Pairs Of Otoliths Research Articles

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.

Otolith Shape Indices of Japanese Threadfin Bream (Nemipterus japonicus, Bloch 1791) from the Makassar Strait, Indonesia

Japanese threadfin bream (Nemipterus japonicus) is a demersal fish that plays a very important role in maintaining ecosystem stability related to webs and food chains. This fish often becomes prey for predatory fish. In efforts to reveal the relationship between predators and prey in food webs and food chains, there is still limited information due to the difficulty of identifying digested food. In connection with this, this study aims to identify the morphology shape index value otolith of Japanese threadfin bream. Sampling was carried out at the Labuang Maros Fish Landing Site with 150 samples and morphometric data were collected from 150 pairs of otoliths in April and May 2023. The calculation of the shape index uses six descriptors, which include form factor (FF), roundness (RO), circularity or compactness (C), rectangularity (Rt), ellipticity (E), and aspect ratio (AR). The results showed that there was no significant difference in the otolith morphometry of the right and left otoliths (P>0.05). Based on the shape index value obtained, it explains that the morphometric shape of the otolith of Japanese threadfin bream tends to be oval, elongated, and has an irregular surface.

On the formation of the pike otoliths

The purpose of the work is to describe the morphological features and time frame of otolith formation in pike embryos for subsequent use of otolith marking for juveniles released to the nature habitats. Observations of the development of eggs were carried out in aquarium conditions. The recirculating aquaculture system was used for incubation of pike eggs. The development of embryos and larvae, as well as preparations of otoliths, were examined using light microscope equipped with digital camera. The sizes of developing embryos, larvae and otoliths were measured in photographs, the scale of the images was determined using reference scale. It was found that the beginnings of hearing organs in form of otic vesicle are formed in pike embryos at the stage of organogenesis on the 6th day of development at the temperature of 9–13 °С. The detectable sign of the processes is the beginning of pigmentation of the embryo’s eyes. The formation of otoliths such as sagittae and lapilluses due to the fusion of primordial spherules and enlargement of globules continues throughout the entire period of embryonic development. By the moment of pre-larvae hatching (on the 10th day after fertilization), they have two pairs of otoliths (sagittae and lapilluses), the average size of which is 66,3±5,1 microns and 53,3±5,3, respectively. The appearance of diurnal rings on otoliths is observed before hatching, at the stage of the mobile embryo or on the first day after hatching. The data on the age of formation of otoliths and appearance of diurnal rings will be used to develop techniques of marking of pike juveniles in the hatcheries.

Decreasing otolith length-to-width ratio with fish length – Atlantic Cod (Gadus Morhua), Southern Baltic Sea

The observation concerns otoliths of Atlantic cod from the Słupsk Bank. A total of 100 pairs of otoliths were selected from 100 specimens, the total length of which ranged from 5.2 cm to 62 cm. It was found that the greater the length of the fish, the smaller the ratio of otolith length to width. Whether this is a regular trend that was observed for the first time, or a matter of analyzing otoliths from different populations, remains an unresolved question. No differences were found between males and females in the relationship between fish size and otolith size, or changes in the ratio of otolith length to width.

Re-evaluating age estimation using daily increments on otoliths of the skipjack tuna Katsuwonus pelamis

This study compared the microstructures of transverse sections and surface of the otoliths of skipjack tuna. Pairs of otoliths were extracted from the same individuals (fork length [FL]: 6.5–77.5 cm) to examine the difference in the counts of the daily increments between the sections. The increments counted on the transverse section were less than those on the surface section, and the difference between the two sections increased with body size. Even high-resolution scanning electron microscopy did not enhance the difference between the two sections. Increments in the transverse section would not occur daily, which makes otoliths from this section unsuitable for age estimation. Subsequently, we re-evaluated the age estimated using the surface reading with new criteria and compared them with the results of a reference study. Despite successful age estimates using surface otoliths exposed by an etching method, practical difficulties in the method and vague criteria for reading increments have been raised against their reliability for age estimation. By reproducing detailed procedures of the etching method and using reading criteria, we estimated the ages of individuals at various life stages. In applying the criteria, the coefficient of variation (CV) for increment counts among readers decreased. In particular, the criteria reduced the CV for the transition area where the width between increments gradually narrows after the 50th–90th increment. The age estimates (FL < 40 cm) using the criteria are reasonably fit to the growth curve reported in the reference study with validation of daily increment deposition for surface reading. Thus, the new criteria are suitable for estimating age estimation in skipjack tuna up to an FL of 40 cm.

