Search Results (18)

Analytical imaging via synchrotron analysis was used to study sagittal otoliths of four freshwater pipefish species exhibiting amphidromous or freshwater resident lifestyles. We undertook a hyperfine elemental scanning of a 25 μm diameter length area centred on the core, namely the pre-hatch zone, corresponding to the sagitta formed during embryogenesis. We analysed calcium (Ca), strontium (Sr), manganese (Mn), chromium (Cr), cobalt (Co), nickel (Ni) and sulphur (S), with the latter serving to count growth increments. Whatever the species, a Ca pit consistently marked the core; the amphidromous species exhibited Mn enrichment at the core and the sagitta formed a week before hatching. These results illustrate common otolith formation mechanistic processes. Sr and heavy metals’ signals in the pre-hatch zone were compared to their signal in the edge of the otolith, an area encompassing the adult freshwater (adFW) environmental signature. We found that Co and Ni otolith signals had no relation to environmental conditions, but it is worth looking into Cr as a marker of early-life environment. While we caution against the use of a Sr:Ca ratio for life history interpretations at the core because of the Ca pit, the Sr signal analysis uncovered possible variations in the parental behaviour that potentially trigger newly-hatched juvenile migration to sea or residency. Finally, our results demonstrate that the microchemistry of otolith formation during early development is a melting of maternal signal during egg yolk elaboration, of the environmental signal during egg incubation, and of individual physiology during early growth. Full article

Coilia nasus are an important fish resource in the Yangtze River, and the Yangtze River Estuary is a crucial migration pathway for them. In this study, we used otolith microchemistry to analyze the strontium/calcium (Sr/Ca) ratios and Sr contents in the sagitta otolith of C. nasus from the south branch (SB) and north branch (NB) of the Yangtze River Estuary and obtained the diversity of migration patterns and spawning ground distribution for C. nasus. The results indicate that C. nasus from both branches include two types of habitat history: freshwater (F)–brackish water (B) (Type I) and F-B seawater (S) (Type II), with Type I being dominant at 62.50% in both branches. The C. nasus from the SB comprise six migration patterns, while that from the NB has seven migration patterns. The C. nasus from both branches hatch in F habitats. At the time of capture, the C. nasus from the SB predominantly remain in F, accounting for 62.5%, while C. nasus from the NB primarily stay in B, accounting for 87.5%. Throughout the migration process, C. nasus from both branches switch between different habitats, with C. nasus from the NB exhibiting more frequent transitions between F and B, showing a greater reliance on the estuarine brackish habitat. The radius of the first blue region near the core (L_f) and freshwater coefficient (Fc) of the otolith for C. nasus from both branches are divided into three groups: long-distance freshwater dependence (LD), medium-distance freshwater dependence (MD), and short-distance freshwater dependence (SD), with the LD only appearing in the SB, while the NB is primarily represented by MD. There is a correlation between the differences in L_f among different groups of C. nasus and the differences in the distance from the spawning grounds of C. nasus in different sections of the Yangtze River to the estuary (D_YRE), reflecting the distribution pattern of C. nasus spawning grounds in different sections of the Yangtze River. This study provides theoretical guidance for the protection of migration pathways and maintenance of spawning grounds for C. nasus, which have significant practical value in the precise management of C. nasus resources in the Yangtze River Estuary. Full article

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. Full article

Resource partitioning may allow species coexistence. Sand dunes in the typical steppe of Alxa Desert Inner Mongolia, China, consisting of desert, shrub, and grass habitats, provide an appropriate system for studies of spatial niche partitioning among small mammals. In this study, the spatial niche characteristics of four rodents, Orientallactaga sibirica, Meriones meridianus, Dipus sagitta, and Phodopus roborovskii, and their responses to environmental changes in the Alxa Desert were studied from 2017 to 2021. Using the capture-mark-recapture method, we tested if desert rodents with different biological characteristics and life history strategies under heterogeneous environmental conditions allocate resources in spatial niches to achieve sympatric coexistence. We investigated the influence of environmental factors on the spatial niche breadth of rodents using random forest and redundancy analyses. We observed that the spatial niche overlap between O. sibirica and other rodents is extremely low (overlap index ≤ 0.14). P. roborovskii had the smallest spatial niche breadth. Spatial niche overlap was observed in two distinct species pairs, M. meridianus and D. sagitta, and P. roborovskii and D. sagitta. The Pielou evenness index of rodent communities is closely related to the spatial distribution of rodents, and the concealment of habitats is a key factor affecting the spatial occupation of rodents. Full article

