The reproductive biology of thresher shark species of the Ecuadorian Pacific was analysed based on 1236 specimens of Alopias pelagicus (711 females and 525 males) and 354 of A. superciliosus (164 females and 190 males) landed in “Playita Mía”, from January to December of 2019. The length of A. pelagicus females ranged between 67.2 and 184 cm PCL (precaudal length) and the males between 69.0 and 178.4 cm PCL, A. superciliosus registered a minimum and maximum size of 76.0 and 202.2 cm PCL for females and 94.0 and 204.8 cm PCL for males. The most frequently captured size class for A. pelagicus was 147.2−157.2 cm PCL and for A. superciliosus was 156.0-166.0 cm PCL. The sex ratio (F:M) for A. pelagicus and A. superciliosus was 1.35F:1M and 0.86F:1M respectively. For A. pelagicus males the inflection point of the clasper length adjustment, was 134.2 cm PCL and size at first sexual maturity (L 50 ) was estimated at 136.0 cm PCL. For A. superciliosus males the inflection point of the clasper length adjustment, was 136.8 cm PCL, and the first sexual maturity (L 50 ) was estimated at 138.7 cm PCL.

Although sharks have a fundamental role in maintaining the balance of aquatic ecosystems, exerting a great influence on lower levels of the food chain, their populations are declining worldwide due, to a large extent, to overfishing. Of the 64 species registered in Ecuador, from January to December 2019, 19 species were recorded in Manta from the 15,455 captured individuals, with the family Carcharhinidae being the most abundant in the catches (69.4%), and the most abundant species was Prionace glauca (57.9%). Regarding threatened species, such as Carcharhinus longimanus, Sphyrna lewini, and Sphyrna zygaena, a greater presence of immature specimens was observed in landings. However, information on the composition and biological aspects of shark species in the Ecuadorian Pacific is very scarce. Therefore, research on the characteristics of life history (age, growth, and maturity) are of utmost importance for the stock assessments that are being exploited, especially in developing countries, where this information is lacking, causing inadequate management of fishery resources.

Although sharks have a fundamental role in maintaining the balance of aquatic ecosystems, exerting a great influence at lower levels, their populations are declining worldwide due, to a large extent, to overfishing. Of the 64 species registered in Ecuador, from January to December 2019, 19 species were recorded in Manta from 15455 captured individuals, with the family Carcharhinidae being the family most present in the catches (69.4%), and the most abundant species was Prionace glauca (57.9%). In the case of threatened species, such as Carcharhinus longimanus, Sphyrna lewini and Sphyrna zygaena, a greater presence of immature specimens was observed in landings, suggesting a possible existence of nursery areas. However, information on the composition and biological aspects of shark species in the Ecuadorian Pacific is very scarce. Therefore, research on the characteristics of life history (age, growth and maturity) are of utmost importance for the analysis evolution of the populations that are being exploited, especially in developing countries, where this information is very scarce, causing inadequate management of fishery resources.