Can otolith microstructure and elemental fingerprints elucidate the early life history stages of the gadoid southern blue whiting (Micromesistius australis australis)?

Abstract

Southern blue whiting (Micromesistius australis australis) was one of the largest fisheries in the Southwest Atlantic with the peak in total annual catches attaining 258.000 tonnes. Intense exploitation over the past 30 years critically decreased its abundance and forced the implementation of a suite of conservation measures to save and rebuild the stocks. Recently improved recruitment levels require more information on the early life history stages of this fish. Using complimentary investigations into otolith microstructure and trace elemental composition by LA-ICPMS, larval, metamorphic and post-metamorphic periods of the early ontogeny were studied. The timing and completion of metamorphosis were estimated at 30.5 ± 0.3 and 60.7 ± 1.8 days after the first increment formation respectively. The timing of a newly defined 'juvenile transition-mark' (corresponding to the transition from the epipelagic larval habitat to a deeper juvenile habitat was estimated to form at age of 76.5 ± 2.0 days. *Manuscript including abstract Click here to view linked ReferencesThe movement of juveniles into deeper waters post-metamorphosis were further confirmed by significant shifts in the element: 42 Ca ratios (for elements 24 Mg, Mn, 88 Sr and Ba).Elemental 'fingerprints' for each of the three otolith zones were further found to be distinct through high classification accuracies of the random Forest model (81.1 ± 0.1%). Holistic approach investigating both otolith microstructure and elemental composition provides further evidence that ontogeny could be a confounding factor in natal (geographic) origin studies if (1) otolith 'core' samples are taken from different ontogenetic otolith zones and (2) if elements predominantly controlled by physiology are included in the respective classification analyses.

Unveiling the wasp-waist structure of the Falkland shelf ecosystem: the role of Doryteuthis gahi as a keystone species and its trophic influences

“…Furthermore, we constructed a new diet matrix relying on different studies and updated the values on biomass, landings and discards. This was especially necessary, as the ecosystem underwent some crucial changes within the last 20 years (Busbridge et al ., 2020). We also focused on single abundant species (in terms of catchability) rather than on functional groups.…”

Revealing Population Connectivity of the Estuarine Tapertail Anchovy Coilia nasus in the Changjiang River Estuary and Its Adjacent Waters Using Otolith Microchemistry

“…The chemical characteristics of otoliths can reflect biographical information of fish habitats throughout their life-history because otoliths are formed before the fish hatches, and elements deposited on them are not metabolized by the fish during their life cycle [30]. In particular, the nucleus region, defined as a small area in the central region of an otolith [31,32], which usually represents its initial growth period (i.e., larvae and juveniles) [33,34], is important as it corresponds to the fish's incubation and early life-history stage; therefore, the chemical characteristics of the otolith nucleus region can be used to determine the characteristics of hatchery/spawning sites and population origin, which can retrospectively determine the origin of the population [35][36][37]. In these studies, the elemental "fingerprint" and stable isotope characteristics are often used to determine the physical and chemical nature of the aqueous environment during the incubation and early life-history of research objects for identification and connectivity studies of populations [38,39].…”