Between September and October 2021, a total of seven adult specimens (five females and two males) of Umbrina ronchus Valenciennes, 1843 were caught in the waters off Portopalo di Capo Passero and Porto Empedocle (the south-eastern coast of Sicily). This was the first record of this species in the Strait of Sicily and the deepest record of this species within the Mediterranean Sea. Individuals of U. ronchus ranged from 180–240 mm total length and 69–149 g total weight. Gonad stages ranged from maturing to spent/resting. Otoliths sagittae were oval shaped with high rectangular yet complex contour. Counting the growth zones by transverse section, the estimated age ranged from 3 to 5 years. Since sciaenids are considered a high-longevity species, a quite recent settlement of U. ronchus in the Strait of Sicily is suggested. As the biogeographic nature of the Strait of Sicily is the main boundary between the western basin, which is characterized by a high affinity for (sub)tropical Atlantic species such as U. ronchus, and the eastern basin, which has an affinity for the indo-pacific warm waters species, the present records could be the limit to the eastward expansion of the geographic distribution of U. ronchus in the Mediterranean Sea. Full article

Tub gurnard, Chelidonichthys lucerna (Linnaeus, 1758), is a Mediterranean-Atlantic benthic species usually captured as by-catch by Portuguese traditional fisheries and considered the most important commercial fish species of the family Triglidae. However, to date, little is known about its habitat residency and whether the species can be considered a marine estuarine-dependent fish. Otolith microchemistry has proven effective in providing information about fish movement patterns throughout different water salinities. In this study, core-to-edge transects of Sr:Ca in the fish saccular otoliths of 35 juveniles of C. lucerna captured in March 2007 by a scientific survey along the Portuguese coast were used to assess the species movement between brackish and marine waters. Data suggest that most individuals (97%) have an estuarine-dependent profile, with 63% showing a clear presence in marine waters during the early life history periods. Evidence of an estuarine residence throughout the fish life cycle was found in only 3% of individuals. Ba:Ca profiles did not reflect an inverse relationship with Sr:Ca salinity results but corroborated findings from other authors about the influence of upwelling processes and freshwater runoffs on Ba incorporation into the otoliths of coastal fish. Furthermore, the data also showed that C. lucerna can occupy and migrate among habitats with diverse salinity degrees, showing high environmental plasticity and adaptation. Full article

The shape of sagitta otoliths was used to compare individuals of little tunny (Euthynnus alleteratus) harvested on board commercial fishing vessels from the coastal areas along the Eastern Atlantic, including the Mediterranean Sea. Fish sampling and selection was designed to cover possible seasonal changes and tuna size. The research encompassed both morphometric and shape analyses of left sagittal otoliths extracted of 504 fish specimens. Four shape indices (Circularity, Roundness, Rectangularity, and Form-Factor) were significantly different between two groups, showing a statistical differentiation between two clear spatial units. The degree of divergence was even more pronounced along the rostrum, postrostrum, and excisura of the generated otolith outlines between these two groups. One group corresponds to the samples from the coastal areas in the Northeast Temperate Atlantic and Mediterranean Sea (NETAM Area) and a second group from the coastal areas off the Eastern Tropical Atlantic coast of Africa (ETA Area). This study is the first to use otolith shape to differentiate tunas from separate spatial units. These results could be used to re-classify previously collected samples and to correct time series of data collected. Full article

The sagitta otoliths of teleostean fishes are usually used in diverse studies. Their shapes are species-specific, and the qualitative description of their morphological features seems to be a simple task, despite its subjectivity. On the other hand, morphometric techniques have been developed with a focus on objectivity, reproducibility, and accuracy. Considering this, the otoliths morphology was reviewed and evaluated in terms of robustness as a taxonomic tool and to highlight ecomorphological patterns. The otoliths morphology of 179 teleostean fishes from the Southern Atlantic were analyzed. For each species, the fish total length range, eighteen otolith morphological features (OMFs), and relative proportions were annotated. Species habitat and habit were also recorded. Data analyses were based on exploratory analysis, correlation, nonmetric multidimensional scaling, and a two-way permutational analysis of variance. The most descriptive OMFs were: colliculum, sulcus acusticus (morphology, position, orientation, and opening), and otolith profile. The otolith morphology was significantly related to species habitat and habit, with a new pattern described for deep-ocean pelagic species. In conclusion, otoliths morphology is robust whenever it is based on the comparative method application (otoliths among otoliths), considering the constant updates of fishes’ taxonomy and the use of proper sample sizes linked to morphometric techniques. Full article

