Relationships between fish size and otolith size of four bathydemersal fish species from the south eastern Arabian Sea,India

The objective of this study was to estimate a prey body size from the hard parts (e.g. otoliths) of a fish species frequently found in the guts of predators. Length–weight relationships between otolith size (length, height, weight and aspect ratio) and fish size (total length and weight) were determined for four fish species captured in the Arabian Sea by bottom trawl (2015 survey on‐board FORV Sagar Sampada, 200–300 m depth), off the west coast of India: Psenopsis cyanea, Pterygotrigla hemisticta, Bembrops caudimacula and Hoplostethus rubellopterus. No significant differences were noted between the size of the left and right otoliths (t test) in any of the four species. The length–weight relationship of the otolith in all four species showed a negative allometric growth pattern (t test, p < .05). The data fitted well to the regression model for otolith length (OL), otolith height (OH) and otolith weight (OW) to total length (TL) and total weight (TW). Results showed that these relationships are a helpful tool in predicting fish size from the otoliths and in calculating the biomass of these less‐studied fish species during feeding studies and palaentology.     

Biometric relation between body size and otolith size of seven commercial fish species of the south‐western Atlantic

Given the importance and applicability of these biometric relations, the present work aimed to verify the existence of correlations between the length of saggitae otoliths and the body size of seven south‐western Atlantic marine fish species and to generate equations to estimate the body size of these species through otolith measurements. Fifty otoliths of Centropomus parallelus, Centropomus undecimalis, Lutjanus analis, Lutjanus jocu, Lutjanus synagris, Chaetodipterus faber and Mugil curema were collected for analysis. Significant relations between otolith length and total length and otolith width and total length were found for all the species. The highest coefficient of determination was observed for Centropomus undecimalis and Lutjanus synagris, for both relations, and the lowest was observed for Mugil curema. The results show that estimates of body size of the species through biometric analyses of otoliths are reliable. Based on this, the equations generated to obtain the total length of the fish using biometric otolith data can be used in dietary studies of top predators and in paleontological recostructions of modern fish.     

Morphology and microchemistry of abnormal otoliths in the ayu, <Emphasis Type="Italic">Plecoglossus altivelis</Emphasis>

The sagittal otolith morphology and microchemistry of reared juvenile ayu, Plecoglossus altivelis, were examined to describe the occurrence and microchemical characteristics of the abnormal otoliths in this species. Juvenile ayu (N = 31) were collected in June 2004 at three different locations, Wakayama, Kumamoto, and Biwa Lake in Japan, where they were being reared in freshwater aquaculture ponds after having been collected in the wild as larvae. Otolith abnormality was found in the sagittae of 26% (N = 8) of the individuals examined, of which five fish had abnormal otoliths only on one side, while the otolith on the other side was normal. Abnormal otoliths were more transparent and crystalline in appearance with irregular shapes compared to normal ones that were more opaque and less irregular. Abnormal otoliths were divided into two types, semi-abnormal (Type 1) with a normal part in the center, and fully-abnormal (Type 2) that were completely crystalline in appearance. The line transects and whole otolith concentration maps showed that the contents of Sr, Na and K were lower in the abnormal otolith regions compared to the normal ones, while those of Ca and S were almost constant in both. The appearance and microchemical properties of the abnormal ayu otoliths were similar to the abnormal otoliths in other species in which vaterite replaces the aragonite. Abnormal formation of otoliths occurred in ayu from Biwa Lake (30%) and Kumamoto (45%), while the Wakayama samples had no abnormality. The microchemical analyses of the normal and abnormal otoliths indicated that some abnormal otoliths had formed before the fish were captured and transferred to the hatchery, so the possible causes of otolith abnormality in ayu are discussed.     

Sexual dimorphism in the otolith shape of shi drum,Umbrina cirrosa (L.), in the eastern Mediterranean Sea: Fish size–otolith size relationships

Little is known about possible differences in sagitta otolith size and shape between sexes of the shi drum, Umbrina cirrosa, and relationships between their body and otolith size. Thus, this study aimed to fill this knowledge gap via examination of 414 sagittal otoliths from 108 male (total length 13.8–26.8 cm) and 99 female (13.5–26.7 cm) U. cirrosa caught between May 2017 and April 2018 in gillnets set at a depth of ~15 m in Mersin Bay, Eastern Mediterranean Sea. No statistical differences were observed between the shape indices of the left-sided and right-sided sagitta. However, there were significant differences in the size and shape of otoliths between males and females. The slopes of allometric power functions from otolith width × fish sizes gave significant differences between males and females (ANCOVA, P < 0.05). The relationship for length × weight of otoliths from both males and females showed isometric growth, whereas the relationship of otolith width × otolith weight showed positive allometry. Negative allometric growth was observed for the relationship otolith length × otolith width. In summary, this study revealed the presence of sexual dimorphism in the otolith shape of U. cirrosa, and the data on regression relationships of fish-otolith sizes can be used to estimate fish size from U. cirrosa otolith sizes.     

