Ontogenetic and Spatiotemporal Changes in Isotopic Niche of Jumbo Squid (Dosidicus gigas) in the Southeastern Pacific

Abstract

Jumbo squid (Dosidicus gigas) plays an important role in food webs throughout the eastern Pacific; however, its trophic ecology is complex, because it is a highly migratory and opportunistic predator. In this study, δ13C and δ15N values were measured along the lateral wall of lower beak to investigate the ontogenetic and spatiotemporal feeding strategy shifts of jumbo squid, respectively. Both year and area had significant influences on δ13C (p < 0.01), while sex and stage had no significant influence on δ13C (p > 0.05). All explanatory variables (sex, stage, year, and area) had significant influences on δ15N (p < 0.05). The differences of niche among life stages indicated that the habitat and feeding habit were likely changed with the growth of individuals. Compared with normal years, the habitat of squids might change during the El Niño year. However, during the strong El Niño year, habitat location changed and niche size decreased compared to normal years. The trophic niche of D. gigas differed between different areas. Stable isotopes in early life stages were most effective for distinguishing different geographic populations. Females and males were likely to inhabit similar geographic areas throughout ontogeny. Unexpectedly, we found evidence to suggest females may have larger habitats and wider trophic niche than males. This study revealed the ontogenetic and spatiotemporal plasticity of habitat and feeding strategy of D. gigas.

Life History of the Arctic Squid Gonatus fabricii (Cephalopoda: Oegopsida) Reconstructed by Analysis of Individual Ontogenetic Stable Isotopic Trajectories

“…This means that high individual variation in habitat usage and different migratory capabilities between sexes are not enough to differentiate niches between females and males due to individual squid’s highly generalist diets. These results contrast with previous studies on other cephalopods where significant differences in niche width were found between sexes [ 30 , 49 , 123 , 125 ].…”

“…This is the first application of s to stable isotopic data from marine invertebrates to the authors’ knowledge. Specialization index s of δ 15 N shows that G. fabricii is a generalist predator, as most predatory squids are e.g., [ 48 , 50 , 120 , 121 , 122 , 123 ]. Significant differences in s of δ 15 N between the sexes in G. fabricii are influenced by only one individual: s values were 0.95–0.98 in all individuals, except female F5 with s = 0.83.…”

“…Thus, at least part of the variation in δ 13 C is explained by these differences between the sexes. The greater migratory capability of females is known in oceanic squids Ommastrephes bartramii (Lesueur, 1821) [ 49 , 124 ] and D. gigas [ 123 ]. The niche width in G. fabricii is similar in females and males, with significant niche overlap between the sexes.…”

“…Previous studies used eye lenses and gladii of cephalopods to analyse individual ontogenetic stable isotopic trajectories; however, they failed to identify the fast pace of changes in cephalopod ecological role early in ontogenesis [ 48 , 49 , 50 , 123 , 142 , 143 , 144 , 145 , 146 , 147 , 148 ]. Unlike beaks, neither eye lenses nor gladii were proven to have daily growth increment deposition [ 62 , 63 , 64 , 65 ].…”

Using stable isotope chronologies within squid gladii (Doryteuthis gahi) to evaluate dietary differences by fishing region and season

“…Containing continuous growth increments, these structures have been used in age and growth studies of squid (Arkhipkin et al 2018), and have also been used to obtain a chronological record of feeding ecology using stable isotope analysis, e.g. gladius (Kato et al 2016), beak (Hu et al 2022), eye lens (Meath et al 2019, Liu et al 2020).…”