Daily growth patterns and their relationship with reproduction was analyzed in the European hake from the Galician Shelf, where it shows a very protracted spawning with three spawning peaks. The daily growth analysis was performed in otoliths of adult females on the transversal section of the sagittae otolith. Daily increments were measured from the border to the nucleus in females until they were discernible. Results show that daily growth of females decreases during the spawning period because they allocate less energy to somatic growth in favor of the production of gametes, with an increase in growth in July. Lastly, daily growth individual trends showed a “spawning pattern” in 28% of medium and large females, suggesting an individual spawning period of one to two months, with 4–5 valleys of narrow daily increments, likely associated to batch release: individual spawning frequency would be 4–5 days. This is the first time that individual spawning frequency in hake is estimated based on individual data. Finally, the spawning pattern is detected only once per year, indicating that a single female participates only in one spawning peak per year, supporting the hypothesis of the existence of two or more spawning components in the stock. Full article

Xenoestrogenic effects have been reported in thicklip grey mullet, Chelon labrosus, used as pollution sentinel organisms in estuaries in the Southeast Bay of Biscay with intersex gonads described in populations from some contaminated estuaries. Despite evidence of reproductive stress in this catadromous fish species, knowledge of mullet reproductive movements and connectivity between estuaries is lacking. This study investigates the population structure of C. labrosus using otolith shape and elemental signatures of 60 adult individuals collected from two estuaries found in the Southeast Bay of Biscay (Gernika and Plentzia). All samples were collected in June–July 2020. Otolith shape analysis was determined using elliptical Fourier descriptors, while elemental signatures (Sr:Ca, Li:Ca, Mg:Ca, Mn:Ca, Co:Ca, Ni:Ca, Cu:Ca and Ba:Ca) of whole sagittae were determined by inductively coupled plasma mass spectrophotometry. Both natural tags were analyzed with univariate and multivariate statistics to determine whether these signatures are geographically distinct and can be used to assess the degree of separation between individuals. The data showed significant differences in the otolith shape and elemental analyses, with canonical analysis of principal coordinates plots identifying two different groups, each one belonging to each estuary of origin. Differences in whole otolith elemental signatures between locations were driven by Sr:Ca, Li:Ca, and Ba:Ca. Sr:Ca and Li:Ca ratios were higher in Plentzia than in Gernika, while Ba:Ca was higher in Gernika. The high re-classification success rate using both tools obtained from stepwise linear discriminant function analysis supports these findings and suggests that Gernika and Plentzia individuals passed enough time in separated water compartments and should be regarded as two different population units. This could suggest that the intersex condition in mullets from Gernika is due to life-long exposure to xenoestrogens after homing during early larval development in that estuary, without migrations to other estuaries. Acknowledgements: Project funded by Basque Gov. (IT1302-19), Spanish MCIN and EU-FEDER/ERDF (PGC2018-101442-B-100) and EU H2020 (Assemble+ 730984). Full article

