Otolith Growth Research Articles

Otolith growth chronologies reveal distinct environmental sensitivities between and within shallow- and deep-water snappers

AbstractFish growth underpins individual fitness and population-level metrics, with fluctuations linked to environmental variability. Growth chronologies derived from otolith increment analysis are a powerful proxy to understand population responses to environmental change and productivity. Yet, long-term patterns of growth and their environmental drivers are better understood for shallow-water species compared to deep-water inhabitants. Additionally, focus is largely on adults, disregarding the potential influence of juvenile growth which is critical to size- and age-at-maturity. Here, we investigate the long-term growth patterns of two commercially important snapper species separated by depth in northwestern Australia’s coastal shelf waters, the shallow-water Lutjanus sebae (70 year chronology, 1950–2020) and the deep-water Etelis boweni (41 year chronology, 1973–2013). Annually-resolved otolith growth chronologies revealed distinct environmental sensitivities within (juveniles vs adults) and among (shallow- vs deep-water habitats) species. Within species, juveniles and adults responded differently to shared environmental stimuli, highlighting the importance of understanding the impacts of environmental effects and sensitivities for different life-history stages. Across species, L. sebae exhibited highly variable growth tied to local climate signals such as sea surface temperature and rainfall, while E. boweni displayed more stable growth patterns that only responded to interannual and decadal shifts in the environment (e.g. Pacific Decadal Oscillation). Our results highlight potential vulnerabilities of shallow-water species to future environmental perturbations compared to species residing at depth, as they are likely to encounter more extreme climate variability under future oceanic conditions. This study contributes valuable insights into understanding and managing the impacts of future environmental variability on fisheries sustainability, emphasising the need for continued research across species and habitats.

Determination of body length regression formulas for the golden grey mullet (Chelon auratus, Risso 1810) based on otoliths found in the feces of the Caspian Seal (Pusa caspica Gmelin, 1788)

The Caspian Seal, the sole mammal endemic to the Caspian Sea, is listed in the IUCN Red List as a species facing the threat of extinction, a status similarly recognized and/or assigned in all countries in the Caspian region.The study of seal nutrition using caprological methods is of great interest for understanding animal adaptation to deteriorating habitat conditions and assessing the adequacy of their food base in the sea. This method involves analyzing the contents of feces from ichthyophages to detect undigested fish otoliths.The results of studying the seal's diet during periods of haulout on breeding grounds showed that the frequency of occurrence of Chelon auratus otoliths ranged from 2-3% to 27.7% of all fish otoliths detected in feces.This study aims to assess changes in Chelon auratus otoliths as they pass through seals' gastrointestinal tracts and estimate formulas for recovering the linear dimensions of fish consumed by these seals.The research indicates that otolith growth slows with fish growth but does not cease entirely. Allometry is evident in the different ratios of otolith length and width to fish length in various size groups and the change in otolith shape as fish grow.To recover the body length of fish consumed by seals based on otoliths found in their feces, applying inverse calculation formulas obtained when studying the relationship between otolith growth and fish body growth using collection material obtained directly from fish is possible.Further research should focus on refining the recovery formula for the length of large fish by dividing the length into several segments, each described by separate formulas describing the relationship between fish body length and otolith length and width growth.

Twin Peaks: Interrogating Otolith Pairs to See Whether They Keep Their Stories Straight

To tackle the question of the reliability of otoliths as recorders of individual life events, we compared the information enclosed in otolith pairs: the sagittae pair and the sagitta/lapillus pair. We used the synchrotron XRF scanning imaging method, which enabled the comparison of this information at both global and hyperfine scales. Using otoliths of diadromous pipefish, we compared element incorporation in each pair with a focus on (i) environment and transition between water bodies with strontium (Sr) and heavy metals, (ii) temporal information and age estimation based on sulphur (S) incorporation, and (iii) otolith growth and biomineralization processes with zinc (Zn). Results show that the global information in terms of Sr and heavy metals given by both otoliths of a pair is the same and that any otolith may be used to retrieve such global data. In terms of S-based growth increment counts, the numbers are the same between two otoliths of the same kind, but the sagitta/lapillus pairs show a significant difference. Hyperfine-scale analysis of element distribution reveals that a given otolith is under the control of specific growth mechanisms, which can lead to heterogeneous elemental incorporation. The present results lead us to consider otolith growth dynamics and biomineralization processes in the context of a fluid mosaic perspective.

