Aspects of female reproductive biology of the orange-back squid, Sthenoteuthis pteropus (Steenstup) (Oegopsina: Ommastrephidae) in the eastern tropical Atlantic

Abstract

Orange-back squid females, Sthenoteuthis pteropus, were found to mature at two different sizes: 230-270 mm and 380-450 mm mantle length (ML). The systematic status of these groups remains unknown. The ML of mature females varied from 155 to 558 mm (body weight 150-5900 g, respectively). Protoplasmic oocytes of 0.1 mm predominated in the ovaries during the entire life cycle providing a resource for further yolk accumulation. The number of yolk oocytes present at any one time represented only a small part of the Potential Fecundity (PF). Ripe eggs were 0.73-0.87 mm, and egg weight was 0.19-0.26 mg. The PF was 0.6 million to 15.8 million in mature animals and 1.2 million to 17.9 million in immature and maturing females, respectively. In mature females, the total number of yolk oocytes was 20 000 to 1.9 million, including 10 000 to 1 million ripe eggs. Spawning was intermittent. Large females presumably released at least 30-50% of the total oocyte stock. Results indicate that S. pteropus is a typical representative of the epipelagic oceanic cephalopod reproductive strategy characterised by small eggs, high fecundity, long intermittent spawning, active feeding, and somatic growth during spawning.