High incidence of otolith abnormality in juvenile European flounder Platichthys flesus from a tidal freshwater area

Otolith abnormality has been reported for a wide range of freshwater and marine fish species. In this study, the sagittal otolith morphology and mineralogy of juvenile European flounder, Platichthys flesus, were examined to describe the incidence and types of structural deformities in this species. Juvenile flounder were collected over the years 2013–2015 in the tidal freshwater section of an estuarine nursery (Minho estuary, NW Portugal). Otolith abnormality was found in 43% of the individuals and, in most cases, occurred in both otoliths. Despite an abnormal mineralogy confirmed by scanning electron microscopy, the morphometry and the mineral polymorph composition of abnormal otoliths did not differ from normal ones (i.e. aragonite). This contrasts with other studies where vaterite and/or calcite were found to replace aragonite in abnormal otoliths. Further studies are needed to elucidate whether abrupt salinity changes associated with habitat transitions may have played a role in the abnormal otolith biomineralization in this species.     

Comparative morphology of the sagittal otolith in three species of south Caspian gobies

Sagittal otolith shapes were investigated in order to identify three sympatric species of south Caspian gobies (Caspian goby Neogobius caspius, deepwater goby Ponticola bathybius and bighead goby Ponticola gorlap). The sagittal otoliths in P. bathybius have a rectangular shape and are thick, whereas in N. caspius they are relatively round and thin. In P. gorlap, otoliths have an elongated shape and are relatively thick. The noticeable difference among the otoliths of the three species is the presence of one anterior and one posterior projection in the otoliths of N. caspius and P. gorlap. Among shape indices, form factor (irregularity of surface area), circularity, aspect ratio and rectangularity are the foremost that indicate interspecific variability. The canonical discriminant analysis correctly classifies 94·7% of the original group cases. The overall analyses show the relevance of applying otolith shape for interspecific distinction of the three species of Caspian gobies.     

Exposure to thyroid hormone in ovo affects otolith crystallization in rainbow trout Oncorhynchus mykiss

Calcareous otoliths in the inner ears of fishes are necessary for proper hearing and vestibular function. Sagittal otoliths are usually composed of the calcium carbonate polymorph aragonite but may contain the polymorph vaterite, a phenomenon called otolith crystallization. The causes of otolith crystallization are poorly understood. Thyroid hormone (TH) can influence the chemical microenvironment and structure of the inner ear, suggesting that TH may influence otolith crystallization. The present study examined the effect of exogenous TH treatment on sagittal otolith crystallization and growth in larval and juvenile rainbow trout, Oncorhynchus mykiss. In the first experiment, 110?C179?day-old fish raised from TH-treated oocytes had significantly fewer sagittal otoliths containing the crystalline calcium carbonate polymorph vaterite as compared to untreated fish. Vaterite-containing otoliths were significantly longer than those containing the typical polymorph aragonite, although there was no effect of TH treatment on otolith length. In the second experiment, juveniles immersed in an exogenous solution of TH for 6?weeks had slightly longer otoliths (relative to fish length) than age-matched controls, but this effect was not significant. This juvenile population had a very high percentage (88.3?%) of vaterite sagittae overall and this percentage did not change significantly with treatment, suggesting the switch from aragonite to vaterite occurred prior to inclusion of the fish in the study. These results suggest that early manipulation of TH levels may affect calcium carbonate deposition on the otolith but that later TH exposure is unable to restore typical otolith composition.     

Age determination of the Antarctic fishes Champsocephalus gunnari and Notothenia rossii marmorata from South Georgia

Summary Investigations were performed on otoliths from Champsocephalus gunnari and Notothenia rossii marmorata as part of an effort to study the population dynamics of Antarctic fishes. Examination of otoliths by scanning electron microscope (SEM) revealed internal microincrements which were similar to daily increments described for other fish species. No easily identifiable annuli could be discerned and fishes were aged by counting microincrements. Multiple regression analyses relating age to otolith morphometrics and fish size, provided a simpler ageing method. It was determined with these techniques that C. gunnari grew to 50 cm in 15 yrs and N. rossii marmorata grew to 50 cm in 6.5 yrs. The lack of larger-sized individuals for N. rossii marmorata may be indicative of recent overfishing with only the younger age groups remaining. It appears that length-at-age data determined on a yearly basis, could provide valuable scientific and management information for these species.     

