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.
Highlights
The orange-back squid Sthenoteuthis pteropus (Steenstrup) belongs to the nectonic squid familyOmmastrephidae
The orangeback squid is characterised by a monocyclic maturation of the reproductive system and intermittent spawning that occurs all year round in epipelagic layers of equatorial waters, mostly at the periphery of meso-scale cyclonic eddies (Burukovsky et al, 1977; Laptikhovsky and Murzov, 1990; Nigmatullin and Laptikhovsky, 1994; Golub et al, 2001)
In the 1980s and 1990s, this squid was the focus of the Soviet investigations aimed at developing oceanic cephalopod fisheries on the high seas of the tropical
Summary
This species is widely distributed in the tropical and subtropical Atlantic and inhabits epi- (night) and meso- (day) pelagic waters of the high seas, mostly between 20oN and 20oS. The oceanographic situation in the region is determined by an interaction between branches of the westward running southern and northern equatorial surface currents and branches of the eastward moving, mostly subsurface, southern and northern equatorial counter currents. This interaction results in the presence of numerous zones of upwelling and sinking as well as in highly dynamic and variable meso-scale eddies that foster water productivity (Khanaychenko, 1974). In the 1980s and 1990s, this squid was the focus of the Soviet investigations aimed at developing oceanic cephalopod fisheries on the high seas of the tropical
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