Academic literature on the topic 'Otolith chronology'

ABSTRACTThe radiocarbon (14C) chronology of hunter-fisher-gatherers’ archaeological settlements along the Brazilian coast is usually based on mollusk shells, charcoal from hearths, and eventually human bones. However, fish otoliths are found in several archaeological contexts and may represent a reliable option as a chronological record. In this work, we compare the 14C dates of whitemouth croakers (Micropogonias furnieri) otoliths with dates obtained from other materials (shell and charcoal), collected from shellmounds on the coast of Rio de Janeiro, with the aim of improving the accuracy in the 14C dating of Brazilian shellmounds, strengthening the comprehension of the native populations’ occupational trends and the coeval palaeoceanographic context. Based on x-ray diffraction results for archaeological otoliths, their geochemical composition indicates minimal diagenesis effect over time even under burial conditions in the studied sites. The comparison between otolith dates and dates obtained from other proxies revealed similar results but with decreased deviations in otolith dates in all of the studied sites.

We report a new ion microprobe method to reconstruct aspects of fish life history based on sulfur isotopes (34S/32S, expressed as δ34S). Selected hatchery raised and naturally spawned juvenile chinook salmon (Oncorhynchus tshawytscha) are shown to have a 12.96 ± 0.27‰ (mean ± 2 standard errors) difference in muscle δ34S values, corresponding to δ34S differences between the hatchery and freshwater diets. Isotopic microanalyses of otoliths demonstrate that this 13‰ difference is preserved in the otoliths. We interpret the otolith δ34S record to be a chronology of dietary δ34S, with approximately one-week temporal resolution, preserved in these banded calcium carbonate structures. Potential applications of this method include identifying hatchery raised fish and reconstructing nutrition sources, migration, and other aspects of fish life history.

Exploiting the chemical and growth properties of otoliths, this study demonstrates how environmental archives with high temporal resolution can be developed. Elemental profiles (Ba:Ca and Sr:Ca) of fish otoliths (ear bones) from the estuarine species Acanthopagrus butcheri (black bream) were related to growth increments on a seasonal time scale. A series of mixed effects models were used to investigate biological, temporal, and environmental factors influencing seasonal otolith elemental profiles. Resultant seasonally resolved chemical chronologies were correlated with environmental data (i.e., salinity) to develop an element–salinity regression function, which when fit to an independently derived chemical chronology showed strong agreement between reconstructed and recorded salinities. Support for the element–salinity regression function through independent verification provided confidence in environmental reconstructions derived from an archaeological otolith. This suggests otoliths can be used to reconstruct past environmental conditions over decadal and centennial time scales. Moreover, the application of mixed effect models to develop chemical chronologies also provides information on drivers of elemental profiles and allows a range of ecological questions to be addressed. This approach may be further adapted and employed across a broader range of taxonomic groups and environments.

The alternating translucent and opaque banding pattern in canary rockfish (Sebastes pinniger) otoliths, aged using a break-and-burn methodology, are annual markings. To validate age assignment, we compared measured radiocarbon levels in canary rockfish otolith cores with a reference chronology developed from known age Pacific halibut (Hippoglossus stenolepis). An average 2- to 3-year phase shift was detected between the canary rockfish and a Pacific halibut reference chronology that was likely the result of differences in the regional oceanography or underageing bias. The assumption of ageing bias consistency was tested with two sampling designs. The first design controled for age-related ageing error, and the second design related birth year to estimated age. No change in the magnitude of ageing bias as a function of age was detected.

