El Mere (Epinephelus marginatus) is one of the most emblematic fish of the waters of the Mediterranean and eastern Atlantic. Its body robust and compact It is perfectly adapted to life on rocky bottoms, where it finds refuge among large boulders, caves, and crevices. Its head and mouth are large, and the lower jaw extends beyond the upper jaw, presenting characteristics that distinguish it from other species of the genus. Serranus, such as the presence of scales on the maxilla and supermaxilla.
Distribution, habitat and longevity of the grouper
The grouper lives mainly in the Atlantic and Mediterranean. It is found at depths ranging from 5 and 400 meters, although it prefers areas down to 50 meters, always depending on fishing pressure. Its longevity is remarkable, often reaching more than 60 years of life and over 1 meter in length, which reflects its slow growth, a key factor in the vulnerability of its populations.
Conservation status and threats
The grouper is included in the red list of threatened species by the IUCN due to the intense overfishing it has experienced throughout its range. Its commercial value has made it a highly coveted species, so the recovery of its populations depends largely on management and conservation measures, such as the establishment of marine reserves and the regulation of minimum catch sizes. Protecting larger and older individuals is essential, as their fertility is directly proportional to these variables.
Grouper reproduction: proterogynous hermaphroditism
The grouper is a sequential proterogynous hermaphrodite species, that is, most individuals are born as females and, over the years and under certain social or environmental circumstances, some of these females transform into males. Sexual maturity is reached as female around five years old, when they reach a size of approximately 49 cm. The change to male generally occurs between 7 and 17 years, or when they exceed 52-77 cm in length, especially if there is a shortage of males in the population. However, some females can remain this way much longer and even reach maximum sizes, which seems to respond to a reproductive strategy to maintain high laying capacity.
La reproductive season of the grouper is concentrated during the summer, particularly between July and August, coinciding with the full moon period, a key moment for spawning. The phenomenon has been observed and confirmed in protected areas such as Medes Islands, where individual monitoring of females has allowed spawning to be confirmed, as they reappear with empty abdomens after a few days.
Eggs, fertility and development
The Grouper eggs are pelagic, which means that after spawning they float freely in the water column, promoting their dispersal. The fecundity of the grouper is directly linked to its size and age: a female can lay more than 300.000 oocytes per kilo of weight, which underlines the importance of protecting larger specimens within populations.
Food and behavior
The grouper is a coastal predator which shows a preference for cephalopods, especially octopuses, although its diet is supplemented with crustaceans and other fish. It is a territorial fish, generally slow-moving, that uses camouflage and patience to ambush its prey. Regarding communication, there are studies that indicate that the grouper is capable of emit sounds associated with reproductive behavior, which adds interest to its biology and ethology.
As a curiosity, all small specimens are female, and sexual transition occurs earlier in overfished populations, where males are scarce. Groupers are generally considered harmless to divers, although respectful observation and avoiding disturbance in their natural environment are recommended.
Detailed knowledge of grouper reproduction and biology is vital for implementing effective conservation and management measures, ensuring the survival of this unique and important species for marine ecosystems.