Intraspecific variability of the saccular and utricular otoliths of the hatchetfish Argyropelecus hemigymnus (Cocco, 1829) from the Strait of Messina (Central Mediterranean Sea).

Mesopelagic species are enjoining increasing attention due to the growing impact of fisheries activities on deep marine biocenosis. Improving the knowledge base on mesopelagic species is required to enhance their conservation due to the knowledge gaps regarding many species and families. In this context, otoliths can be fundamental to assessing their life history, ecomorphological adaptation to the deep environment and stock composition. The present paper aims to explore the saccular and utricular otoliths morphology and intra-specific variability of the hatchetfish, Argyropelecus hemigymnus, from the Strait of Messina. Lapilli and sagittae were collected from 70 specimens and separated into four size classes. Morphometric, shape and SEM investigations were performed to describe their morphology, contours, and external structural organization, also studying their intraspecific variability related to sample sizes and differences between otolith pairs. Results showed an otolith morphology different from those reported in the literature with fluctuating asymmetry in sagittae and lapilli belonging to Class IV, and a high otolith variability between all the size classes. Data herein described confirm the otoliths singularity of the population from the Strait of Messina, shaped by a unique marine environment for oceanographic and ecological features.

Morphology of sagitta, lapillus and asteriscus of Patagonian Genidens barbus

Otoliths are calcium carbonate structures, deposited as aragonite, located in the inner ear of bony fish. In recent years, they have become a useful tool for the determination of fish species, trophic content, age studies, and the identification of fish stocks. The objective of this work was to describe the morphology of the three pairs of otoliths of the marine catfish Genidens barbus of Patagonian distribution. Otoliths of specimens obtained at four sampling points in the Negro River were analyzed. It was observed that otoliths presented the general morphological pattern proposed for Siluriforms, where lapilli are the largest and most robust of the three. Lapillus presented a rounded shape, a pronounced elevation in the central position, a delimited sulcus, but not very evident, without evidence of a minor sulcus. The sagitta is claviform, with an elongated conical posterior region, dorsal wings that continue as lateral expansions called basal wings, and the presence of a fissure. The asteriscus has an ear shape, a median opening, a short pointed rostrum, a poorly developed anti-rostrum and a slightly curved acoustic fossa. In this work, sagitta and asteriscus otoliths were described for the first time for G. barbus, thus completing the description of the three pairs.

Growth and Microstructural Features in Otoliths of Larval and Juvenile Sinogastromyzon wui (F. Balitoridae, River Loaches) of the Upper Pearl River, China

Otolith growth and microstructural features of fish are essential to the understanding of the early fish lifecycle. This paper assesses the features of otoliths from laboratory-reared larval and juvenile Sinogastromyzon wui (S. wui, 0 to 25 days post-hatching) that were obtained as eggs from the Shilong Reach of Xijiang River between April and August 2021. We observed the development of the three pairs of otoliths (lapilli, sagittae, and asterisci) and compared the shape changes and growth of the lapilli and sagittae, as well as the timing and deposition rate of increments of the lapilli. The lapilli and the sagittae were visible on hatching, whereas the asterisci were present at four days post-hatching (dph). The shape of the sagitta changed more obviously than that of the lapillus, and a strong correlation was observed between sagitta shape changes and fish ontogenesis. The otolith shape greatly modulated during the post-flexion larval stage (Post-FLS), it corresponded with the formation period of individual fins. Analysis of the microstructural features indicated that lapilli were the optimal otolith for age determination and increment deposition rate confirmation. Using regression analysis of the known age and the number of lapillus daily increments, we demonstrated that the lapillus developmental increments were deposited daily, and the first increment formed at two days post-hatching. Our conclusions support employing the lapillus increment deposition rate and the time of the first daily increments in the determination of the age of wild larval and juvenile S. wui.

