Reading the biomineralized book of life: expanding otolith biogeochemical research and applications for fisheries and ecosystem-based management

AbstractChemical analysis of calcified structures continues to flourish, as analytical and technological advances enable researchers to tap into trace elements and isotopes taken up in otoliths and other archival tissues at ever greater resolution. Increasingly, these tracers are applied to refine age estimation and interpretation, and to chronicle responses to environmental stressors, linking these to ecological, physiological, and life-history processes. Here, we review emerging approaches and innovative research directions in otolith chemistry, as well as in the chemistry of other archival tissues, outlining their value for fisheries and ecosystem-based management, turning the spotlight on areas where such biomarkers can support decision making. We summarise recent milestones and the challenges that lie ahead to using otoliths and archival tissues as biomarkers, grouped into seven, rapidly expanding and application-oriented research areas that apply chemical analysis in a variety of contexts, namely: (1) supporting fish age estimation; (2) evaluating environmental stress, ecophysiology and individual performance; (3) confirming seafood provenance; (4) resolving connectivity and movement pathways; (5) characterising food webs and trophic interactions; (6) reconstructing reproductive life histories; and (7) tracing stock enhancement efforts. Emerging research directions that apply hard part chemistry to combat seafood fraud, quantify past food webs, as well as to reconcile growth, movement, thermal, metabolic, stress and reproductive life-histories provide opportunities to examine how harvesting and global change impact fish health and fisheries productivity. Ultimately, improved appreciation of the many practical benefits of archival tissue chemistry to fisheries and ecosystem-based management will support their increased implementation into routine monitoring. Graphical abstract</jats:p

Data from: Partial migration: growth varies between resident and migratory fish

Partial migration occurs in many taxa and ecosystems and may confer survival benefits. Here, we use otolith chemistry data to determine whether fish from a large estuarine system were resident or migratory, and then examine whether contingents display differences in modelled growth based on changes in width of otolith growth increments. Sixty-three per cent of fish were resident based on Ba : Ca of otoliths, with the remainder categorized as migratory, with both contingents distributed across most age/size classes and both sexes, suggesting population-level bet hedging. Migrant fish were in slightly better condition than resident fish based on Fulton's K condition index. Migration type (resident versus migratory) was 56 times more likely to explain variation in growth than a model just incorporating year- and age-related growth trends. While average growth only varied slightly between resident and migratory fish, year-to-year variation was significant. Such dynamism in growth rates likely drives persistence of both life-history types. The complex relationships in growth between contingents suggest that management of species exhibiting partial migration is challenging, especially in a world subject to a changing climate

The universal imprint of oxygen isotopes can track the origins of seafood

Identifying the source of seafood is critical for combatting seafood fraud, but current tools are predominantly developed and applied on a species-specific basis. This study investigates how multiple marine taxa could be geolocated at global scales by exploiting stable oxygen isotope compositions in carbonate biominerals (δ 18O biomin), where we expect to see universally expressed and predictable spatial variation in δ 18O biomin values across taxa. We constructed global ocean isoscapes of predicted δ 18O biomin values specific to fish (otoliths), cephalopod (statoliths) and shellfish (shells), and a fourth combined “universal” isoscape, and evaluated their capacity to derive δ 18O biomin values among known-origin samples. High correspondence between isoscape-predicted δ 18O biomin values and a compiled database of measured, georeferenced values (3954 datapoints encompassing 68 species) indicated that this δ 18O biomin approach works effectively, particularly in regions with highly resolved projections of seawater δ 18O composition. When compared to taxon-specific isoscapes, the universal isoscape demonstrated similar accuracy, indicating exciting potential for universal provenance applications. We tested the universal framework via a case study, using machine-learning models to identify sample origins amongst regions of divergent (Tropical Asia vs Temperate Australasia) and similar (Temperate Asia vs Temperate Australasia) climates and latitudes. Classification accuracy averaged 75.3% between divergent regions, and 66% between similar regions. When endothermic tuna species were excluded from the analysis, the accuracy between divergent regions increased up to 90% between divergent regions. This study presents the first empirical step towards developing universal chemical markers, which have the potential to support a more inclusive and global approach of validating provenance of seafood. </p

Gillanders et al BL growth measurements etc on fish otoliths

Information from sectioned fish otoliths collected in the Coorong estuary, South Australia between 2008 and 2012. Includes fish code (fishid), year of capture (year cap), salinity (salinity), age at capture (agecap), length (length; fish total length in mm), sex (sex; female, F vs male, M), partial migration status (partial; R, resident vs M, migratory), Fulton's K condition index (fulton) and anu1 … anu31 (growth increment measurements for each annulus commencing at the 1st full increment (i.e. excludes from core to 1st increment) and moving towards the edge of the otolith, but excluding the incomplete growth increment on the edge of the otolith). NA indicates missing data. Where NA occurs for growth increment data, these increments had unclear growth zones

How calorie-rich food could help marine calcifiers in a CO2-rich future

Increasing carbon emissions not only enrich oceans with CO2 but also make them more acidic. This acidifying process has caused considerable concern because laboratory studies show that ocean acidification impairs calcification (or shell building) and survival of calcifiers by the end of this century. Whether this impairment in shell building also occurs in natural communities remains largely unexplored, but requires re-examination because of the recent counterintuitive finding that populations of calcifiers can be boosted by CO2 enrichment. Using natural CO2 vents, we found that ocean acidification resulted in the production of thicker, more crystalline and more mechanically resilient shells of a herbivorous gastropod, which was associated with the consumption of energy-enriched food (i.e. algae). This discovery suggests that boosted energy transfer may not only compensate for the energetic burden of ocean acidification but also enable calcifiers to build energetically costly shells that are robust to acidified conditions. We unlock a possible mechanism underlying the persistence of calcifiers in acidifying oceans

Comparison of risk scores from expert elicitation survey within and between habitats.

<p>Each point represents a risk score (most-likely scenario) for a threat-habitat combination and the grey horizontal line represents the mean of those risk scores.</p

Description of marine habitats (risk units) assessed and number of survey responses per habitat.

<p>Description of marine habitats (risk units) assessed and number of survey responses per habitat.</p

Location of study region (Spencer Gulf, South Australia).

<p>Location of study region (Spencer Gulf, South Australia).</p

Top-five threats for each habitat, ranked by the highest uncertainty scores (*).

<p>‘Y’ indicates whether a threat-habitat combination also received a “top five” effect and/or risk score (see <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0177393#pone.0177393.t002" target="_blank">Table 2</a>).</p