Due to the availability of both freshwater and saltwater resources in Mexico, the country is endowed with a rich diversity of fish, estimated to include around 500 known fish species. Out of these, about 200 are endemic with a large number of them being endangered. The fish mainly occupy the Mexican coast, lakes, and rivers. These marine and inland waters provide for the habitats of these fish. In the recent years, some of these species have been threatened due to over-exploitation, habitat destruction and introduction of alien species into the water making them prey on native fish.
The Widemouth Gambusia is a critically endangered fish species endemic to Mexico. It occupies the deeper areas of the Grijalva River Basin where the concentrations of hydrogen sulfide are low. Its body is compact with short rounded fins, a large head, and a broad mouth, thirty scales in the lateral line and black spots on the ventral side and the unpaired fins. The total body length of this species is about 3.5 centimeters. The primary threats facing this species are the rapid habitat alteration and intense cattle grazing which destroys riparian vegetation in the spring areas. The species has been protected under the Mexican Law, but no direct conservation measures have been taken.
The Balsas Shiner is a freshwater fish endemic to Mexico. Balsas shiner occupies shallow streams with a rocky bottom. Its diet is mainly insects. The body of this species is elongated to about 12 centimeters. The Balsas have a sub-terminal mouth, a silver-colored body and a black stripe running from the eye to the caudal fin. The fish has been classified as critically endangered due to its narrow range.
The Variable Platy is a freshwater fish that is also endemic to Mexico. The platy is famous for aquarium trade due to its colorful pattern, prolific breeding and ability to survive in low temperatures. The species mainly occupies slow moving water of vegetated canals and warm springs. The diet is primarily composed of plants, insects, crustaceans and annelid worms. The variable platy’s body has an olive color with black spots that are unevenly distributed on its side. Their fourth pectoral ray has saw-like notches. The fish has 20 to 24 lateral scales, 10 to 12 dorsal rays, and two rows of jaw teeth. The males can be distinguished from the females due to their pointed anal fin, unlike the female triangular shaped anal fin.
The California Halibut is native to the shores of the Pacific Coast of North America, including those of Baja California in Mexico. The fish is a stealth predator feeding on crustaceans and small and large fish. Juvenile halibuts are found in bays and estuaries after which they migrate to the open coast. In the open beaches, the halibut occupies soft bottoms, sand dollar beds, kelp beds and rocky beds with which it camouflages. The halibut’s body is oval and flat with both eyes either on the left or right side of the body. Their lifespan is about 30 years in the wild and breed once per year. The major threat endangering them is sports fishing which has greatly reduced their populations.
Other Native Fish of Mexico
Other fish species found in Mexico's waters include the Mimic Sanddab, the Dark-Edged Splitfin, the Rainwater Killifish, the Giant Oarfish, the Pacific White Skate, and the Mexican Blind Brotula. Despite these species facing threats to their populations, not much effort on the national level has been put forth to conserve them. The few maritime conservation laws on the books in Mexico are often not enforced, and they are ignored by a large share of the country's people. Thus, these and other Mexican fish species face risks of further endangerment.