Intra-population variability of the saccular, utricular and lagenar otoliths of the garfish Belone belone (Linnaeus, 1760) from South-Western Ionian Sea (Central Mediterranean Sea).

The garfish Belone belone represents the only valid endemic Belone species for the Mediterranean Sea and the eastern Atlantic Ocean. It shows a wide global distribution range, with a high commercial value and ecological relevance in the pelagic domain. Despite this, there needs to be more knowledge regarding the otoliths of this species, with the total absence of descriptions regarding asterisci and lapilli from Mediterranean populations and a lack of studies on the reliability of shape analysis on its sagittae. The present paper aims to provide the first main contours description of the three otoliths pairs from a Mediterranean population, providing an accurate investigation of morphology, morphometry, and intra-specific variability of sagittae, lapilli, and asterisci. Results showed (i) the absence of directional bilateral asymmetry and sexual asymmetry for the three otoliths pairs, (ii) a different morphology and morphometry of sagittae, lapilli and asterisci than those described in the literature, and (iii) an enhanced variability between sagittae morphometry and shape between the three investigated size classes. All these data confirmed the reliability of the studied species of shape analysis, showing a geographical and size-related variability of otoliths features probably related to genetics, environmental conditions, and life habits variations.

Comparing otolith shape descriptors for population structure inferences in a small pelagic fish, the European sardine Sardina pilchardus (Walbaum, 1792).

Otolith shape analysis has been one of the most used approaches to study population structure in the past decades. Currently, two sets of shape descriptors are used to perform otolith shape analysis, namely, Elliptic Fourier descriptor (EFd), which focuses on the overall otolith shape differences, and Discrete Wavelet descriptor (DWd), which is sensible to local differences along the otolith contour. Here, the authors conducted a comparative analysis of the performance of both the descriptors in reconstructing the population structure and connectivity patterns in a small pelagic fish species with a wide geographical distribution and fast growth rate, the European sardine Sardina pilchardus (Walbaum, 1792), for the first time. A combination of each otolith shape descriptor and shape indices was explored using multivariate statistical methods. The two otolith shape descriptors showed similar, although limited, overall classification success associated with the population dynamic characteristics of the species. Both descriptors point to migration among adjacent areas, such as northern Atlantic locations, eastern Mediterranean and even across well-defined physical obstacles, such as the Strait of Gibraltar, among Atlantic and western Mediterranean locations. Both descriptors supported the division of the populations of Mediterranean waters into three main groups but slightly differed in the group limits of the Atlantic waters. A comparison of the present results with those from previous otolith shape analysis studies using EFd on a decadal time scale revealed differences in the population structure and connectivity patterns compared to the earlier period. These differences not only may be attributed to changes in environmental variables leading to changes in population dynamics but can also be the result of the sardine biomass sharp decrease that occurred in the past decade.

Shape and ontogenetic changes in otolith of the ocellated icefish (Chionodraco rastrospinosus) from the Bransfield Strait, Antarctic.

Fish otolith shapes record ecological information of fish and are an important tool in taxonomic, phylogenetic, and dietary studies. Shape and ontogenetic variations in the otoliths of ocellated icefish (Chionodraco rastrospinosus) in the Bransfield Strait, northern Antarctic Peninsula, were analyzed. Ontogenetic changes in otolith morphology were evident. The size of the otoliths mainly grew along the antero-posterior axis. The rostrum and pararostrum developed more than the antirostrum and postrostrum. Otolith variation occurred mainly in the dorsal side compared to ventral side. A row of small holes in the central region of the medial side and an irregular protruded structure on both sides of them, were specific diagnostic characteristics of C. rastrospinosus otoliths compared to other species of Chionodraco. Based on hierarchical clustering analysis, four types of otolith shapes are clearly distinguished, corresponding to larval, juvenile, young, and adult stages of C. rastrospinosus. This work contributes to the understanding of the ecology of commercially important benthic fishes and provides key information for ecomorphology study and fishery management of this species. We suggest the effect of ontogeny needs to be considered when otolith shape data are used to study population structure and life history of this species.

