They also tend to be deeper-bodied, which is useful for identifying sex from a side view. As breeding season approaches, the females will begin to develop roe (eggs), which may cause a bulge on one side, making the female look asymmetrical or lop-sided. [1] X Research source
When viewed from the side, the vent may appear as a raised surface on the female’s abdomen. In addition to a protruding vent, the female’s anal fin may appear slightly thicker than the male’s. [3] X Research source
Usually the breeding tubercles will only last during the fish’s breeding period, however in older males who have lived through several breeding seasons, the tubercles may be present all year round. The tubercles may also appear on the pectoral fins, on the face and on the scales on the body of the fish. Be aware that although the presence of tubercles is a good indication that your goldfish is male, their absence does not necessarily mean that your fish is female, as not all males will develop tubercles. [5] X Research source
A male goldfish will chase a female around the tank or pond, staying close behind and slightly beneath her, sometimes nudging her rear. [6] X Research source The male will also attempt to push the female against the side of the tank or into any plants, in order to force her to spawn. However, in the absence of females, male goldfish will also chase each other around, so it’s a good idea to use physical indications as well as behavioral ones to identify sex. [7] X Research source
However, the rate of maturation will depend on species and sex. Some breeds of male goldfish will reach maturity by the time they are 9 months old, while some females may take up to three years to reach maturity. Short of DNA analysis, identifying the sex of young goldfish is practically impossible. If you wish to increase your chances of having both male and female fish, your best bet is to purchase at least six healthy fish of the same variety. Statistically, there is a 98% chance that at least one fish will be a different sex from the others. [7] X Research source
Some male goldfish will not develop tubercles, while in rare cases a female goldfish will. [9] X Research source Some female goldfish will not have protruding vent, while male goldfish sometimes will. In addition, some breeds of goldfish do not comply with general rules - for example, some breeds (such as ranchu or ryukin) naturally have very round, thick body shapes, which makes gender identification through body shape almost impossible. {“smallUrl”:“https://www. wikihow. com/images/thumb/a/a8/Tell-if-Your-Goldfish-Is-a-Male-or-Female-Step-9Bullet2. jpg/v4-460px-Tell-if-Your-Goldfish-Is-a-Male-or-Female-Step-9Bullet2. jpg”,“bigUrl”:"/images/thumb/a/a8/Tell-if-Your-Goldfish-Is-a-Male-or-Female-Step-9Bullet2. jpg/aid580826-v4-728px-Tell-if-Your-Goldfish-Is-a-Male-or-Female-Step-9Bullet2. jpg",“smallWidth”:460,“smallHeight”:345,“bigWidth”:728,“bigHeight”:546,“licensing”:"<div class="mw-parser-output">
License: <a target="_blank" rel="nofollow noreferrer noopener" class="external text" href="https://creativecommons.
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<br />\n</p></div>"} As a result, it is best to identify the sex of your goldfish by observing multiple signs, rather than trusting a single sign alone.
For example, an unhealthy male goldfish may not develop the tubercles usually seen during spawning season, while an unhealthy female may not have a convex vent. Body shape can also be misleading. A thin goldfish may be mistakenly identified as male (as males are usually smaller), but you may be looking at an underfed female. On the other hand, you may read a distended abdomen as a sign that the fish is female, but the swelling may be a sign of dropsy (an internal bacterial infection). [7] X Research source
