Repeated boat noise exposure damages inner ear sensory hair cells and decreases hearing sensitivity in Atlantic croaker (Micropogonias undulatus).

Anthropogenic noise is becoming a major underwater pollutant because of rapidly increasing boat traffic worldwide. But its impact on aquatic organisms remains largely unknown. Previous studies have focused mainly on high-frequency and impulsive noises (i.e. sonar); however, boat noise is more pervasive, continuous, and its highest intensity and component frequencies overlap the auditory bandwidth of most fishes. We assessed the impacts of boat noise on saccular sensory hair cell density and hearing thresholds of a soniferous species, Atlantic croaker (Micropogonias undulatus). In two laboratory experiments, individuals were subjected to simulated boat noise: a single 15-min exposure and 3 days of intermittent noise (simulating passing vessels). Immediately after both experiments, fish were either (1) tested for hearing sensitivity with auditory evoked potential (AEP) tests or (2) euthanized for fluorescent phalloidin and TUNEL labeling for hair cell density counts. Relative to controls, no differences were observed in auditory thresholds nor hair cell density between individuals subjected to a single 15-min noise exposure. However, fish from the 3-day experiment showed decreased sensory hair cell density, increased apoptotic cells, and higher hearing thresholds than control fish at 300, 800 and 1000 Hz. Our results demonstrate that impacts from boat noise depend upon the duration and frequency of exposure. For a species reliant on vocalization for communication, these impacts may hinder spawning success, increase predation risks and significantly alter the ecosystem.

Application of high-throughput sequencing to analyze the diet of black croaker (Atrobucca nibe) in southern coastal waters of Zhejiang.

This study investigated the feeding habits of black croaker (Atrobucca nibe) to fully understand its role in the food web in southern coastal waters of Zhejiang, China. In total, 225 black croakers were collected in a bottom trawl survey, of which 195 were used for the stomach contents analysis and 30 for high-throughput sequencing (HTS). Both approaches showed that the main prey was shrimp, with Alpheus japonicus being the most predominant. In addition, black croaker also fed on other benthic species, suggesting that it was a demersal predator. Feeding intensity also varied with black croaker body length, as did prey preference, from small-sized species to larger species with increases in fish size; in addition, prey species were more diverse in the large-bodied prey group. Canonical correspondence analysis indicated that the feeding habit of black croaker was most significantly correlated with temperature and dissolved oxygen. HTS was shown to be a feasible high precision semi-quantitative analytical approach, although it must be combined with morphological methods to obtain more complete feeding data; thus, it could provide an effective scientific basis for feeding ecology studies of marine organisms.

Description of two new species of Diplectanum Diesing, 1858 (Monogenea: Diplectanidae) collected from Protonibea diacanthus (Lacepède, 1802) (Teleostei: Sciaenidae) from waters off northern Australia.

Two new species of the family Diplectanidae Monticelli, 1903 from the gills of Protonibea diacanthus (Lacepède, 1802) (Teleostei: Sciaenidae) off the northern Australian coast are described. Previous studies have either morphological or genetic results, whereas this study combines morphological and advanced molecular methods to provide the first detailed descriptions for species of Diplectanum Diesing, 1858 from Australia utilising both methodologies. Two new species, Diplectanum timorcanthus n. sp. and Diplectanum diacanthi n. sp., are morphologically described and genetically characterised using the partial nuclear 28S ribosomal RNA gene (28S rRNA) and the internal transcribed spacer 1 (ITS1) partial sequence.

Identifying Whitemouth Croaker (Micropogonias furnieri) Populations along the Rio de Janeiro Coast, Brazil, through Microsatellite and Otolith Analyses.

The inshore area of the Southwestern Atlantic between 22 °S and 29 °S (South Brazilian Bight) is a transitional climatic zone, where the tropical and warm temperate provinces mix. In its northern part, i.e., in the coastal waters of Rio de Janeiro, Brazil, local oceanographic conditions, such as upwelling in the north, and great bays with different degrees of anthropogenic influences in the center and south can determine the population structure of several fish stocks. The Whitemouth croaker (Micropogonias furnieri) is one the most heavily exploited fishing resources in this area, but there are still some doubts about its population structure. In this study, through combined analyses using nuclear genetic markers and morphological and geochemical signatures of otoliths, a divergence of individuals between two populations was identified using microsatellites, while a finer spatial structure with three populations (north, center and south, respectively) was found based on otolith shapes and elemental signatures. This regional population structure may have direct implications for rational fisheries management and conservation of the species.