Quantifying fish otolith mineralogy for trace-element chemistry studies

Otoliths are frequently used to infer environmental conditions or fish life history events based on trace-element concentrations. However, otoliths can be comprised of any one or combination of the three most common polymorphs of calcium carbonate—aragonite, calcite, and vaterite—which can affect the ecological interpretation of otolith trace-element results. Previous studies have reported heterogeneous calcium carbonate compositions between left and right otoliths but did not provide quantitative assessments of polymorph abundances. In this study, neutron diffraction and Raman spectroscopy were used to identify and quantify mineralogical compositions of Chinook salmon Oncorhynchus tshawytscha otolith pairs. We found mineralogical compositions frequently differed between otoliths in a pair and accurate calcium carbonate polymorph identification was rarely possible by visual inspection alone. The prevalence of multiple polymorphs in otoliths is not well-understood, and future research should focus on identifying otolith compositions and investigate how variations in mineralogy affect trace-element incorporation and potentially bias environmental interpretations.

Evaluation of cooking effects on otolith stable carbon and oxygen isotope values of teleostean fish Pomadasys kaakan (Cuvier, 1830).

For years, archaeologists, climatologists, and ecologists have used stable oxygen isotope values (δ13 C, δ18 O) in fish otoliths from archaeological sites to reconstruct the habitats, paleo-temperature, and seasonality of the fish captures. Otoliths from archaeological sites might have been heated when ancient people cooked the fish for food. Therefore, there are debates as to whether the cooking behaviors would cause further isotopic fractionations of the carbonate in the otoliths. In this study, we have evaluated the effects of the cooking methods on the otolith δ13 C and δ18 O values by comparing the otoliths of the javelin grunter (Pomadasys kaakan) from the same individuals, with the left otoliths taken out before the different cooking processes. Otolith sections of the fish were then made and several subsamples were milled along the microstructures visible in the otolith pairs, mostly annual check rings, followed by the stable isotope analyses. There were no morphological changes between the cooked and uncooked otoliths. The δ13 C and δ18 O values were highly consistent for the otolith subsamples between the cooked and uncooked pairs, suggesting none or trivial effects of the cooking processes on the isotopic values of the otoliths. In addition, some javelin grunters showed lower δ13 C (-5‰ to -6‰) and δ18 O (-4‰ to -5‰) values deposited in the wide translucent zone of the otoliths, suggesting seasonal migration of the fish to estuaries during the summer. This study suggests that cooking processes do not change otolith stable isotopic compositions and will therefore allow for future research to use the otolith δ13 C and δ18 O values to better understand the life history and used habitats of the preserved fish remains in the middens.

Intra- and interspecific variability among congeneric Pagellus otoliths

Otolith features are useful tools for studying taxonomy, ecology, paleontology, and fish biology since they represent a permanent record of life history. Nevertheless, the functional morphology of otoliths remains an open research question that is useful to completely understand their eco-morphology. This study aims to deepen the knowledge of intra- and interspecific variation in sagitta morphology in three congeneric seabreams, to understand how such variability could be related to the lifestyles of each species. Therefore, the sagittae (n = 161) of 24 Pagellus bogaraveo, 24 Pagellus acarne, and 37 Pagellus erythrinus specimens, collected from the south Tyrrhenian Sea, were analyzed using scanning electron microscopy and a stereomicroscope to assess morphometric features, variability between otolith pairs and the external crystalline structure the of sulcus acusticus. Statistical analysis demonstrated that, between the species, variability in sagittal otolith rostral length growth and sulcus acusticus features, correlated with increased fish total length and body weight. Moreover, slight differences between otolith pairs were detected in P. acarne and P. erythrinus (P < 0.05). The results confirm changes in otolith morphometry and morphology between different congeneric species and populations of the same species from different habitats.

