Spatial structuring and life history connectivity of Antarctic silverfish along the southern continental shelf of the Weddell Sea

Abstract

A multi-disciplinary approach was employed to examine a physical-biological population hypothesis for a critical forage species, the Antarctic silverfish Pleuragramma antarctica. Caccavo et al. (2018; Sci Rep 8: 17856) had shown strong gene flow along the westward Antarctic Slope Current, in addition to spatially recurring length modes that provided evidence for episodic connectivity. In this paper, otolith nucleus chemistry from a subset of fish collected in the southern Weddell Sea as part of a hydrographic survey of the Filchner Trough system was used to test between connectivity scenarios. Nucleus chemistry, which reflects environmental exposure during early life, showed significant spatial structuring despite homogeneity in microsatellite allele frequencies. Mg:Ca and Sr:Ca differentiated length modes, and Mg:Ca showed significant contrasts between Atka Bay, Halley Bay, and Filchner Trough. Physical-biological mechanisms may help reconcile structuring shown by otolith chemistry, length, and abundance data with prior evidence of gene flow. Such mechanisms include self-recruitment shaped by circulation associated with the Filchner Trough, fluctuations in mixing between immigrant and locally recruited fish, and feeding opportunities between inflowing Modified Warm Deep Water and outflowing Ice Shelf Water. The results illustrate how comparisons between multi-disciplinary techniques based on integrated sampling designs that incorporate hydrography can enhance understanding of population structure and connectivity around the Southern Ocean.

Weddell seal behaviour during an exceptional oceanographic event in the Filchner-Ronne Ice Shelf in 2017

“…Weddell seals feed predominantly on Antarctic silverfish, which have a life history that is hypothesized to be structured by circulation associated with glacial trough systems (Ashford et al 2017). Adult Antarctic silverfish spawn in the vicinity of the ice shelf during late winter and early summer, exposing them to the outflow of ISW (Caccavo et al 2019). Caccavo et al (2019) sampled exclusively large-length fish in ISW at 77°S just east of the trough flank at 700 m compared to sharply decreasing numbers at shallower depths over the adjoining shelf.…”

Otolith chemistry of Electrona antarctica suggests a potential population marker distinguishing the southern Kerguelen Plateau from the eastward‐flowing Antarctic Circumpolar Current

“…Instead, otolith MgCa −1 is considered to reflect fish activities that directly influence physiology (Martin and Thorrold 2005). Reproduction, feeding, and movement are thought to contribute, modified by responses to spatially variable water properties between water masses (Ashford et al 2005; Zhu et al 2018; Caccavo et al 2019). The moderated ACC signature over the SKP (Bestley et al 2018), quiescent water, slow anticyclonic drift (Fig.…”

“…Alternatively, immigrants may simply be distributed patchily, associated with eroding ACC eddies over the SKP in spatial concentrations that our biological sampling did not capture. Recently, a multidisciplinary approach used otolith chemistry and genetics to demonstrate structuring of Antarctic silverfish and strong gene flow along the Antarctic Slope Current (Caccavo et al 2018, 2019). Strong differences between regional variations of Circumpolar Deep Water around the Southern Ocean augur well for discriminating the origin of our ACC fish, and genetics may help resolve how much immigration occurs over the SKP.…”

“…Although the underlying mechanisms of incorporation have yet to be fully described, differences in BaCa −1 are thought to reflect ambient levels of dissolved Ba (Campana 1999, Ashford et al 2005), whereas MgCa −1 and SrCa −1 are directly influenced by physiology. SrCa −1 is considered to reflect growth mediated by ambient temperature and food availability (Campana 1999) and MgCa −1 to reflect fish activity like reproduction and movement (Ashford et al 2005; Zhu et al 2018; Caccavo et al 2019). Chemistry deposited during early life in otolith nucleus has been used to test population hypotheses in Patagonian toothfish ( Dissostichus eleginoides ) (Ashford et al 2006, 2008, 2012 a ), Scotia Sea icefish ( Chaenocephalus aceratus ) (Ashford et al 2010), Antarctic toothfish ( Dissostichu smawsoni ) (Ashford et al 2012 b ), and Antarctic silverfish ( Pleuragramma antarcticum ) (Caccavo et al 2019).…”

Application of the analysis of trace elements composition for calcified structures of fish to solve fundamental and applied scientific tasks: a review

“…выше). К работам, посвященным исключительно миграциям морских видов рыб, можно отнести опубликованные результаты идентификации смены мест обитания желтополосого хемулона Haemulon flavolineatum атолла Тунефф, Белиз [Chittaro et al, 2005], рыбы-ласточки Pomacentrus amboinensis Большого Барьерного Рифа [Sih et al, 2016], сайки Boreogadus saida и арктического шлемоносца Gymnocanthus tricuspis Чукотского моря [Gleason et al, 2016], а также антарктической серебрянки Pleuragramma antarcticum моря Уэдделла [Caccavo et al, 2019]. Во всех случаях для реконструкции миграций особей использовался анализ динамики химического состава вдоль оси кальцинированной структуры от ее центра к периферии.…”