The Phylogenetic Relationships of the Family Sciaenidae Based on Genome-Wide Data Analysis.

Uncertainty and controversy exist in the phylogenetic status of the Sciaenidae family because of the limited genetic data availability. In this study, a data set of 69,098 bp, covering 309 shared orthologous genes, was extracted from 18 genomes and 5 transcriptomes of 12 species belonging to the Sciaenidae family and used for phylogenetic analysis. The maximum likelihood (ML) and Bayesian approach (BA) methods were used to reconstruct the phylogenetic trees. The resolved ML and BA trees showed similar topology, thus revealing two major evolutionary lineages within the Sciaenidae family, namely, Western Atlantic (WA) and Eastern Atlantic−Indo−West Pacific (EIP). The WA group included four species belonging to four genera: Cynoscion nebulosus, Equetus punctatus, Sciaenops ocellatus, and Micropogonias undulatus. Meanwhile, the EIP group formed one monophyletic clade, harboring eight species (Argyrosomus regius, A. japonicus, Pennahia anea, Nibea albiflora, Miichthys miiuy, Collichthys lucidus, Larimichthys polyactis, and L. crocea) from six genera. Our results indicated that the Western Atlantic (WA) group was more ancient in the studied species, while the Eastern Atlantic−Indo−West Pacific (EIP) group was a younger group. Within the studied species, the genera Collichthys and Larmichthys were the youngest lineages, and we do not suggest that Collichthys and Larmichthys should be considered as one genus. However, the origin of the Sciaenidae family and problems concerning the basal genus were not resolved because of the lack of genomes. Therefore, further sampling and sequencing efforts are needed.

Integrative Taxonomy Reveals a Panmictic Population of Henneguya longisporoplasma n. sp. (Cnidaria: Myxozoa) in the Amazon Basin.

PURPOSE: Henneguya Thélohan, 1892 is one of the most species-rich genera of myxosporean parasites and infects fish around the world. The present study describes a new species infecting the gill filaments, fins, and kidneys of Plagioscion squamosissimus (Heckel, 1840), an economically important freshwater fish distributed in watersheds in the north of South America. METHODS: A total of 108 P. squamosissimus specimens were examined from three geographic localities in the Amazon basin: the Lago Grande do Curuai, a marginal lake of the Amazon River; the Tapajós River, in the state of Pará; and the Solimões River, in the state of Amazonas, Brazil. The analyses were based on the myxospore morphology, ribosomal DNA sequencing, phylogeny, prevalence, and geographic distribution of the host and its parasite. RESULTS: Parasite prevalences were 50% in both the Tapajós and Solimões rivers, and 35.4% in the Lago Grande do Curuai. In terms of the site of infection, the prevalence total was 23.1% in the gill filament, 29.6% in the fins, and 1.8% in the kidney. Regarding gender, the prevalence was 59.5% for males, 32.5% for females, and 21.7% for undetermined sex. The specimens found here were both morphologically and molecularly identical regardless of the infected organ and geographic locality, but distinct from all other Henneguya species, revealing that the parasite reported represents a novel species named Henneguya longisporoplasma n. sp. Despite the sampling being carried out in three different geographic localities of the Amazon basin, no population-level genetic variation was observed, even in the typically more variable ITS-1 region, revealing a panmictic population of H. longisporoplasma n. sp. in this large watershed. Maximum likelihood and Bayesian analyses showed the novel Henneguya clustered as a sister branch of the subclade formed of Henneguya that infect fish belonging to the family Cichlidae. CONCLUSIONS: A novel Henneguya species was identified parasitizing P. squamosissimus. The parasite presented wide geographic distribution in the Amazon basin and genetic analyses showed it as revealing a panmictic population.

Past and Contemporaneous Otolith Fingerprints Reveal Potential Anthropogenic Interferences and Allows Refinement of the Population Structure of Isopisthus parvipinnis in the South Brazil Bight.

