Reproductive biology of jumbo squid Dosidicus gigas in relation to environmental variability of the northern Humboldt Current System

Abstract

Dosidicus gigas is a monocyclic ommastrephid squid and is an important component of its ecosystems in the Eastern Pacific Ocean. The species shows variable reproductive characteristics; among these are 3 spatially separated groups of size-at-maturity. Biological data from the industrial fisheries of the Peruvian Humboldt Current System (HCS) from 1991 to 2007 were analyzed. Changes in reproduction patterns allow jumbo squid to cope with productivity changes in their environment. In the HCS, low productivity is related to warm water masses prevailing during warm periods, and high productivity is found for cool water masses during cool periods. Three general features related to reproduction enabling the squid to adjust to changes have been identified: (1) variable size-at-maturity, (2) temporal decoupling of male and female formation of reproductive tissue in order to temporally distribute the required energy and (3) changing sex-ratios. Smaller sizes-at-maturity are found in warm water masses, specimens maturing at larger sizes in cool water masses. Females mature at the end of their life which leads to a j-shaped increase in maturity when plotted against mantle length, while males mature at a medium size which results in an s-shaped form of maturation. The 3 groups of size-at-maturity proposed in earlier studies may not actually exist, and may only be an observational artifact from a continuous change in size-at-maturity between 2 extremes. KEY WORDS: Dosidicus gigas · Cephalopoda · Reproductive patterns · Interannual variability · Size-at-maturity · Energy availability · Peru Resale or republication not permitted without written consent of the publisherMar Ecol Prog Ser 400: [127][128][129][130][131][132][133][134][135][136][137][138][139][140][141] 2010 tive biology (Markaida 2006b, Argüelles et al. 2008, as well as population structure in general (Bazzino et al. 2007). Analyzing size-at-maturity of females of the Peruvian exclusive economic zone only, a transition period lasting from 1999 to 2000 was identified that separates a period of small mature females in the 1990s from the period of large mature females in the 2000s (Argüelles et al. 2008). At the same time, landings of jumbo squid have greatly increased (IMARPE unpubl. data: see also FAO ftp://ftp.fao.org/FI/STAT/summary/ a1e.pdf). Temporal variation in size-at-maturity has also been observed in the northern hemisphere, although in a different form; here jumbo squid generally matured at large sizes (at least since the late 1980s), and only during the El Niño event of 1997/1998 did size-at-maturity drop to sizes similar to those found in Peru during the early 1990s (Markaida 2006b, Bazzino et al. 2007). However, small specimens were also reported from Mexican waters in the 1970s and the 1980s ( Table 1).The northern Humboldt current system (HCS) shows high variability in abiotic and associated biotic conditions. Water temperature, salinity and ecosystem productivity are coupled to water masses that change their extent according to global...

Eulerian Approach to the Estimation of Growth Rates and Population Structure of Jumbo Squid (Dosidicus gigas) in the Central Gulf of California

“…7), which could indicate the periodicity of arrival of new specimens to the fishing area. The sex ratio obtained for the entire fishing period showed an apparent dominance of D. gigas males over females, which is the opposite of what has been reported in previous studies from the Gulf of California (Markaida & Sosa-Nishizaki 2001, Bazzino et al 2007) and Peruvian waters (Tafur et al 2001, Tafur et al 2010. This condition could be the product of the selective effect of the jigs when specimens are immature or the product of spatial segregation and migration between sexes in the study area.…”

Ambient temperature influences adult size and life span in jumbo squid (Dosidicus gigas)

“…However, in all validated species of both myopsid and oegopsid squids the 302 hypothesis 'one increment=one day' was confirmed (reviews: Arkhipkin 2004; Jackson 2004). This was confirmed by small size of mature squid caught at the end of their 399 1998-1999 spawning period in austral winter of 1999(Tafur et al 2010). J.…”

“…The marginal R 2 was 0.13 and the conditional R 2 was 0.88. This event is clearly visible in Figure 5 by Tafur et al (2010), when a substantial proportion of 404 females were still immature and growing during their spawning period in summer 1999-2000. The effect of SSST 5 for average FSST 8 , FSST 11 and SSST 1 values 291 is presented in Fig.…”

“…Therefore, a preliminary exploratory analysis of monthly length frequencies 117 of females at different maturity stages was carried out to identify the peak of spawning and 118 modal length of mature females in every year between 1992 and 2011. It is also notable that peaks of spawning of the small size group and large size 124 group could take place in different months and seasons in a given year (Tafur et al, 2010). In 121 some years, only one modal group was present in catches, either small with ML < 490 cm or 122 large >520 cm, in some other years both modal groups were present (Argüelles et al 2001 ;Tafur 123 et al, 2010).…”

Genetic diversity and demographic history of Dosidicus gigas (Cephalopoda: Ommastrephidae) in the Humboldt Current System

“…This squid reaches velocities up to 20 km h -1 during massive migrations of adults (Nesis 1970, Nigmatullin et al 2001, Gilly et al 2006b). It is a monocyclic species; it dies after one reproductive cycle (Rocha et al 2001, Tafur et al 2010. During the reproductive cycle, female jumbo squids undergo multiple spawnings of 10 to 14 spawning batches with 32 million eggs or more; it has the highest fecundity of all cephalopods (Nigmatullin & Markaida 2009).…”