Investigating otolith mass asymmetry in six benthic and pelagic fish species (Actinopterygii) from the Gulf of Tunis

Otolith mass asymmetry can significantly affect the vestibular system functionalities; usually, the X values of mass asymmetry vary between −0.2 and + 0.2 (−0.2 &amp;lt; X &amp;lt; + 0.2). These values can change during a fish life and therefore they are not related to the fish total length. We collected a total of 404 fish specimens from the Gulf of Tunis, including three pelagic species: Sardina pilchardus (Walbaum, 1792) (74 otolith pairs), Trachurus mediterraneus (Steindachner, 1868) (66 otolith pairs), and Chelon auratus (Risso, 1810) (60 otolith pairs) and three benthic species: Gobius niger Linnaeus, 1758 (77 otolith pairs), Mullus barbatus Linnaeus, 1758 (60 otolith pairs), and Trachinus draco Linnaeus, 1758 (67 otolith pairs). The relation between the total length and the otolith mass asymmetry was first calculated and compared, and then was evaluated. The comparison of the otolith mass asymmetry between benthic and pelagic species showed a significant difference (P &amp;lt; 0.05), where the absolute mean value of X does not exceed the critical value (0.2) for all the studied species. No relation has been found between the magnitude of the otolith mass asymmetry and the length in both benthic and pelagic specimens. Environmental factors have an indirect effect on somatic growth and otolith accretion. The significant difference found in this study can be due to the difference between the benthic and pelagic environments.

Sagitta otolith of three demersal species in a tropical environment

The objective of this study was to describe the morphology and morphometry of saggitta otoliths of Polydactylus virginicus, Menticirrhus cuiaranensis and Conodon nobilis in a tropical environment. Fishes were caught with rod and reel in competitive fishing events promoted in 2014-2015 along the coast of Sergipe. A total of 174 pairs of sagitta otoliths of P. virginicus, 181 of M. cuiaranensis and 77 of C. nobilis was extracted. In general, the sagitta otoliths of all three species analyzed here presented different morphology and shape indices. The permutational multivariate analysis of variance (PERMANOVA) demonstrated significant differences among species and ontogenetic phases within each species using morphometry and shape indices. The linear discriminant analysis (LDA) presented a 98.3% correct reclassification of the otoliths by species.

Morphology and composition of Goldeye (Hiodontidae; Hiodon alosoides) otoliths

We provide up-to-date morphological and compositional data on otoliths of the osteoglossomorph Goldeye (Hiodon alosoides). Using computed tomography (CT) X-ray, we documented the location of each of the three pairs of otoliths (lapilli, sagittae, and asterisci) in relation to the swim bladder, which extended forward in close proximity to the sagittae and asterisci. The lappili were the largest otoliths in terms of surface area and volume, but the sagittae were highly modified, appearing spiral in shape when viewed dorsally, with a surface area to volume ratio more than double that of the lapilli. Using scanning electron microscopy, the surface of each otolith was viewable in great detail, and small otoconia (~10.5 μm diameter) were observed on each, but were most numerous on the sagittae. On scanning electron micrographs, the sagittae appeared to be bi-lobed, with asymmetrical lobes each oriented in the same general direction. Using neutron and X-ray diffraction methods, we found three polymorphs of calcium carbonate crystals (aragonite, vaterite, and calcite), sometimes all within the same otolith. However, in general, lapilli and sagittae were composed predominately of aragonite whereas asterisci were composed chiefly of vaterite. With these results, we provide information on a unique species, whose inclusion in future studies would benefit our understanding of fish hearing, fish evolution, and fisheries ecology.