Exploring Growth Patterns of Maurolicus muelleri across Three Northeast Atlantic Regions

Maurolicus muelleri is an important component of mesopelagic ecosystems; nevertheless, we possess only limited knowledge about its biological features. We collected samples of M. muelleri from six scientific surveys between 2019 and 2021 in three geographical areas in the Northeast Atlantic waters (from South to North): the Bay of Biscay, the Celtic Sea, and the Norwegian Sea. Geographical variations in otolith growth, fish age, length, weight, and condition, as well as length–weight relationships and von Bertalanffy growth models (VBGMs), were investigated. Length-weight relationships revealed differences associated with the fish’s origin, paralleling the annual and daily otolith growth. VBGM parameters increased progressively northwards, in accordance with Bergmann’s rules. Fish length was positively related to the otolith radio, and Lee’s phenomenon was undetected. The impact of environmental variables, such as temperature and food availability, is debated, with these considered potential drivers of this variability. Populations may belong to separated units, either genetically or morphologically, representing differences in biological parameters as a signal of geographical divergence.

Decadal growth pattern of an indicator species Sebastes koreanus in the Yellow Sea and its response to environmental changes at differing scales

Climate change and human activities are significantly impacting coastal ecosystems and the species that inhabit them. Understanding how individual growth of key species varies and responds to environmental changes is essential for a better understanding of population dynamics and prediction of ecological responses to environmental changes. Here, a 20-year growth history of Sebastes koreanus was reconstructed based on otolith chronology analysis. Then the relationships between environmental factors (local and basin scales) and the growth variability were analyzed using a mixed effect model. The reconstructed growth chronology showed distinct inter-annual variability that alternatively increased and decreased, and a rapid increasing trend was observed during 2011–2014. The growth pattern significantly correlated with summer Chlorophyll-a concentration, indicating bottom-up control in the coastal ecosystem of the Yellow Sea. Significant relationships were also detected between otolith growth and winter bottom temperature and summer Southern Oscillation index, the two significant factors that also represent intensity of the Yellow Sea Cold Water Mass (YSCWM), which is the most important hydrographic feature influencing the Yellow Sea. The study result contributes to better understand fish growth plasticity under environmental changes. This result also reveals the relationship between fish dynamics and the YSCWM intensity in the Yellow Sea. The growth condition of S. koreanus could be used as a biological index for the YSCWM intensity and contribute to better understand the influence of the YSCWM on fish populations.

Alligator gar as a centenarian species: extending lifespan estimates using bomb radiocarbon and laser ablation–accelerator mass spectrometry

Context The potential lifespan of alligator gar (Atractosteus spatula) is currently unknown. A previous study applied bomb radiocarbon (14C) dating to establish ages >60 years, but maximum age was limited by the rise of bomb-produced 14C in the 1950s. Aims An exceptionally large specimen (2.6 m, 148 kg) was captured in Mississippi and otolith growth zones revealed an age estimate of 95 years. This specimen provided an opportunity to apply new technology to validate the lifespan of alligator gar. Methods Developments in accelerator mass spectrometry (AMS) led to technology that measures 14C continuously from carbonates (laser ablation-AMS), as opposed to single sample 14C analysis. Key results Use of laser ablation AMS on the 2.6-m alligator gar otolith, and two smaller fish aged >60 years, supported ages that were older than original estimates by 5–20 years. Conclusions Our study indicates that alligator gar age can be underestimated for the largest fish, maximum recorded length is 2.6 m based on a historical photograph, and lifespan is at least 75–95 years with support for an age of 100 years for the 2.6-m fish. Implications An increase in lifespan of this magnitude would affect our understanding of population dynamics and recovery efforts.

Daily age, growth rate, and pelagic larval duration of commercially important snapper species in Abrolhos National Marine Park.

