Reproductive aspects of the jumbo flying squid Dosidicus gigas (d’Orbigny, 1835) in Peruvian waters

Abstract

In this paper, biological information has been collected and analyzed from the monitoring of the fishery for jumbo flying squid Dosidicus gigas from 1989 to 2016, which has allowed us to know the annual and interannual variability of the reproductive cycle of the species in the Peruvian sea, its regime changes over time, as well as the basic structures of gonadal maturity. The analysis of the reproductive indices of D. gigas, GSI (gonadosomatic index), NGI (nidamental gland index), RA (reproductive activity) and SCI (spermatophoric complex index, males only), indicate that there is a period of greater reproductive activity, which begins in August and ends in February of each year, with greater intensity between October and January. The highest proportion of mature females was found in 1996, the year of La Niña event, which preceded the last Extraordinary El Niño (1997/1998), suggesting that this type of event (La Niña) favors the maturation of the ovaries of individuals in the large group. In females, the GSI shows a tendency to increase, which is not observed in males. The estimate of the size at first maturity for females, calculated with the complete series, was 306 mm mantle length (ML) for the ‘small shape’ group and 642 mm ML for the ‘large shape’ one; while, for males it was 201 mm ML for the ‘small shape’ group and 514 mm ML for the ‘large shape’ one. This intraspecific structure is complicated and is the case of other Ommastrephides, presenting overlaps between the spatial distributions of these groups (Nesis 1970, 1983; Nigmatullin et al. 2001). The existence of intraspecific groups in the jumbo flying squid population with different reproductive and population parameters has been previously reported for this species (Nesis 1983, Arkhipkin & Murzov 1986, Nigmatullin et al. 2001, Argüelles et al. 2001, Markaida & Sosa-Nishizaki 2001, Argüelles et al. 2008, Argüelles & Tafur 2010, Arkhipkin et al. 2015).