In this study, otolith geochemical signatures (Element:Ca ratios) were used to investigate the long-term spatial shifts of the population structure of Isopisthus parvipinnis, Bigtooth corvina, an economically and ecologically important Brazilian fish species. Two-hundred and ninety-seven juvenile individuals from historical (1975) and contemporary (2018/2019) samples were collected in five subareas [São Paulo: North-NSP, Center-CSP and South-SSP; Paraná (PR) and Santa Catarina (SC)] of the shallow waters off the coast of the South Brazil Bight were analyzed. The main informative single elements were Co:Ca, Cu:Ca, Li:Ca, Mg:Ca, Mn:Ca, Ni:Ca, Na:Ca, and Rb:Ca. Multivariate analysis showed spatial differences in otolith chemical composition over the years. Samples from 1975 presented an overall low reclassification rate (58%), suggesting the existence of two population units: (1) SP + PR; and (2) SC. However, samples from 2018/2019 discriminated four distinct population units with a good overall reclassification (80%): (1) NSP; (2) CSP; (3) SSP + PR; and (4) SC. This spatial differentiation on the geochemical signatures probably reflects the effects of long-term temporal variability in oceanographic conditions, anthropogenic influence, and climate change on this coastal ecosystem. The data also corroborate and refines the population structure scenario of I. parvipinnis recently described using complementary phenotypic tags.

From development to taxonomy: the case of Sciaenacotyle pancerii (Monogenea: Microcotylidae) in the Mediterranean meagre.

The microcotylid Sciaenacotyle pancerii is a pathogenic monogenean infecting Argyrosomus regius, a candidate for species diversification in the Mediterranean aquaculture. Life-history stages of S. pancerii commonly co-occur in field infections, but to date, morphological data have only been provided for oncomiracidia and adults although identifying life-history stages can be useful in infection management. A total of 114 specimens of S. pancerii were analysed to characterize the developmental events and to assess morphological and morphometric variations before and after maturity. The post-larval development of S. pancerii is characterized by: expansion and bifurcation of the gut, loss of the larval haptor, protandrous development of the genitalia and vitellaria formation. The size variability of larval hooks, hamuli and germanium of S. pancerii is firstly reported and dimensional ranges of parasite body, haptor, testes, posteriormost clamps and eggs are widened. The size of most of the diagnostic features of S. pancerii significantly increases after parasite maturity and therefore, only those specimens with more than 116 clamps should be considered for minimising development-related variability in size. The high number of clamps, their fast development and the asymmetry in their size and arrangement suggest that S. pancerii may use a mixed attachment strategy between the closely related microcotylids and heteraxinids. This combination of features may be host related and linked to the gill structure of the sciaenid fish and the phylogenetic position of the genus Sciaenacotyle; distant from other microcotylids while close to heteraxinid species.

Habitat transitions by a large coastal sciaenid across life history stages, resolved using otolith chemistry.

Many coastal species move between estuarine and coastal environments throughout their life. Migration patterns develop as a result of ecology and evolution and must be understood to effectively manage harvested stocks. This study examined movements across estuarine and coastal marine habitats in adult Mulloway (Argyrosomus japonicus); a commercially, indigenous and recreationally harvested sciaenid of south-eastern Australia. Chemical profiles across the otolith (ear bone) were used to examine transitions between estuary and marine habitats over life history. Patterns in otolith Ba:Ca concentrations indicated that the majority of fish migrated between estuary and marine habitats, but a small proportion of fish appeared to remain in either the estuary or the marine habitat. Such movements may potentially be driven by a range of biological and environmental factors. This approach allows questions about the life history and habitat use of Mulloway to be addressed, which will aid management and provide a platform for future research on Mulloway, other sciaenid's and coastal migratory species.

Parasite assemblages of whitemouth croaker, Micropogonias furnieri: comparison between marine and brackish waters from the Argentine Sea.