Do contemporary age-growth models overlook life-history complexities in protandrous fishes? A case study on the large protandrous polynemid, the giant African threadfin Polydactylus quadrifilis

Sagittal otolith pairs were extracted from two-hundred-and-twenty-six giant African threadfin Polydactylus quadrifilis collected from the Kwanza Estuary in Angola between 2016 and 2018 ranging in size from 160 to 1360 mm fork-length (FL) and from one to 23 years of age (26 juvenile, 170 male, nine intersex and 27 female). An additional 85 otolith pairs (24 male, six female and 55 unsexed) were extracted in the same region between 2007 and 2014 (475−1525 mm FL, 2–23 years) and were utilised solely for modelling growth. Otolith aging revealed rapid growth and early maturation (L50 = 399.2 mm FL, A50 = 1.50 years). Sex change occurred over a wide size (790−1125 mm FL) and age (3–8 years) range and was initiated at 1082.3 mm FL and 6.2 years and completed at 1127.4 mm FL and 7.06 years. Strong evidence was provided for partial protandry in P. quadrifilis via the presence of several extremely old male fish, including one individual of 22 years and noticeable differences in length-at-age were observed between older male and female fish. To investigate potential life-history variability, three approaches were taken to group individuals and assess for improvements in model fit using the von Bertalanffy Growth Function (VBGF). Subgroups were determined by sex in Approach 1 and by predicted life-history pathway (‘changers’ & ‘non-changers’) in Approaches 2 (individuals on sex change pathways have increased growth following sex change) & 3 (individuals on sex change pathways have increased growth throughout ontogeny). In all approaches, differences were observed in the L∞ and k values between fish presumed to change sex and those presumed not to change sex. When compared to the conventional model produced for the entire population, all approaches produced considerably better model fit (Approach 1 = ΔAkaike Information Criterion (ΔAIC) = 64.7, Approach 2 – ΔAIC = 56.1 and Approach 3 – ΔAIC = 136.3) and Approach 3 produced better fit than Approach 1. This suggests that utilising conventional modelling techniques may be inappropriate for the stock assessment and management of sequential hermaphrodites and indicates that a revision of age-growth modelling techniques is required for species with multiple developmental pathways in order to maintain intrapopulation diversity and preserve resilience.

When the presence of a vateritic otolith has morphological effect on its aragonitic partner: trans-lateral compensation induces bias in microecological patterns in one-side-only vateritic otolith

In many teleost species, aragonite is the normal form of calcium carbonate in sagittal otoliths. In the case of one-side-only (OSO) vateritic otoliths (abnormal crystalline structure), morphological investigations are systematically conducted on the other side. The implicit assumption is that the morphological information on the aragonitic side remains unaffected by the presence of vaterite on the other side. However, the extent to which this assumption is met has never been explored. Applying geometric morphometrics on experimentally maintained brown trout (Salmo trutta) revealed incongruent variational patterns and mean shape differences between OSO and two-sided aragonitic otoliths, possibly due to trans-lateral compensation to preserve their auditory function. More specifically, fully aragonitic pairs of otoliths are more prone to exhibit microecological variations compared with OSO vateritic pairs. Simulation emphasizes the relative robustness of both micro- and macroecological effects until a high proportion of OSO vateritic otoliths is used. Given that otolith shape analysis provides a useful basis for stock separation, care should be taken when interpreting otolith shape in the presence of vateritic otoliths.

Otolith shape as a stock discrimination tool for ling (Genypterus blacodes) in the fjords of Chilean Patagonia

ABSTRACT Genypterus blacodes, in terms of its fishing history and local economic importance, is an emblematic species harvested in Chilean Patagonia (41°00’–57°00’S). Most of the current fisheries and biological knowledge of this species come from the open ocean, whereas information about the species in fjords and inner channels is fragmentary. In 2018, two research surveys targeting G. blacodes were conducted in the fjords and inner channels of Chilean Patagonia. A total of 253 pairs of sagittal otoliths were sampled at three different localities, and their contours were modelled using wavelet analysis as a tool for stock discrimination. Contours were compared using canonical analysis, and classification was performed using linear discriminant and Random Forest analyses. The results indicated that the wavelet method is efficient in modelling otolith contours, and the discriminant analyses showed differences among fishing grounds across the latitudinal gradient, thus confirming the hypothesis that G. blacodes conform to at least two separate stock units in Chilean Patagonia. Fishing grounds that were closer in space showed higher levels of misclassification. The discussion focuses on how environmental variables and the geography of fjords shape stock differences and how this information can be used for the sustainable management of G. blacodes.