The age and daily growth of fish are registered through the deposition of increments in their otoliths, which are concretions formed by the precipitation of substances present in the endolymphatic fluid, mainly calcium carbonate (CaCO3). Faced with the need to fill some of the gaps in the knowledge on the occurrence and duration of the initial stages of snapper species' life cycles in the Abrolhos Bank, this study aimed to describe the growth rates, age, and period of pelagic larval duration (PLD) of three snapper species during the larval pre-settlement phase, in the Abrolhos Bank region. The post-larvae were captured using light traps. Otoliths were removed from 117 samples of snapper species; however, only 69 were viable for age estimation, of which 15 were Lutjanus analis, 25 were Lutjanus jocu, and 29 were Lutjanus synagris. Together, the samples presented individuals with total lengths ranging from 16.14 to 24.76 mm and ages from 21 to 39 days. Settlement marks were found for all three species, and the average PLD was ~25 days. The somatic growth of the snapper species was positively correlated with otolith growth. L. jocu presented the greatest daily growth compared to the other species. The three species use the Abrolhos Bank as a larval settlement site, demonstrating plasticity by using different habitats throughout their lives.

Otolith morphology and total length relationships in Schizothorax grahami

Otolith is important for studying fish populations and life histories. In this study, the dominant species of Schizothorax grahami in the source section of the Chishui River was taken to understand the relationships between otolith morphology and total length (TL). Results showed a large difference between the four TL groups (A/B/C/D), except group B is similar to group C. The combined discrimination success rate of linear discriminant analysis was 62.2%. Group A and D’s success rate is the highest, at around 75%. Meanwhile, the success rate for Group B and Group C is below 65%. The one-way ANOVA of the Shape Index and the Canonical analysis of Principal Coordinates with two coefficients (Fourier coefficients and Wavelet coefficients) showed that Group B is similar to Group C, with a large difference from the other two groups. When TL was greater than 100 mm (the pearl organs appearing), the otolith growth was lower changing. Otolith morphology still changes with growth after sexual maturity in fish, so the larger fish is more useful for conducting otolith morphology studies for accurate evaluation and management of local fishery resources.

Freshwater fish otoliths record signals from both water and physiological processes: new insights from Sr/Ca and Ba/Ca ratios

Using strontium (Sr) and barium (Ba) in otoliths to determine natal origins and understand patterns of fish movements is based on the fundamental assumption that otoliths record water chemistry signals without any major alterations. Although prior studies highlighted that fish physiology can modify the water signal in otoliths, studies for freshwater fish are scarce. We exposed different groups of Atlantic salmon parr Salmo salar to different scenarios of ambient-level variations in Sr/Ca and Ba/Ca ratios and then combined otolith chemical profiles with environmental data (water chemistry and temperature), Fulton's index, and otolith growth rates to assess what factors explain/influence the elemental ratios of Sr and Ba in otoliths. Generalized additive mixed models (GAMMs) using water-based otolith composition, temperature, Fulton's index, and “individual” as explanatory variables allow to demonstrate that water chemistry alone cannot fully explain measured ratios in otoliths, except in scenarios involving significant changes in water chemistry. Other factors (physiological effects) should be accounted for reproducing short and minimal seasonal variations in water composition, considering that inter-individual variability contributes quite significantly in most scenarios.

Different growth patterns reveal the potential origins of two Pacific saury (Cololabis saira) groups in the northwest Pacific Ocean

Identification of stock composition is essential for fish stock assessment and management. Previous studies have suggested that a mixed stock composition of Pacific saury Cololabis saira exists in the northwest Pacific Ocean, but the origins of the stock’s components are poorly understood. We analyze the otolith microstructure of Pacific saury collected in high-seas fishing grounds from June–November, 2016–2019, and estimate hatch date and reconstruct otolith growth trajectory before hyaline zone formation. Results confirm that Pacific saury recruiting to the high-seas fishing ground are mainly from a winter-spawned cohort, secondarily from an autumn-spawned cohort, but also with a small proportion from a spring-spawned cohort. Ages of medium (knob length 240–280 mm) and large (knob length > 280 mm) individuals are mainly 8–12 and 18–21 months, respectively. Two growth patterns are reported for individuals with different otolith growth axes in their early life stages. Each year, unsupervised random forest clustering analysis of otolith daily increment widths reveals two Pacific saury groups. One group, with younger age and a later hatching period, shows a consistently higher growth rate than the other, suggesting that the two groups have different hatch dates and locations. These findings permit more accurate prediction of Pacific saury recruitment, and improve the understanding of short-term stock fluctuations to enable more sustainable management of fisheries.