Morphology and taxonomic significance of the otoliths of some bathypelagic Anguilloidei and Saccopharyngoidei from the Sargasso Sea

The sagittal otoliths of seven anguilliform species belonging to the families Nemichthyidae, Serrivomeridae and Eurypharyngidae are described and illustrated, and a key for their identification is provided. Although the leptocephali of the various fish species treated here have similar otoliths, some species develop specific otolith characteristics during the adult stage. The shape as well as the ratio of fish length to otolith length ratio in adults may serve as a taxonomic aid. Since the sagittae of these fishes can be used for specific identification, the digested remains of prey in the stomachs and guts of predators can be identified.     

Lesser Sandplover,Charadrius mongolus,in Turkey

Sagittal otoliths are widely used to determine taxon, age and size of the teleost fishes, and are useful tools for studies of prey-predator relationships, population dynamics and ichthyo-archaeology. They can also be used to estimate the size of the prey. We examined the relationships between otolith measurements (length, height and weight) and fish size (total length and weight) for two species of Argentinidae (Argentina sphyraena and Glossanodon leioglossus) from the Southern Aegean Sea, Turkey. Length, height and mass of sagittae were shown to be good indicators for the length and weight of fish in both species. Glossanodon leioglossus has relatively larger sagittae than Argentina sphyraena. Linear and exponential functions provided the best fit for relations between otolith and fish measurements. No significant differences were found between left and right otolith sizes.     

Morphometry and composition of red drum otoliths: Changes associated with temperature,somatic growth rate,and age

• 1.1. Size and composition of sagittal otoliths from red drum, Sciaenops ocellatus (Sciaenidae), reared at various constant temperatures were compared with otoliths from wild-caught fish.
• 2.2. Uncoupling of otolith growth and somatic growth in laboratory-reared fish was evident in otolith length, area, volume, weight, density, and organic fraction.
• 3.3. Fish grown at low temperatures had significantly smaller and less dense otoliths having a greater organic content than fish of the same size grown at higher temperatures.
• 4.4. Changes in inorganic elements were poorly related to temperature in laboratory-reared fish.
• 5.5. The effect of temperature on otolith elemental composition was small relative to the effects of age and its associated physiological changes.

     

Factors affecting morphological development of the sagittal otolith in juvenile and adult small yellow croaker (Larimichthys polyactis Bleeker, 1877)

The morphology and morphometrics of the sagittal otoliths of small yellow croaker (Larimichthys polyactis) from the southern Yellow Sea were investigated. Study objectives were to evaluate the shape variability and morphometric variables of sagittae of juveniles and adults as related to developmental changes and habit shift. A total of 152 fish were sampled from April to June of 2012 and 2013, along the coastal waters of the Lüsi spawning ground in the southern Yellow Sea. Changes in otolith shapes from the juvenile to the adult were presented with the rim development through the entire‐lobed‐entire transition and with the curvature of the cauda toward the ventral margin. The otolith elongation in the juvenile stage occurred at 10–20 mm standard length (SL) and was likely associated with the formation of otolith accessory growth centers from larvae to juvenile. The L. polyactis sagittal otoliths acquired their definitive shape at 130 mm SL maturity. Ontogeny on otolith shape might be related, for example, to the factors of metamorphic development, feeding habitat, and ambient water salinity, which varied throughout the growth of L. polyactis.     