Reef fishes support important fisheries throughout the Caribbean, but a combination of factors in the tropics makes otolith microstructure difficult to interpret for age estimation. Therefore, validation of ageing methods, via application of Δ14C is a major research priority. Utilizing known-age otolith material from north Caribbean fishes, we determined that a distinct regional Δ14C chronology exists, differing from coral-based chronologies compiled for ageing validation from a wide-ranging area of the Atlantic and from an otolith-based chronology from the Gulf of Mexico. Our north Caribbean Δ14C chronology established a decline series with narrow prediction intervals that proved successful in ageing validation of three economically important reef fish species. In examining why our north Caribbean Δ14C chronology differed from some of the coral-based Δ14C data reported from the region, we determined differences among study objectives and research design impact Δ14C temporal relationships. This resulted in establishing the first of three important considerations relevant to applying Δ14C chronologies for ageing validation: 1) evaluation of the applicability of original goal/objectives and study design of potential Δ14C reference studies. Next, we determined differences between our Δ14C chronology and those from Florida and the Gulf of Mexico were explained by differences in regional patterns of oceanic upwelling, resulting in the second consideration for future validation work: 2) evaluation of the applicability of Δ14C reference data to the region/location where fish samples were obtained. Lastly, we emphasize the application of our north Caribbean Δ14C chronology should be limited to ageing validation studies of fishes from this region known to inhabit shallow water coral habitat as juveniles. Thus, we note the final consideration to strengthen findings of future age validation studies: 3) use of Δ14C analysis for age validation should be limited to species whose juvenile habitat is known to reflect the regional Δ14C reference chronology.

Bluespine unicornfish (Naso unicornis) from Hawaii were aged to >50 years using cross-sectioned sagittal otoliths. Fish length was a poor indicator of age because of rapid and variable early growth, exemplified by fish aged to be 4 years near maximum length. Growth was deterministic with adult ages decoupled from body length. Otolith mass and thickness were evaluated as proxies for age and both were encouraging; thickness explained more variance but mass was easier to measure. An age estimation protocol was validated through ontogeny using bomb radiocarbon (14C) dating. Use of the postbomb 14C decline period from a regional reference chronology enabled age validation of young fish — a novel approach for the Pacific Ocean. A probabilistic procedure for assigning bomb 14C dates (CALIBomb) was used for the first time to determine fish birth years. The age-reading protocol was generally validated, and it was possible to describe length-at-age despite difficulties in counting otolith annuli beyond 30–40 years. Growth curves differed between the sexes, and a four-parameter generalized von Bertalanffy growth function provided the best fit.

Analysis of otolith strontium (Sr) or strontium-to-calcium (Sr:Ca) ratios provides a powerful tool to reconstruct the chronology of migration among salinity environments for diadromous salmonids. Although use of this method has been validated by examination of known individuals and translocation experiments, it has never been validated under controlled experimental conditions. In this study, incorporation of otolith Sr was tested across a range of salinities and resulting levels of ambient Sr and Ca concentrations in juvenile chinook salmon (Oncorhynchus tshawytscha), coho salmon (Oncorhynchus kisutch), sockeye salmon (Oncorhynchus nerka), rainbow trout (Onco rhynchus mykiss), and Arctic char (Salvelinus alpinus). Experimental water was mixed, using stream water and seawater as end members, to create experimental salinities of 0.1, 6.3, 12.7, 18.6, 25.5, and 33.0 psu. Otolith Sr and Sr:Ca ratios were significantly related to salinity for all species (r2 range: 0.80–0.91) but provide only enough predictive resolution to discriminate among fresh water, brackish water, and saltwater residency. These results validate the use of otolith Sr:Ca ratios to broadly discriminate salinity histories encountered by salmonids but highlight the need for further research concerning the influence of osmoregulation and physiological changes associated with smolting on otolith microchemistry.

Radiocarbon generated by atmospheric testing of nuclear weapons (bomb radiocarbon) produced a strong signal with an abrupt onset in the 1950s, which serves as a dated marker for tracing oceanic circulation and confirming age in animals forming growth bands. Here, we report the first prebomb and postbomb radiocarbon chronologies for marine and freshwater environments in the Canadian Arctic, extend the radiocarbon chronology for the northwest Atlantic Ocean, and use the onset of the bomb signal to validate our age interpretations of lake trout (Salvelinus namaycush) in Arctic lakes. Both surface and deepwater Arctic chronologies became detectable on or around 1958, similar to the year of onset elsewhere in the world. In contrast, the freshwater Arctic chronology increased sharply in 1957, with a peak value sixfold higher than the adjacent marine environment. The radiocarbon content of the adult otolith core validated our age interpretation criteria for Arctic lake trout to an age of at least 50 years. Otolith growth in such slow-growing fish was so low as to be unresolvable under conventional examination with a dissecting microscope. With these new radiocarbon reference chronologies, age validation of a large number of Arctic organisms should now be possible.