Modeling somatic and otolith growth of the central subpopulation of northern anchovy (Engraulis mordax) by incorporating seasonality: Suppl. table 1

Modeling somatic and otolith growth of the central subpopulation of northern anchovy (Engraulis mordax) by incorporating seasonality: Suppl. table 1

Modeling somatic and otolith growth of the central subpopulation of northern anchovy (Engraulis mordax) by incorporating seasonality: Suppl. table 2

Modeling somatic and otolith growth of the central subpopulation of northern anchovy (Engraulis mordax) by incorporating seasonality: Suppl. table 2

Modeling somatic and otolith growth of the central subpopulation of northern anchovy (Engraulis mordax) by incorporating seasonality

Modeling somatic and otolith growth of the central subpopulation of northern anchovy (Engraulis mordax) by incorporating seasonality

Modeling somatic and otolith growth of the central subpopulation of northern anchovy (Engraulis mordax) by incorporating seasonality: Suppl. table 3

Modeling somatic and otolith growth of the central subpopulation of northern anchovy (Engraulis mordax) by incorporating seasonality: Suppl. table 3

Annual growth of brown trout in alpine lakes is highly influenced by spring snow depth and ice-out day

Growth of annular zones in otoliths of brown trout from the alpine lakes Litlosvatn and Kollsvatn on western part of the Hardangervidda mountain plateau have been studied during the period 2004–2021, concurrent with recordings of accumulated snow in spring and dates of ice-out. Unlike the conditions in lowland areas, years with much accumulated snow have not decreased during the last decades, and years with delayed ice break-up are still frequent, opposite the trend observed elsewhere in Europe and in North America. The annual growth of the brown trout otoliths is significantly reduced in years with much snow in April and late ice-out dates, irrespective of age of the fish, indicating that somatic growth of brown trout is considerably reduced in such years. Accumulated snow in spring and ice-out day may thus be useful parameters in predictions of fish production and potential yield in such alpine lakes.

Türkiye’den üç sardalya, Sardina pilchardus (Walbaum, 1792) stoğunun otolit kütle asimetrisinin incelenmesi

It was aimed to investigate sagittal otolith mass asymmetry Sardina pilchardus sampled from Aegean, Marmara and Mediterranean seas of Türkiye in present study. In this study, differences between right and left otoliths were statistically significant for Marmara and Mediterranean seas (P<0.05) not significant for Aegean Sea, (P˃0.05). The mean values of otolith mass asymmetry (X) were found between 0.0393 and 0.0144 according to Aegean Sea, Marmara Sea and Mediterranean Sea, respectively. In addition, absolute mass asymmetry │X│ were calculated as 0.03226±0.00514, 0.02057±0.00439 and, 0.05141±0.00755 for S. pilchardus samples according to Aegean Sea, Marmara Sea and Mediterranean Sea, respectively. The present study showed that the otolith mass asymmetry in S.pilchardus does not depend on fish length and otolith growth. Also, when there were no significant differences between localities for otolith mass asymmetry (P˃0.05), there were significant differences for absolute otolith mass (P˂0.05). The value of the otolith mass asymmetry can reveal information about pollutants such heavy metals, pesticides, stressors, and changes in the physico-chemical characteristics of water in relation to the environment of fishes. This is the first study about otolith mass in three stocks of S. pilchardus (Walbaum, 1792) from Türkiye.

Different mechanisms underpin the decline in growth of anchovies and sardines of the Bay of Biscay.

Declines in individuals' growth in exploited fish species are generally attributed to evolutionary consequences of size-selective fishing or to plastic responses due to constraints set by changing environmental conditions dampening individuals' growth. However, other processes such as growth compensation and non-directional selection can occur and their importance on the overall phenotypic response of exploited populations has largely been ignored. Using otolith growth data collected in European anchovy and sardine of the Bay of Biscay (18 cohorts from 2000 to 2018), we parameterized the breeder's equation to determine whether declines in size-at-age in these species were due to an adaptive response (i.e. related to directional or non-directional selection differentials within parental cohorts) or a plastic response (i.e. related to changes in environmental). We found that growth at age-0 in anchovy declined between parents and their offspring when biomass increased and the selective disappearance of large individuals was high in parents. Therefore, an adaptive response probably occurred in years with high fishing effort and the large increase in biomass after the collapse of this stock maintained this adaptive response subsequently. In sardine offspring, higher growth at age-0 was associated with increasing biomass between parents and offspring, suggesting a plastic response to a bottom-up process (i.e. a change in food quantity or quality). Parental cohorts in which selection favoured individuals with high growth compensation produced offspring high catch up growth rates, which may explain the smaller decline in growth in sardine relative to anchovy. Finally, on non-directional selection differentials were not significantly related to the changes in growth at age-0 and growth compensation at age-1 in both species. Although anchovy and sardine have similar ecologies, the mechanisms underlying the declines in their growth are clearly different. The consequences of the exploitation of natural populations could be long lasting if density-dependent processes follow adaptive changes.