Using the otolith sulcus to aid in prey identification and improve estimates of prey size in diet studies of a piscivorous predator

Diet studies are fundamental for understanding trophic connections in marine ecosystems. In the southeastern US, the common bottlenose dolphin Tursiops truncatus is the predominant marine mammal in coastal waters, but its role as a top predator has received little attention. Diet studies of piscivorous predators, like bottlenose dolphins, start with assessing prey otoliths recovered from stomachs or feces, but digestive erosion hampers species identification and underestimates fish weight (FW). To compensate, FW is often estimated from the least affected otoliths and scaled to other otoliths, which also introduces bias. The sulcus, an otolith surface feature, has a species‐specific shape of its ostium and caudal extents, which is within the otolith edge for some species. We explored whether the sulcus could improve species identification and estimation of prey size using a case study of four sciaenid species targeted by fisheries and bottlenose dolphins in North Carolina. Methods were assessed first on otoliths from a reference collection (n = 421) and applied to prey otoliths (n = 5,308) recovered from 120 stomachs of dead stranded dolphins. We demonstrated in reference‐collection otoliths that cauda to sulcus length (CL:SL) could discriminate between spotted seatrout (Cynoscion nebulosus) and weakfish (Cynoscion regalis) (classification accuracy = 0.98). This method confirmed for the first time predation of spotted seatrout by bottlenose dolphins in North Carolina. Using predictive models developed from reference‐collection otoliths, we provided evidence that digestion affects otolith length more than sulcus or cauda length, making the latter better predictors. Lastly, we explored scenarios of calculating total consumed biomass across degrees of digestion. A suggested approach was for the least digested otoliths to be scaled to other otoliths iteratively from within the same stomach, month, or season as samples allow. Using the otolith sulcus helped overcome challenges of species identification and fish size estimation, indicating their potential use in other diet studies.     

Validation of daily otolith increments in larval and juvenile Chinese sucker, <Emphasis Type="Italic">Myxocyprinus asiaticus</Emphasis>

Otolith development was observed and the formation of daily growth increments in otoliths of Chinese sucker, Myxocyprinus asiaticus, was validated by monitoring known-age larvae and juveniles in the laboratory from 2003 to 2005. Otolith shape changed with larval and juvenile development, and there was an exponential relationship until a body length of 16 mm or so, and a linear relationship after a body length of 16 mm between otolith size and fish size. The first increment was identified in larvae 1 day after hatching. The regressed equations between daily age (D) and increment number in otoliths (N) were N = −0.64 + 0.96D in lapillus, and N = −0.31 + 0.98D in sagitta. The slopes were not significantly different than 1.0. This demonstrated that otolith increments in this species were formed daily and can be used for daily age determination.     

Assessment of growth zones on whole and thin-sectioned otoliths in <Emphasis Type="Italic">Sperata aor</Emphasis> (Bagridae) inhabiting the River Ganga,India

The present study was undertaken with the objective to assess the clarity of growth zones on whole and thin-sectioned otoliths in Sperata aor. A total of 125 sagittal otoliths of S. aor were collected monthly from the river Ganga during the period, April to December 2013 at Narora, Uttar Pradesh, India. Thin sections (approximately 0.5 mm) of one of the sagittal otoliths of each fish were cut using IsoMet® Low Speed Saw. Both whole otoliths and thin-sectioned otoliths were then examined under stereozoom microscope. Parameters of agreement on growth zones were calculated by comparing the number of growth zones obtained independentlyby the two readers (R1 and R2) from the two methods (whole otolith and thin-sectioned otolith method). Thin-sectioned otolith method exhibited higher agreement than whole otolith method based on linear regression analysis and growth zones bias plot. Between readers, higher agreement was noted for reader 1 than reader 2, plausibly due to his relatively more experience in examining the growth zones on the otoliths. However, both readers reported independently that the growth zones were clearer on thin sections than on whole otoliths especially those from older individuals. Thus, it may be concluded that the thin-sectioned otolith method should be utilized for assessment of growth zones in S. aor populations from the river Ganga.     

The use of sectioned otoliths to age barramundi (Lates calcarifer) (Bloch, 1790) [Centropomidae]

The relationship between the number of rings present in sagittal otoliths and the age of barramundi, Lates calcarifer (Bloch, 1790) [Centropomidae], was investigated by examining cross sectioned otoliths of 37 tagged fish of known age between 1 and 5 years from the Johnstone River, north Queensland. Concentric rings were clearly visible in all otolith sections and were validated as annual marks. The technique was then used to estimate the age and calculate von Bertalanffy growth parameters for 70 barramundi from the Fitzroy River, central Queensland. Growth appeared to be rapid but variable in the first year; the von Bertalanffy growth parameters for length versus age were L =690 mm, K=0.53, t ₀= 0.003 years. October 1 was designated as the birth date. Whole otolith length, width and thickness were also approximated well by the von Bertalanffy equation. We suggest that examination of otoliths is a useful technique for ageing barramundi but note that further validation of the ageing method is still needed for fish older than six years.     

