Discriminating Natal Source Populations of a Temperate Marine Fish Using Larval Otolith Chemistry

Abstract

The life cycles of many marine species depend on a dispersive larval stage that connects spatially segregated populations. However, quantifying larval movement among populations remains one of the greatest challenges in marine ecology. Such movement determines whether a population is essentially a self-recruiting stock, or if it forms part of a larger meta-population where recruits originate from multiple sources. Previous research has struggled to differentiate between such stock structure models for King George whiting (Sillaginodes punctatus; Perciformes) in southern Australia, largely due to difficulties in identifying the source populations of dispersing larvae. In this study, pelagic larvae were collected throughout the only recognized spawning area in South Australia in 2017 and 2018. First, we identified that the distribution of larvae was broadly divisible into two groups-those in southern Spencer Gulf and those in Investigator Strait. Then, the incremental structure and elemental composition of otoliths of larvae from the two regions were compared to determine if they had originated from a common source population. There were no spatial differences in the sizes (3.0-5.0 mm SL), ages (5-21 days), hatch dates (April 7-24) or average growth rates (0.09-0.21 mm d −1) of larvae. However, multi-elemental (Li, Mg, Mn, Sr, and Ba) otolith signatures differed significantly between the two regions, primarily driven by differences in concentrations of Li and Ba. Although otolith signatures were year-specific, larvae were assigned to their region of capture with 70-82% accuracy. Larvae in each region hatched at the same time yet had significantly different otolith chemistry, providing strong evidence that those in southern Spencer Gulf and Investigator Strait originated from spatially segregated water masses. This study has demonstrated the ability of otolith chemistry to discriminate source populations of pelagic larvae in a fully marine environment, which provides a basis to quantify larval movement between fish populations.

Spatial environmental variability of natural markers and habitat use ofCathorops spixiiin a neotropical estuary from otolith chemistry

“…In addition, physiological changes could occur in the transition to free-embryo or juvenile life (Lima et al ., 2012), which could cause changes in the rates of incorporation of Mn/Ca, Ba/Ca and Li/Ca. Similar to the present study, Mn/Ca (Rogers et al ., 2019) and Ba/Ca (Tabouret et al ., 2011) peaks were associated with the early stages (primordium) of several species such as Sicydium punctatum Perugia, 1896 and Sillaginodes punctatus (Cuvier, 1829). In C. spixii , the peaks were found on the margin of the primordium; there could be a potential physiological effect caused by metabolic changes (perhaps associated with ontogenetic changes) or a strong maternal/yolk influence which could mask the effect of other variables, such as environmental or physiological.…”

White mullet Mugil curema population structure from Mexico and Brazil revealed by otolith chemistry

“…The incorporation of trace elements into otoliths can be influenced by environment (depth, salinity and temperature) (Lin et al, 2007;Reis-Santos et al, 2013); surrounding water chemistry (Avigliano et al, 2019;Elsdon, & Gillanders, 2003;Walther, & Thorrold, 2006); food (Ranaldi & Gagnon, 2008); genetics (Clarke et al, 2011); and physiological events such as hatching, transition to free embryo or juvenile life (Rogers et al, 2019;Tabouret et al, 2011);…”

“…The incorporation of trace elements into otoliths can be influenced by environment (depth, salinity and temperature) (Lin et al ., 2007; Reis‐Santos et al ., 2013); surrounding water chemistry (Avigliano et al ., 2019; Elsdon, & Gillanders, 2003; Walther, & Thorrold, 2006); food (Ranaldi & Gagnon, 2008); genetics (Clarke et al ., 2011); and physiological events such as hatching, transition to free embryo or juvenile life (Rogers et al ., 2019; Tabouret et al ., 2011); and even a differential fishing pressure among catchment areas could alter the otolith composition (Catalán et al ., 2018). Also, in species with prolonged yolk feeding, the recent life history of mothers (maternal effect) could have an influence on the incorporation of trace elements into the larval otolith (Kalish, 1990; Liberoff et al ., 2014).…”

Using a biophysical model to investigate connectivity between spawning grounds and nursery areas of King George whiting (Sillaginodes punctatus: Perciformes) in South Australia’s gulfs

“…Consistent with previous studies, the model predicted that larvae settle to nursery areas short distances from regional spawning grounds. In both gulfs, simulated connectivity between spawning grounds and nursery areas was supported by similarities in otolith chemistry between larvae and recruits (Fowler, Black, et al, 2000;Rogers et al, 2019aRogers et al, , 2019c.…”

“…The third study identified two spatially segregated groups of larvae within the large spawning area that had different otolith chemistries. This indicated that southern Spencer Gulf and Investigator Strait supported two independent spawning populations (Rogers, Fowler, Steer, & Gillanders, 2019a). The aim of this study was to investigate the connectivity between spawning grounds and nursery areas by simulating dispersal using a biophysical model.…”