Otolith shape and isotopic ratio analyses as a tool to study Spondyliosoma cantharus population structure.

Knowledge on population units is critical for understanding population dynamics and providing an adequate fisheries management. Despite its vast distribution and commercial importance, there is no information on black seabream population structure. Different approaches to otolith analysis were used to elucidate on the stock structure of this species. Otoliths from seven areas along the eastern Atlantic: English Channel, Bay of Biscay, Galicia (Spain), Peniche (west coast of Portugal), Algarve (south coast of Portugal), the Canary Islands and Angola were compared through elliptical Fourier analysis and oxygen and carbon stable isotopes ratio. Otolith shape analysis data achieved 80% of correct assigned specimens in discriminant analysis while poor correct assignment levels were achieved with the stable isotopes ratio. However, the PERMANOVA conducted on δ13C and δ18O values revealed significant differences between all areas, with exception of the two Portuguese areas. The results of this study indicate that black seabream spends most of its life in the same area and that the studied populations should probably be considered as different stock units. However, some mixture was detected in the European region pointing for the usefulness of life history parameters and genetic studies to enlighten the stock structure of the species.

Mn2+ concentrations in coastal fish otoliths: understanding environmental and biological influences from EPR.

The Mn2+ concentrations in the sagittae otoliths of 12 fish families (and 19 species) that co-occur in a coastal area of southeastern Brazil (~21°S) were quantified using electron paramagnetic resonance (EPR). Inferences were made about the relationship between fish habitat and trace element incorporation. Inferences were made on the relationship between trace element concentration and otolith shape. The differences in Mn2+ concentrations among the species suggest that habitat (and feeding habits) might drive the incorporation of this trace element into fish otoliths, with higher values in bottom-associated fish species than in surface-associated species. In surface-associated fish species, the correlation between trace element concentrations and otolith shape was stronger than in bottom-associated species. Thus, while the Mn bioavailability in a fish's habitat, especially from feeding resources, is a local driving influence of trace element incorporation in sagittae otoliths, species-specific requirements also have an influence. Quantitative EPR is a non-destructive technique that is very useful when the available samples cannot be damaged, like with otolith collections.

Relationships between otolith size and fish length in some mesopelagic teleosts (Myctophidae, Paralepididae, Phosichthyidae and Stomiidae).

Length-mass relationships and linear regressions are given for otolith size (length and height) and standard length (LS ) of certain mesopelagic fishes (Myctophidae, Paralepididae, Phosichthyidae and Stomiidae) living in the central Mediterranean Sea. The length-mass relationship showed isometric growth in six species, whereas linear regressions of LS and otolith size fit the data well for all species. These equations represent a useful tool for dietary studies on Mediterranean marine predators.

Common otolith microstructure related to key early life-history events in flatfishes identified in the larvae and juveniles of cresthead flounder Pseudopleuronectes schrenki.

Otolith microstructure of reared and wild cresthead flounder Pseudopleuronectes schrenki larvae and juveniles was used to investigate the daily periodicity of ring formation, morphological change and unique otolith structure related to important life events. By comparing microstructural features of P. schrenki with those reported for other flatfish species, it was shown that there may be microstructural features that are common to all flatfishes. In the sagittae and lapillus, a check (a distinct ring) was formed in the centre of otoliths at c. 6 days post hatching, and the daily formation of rings observed outside the check was confirmed. During metamorphosis, accessory primordia (AP) of otolith growth were formed on the outer edge of the sagittae, and the shape of the sagittae became more complex. No AP was formed on the lapilli, however, and otolith rings were concentrically formed throughout the larval and juvenile (≤51·6 mm standard length, LS ) stages. It is proposed, therefore, that lapilli are more appropriate than sagittae for analysis throughout the larval and juvenile (≤51·6 mm LS ) stages. During metamorphosis, unique rings that are relatively wide and show weak contrast are formed on lapilli (metamorphosing zone, MZ). Hence, the duration of metamorphosis, larval duration and the days of juvenile life can be estimated by the number of rings within the MZ, using rings from the check to outermost ring of the MZ, and that of rings formed outside MZ, respectively. The formation of AP on sagittae as well as the absence of AP, bilateral asymmetry and the formation of a unique structure during metamorphosis on lapilli have also been reported for other flatfishes.