Otolith size changes related with body growth,habitat depth and temperature

Synopsis Size variation in the sagittal otoliths of six species of the genus Merluccius, and five species of the genus Coelorhynchus was compared, using a digital image processing system and multivariate analysis. It is proposed that otolith growth occurs under dual regulation, overall shape is regulated genetically, and otolith size is influenced by environmental conditions. The decline of temperature with increasing habitat depth seems to be an important factor regulating the growth of otoliths in carbonate-saturated levels. The relative growth of the otoliths is usually negatively allometric.     

Using otolith shape and morphometry to identify four Alburnus species (A. chalcoides,A. escherichii,A. mossulensis and A. tarichi) in Turkish inland waters

Asteriscus otolith shapes as well as their morphometry and shape contours were investigated in order to identify four allopatric Alburnus species: A. chalcoides (Güldenstädt, 1772) (Ordu), A. escherichii Steindachner, 1897 (Eski?ehir), A. mossulensis Heckel, 1843 (Tunceli), and A. tarichi (Güldenstädt, 1814) (Van) in Turkish inland waters. These were compared using the shape indices (form factor, roundness, circularity, ellipticity, rectangularity and aspect ratio), and the morphological characters [otolith weight (OWE), otolith length (OL), otolith width (OW), otolith perimeter (OP), and otolith area (OA)]. The overall canonical discriminant analysis (CDA) classification score was 93.8%, with the lowest score for A. escherichii (82.5%) and the highest for A. chalcoides (100%). The otolith shapes, morphology and shape contours of all sampled fish were a clear species differentiator, thereby demonstrating that the otolith shape is species‐specific. The current study presents for the first time comprehensive variation information on interspecific left‐right asteriscus otoliths in males and females of each Alburnus species: A. chalcoides from Ordu, A. escherichii from Eski?ehir, A. mossulensis from Tunceli and A. tarichi from Van, based on a total of 307 individuals. Scanning electron microscopy (SEM) images, shape contours and other otolith characters vary within the same genus; these differences should be investigated not only in other freshwater fish species or genera but also in the same species living in different habitats. In addition, further investigation is required not only with respect to the morphometry, biometry, shape, geometry, and shape contours of the otoliths, but also regarding the genetic methods for robust identification of various sympatric and allopatric fish populations.     

Ageing Belanger's croaker,Johnius belangerii (Cuvier, 1830), based on otolith shape analysis

The use of morphological characters and otolith weight as predictors of fish age has proven to be an efficient, objective and precise method, but studies were heretofore focused primarily on fast‐growing fish species. In the present study, Belanger's croaker, Johnius belangerii (Cuvier, 1830), is presented as a model species for slow‐growing fish where it is hypothesized that age has a significant effect on the otolith shape, and that the otolith weight has the potential to predict individual fish age as an alternative and objective method. Discriminant function analysis (DFA) of shape variables and cross‐validation were applied to a total of 359 sagittal otoliths in the age groups 0, 1 and 2. The shape variables demonstrated 64.1% correct age classification, and a 93.5% correct age classification with the inclusion of otolith weight in the discriminant function. Results show that a combination of shape variables and otolith weight work well in age determination of Belanger's croaker, and demonstrate its application potential for sciaenids that are distributed throughout the coastal waters of China.     

Stock discrimination of the Japanese Spanish mackerel (Scomberomorus niphonius) based on the otolith shape analysis in the Yellow Sea and Bohai Sea

Geographic variability in sagittal otoliths shape of the Japanese Spanish mackerel (Scomberomorus niphonius) was studied to test whether stock discrimination might be possible using this method. It was hypothesized that S. niphonius would show little difference in otolith shape, likely as a result of mixing between seas. A total of 164 sagittal otoliths were collected from commercial fishing vessels between April and June 2010 in three spawning grounds, that of Qingdao in the middle Yellow Sea, Lvsi in the southern Yellow Sea, Huanghua in the the Bohai Sea. To minimize the potential effect of the fish size among the three fishing grounds, a narrow size range (400–550 mm fork length) was selected. The discriminant function analysis conducted with standardized otolith shape indices and Fourier harmonics produced classification success rates ranging from 57.0 to 88.2% and worked well in the separation between the Bohai Sea group and the Yellow Sea group. No significant differences were detected among the three groups for the Lvsi spawning grounds. The otolith variables showed a distinct gradual variation tendency with the movement of fish schools from south to north. The results suggest that stock from the Bohai Sea could be managed as a separate entity from those found in the Yellow Sea.