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The objective of the present work was to establish modal lengths, empirical lengths at sexual maturity, and proportions of mature individuals of six deep-sea species from the bycatch of the experimental fishery for Patagonian toothfish (Dissostichus eleginoides). Fishing was conducted in Ecuadorian oceanic waters by only one vessel, between 2017 and 2021. Modal lengths were identified using frequency distributions. The length at sexual maturity (Lm) was estimated using the empirical equation: Ln Lm = -0.1189 + 0.9157 * Ln (Lmax). Modal lengths presented a little annual increment in Antimora rostrata and Coryphaenoides armatus while the values decreased for Centroscymnus owstonii, C. delsolari, and Hydrolagus melanophasma. Interannual lengths were similar for Etmopterus granulosus. Modal lengths were higher than the sexual maturity length for H. melanophasma, C. delsolari, C. owstonii and A. rostrata. Furthermore, Coryphaenoides armatus showed a similar value and E. granulosus a lower modal length. Empirical length at sexual maturity was between 56.35 and 66.26 cm TL for all species except for H. melanophasma, which was 100.53 cm TL. Antimora rostrata and C. armatus presented an increment of mature individuals while the annual percentage decreased for H. melanophasma, C. owstonii, and C. delsolari. Etmopterus granulosus showed a lower proportion of mature individuals.

The present work reported the length-weight relationship of four deep-sea chondrichthyan species (i.e., Hydrolagus spp., E. granulosus, C. owstonii and C. squamosus) captured by the experimental fishery of the depth cod (Dissostichus eleginoides) in Ecuadorian oceanic waters, from 2018 to 2020. The fishing included 592 hauls, starting at 1,000 m depth, using between 1,000 to 1,500 N° 14/0 circle hooks. Length-weight relationship (LWR) was estimated by the power model (y = axb). The determination coefficient (r2) value was always above 0.94. The slope (b) showed negative allometric growth (b 3) in females of E. granulosus and Hydrolagus spp. as well as, in males of C. owstonii and C squamosus. In addition, the allometry for the combined sexes was negative in C. owstonii and was positive in C. squamosus and E. granulosus.