails to spawn, remove all other fish except for the breeding pair. Continue observing them to determine whether they’ll take part in rearing the eggs.
If they ignore or begin snacking on the eggs, take them out of the tank and monitor the eggs.
So, is your red tail shark male or female?
Identifying between the sexes can be confusing because they appear nearly identical and behave similarly. It’s impossible to sex juvenile specimens accurately by just looking.
However, you can spot physical and behavioral indicators in sexually mature red tail sharks. Generally, the slimmer males have more intense coloration and more pointed dorsal fins.
Hopefully, with this knowledge, we can better understand this elusive species and work toward its preservation and recovery.
Jeff has always enjoyed having pets, but as a child, he was drawn to his family’s fish tank. Being able to maintain a small ecosystem and observe the behaviors and interactions in the underwater world peaked his interest early on and has kept him hooked until this day. On Avid Aquarist, Jeff shares everything he’s learned about helping aquatic life survive and thrive in a home aquarium.