Otolith atlas of fish of the Sinos River / Atlas de otólitos de peixes do Rio dos Sinos

Otoliths are calcium carbonate structures located in the inner ear of fish; they are responsible for hearing and balance. The inner ear has three pairs of otoliths: the lapilli, the sagittae and the asterisci. The sagittae otoliths are the largest and their format is species-specific. Because of their composition, otoliths can resist to the digestive tract of ichthyophagous species, and they can be used as an important tool for identifying species of fish found in stomach contents. The purpose of this work is to provide a photographic guide of the sagittae otoliths of the main fish species from the Sinos River. This atlas consists of photographs of the sagittae otoliths of 36 species belonging to 15 families distributed in five orders.

Otólitos são estruturas formadas por cristais de carbonato de cálcio, localizadas no labirinto do ouvido interno dos peixes. São responsáveis pela audição e pelo equilíbrio. O ouvido interno possui três pares de otólitos, os lapilli, os sagittae e os asterisci. Os denominados sagittae são os maiores e seu formato é espécie-específico. Devido a sua composição os otólitos conseguem resistir ao trato digestivo das espécies ictiófagas, dessa maneira podem ser empregados como uma importante ferramenta para a identificação de espécies de peixes em trabalhos com conteúdos estomacais. O objetivo deste trabalho é a disponibilização de uma referência visual dos otólitos sagittae das principais espécies de peixes do Rio dos Sinos, para que possam servir de base para trabalhos com conteúdos estomacais de espécies ictiófagas. Este atlas é composto de fotografias dos otólitos sagittae de 36 espécies de 15 famílias distribuídas em cinco ordens.

Growth of the Pacific jack Caranx caninus (Pisces: Carangidae) from the coast of Colima, México

The Pacific jack Caranx caninus is a common species fished by artisanal fishermen off the coast of Colima, México. During 2002, monthly samples of morphometric data and otoliths were taken to determine age and growth. Seven age groups were identified. The highest growth, 14.4 cm, takes place during the first year of life. During the second year, C caninus grows 11.76 cm; the third year 9.61 cm; the fourth 7.85 cm; the fifth 6.41 cm and sixth year 5.24 cm. The constants of von Bertalanffy's growth equation were: L(infinity) = 83.26 cm, W(infinity) = 18.138 g, K = 0.202, t(0) = -0.283 and A(0.95) = 15 years. Growth curves of other species of the same genus were calculated in order to compare them with the one obtained in the present work. The gonadosomatic index presented higher values during November and May. The periods of more intensive feeding are from August to February.

El jurel Caranx caninus es una especie común que se captura en la pesca artesanal frente a las costas de Colima, México. Mensualmente, durante 2002, se tomaron datos morfométricos y muestras de otolitos para determinar la edad y el crecimiento. Se encontraron siete grupos de edad; durante el primer año de vida se da el mayor crecimiento, hasta 14.4 cm. Durante el segundo año, C. caninus crece 11.76 cm; el tercero 9.61 cm; el cuarto 7.85 cm; el quinto 6.41 cm y el último año crece 5.24 cm. Las constantes de la ecuación de crecimiento de von Bertalanffy fueron: L∞ = 83.26 cm, W∞ = 18.138 g, K = 0.202, to = -0.283 y la longevidad A0.95 = 15 años. Las curvas de crecimiento de otras especies del mismo género se compararon con las obtenidas en el presente trabajo. El índice gonadosomático presentó valores más altos durante noviembre y mayo. Los periodos de tiempo de alimentación más intensa son de agosto a febrero.