Exploring European Eel Anguilla anguilla (L.) Habitat Differences Using Otolith Analysis in Central-Western Mediterranean Rivers and Coastal Lagoons from Sardinia

An otolith shape and morphometric analysis was performed on European eel (Anguilla anguilla) subpopulations from five rivers and three coastal lagoons of Sardinia (central-western Mediterranean) to assess the role of different habitats on otolith development. Sagittal otolith shape was described by 11 harmonics from elliptic Fourier descriptors. Comparisons among the harmonics were run through canonical discriminant analyses (CDAs). The CDA reclassification rate (75.7%) demonstrated a spatial environmental discrimination among local eel subpopulations of Sardinia. The Euclidean distance values demonstrated a dissimilarity between the river and lagoon groups. The form factor and roundness shape indices were significantly higher in the river group than in the lagoon group. The distances of the first three rings to the otolith core revealed site-specific otolith development. Moreover, the annual otolith growth rate was faster in the lagoon group than in the river group. The differences among the studied sites in terms of sagittal otolith shape could relate to changes in different local stocks potentially related to environmental peculiarities. Establishing a direct correlation between otolith morphology and environmental factors is challenging, and further studies are needed to investigate the relationship between habitat type/environmental variation and growth/body characteristics of eels. Nevertheless, the achieved results suggest that this method can be considered to be a valuable tool for studying the ontogeny of the European eel.

Opposing growth trends in juvenile and mature Humpback Whitefish within the upper Tanana River drainage, Alaska, revealed using otolith biochronology

AbstractObjectiveWithin areas of Alaska, Humpback Whitefish Coregonus pidschian are an important subsistence resource for many Alaska Native communities. Recently, Humpback Whitefish in the upper Tanana River drainage were reported to be smaller at a given age and reach smaller maximum sizes than fish sampled 20 years ago. The objective of this study was to identify the factors that influence annual growth of Humpback Whitefish within the upper Tanana River drainage based on an analysis of otolith increments.MethodsA series of mixed‐effects models were used to determine the relative importance of biotic (i.e., age, age at capture) and abiotic (i.e., year, sampling time period) factors on the growth of Humpback Whitefish. Juvenile (<5 years of age) and mature (≥5 years of age) growth periods were examined separately due to the unique habitats occupied by each life stage. Climate variables were correlated with the mature Humpback Whitefish biochronology to assess environmental drivers of adult growth.ResultBiochronologies spanning over three decades (1982–2018) revealed patterns of variation in Humpback Whitefish otolith growth across years. A negative temporal trend spanning the entire study period was evident for juvenile growth, while a mostly positive trend was observed for mature growth. Between time periods, otolith growth was significantly different from zero for juvenile (estimate: −0.087; 95% CI = −0.151 to −0.023) but not mature (estimate: −0.030; 95% CI: −0.092 to 0.032) growth periods. Several environmental factors were positively (i.e., mean monthly temperature, growth degree days) and negatively (e.g., snow depth) correlated with the mature Humpback Whitefish biochronology. However, the model with mean April snow depth was the best‐performing environmental model.ConclusionThese results suggest years with elevated snow depths negatively impact mature Humpback Whitefish growth. Cumulatively, these results illustrate the importance of juvenile growth periods and how early‐in‐life declines in growth may not be offset by above average growth as adults and help further our understanding of how environmental conditions influence growth.

Corrigendum: Compensatory feeding in Eastern Baltic cod (Gadus morhua): recent shifts in otolith growth and nitrogen content suggest unprecedented metabolic changes

Corrigendum: Compensatory feeding in Eastern Baltic cod (Gadus morhua): recent shifts in otolith growth and nitrogen content suggest unprecedented metabolic changes