The whitemouth croaker, Micropogonias furnieri, a coastal demersal fish with wide distribution in the Southwest Atlantic Ocean, is a euryhaline species, inhabiting waters with a wide range in salinity. Here, the composition of parasite assemblages of M. furnieri caught along the coastal area off Mar del Plata, Argentina, was described and the infracommunity structure compared with fish from brackish waters to determine variations of its parasite communities due to fish migration between these environments. The relationships between the presence of parasites and the diet and ecological traits of this fish host were discussed. A total of 61 fish from Mar del Plata (MDP) were examined for parasites and compared with previously published data for whitemouth croakers from Mar Chiquita coastal lagoon (MCH), an estuarine system connected to the sea. Corynosoma australe, Dichelyne sciaenidicola, and Neopterinotrematoides avaginata were the most prevalent and abundant species in MDP. Comparisons of infracommunity descriptors showed that fish from MDP harbored a higher number of parasites, as well as richer and more diverse infracommunities than those of MCH. Significant differences occurred in the structure and composition of parasite assemblages of whitemouth croaker from MDP compared to those from MCH, in which Neomacrovalvitrema argentinensis, N. avaginata, Neobrachiella chevreuxii, D. sciaenidicola, and C. australe were the key discriminating species related to these differences. The present study provides comparative data, of great importance for the understanding of parasite-host-environment interactions, particularly in a host that alternates between brackish and marine waters during its life cycle.

Geographical variation in age and growth of the endemic Australian sciaenid Atractoscion atelodus.

Growth rates and other age-related population characteristics are essential parameters underpinning management of a stock. This is the first study to estimate length-at-age of Atractoscion atelodus (family Sciaenidae) in New South Wales (NSW), despite the species being exploited since the 1940s. The aim of the current study was to quantify the age-based biological characteristics of A. atelodus and in particular: (a) validate the use of sagittal otoliths to quantify age; (b) estimate the growth rates and longevity of males and females; (c) examine geographical variation in age and growth; (d) document the age composition in commercial landings and (e) estimate mortality rates. A. atelodus is relatively fast growing, reaching 40 cm fork length (LF ) in the first year of life and living to at least 14 years. Growth was significantly different between sexes, with modelled asymptotic lengths of females (L∞  = 84.6 cm LF ) greater than males (L∞  = 69.0 cm LF ). Growth rates were also significantly different between northern and southern populations. Fish sampled from the southern region were younger and faster growing than those sampled in the northern region, supporting the counter-gradient growth theory and the influence of upwelling providing greater nutrient and food availability. The commercial fishery was predominantly based on young fish <3 years. with few (c. 5%) greater than 5 years. Fishing mortality estimates (F = 0.42) were similar to natural mortality estimates (M = 0.44). The age-based parameters estimated in the present study suggest that A. atelodus should be relatively resilient to fishing; nonetheless, the sizes and ages in landings are indicative of a stock heavily fished. The fishery is experiencing truncated age distributions and appears to be largely recruitment driven, increasing susceptibility to overexploitation. Determining geographical differences in growth rates of a population has important implications when considering impacts of anthropogenic drivers such as global warming and overexploitation and is important to determine in managing exploited fish populations.

Chromosome genome assembly for the meagre, Argyrosomus regius, reveals species adaptations and sciaenid sex-related locus evolution.

The meagre, Argyrosomus regius, has recently become a species of increasing economic interest for the Mediterranean aquaculture and there is ongoing work to boost production efficiency through selective breeding. Access to the complete genomic sequence will provide an essential resource for studying quantitative trait-associated loci and exploring the genetic diversity of different wild populations and aquaculture stocks in more detail. Here, we present the first complete genome for A. regius, produced through a combination of long and short read technologies and an efficient in-house developed pipeline for assembly and polishing. Scaffolding using previous linkage map data allowed us to reconstruct a chromosome level assembly with high completeness, complemented with gene annotation and repeat masking. The 696 Mb long assembly has an N50 = 27.87 Mb and an L50 = 12, with 92.85% of its length placed in 24 chromosomes. We use this new resource to study the evolution of the meagre genome and other Sciaenids, via a comparative analysis of 25 high-quality teleost genomes. Combining a rigorous investigation of gene duplications with base-wise conservation analysis, we identify candidate loci related to immune, fat metabolism and growth adaptations in the meagre. Following phylogenomic reconstruction, we show highly conserved synteny within Sciaenidae. In contrast, we report rapidly evolving syntenic rearrangements and gene copy changes in the sex-related dmrt1 neighbourhood in meagre and other members of the family. These novel genomic datasets and findings will add important new tools for aquaculture studies and greatly facilitate husbandry and breeding work in the species.

