Age and growth of planktonic squids Cranchia scabra and Liocranchia reinhardti (Cephalopoda, Cranchiidae) in epipelagic waters of the central-east Atlantic

Statolith microstructure was studied in two abundant planktoniccranchiids, Cranchia scabra (56 specimens, 38–127 mm mantlelength, ML) and Liocranchia reinhardti (34 specimens, 99–205mm ML) sampled in epipelagic waters of the western part of theGulf of Guinea (tropical Atlantic). Growth increments were revealedin ground statoliths of both species. It was possible to distinguishtwo growth zones in statolith microstructure by their colourin reflected light of the microscope: the translucent postnuclearzone and pale white opaque zone. Assuming that growth incrementsin statoliths were produced daily, ages of the largest immatureC.scabra and L.reinhardti were 166 and 146 days, respectively.Both cranchiids are fast-growing squids with growth rates inlength resembling those of juveniles of tropical ommastrephidsand Thysanoteuthis rhombus. Liocranchia reinhardti grows faster:its growth rate in ML is approximately twice that of same-agedC.scabra. The life cycle of both cranchiids consists of twophases. During their epipelagic phase, C.scabra and L.reinhardtifeed and grow rapidly from paralarvae to immature young in theepipelagic waters, attaining 120–130 and 170–200mm ML by ages of 4–5 months, respectively. Then they changetheir life style to a deepwater phase.