Growth and survival of Maurolicus muelleri larvae in Herdlefjorden, Norway, were investigated by daily otolith increment analysis. While high egg densities were generally observed throughout the spawning season, three cohorts each with a narrow window of hatching dates were identified. The first of these cohorts was characterized by low growth and poor morphometric condition and disappeared from the fjord during autumn. High-resolution drift modeling indicated that Herdlefjorden had a net export of larvae and negligible import in the period cohort 1 disappeared. Yet, the advective loss rate of larvae was not considered high enough to explain the near complete disappearance of the first cohort. An otolith-based growth chronology indicated that growth conditions in Herdlefjorden improved noticeably around mid-September and remained favorable the following month. The analysis of daily otolith increments could thus be used to document within-season variability in larval growth and survival. The low and variable survival due to short-term fluctuations in environmental conditions indicate that multiple batch spawning is an adequately evolved life-history strategy for marine planktivorous fish such as M. muelleri.

Environmental variability affects the physiology of marine ectotherms, causing changes to metabolic rate, locomotion and growth. Species that move between habitats with different temperature and salinity for spawning purposes may experience significant changes in their growth rate and physiology compared to those that live in stable environments. Ectotherms have a temperature and salinity range at which growth and survival are optimal. Although, ectotherms are capable of tolerating a range of temperatures and salinities, moving from optimal to extreme ranges can affect oxygen consumption, locomotion and growth. The physiological responses of many marine ectotherms to environmental variability are not well known. King George whiting (Sillaginodes punctatus; Sillaginidae) is an important commercial and recreational temperate fish in Southern Australia, with concerns it may be at risk to future climate change. Due to the deficit of information on physiology and growth of this species, they were targeted to evaluate their physiological response to environmental change. Climate-growth relationships were reconstructed for King George whiting using growth chronologies derived from fish ear bones (otoliths). Otolith samples were collected from Kangaroo Island, Spencer Gulf and Gulf St Vincent in South Australia. A chronological approach was used to examine the inter-annual variation in growth and the influence of region, sea surface temperature (SST), El-Niño Southern Oscillation (ENSO) events (SOI), and recruitment. The growth chronology showed a negative correlation with winter SST. Recruitment and region did not affect growth rate. The swimming performance and metabolic rate of adult fish was investigated at two temperatures (16°C and 26°C), as well as their potential to recover after a prolonged swimming period, in a resting chamber. Fish were initially swum in a swim chamber, while water velocity was increased, until exhaustion, then their critical swimming speed (Ucrit) was calculated. Following exhaustion, fish were transferred into a resting chamber and the maximum metabolic rate (MMR) was calculated. Thereafter, they were allowed to recover in the chamber overnight and their standard metabolic rate (SMR) was measured. The Ucrit and aerobic metabolic rate were higher at the higher temperature and the fish recovered quicker in warmer water. A similar study was performed on juvenile fish, but across four temperatures (16, 19, 22 and 25°C) and two salinities (30 and 40ppt), using swim chamber. Metabolic rate of the juveniles was explained by a curvilinear relationship with temperature, but temperature had no influence on Ucrit. Salinity did not affect the MMR and aerobic scope, but SMR decreased and Ucrit increased as salinity decreased. The temperature optimum for SMR and aerobic scope was between 16°C and 19°C and their thermal window was between 16°C and 22°C with a critical temperature (Tc) of 25°C. The effects of temperature and salinity (the same treatments as mentioned above) on otolith elemental composition were investigated as a precursor to tracing environmental history of King George whiting. The concentration of Mg, Mn, Sr and Ba, ratioed to calcium, in juvenile otoliths was influenced by salinity, with a minor effect of temperature and no interaction between temperature and salinity for all element:Ca ratios. This indicated that otolith chemistry maybe useful for reconstructing the salinity history of King George whiting. I developed methods for evaluating the effects of environmental parameters (e.g. SST, SOI and salinity) on King George whiting growth, physiology and otolith chemistry. Outcomes can be used to assess the growth and metabolic response of King George whiting to temperature and salinity change. The otolith chemistry results can be used for reconstructing the environmental salinity history, and potentially movement patterns, of King George whiting. The temperature examined did not significantly affect the swimming speed and otolith elemental composition of the fish. A plausible reason for these results might be that the temperature range examined was within the species’ optimal thermal tolerance window, but any further temperature increase or decrease at both ends of the thermal window can possibly affect the growth and survival of this species.
Thesis (Ph.D.) (Research by Publication) -- University of Adelaide, School of Biological Sciences, 2016.

