Reproductive biology aspects of Alopias pelagicus and A. superciliosus (Lamniformes: Alopiidae) in the Ecuadorian Pacific

Abstract

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.

Catch Composition, Seasonality and Biological Aspects of Sharks Caught in the Ecuadorian Pacific

“…The biological aspects of Alopias pelagicus and Alopias superciliosus were previously published by Briones-Mendoza et al (see [36]).…”

Review of catch records of the bigeye thresher sharkAlopias superciliosusLowe, 1841 (Lamniformes: Alopiidae) in the Mediterranean Sea: historical and recent data with biological notes

“…Similar to all thresher sharks, A. superciliosus has an exceptionally low annual rate of population growth and is highly susceptible to overfishing. According to the IUCN, the species is classified as "Vulnerable" globally (Rigby et al, 2019) and "Endangered" at Mediterranean scale (Walls & Soldo, 2016) Although A. superciliosus is caught as by-catch in several longline fisheries targeting tunas and swordfish, it is usually identified at family level, and only a few species-specific data exist about its biology, coming mainly from the Atlantic, Pacific and Indian oceans (e.g., Chen et al, 1997;Liu et al, 1998;Fernandez-Carvalho et al, 2011;Varghese et al, 2015;Rigby et al, 2019;Briones-Mendoza et al, 2021). To the best of the authors' knowledge, the studies concerning A. superciliosus in the central-eastern Mediterranean Sea present mainly occurrence records with no or limited information about its biology, while based on a combined data set from the western Mediterranean and northeastern Atlantic, the reproductive biology of the species was examined (Moreno & Mor on, 1992).…”