Strong population structure deduced from genetics, otolith chemistry and parasite abundances explains vulnerability to localized fishery collapse in a large Sciaenid fish, Protonibea diacanthus

Abstract

As pressure on coastal marine resources is increasing globally, the need to quantitatively assess vulnerable fish stocks is crucial in order to avoid the ecological consequences of stock depletions. Species of Sciaenidae (croakers, drums) are important components of tropical and temperate fisheries and are especially vulnerable to exploitation. The black‐spotted croaker, Protonibea diacanthus, is the only large sciaenid in coastal waters of northern Australia where it is targeted by commercial, recreational and indigenous fishers due to its food value and predictable aggregating behaviour. Localized declines in the abundance of this species have been observed, highlighting the urgent requirement by managers for information on fine‐ and broad‐scale population connectivity. This study examined the population structure of P. diacanthus across north‐western Australia using three complementary methods: genetic variation in microsatellite markers, otolith elemental composition and parasite assemblage composition. The genetic analyses demonstrated that there were at least five genetically distinct populations across the study region, with gene flow most likely restricted by inshore biogeographic barriers such as the Dampier Peninsula. The otolith chemistry and parasite analyses also revealed strong spatial variation among locations within broad‐scale regions, suggesting fine‐scale location fidelity within the lifetimes of individual fish. The complementarity of the three techniques elucidated patterns of connectivity over a range of spatial and temporal scales. We conclude that fisheries stock assessments and management are required at fine scales (100 s of km) to account for the restricted exchange among populations (stocks) and to prevent localized extirpations of this species. Realistic management arrangements may involve the successive closure and opening of fishing areas to reduce fishing pressure.

Non‐diadromous life history and limited movement in northern lineages of Australian smelt: Evidence from otolith chemistry analysis

“…Similar misclassifications in otolith chemical signatures among sites have been observed in studies of other fish species including black-spotted croaker Protonibea diacanthus(Taillebois et al, 2017), Black Rock fish, Sebastes melanops(Miller, Banks, Gomez-Uchida, & Shanks, 2005) and Common carp, Cyprinus carpio. Classification success was similar for core, near core and edge, suggesting similar patterns of dispersal and mixing of individuals across ontogeny.…”

“…Misclassifications of individuals are likely due to the high number of locations relative to the number of elements used in the discriminant function analysis. Similar misclassifications in otolith chemical signatures among sites have been observed in studies of other fish species including black-spotted croaker Protonibea diacanthus(Taillebois et al, 2017), Black Rock fish, Sebastes melanops(Miller, Banks, Gomez-Uchida, & Shanks, 2005) and Common carp, Cyprinus carpio. In the three cases where the edge signatures (reflecting recent growth) were distinct between paired sites (Brisbane, Logan and Nerang River), the core and near-core signatures were also significantly different.…”

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

“…While allele frequency distributions highlight population processes on a multi-generational timescale and length distributions can indicate spatial structuring at the time of sampling, otolith chemistry records environmental and physiological influences over an individual's life history. Otolith chemistry, therefore, has the potential to resolve population structure where gene flow homogenizes genetic differences, and throw light on the mechanisms explaining spatial length distributions and genetic connectivity (Ashford et al 2006, Taillebois et al 2017.…”

Otolith microchemistry: a useful tool for investigating stock structure of yellowfin tuna (Thunnus albacares) in the Indian Ocean

“…Different stocks may possess specific genetic, physiological and behavioural traits that can influence life processes such as growth rates, fecundity, abundance and disease resistance (Stepien 1995), and thus different resilience to exploitation and environmental changes. As such, when stock structure is more complex than recognised, the sustainability of the resource and the profitability of the fishery can be jeopardised (Kerr et al 2017;Taillebois et al 2017).…”