Evaluating estuarine nursery use and life history patterns of Pomatomus saltatrix in eastern Australia

Abstract

Estuaries provide important nursery habitats for juvenile fish, but many species move between estuarine and coastal habitats throughout their life. We used otolith chemistry to evaluate the use of estuaries and the coastal marine environment by juvenile Pomatomus saltatrix in eastern Australia. Otolith chemical signatures of juveniles from 12 estuaries, spanning 10° of latitude, were characterised using laser ablation-inductively coupled plasma-mass spectrometry. Based upon multivariate otolith elemental signatures, fish collected from most estuaries could not be successfully discriminated from one another. This was attributed to the varying influence of marine water on otolith elemental composition in fish from all estuaries. Using a reduced number of estuarine groups, the multivariate juvenile otolith elemental signatures and univariate Sr:Ca ratio suggest that between 24 and 52% of adult P. saltatrix had a juvenile period influenced by the marine environment. Elemental profiles across adult (age-1) otoliths highlighted a variety of life history patterns, not all consistent with a juvenile estuarine phase. Furthermore, the presence of age-0 juveniles in coastal waters was confirmed from historical length-frequency data from coastal trawls. Combining multiple lines of evidence suggests considerable plasticity in juvenile life history for P. saltatrix in eastern Australia through their utilisation of both estuarine and coastal nurseries. Knowledge of juvenile life history is important for the management of coastal species of commercial and recreational importance such as P. saltatrix.

Multiple spawning events promote increased larval dispersal of a predatory fish in a western boundary current

“…Mortality was not incorporated as the settlement locations of the particles are already known, and this model seeks to identify the potential spawning locations that could have resulted in transport to these settlement locations, rather than any measure of density. Locations were determined by juvenile tailor observations (Table 1; Leigh et al, 2017; Schilling, 2019; Schilling et al, 2018). Because the poleward flowing EAC dominates the circulation upstream of 31°S, we did not simulate any backwards tracking releases north of 31°S as the majority of the particles were estimated to leave the northern boundary of the ROMS model (which corresponds to the most northern spawning for this population).…”

“…Because P. saltatrix are most commonly caught at age 2 in the southwestern Pacific Ocean (Leigh et al, 2017; Schilling, 2019), the relative predicted number of settled larvae south of 36°S during July–June (to cover the spawning season) were lagged by 2 years. Despite P. saltatrix being well recognised for its migratory nature (Brodie et al, 2018; Juanes et al, 1996), in the southwest Pacific population, juveniles (<30 cm) are not known to undertake migrations and usually remain in or near estuaries (Morton, Halliday, & Cameron, 1993; Schilling et al, 2017, 2018). This means despite the migratory nature of this species, it should be possible to align predicted settlement with estuarine CPUE as the fishery is largely based upon fish which would have had limited opportunity to migrate, particularly at the southern extreme of the populations' distribution.…”

Using otolith microchemistry to assess nursery habitat contribution and function at a fine spatial scale

“…Distance-based permutational multivariate analysis of variance (PERMAN OVA; Anderson 2001, Ander son et al 2008) was used to assess variation in the elemental and stable isotopic composition of sample otoliths (Reis-Santos et al 2012, Schilling et al 2018 among the 9 stations in the LMR (Fig. 1).…”

“…Microchemical composition of a fish's otoliths is increasingly used as a natural tag for marking an individual, helping to track a fish as it grows and moves among a mosaic of habitats (e.g. Gillanders 2005, Schilling et al 2018. Most estuarine applications of otolith microchemistry have characterized variation at a broad scale (i.e.…”

Coastal winds and larval fish abundance indicate a recruitment mechanism for southeast Australian estuarine fisheries

“…For many marine species, the transition from larva to juvenile is often characterised by high 31 mortality (Houde, 2008), and a shift in habitat from open water to more protected habitats such as 32 estuarine nursery areas (Houde, 2008;Schilling et al, 2018). Some environmental conditions are 33 more favourable for larval transport or advection towards juvenile habitat (Wenner et al, 1998;34 Reichert et al, 2010).…”