Complete mitochondrial genome for the whitemouth croaker Micropogonias furnieri (Perciformes: Sciaenidae).

This study is the first to research to report the complete 16,496 bp mitochondrial genome of Micropogonias furnieri, which consists of 13 protein-coding genes, two ribosomal RNA genes, 22 transfer RNA genes, and a control region (D-loop). The overall base composition of the complete genome is 27.26% A, 25.65% T, 16.46% G, and 30.63% C, with a high A + T content of 52.91%. Phylogenetic analysis showed that M. furnieri was most closely related to Sciaenops ocellatus. In this study, the mitogenome of M. furnieri will provide useful information for phylogenetic and evolutionary understanding in the family Sciaenidae.

Comparative Phylogeography and Phylogeny of Pennah Croakers (Teleostei: Sciaenidae) in Southeast Asian Waters.

A broad-scale comparative phylogeographic and phylogenetic study of pennah croakers, mainly Pennahia anea, P. macrocephalus, and P. ovata was conducted to elucidate the mechanisms that may have driven the diversification of marine organisms in Southeast Asian waters. A total of 316 individuals from the three species, and an additional eight and six individuals of P. argentata and P. pawak were employed in this study. Two genetically divergent lineages each of P. argentata and P. anea (lineages L1 and L2) were respectively detected from the analyses based on mitochondrial cytochrome b gene data. Historical biogeography analysis with a multi-gene dataset revealed that Pennahia species most likely originated in the South China Sea and expanded into the eastern Indian Ocean, East China Sea, and northwestern Pacific Ocean through three separate range expansions. The main diversifications of Pennahia species occurred during Miocene and Pliocene periods, and the occurrences of lineage divergences within P. anea and P. argentata were during the Pleistocene, likely as a consequence of cyclical glaciations. The population expansions that occurred after the sea level rise might be the reason for the population homogeneity observed in P. macrocephalus and most P. anea L2 South China Sea populations. The structure observed between the two populations of P. ovata, and the restricted distributions of P. anea lineage L1 and P. ovata in the eastern Indian Ocean, might have been hampered by the northward flowing ocean current at the Malacca Strait and by the distribution of coral reefs or rocky bottoms. While our results support S. Ekman's center-of-origin hypothesis taking place in the South China Sea, the Malacca Strait serving as the center of overlap is a supplementary postulation for explaining the present-day high diversity of pennah croakers centered in these waters.

Whole-Genome Sequencing and Genome-Wide Studies of Spiny Head Croaker (Collichthys lucidus) Reveals Potential Insights for Well-Developed Otoliths in the Family Sciaenidae.

Spiny head croaker (Collichthys lucidus), belonging to the family Sciaenidae, is a small economic fish with a main distribution in the coastal waters of Northwestern Pacific. Here, we constructed a nonredundant chromosome-level genome assembly of spiny head croaker and also made genome-wide investigations on genome evolution and gene families related to otolith development. A primary genome assembly of 811.23 Mb, with a contig N50 of 74.92 kb, was generated by a combination of 49.12-Gb Illumina clean reads and 35.24 Gb of PacBio long reads. Contigs of this draft assembly were further anchored into chromosomes by integration with additional 185.33-Gb Hi-C data, resulting in a high-quality chromosome-level genome assembly of 817.24 Mb, with an improved scaffold N50 of 26.58 Mb. Based on our phylogenetic analysis, we observed that C. lucidus is much closer to Larimichthys crocea than Miichthys miiuy. We also predicted that many gene families were significantly expanded (p-value <0.05) in spiny head croaker; among them, some are associated with "calcium signaling pathway" and potential "inner ear functions." In addition, we identified some otolith-related genes (such as otol1a that encodes Otolin-1a) with critical deletions or mutations, suggesting possible molecular mechanisms for well-developed otoliths in the family Sciaenidae.

