How to Identify Male and Female of the Four Major Chinese Carps: Black Carp, Grass Carp, Silver Carp, and Bighead Carp

There are many species of fish, and many fish are easy to distinguish as male or female by various features of their appearance, but there are also many fish whose sex is very difficult to tell from their external form.So how do you identify the male and female of the four major Chinese carps--black carp, grass carp, silver carp, and bighead carp?

For sex identification of the four major Chinese carps: during the reproductive season, it is mainly judged by the external features and secondary sexual characteristics of the brood fish during the period of rapid gonad development. For example, a well-matured female fish has an abdomen noticeably more swollen than that of a male, and the female's vent is slightly protruding and faintly reddish, while the male has a smaller abdomen and white milt can be squeezed out with light pressure. During the non-reproductive season, sex is mainly identified by the shape and length of the pectoral fins. Generally speaking, the male's pectoral fins are narrow and long, while the female's pectoral fins are relatively short and fan-shaped. Detailed introduction as follows:

1. Black carp

(1) Male fish: during the reproductive season when the gonads are well developed, nuptial tubercles appear on the inner side of the pectoral fins and on the gill covers, giving a rough feel when stroked by hand; during the non-reproductive season, there are 6 to 9 connected bony hard scales on the lateral line scales below the dorsal fin.

(2) Female fish: during the reproductive season when the gonads are well developed, the pectoral fins are smooth with no nuptial tubercles; during the non-reproductive season, there are no bony hard scales on the lateral line scales below the dorsal fin.

2. Grass carp

(1) Male fish: during the reproductive season when the gonads are well developed, nuptial tubercles appear on the inner side of the pectoral fins and on the gill covers, giving a rough feel when stroked by hand; during the non-reproductive season, the pectoral fin rays are longer and thick, especially the I to II fin rays, which are longer and spread naturally in a pointed knife shape, and can cover more than 7 large scales when pressed against the fish body.

(2) Female fish: during the reproductive season, generally no nuptial tubercles, or only a small number of nuptial tubercles on the pectoral fins; during the non-reproductive season, the pectoral fin rays are thinner, among which the I to IV fin rays are longer, spreading naturally in a slightly fan shape, and the pectoral fins cover only 6 large scales when pressed against the fish body.

3. Silver carp

(1) Male fish: during the non-reproductive season, on the inner side of the front several fin rays of the pectoral fin, especially on the first fin ray, there is clearly a row of small bony comb teeth; when stroked along the fin rays by hand, there is a rough, prickly feeling, and these comb teeth do not disappear once they have grown.

(2) Female fish: the pectoral fins are relatively smooth, and individual fish have some comb teeth on the inner side of the middle-lower part of the pectoral fins.

4. Bighead carp

(1) Male fish: during the non-reproductive season, on the upper edge of the front several fin rays of the pectoral fin there are backward-slanting blade-like protrusions, giving a cutting feel when stroked sideways by hand.

(2) Female fish: the pectoral fins are smooth, with no cutting feel.