Biogeochemical tracers and sclerochronologies are used to answer many ecological questions that require linking organisms with the environment. Calcified hard parts of organisms that remain chemically inert after formation are particularly advantageous for extracting information (e.g. otoliths, shells, coral) on both the organism and the environment. These structures have growth increments enabling time-resolved information to be extracted on a range of time-scales (sub-daily to centennial). For my research, otoliths (fish earstones) were chosen as an environmental proxy, as they contain both biogeochemical (i.e. radiocarbon and trace elements) and sclerochronological (i.e. growth) signals that reflect environmental change in marine systems. My overarching aim is to use otolith-based proxy records to provide new data describing environmental change in marine systems of southern Australia and New Zealand. More specifically, I employ biogeochemical tracers and sclerochronologies to: (1) detect changes in radiocarbon transport through time in marine waters; (2) establish a radiocarbon record for upwelled waters in the southeastern Indian Ocean; (3) examine local and regional effects of climate forcing on fish growth, and (4) determine the physiological controls acting upon trace element assimilation into otoliths and the differences in chemical constituents of an upwelled water mass. Otoliths of deep water fish – ocean perch from the genus Helicolenus – are used in all applications and originate from areas along southern Australia and New Zealand. Thus, the biogeochemical and sclerochronological data derived from these fish describe changes occurring in the marine environments of the southwest Pacific and southeastern Indian Oceans. Radiocarbon records from the otoliths of H. barathri, combined with published records of other fish species in the southwest Pacific Ocean, show transport of the bomb radiocarbon signal from marine surface waters to depths approaching 1000 m. Transports lags ranging from 5 to 20 years are documented, and radiocarbon reservoir ages are calculated for water masses associated with the Tasman Sea. Radiocarbon measurements from H. percoides, in an upwelling area along the southern coast of Australian (southeastern Indian Ocean), are the very first radiocarbon time series documented for the region and reflect the lower radiocarbon values expected for seasonally upwelled water. Long term growth responses resulting from sclerochronologies from a Helicolenus species complex from southern Australia to New Zealand are compared across regions and species with broad- and local-scale climatic/oceanographic variables using univariate mixed effects models. These data demonstrate how broad scale climate patterns and weather can have additive or synergistic effects on the local environment, which are reflected in the growth of the fish. Biogeochemical tracers (Na, Sr, Mg, Ba, Li) and sclerochronologies (growth) are also extracted from otoliths of the same fish in this upwelling region. These data are used simultaneously in combination with univariate and multivariate mixed effects modelling to describe physiological and environmental controls on otolith chemistry. Temporal signals within these data are correlated with seasonal upwelling events. Ba:Ca and Li:Ca are more influenced by the environment, while Sr:Ca and Na:Ca are controlled by physiological processes. Ba:Ca negatively tracks upwelling events, suggesting an upwelled water mass not enriched in Ba. Li:Ca correlates positively with chlorophyll-a, indicating a possible proxy for marine productivity. Thus, the overarching aim of this research has been achieved: biogeochemical tracers and sclerochronologies derived from Helicolenus otoliths have provided new data describing environmental change in marine systems of southern Australia and New Zealand.
Thesis (Ph.D.) (Research by Publication) -- University of Adelaide, School of Biological Sciences, 2015.