The Brazilian mojarra, Eugerres brasilianus, is an economically important species for the artisanal fisheries that exist in the estuarine environments along the Southwest Atlantic Ocean. Despite this, knowledge about its population structure is scarce, and no management strategies have been applied to ensure the sustainability of E. brasilianus fisheries in Brazil. Thus, the present study intended to understand the population structure of E. brasilianus in a complex system of lagoons in the Southwest Atlantic Ocean. A total of 90 individuals were collected in the lagoons of Piratininga-Itaipu (IP), Saquarema (SQ) and Araruama (AR) between December 2019 and March 2020. For the analyses, 30 individuals per location from the same age group (2 years old), following age estimation by counting the annual growth increments, were used. The contour of the shape of each otolith was evaluated using elliptical Fourier descriptors (EFD). Multi-elemental signatures (MES) of the whole otoliths were obtained using solution-based inductively coupled plasma mass spectrometry. Data were analyzed using univariate and multivariate statistics to assess the degree of separation between individuals from different lagoons. EFD data showed differences between regions. MES exhibited distinct regional patterns, mainly driven by differences in Sr/Ca, Mg/Ca, Mn/Ca, Li/Ca and Cu/Ca ratios. Reclassification accuracy rates obtained from linear discriminant function analyses using both EFD and MES of otoliths were 100% (IP), 90% (SQ) and 97% (AR). Therefore, a clear distinction between the population groups was observed, probably related to the inherent characteristics of each lagoon system, their semi-restricted connectivity with the adjacent coastal zone, as well as the estuarine-opportunistic behavior of the species. Thus, the results suggest that these fisheries should be managed as different population-units. Full article

Zooplankton play a pivotal role in connecting primary producers and high trophic levels, and changes in their temporal and spatial distribution may affect the entire marine ecosystem. The spatial and seasonal taxonomic composition patterns of mesozooplankton in Bohai Bay were investigated in relation to a number of water parameters. Bohai Bay is a eutrophic semi-enclosed bay with dynamic physico-chemical conditions influenced by terrestrial inputs and seawater intrusion. The results showed that under the condition of terrigenous input, the diversity of mesozooplankton species near the eutrophic Haihe River Estuary and Jiyun River Estuary was lower than that in the central Bohai Bay, with gelatinous Oikopleura dioica as the dominant species. The mesozooplankton diversity was highest in the bay mouth affected by seawater intrusion, and the dominant oceanic species, mainly copepods Corycaeus affinis, Calanus sinicus, and Oithona similis, entered the inner bay from the bay mouth. Meanwhile, the abundance of mesozooplankton in summer was significantly higher than that in autumn. Compared with historical data, the dominant species in Bohai Bay has evolved from arrow worm Sagitta crassa to copepod Paracalanus parvus, probably due to global warming, indicating the effects of human activities on the succession of mesozooplankton community. Full article

The release of hatchery-reared fish fry for restocking is important for the enrichment of fishery resources; however, the effective evaluation of the success rate of marking such fish is challenging. We exposed juvenile crucian carp (Carassius carassius) to a single concentration of SrCl₂·6H₂O for 5 d and evaluated the efficiency of Sr marking of the fish otoliths (sagittae, asterisci, and lapilli) using an electron probe micro-analyzer. Sr marking signatures formed a peak in all otolith types, with a marking success rate of 100%. The ratio of Sr to Ca in the lapilli and sagittae was higher than that in the asterisci. It took 2 d from the beginning of immersion to the deposition of Sr on the lapilli and sagittae, and the time delay for asterisci was 1 d. For the lapilli and sagittae, it took 16 d to terminate Sr marking and fully recover to the pre-marking Sr level, whereas it was 12 d for the asterisci. The application of the Sr dose had no effect on the survival or growth of the carp. This study demonstrated that the lapilli are the most suitable otolith type for Sr marking observations in crucian carp and provides a theoretical basis and technical support for carp restocking using the Sr marking approach. Full article

Tree morphological characteristics, particularly straightness and lean, significantly influence the value of the commercial products that can be obtained. Despite this, they are not usually evaluated in timber field inventories because traditional techniques are labor-intensive and largely subjective, hence the use of these parameters is limited to research and genetic breeding programs. Here, a non-destructive, fully automated methodology is presented that estimates the parameters for describing straightness and lean using terrestrial laser scanning (TLS) data. It is based on splitting stems into evenly spaced sections and estimating their centers, which are then used to automatically calculate the maximum sagitta, sinuosity, and lean of each tree. The methodology was applied in a breeding trial plot of Pinus pinaster, and the results obtained were compared with field measurements of straightness and lean based on visual classification. The methodology is robust to errors in the estimation of section centers, the basis for calculating shape parameters. Besides, its accuracy compares favorably with traditional field techniques, which often involve problems of misclassification. The new methodology is easy to use, less expensive, and overcomes the drawbacks of traditional field techniques for obtaining straightness and lean measurements. It can be modified to apply to any species and stand typology. Full article

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. Full article