Validation of the periodicity of growth zone deposition in otoliths of two large endemic Labeobarbus species in Lake Tana, Ethiopia

Although validation of the rate of growth zone deposition is a prerequisite for accurate age estimation, such studies are non-existent for the endemic Labeobarbus species in Lake Tana. Therefore, the aim of the current study was to validate the periodicity of growth zone deposition in asteriscus otolith of L. tsanensis and L. platydorsus. A total of 723 and 496 asteriscus otolith pairs from L. tsanensis and L. platydorsus, respectively, were examined. Binary- circular models, based on edge analysis (EA) and linear-circular models, based on marginal increment analysis (MIA) were employed to validate the rate of growth zone deposition. The results of EA indicate that there is an annual growth zone deposition for L. tsanensis and L. platydorsus. For both species, the highest proportion of translucent zones was detected between October and January, with a peak in January. The results of the MIA corroborated this for both species. In addition, the lowest marginal increment ratio (MIR) was recorded in January for both species. The annual growth zone deposition in asteristicus otoliths of these species is likely caused by the relatively low water temperature coinciding with the peak breeding activity of the species.

Age and growth of Brauer's lanternfish Gymnoscopelus braueri and rhombic lanternfish Krefftichthys anderssoni (Family Myctophidae) in the Scotia Sea, Southern Ocean.

This study examines age and growth of Brauer's lanternfish Gymnoscopelus braueri and rhombic lanternfish Krefftichthys anderssoni from the Scotia Sea in the Southern Ocean, through the analysis of annual growth increments deposited on sagittal otoliths. Otolith pairs from 177 G. braueri and 118 K. anderssoni were collected in different seasons from the region between 2004 and 2009. Otolith-edge analysis suggested a seasonal change in opaque and hyaline depositions, indicative of an annual growth pattern, although variation within the populations of both species was apparent. Age estimates varied from 1 to 6 years for G. braueri (40 to 139 mm standard length; LS ) and from 0 to 2 years for K. anderssoni (26 to 70 mm LS ). Length-at-age data were broadly consistent with population cohort parameters identified in concurrent length-frequency data from the region for both species. The estimated values of von Bertalanffy growth curves for G. braueri were L∞ = 133.22 mm, k = 0.29 year-1 and t0 = -0.21 year and the values for K. anderssoni were L∞ = 68.60 mm, k = 0.71 year-1 and t0 = -0.49 year. There were no significant (P > 0.05) differences in growth between sexes for either species, suggesting that males and females have similar growth and development trajectories in the Scotia Sea. A positive allometric relationship between LS and wet mass was found for each species, as well as a significant (P < 0.0001) linear relationship between otolith size and LS . Growth performance (Ф') was similar between the two species and congruent with other myctophid species across the Southern Ocean. This study provides important parameters for future Southern Ocean ecosystem studies in a resource management context.

Fluctuating asymmetry of adult Chinook Salmon (Oncorhynchus tshawytscha) otoliths from wild and hatchery origins

Fluctuating asymmetry is the non-directional deviations from bilateral symmetry and occurs across organisms. Fish otoliths are often used to test for differences in symmetry as otoliths aid in hearing, homing, and balance. Here, we evaluated the symmetry of otolith pairs in adult Chinook Salmon between wild and hatchery-origin stocks. Pacific salmon are economically and ecologically important to the Pacific Northwest, USA. Chinook Salmon are widely distributed throughout the North Pacific Ocean, yet several wild populations are federally listed as endangered or threatened due to depleted stocks, loss of genetic diversity, and hatchery contribution to wild stocks. As such, fishery managers are concerned with the health and condition of hatchery-origin fish and their impacts on wild populations. We included both hatchery and wild-origin Chinook Salmon from the Coast Mountain and Willamette regions in Oregon as well as hatchery populations from southeast Alaska. We evaluated several metrics to test shape variation and symmetry between the left and right sagittal otoliths. We found consistently more asymmetry in otoliths from hatchery origin than wild Chinook Salmon within seven out of eight total metrics. These results could have conservation and management implications as hatchery-origin Chinook Salmon can reduce pressure from wild stocks while continuing to support commercial and recreational industries.