The influence of climatic and lunar drivers on landings cycles of the temperate Australian sciaenid (Atractoscion atelodus) at two temporal scales: A working hypothesis for future management of this resource.

Commercial line-fishing catch rates of the endemic sciaenid Atractoscion atelodus in eastern-Australia were significantly affected by lunar phase. Periodic regression analysis indicated that catch rates were greatest during the full moon period and lowest during the new moon period. It is hypothesized that this observation is the result of the visual nocturnal feeding nature of A. atelodus, with schools of fish using the increased ambient light in the water column during the brighter part of the lunar phase to feed intensively. Increased feeding intensity during the brighter phase of the lunar month may also be related to spawning activity during the new moon phase; however this hypothesis remains to be tested. Annual commercial landings through a 71 year dataset (1950-2020) showed an approximately exponential decline, overlaid with periodic years of higher and lower landings. Such periods of higher landings were significantly positively correlated with coastal rainfall two and three years earlier, but not with rainfall in the same year or one, four or five years earlier. We hypothesize that increased coastal rainfall, likely in combination with unknown co-occurring factors, promotes increased recruitment success of A. atelodus, potentially through increased primary productivity in the nearshore marine environment. This translates into an increase in the fishable stock mainly two and three years later. If our hypothesis is correct, climate predictions of reduced rainfall in eastern Australia suggest a pessimistic outlook for this fishery.

Boat noise affects meagre (Argyrosomus regius) hearing and vocal behaviour.

Aquatic noise has increased in last decades imposing new constraints on aquatic animals' acoustic communication. Meagre (Argyrosomus regius) produce loud choruses during the breeding season, likely facilitating aggregations and mating, and are thus amenable to being impacted by anthropogenic noise. We assessed the impact of boat noise on this species acoustic communication by: evaluating possible masking effects of boat noise on hearing using Auditory Evoked Potentials (AEP) and inspecting changes in chorus sound levels from free ranging fish upon boat passages. Our results point to a significant masking effect of anthropogenic noise since we observed a reduction of ca. 20 dB on the ability to discriminate conspecific calls when exposed to boat noise. Furthermore, we verified a reduction in chorus energy during ferryboat passages, a behavioural effect that might ultimately impact spawning. This study is one of few addressing the effects of boat noise by combining different methodologies both in the lab and with free ranging animals.

The complete mitochondrial genome of the longneck croaker, pseudotolithus typus Bleeker, 1863 from Sierra Leone.

The complete mitochondrial DNA information of Pseudotolithus typus Bleeker, 1863, collected from Sierra Leone was determined using next-generation sequencing (NGS) and bioinfromatic analysis. Its mitogenome (16,504 bp) encoded the typical 13 protein-coding genes (PCGs), 2 ribosomal RNAs (12S & 16S), and 22 tRNAs. All 13 PCGs showed a standard start codon (ATG) but an unusual stop codon (AGA) was identified in COX1 gene. Except for ND6, all 12 PCGs were encoded on the light strand. Except for tRNASer-GCT, 21 tRNAs formed the typical clover-leaf structures. Phylogenetic analysis showed three mitochondrial genomes in the genus Pseudotolithus formed a clade distinct from the other species in the same family. The mitogenome of P. typus identified in this study exhibited 96.27% and 88.86% identity to T. typus in the Guinean water and P. elongatus, respectively. Additional mitogenome sequences of Pseudotolithus species will provide useful information for their scientific management in western African countries.

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.

Bilateral asymmetry in size of otolith of Otolithes ruber (Bloch & Schneider, 1801) collected from the marine waters of Iraq.

The otolith length and width of adult teleost Otolithes ruber (Bloch & Schneider, 1801) were used to calculate the fluctuating asymmetry in these two characters. The results displayed that the amount of asymmetry of the otolith width was the highest between the two asymmetry values attained for the otolith of O. ruber. Further, the lowest level of asymmetry in the two otolith characters is at the fish length ranging between 150 and 180 mm and the highest at the fish length ranging between 461 and 2490 mm. The conceivable reason for the asymmetry in this species has been deliberated relative to different pollutants and their presence in the area. A tendency of increase in the asymmetry levels with the fish length was observed for the otolith length and width.