Importance of male gafftopsail catfish, Bagre marinus (Pisces: Ariidae), in the reproductive process

The objective of this research was to analyze the role of male gafftopsail catfish, Bagre marinus, in the reproductive process. Twelve monthly samples of male B. marinus were obtained from the small-scale longline fleet operating out of the port of San Pedro in Tabasco, Mexico. Mouthbrooding males were also obtained from the illegal purse seine fishery targeting shoals of B. marinus at the mouth of the Grijalva River. Maximum reproductive activity in B. marinus (July to August) was evinced by the high gonadosomatic index values in June (0.16 +/- 0.04, CI 95%), July (0.31 +/- 0.03), and August (0.19 +/- 0.02), by the high frequency of mature males (more than 40%) caught by the bottom-longline fleet between June and August, and by the presence of shoals of mouthbrooding males at the mouth of the Grijalva River from June to August. The eggs incubated by male B. marinus ranged from 1.4 to 1.9 cm in diameter, 1.9 cm being the most frequent (64.8%). Mouthbrooding males ranged from 36.2 to 44.0 cm total length and could carry from 17 to 40 eggs of 1.9 cm diameter. The reproductive strategy of mouthbrooding gives B. marinus survival advantages in a marine-estuarine environment; however, this strategy also represents a severe risk because shoals of mouthbrooding males are traceable by fishermen, resulting in high mortalities and, consequently, a high loss of eggs and embryos.