The relationship between fish length and otolith size and weight of Acanthopagrus arabicus Iwatsuki, 2013 (Sparidae) collected from the Iraqi marine waters

Fish specimens (n=75) of A. arabicus were collected from the marine waters of Iraq at Khor al-Zubair. Collection was conducted in the period February–September 2019 at depth of 10–25 m. Relationships between fish length and otolith length, width and weight were calculated for the Arabian yellowfin seabream, Acanthopagrus arabicus using linear models. This study represents the first data available on the relationship of fish size and otolith size and weight for A. arabicus in the Arabian Gulf area. The various relationships between fish length otolith length, width and weight were calculated: Y = -1E – 0.06X2 + 0.0106X + 5.2628, Y = 4E – 06X2 + 0.0077X + 2.1834, and Y = 9E – 07X2 + 0.0013X – 0.191 respectively.

Discrimination of Diplodus vulgaris (Actinopterygii, Sparidae) stock from two Tunisian lagoons using otolith shape analysis

Saccular otolith shape and size were analysed for the first time in 120 adult individuals of D. vulgaris collected from two localities, the Bizerte and Ghar El Melh lagoons (north-east Tunisia). The objectives were (1) to examine the specific inter- and intra-individual variation in the otolith shape using elliptical Fourier analysis combined with measures of length (LO), width (WO) and area (AO); (2) to use the otolith shape and size analysis as a phenotypic-based approach to discriminate the stock structure of this species in the two localities to investigate whether they represent two separate stocks to inform on appropriate management procedures; and (3) to test for biases resulting from potential fluctuating asymmetry (FA) in the otolith size on the discrimination of stock structure. Discriminant function analysis performed with the normalized elliptical Fourier descriptors coefficients showed statistically significant differences (P < 0.0001) in the otolith contour shape, i.e. asymmetry, either between the left and right sides or between the same sides (left-left and right-right) within and among individuals of the two localities. Besides, a significant asymmetry (P < 0.05) was found in WO and AO among individuals within the Bizerte locality and in WO only within the Ghar El Melh locality. Moreover, significant FA was observed in the otolith size parameters among individuals of the two localities. This significant asymmetry detected in the otolith shape, as well as in the size due to FA, within and among individuals of D. vulgaris collected from the Bizerte and Ghar El Melh localities confirms that the two stocks could be discriminated from each other and should be managed separately. This asymmetry is discussed in light of the instability of development caused either by environmental stress associated with the variation in water temperature, salinity, depth, feeding conditions and pollutants that have led to abnormalities in the development of individuals or by the presence of poor living conditions for the larvae resulting from unfavourable environments.

Th e Relationship Between Fish Length and Otolith Size and Weight of the Australian Ancnovy, En-graulis australis (Clupeiformes, Engraulidae), Retrieved from the Food of the Australasian Gannet, Morus serrator (Suliformes, Sulidae), Hauraki Gulf, New Zealand

Relationships between fish length and otolith length, width and mass were examined in the Australian anchovy Engraulis australis (White, 1790) recovered from the food of Gannet examined from colonies at islands of Horuhoru Rock and Mahuki Islands in the Hauraki Gulf, New Zealand. The relationships between otolith length- fish total length (TL), otolith-weight-TL, and otolith-width-TL were investigated by means of non-linear regression models (TL = 0.54 OL 16.86, TL = 4.39 OW 7.61 and TL = 26.19 OWe 2.2). This study characterizes the first reference available on the relationship of fish size and otolith size and weight for E. australis obtained from bird’s food in the Pacific Ocean region

The Size and The Shape of Sagittal Otolith of Redtail Scad, Decapterus kurroides Blekeer 1855 from Kema Bay, North Minahasa Regency, North Sulawesi, Indonesia

This study aimed to examine the difference in the otolith size and otolith shape of redtail scad Decapterus kurrodes between sex in North Sulawesi. The otoliths of D. kurroides were studied for sagitta otolith pair samples of 34 juveniles, 58 females and 75 males from Kema Bay. These pairs sagitta otolith images were interpreted using ImageJ tool to describe the otolith size (length, width, perimeter, and area), then we calculated the shape index (form factor, roundness, circularity, rectangularity, ellipticity and aspect ratio or length-width ratio). No significant difference was found in otolith length between left and right otoliths of juveniles of D. kurroides or called symmetrical but significant differences or asymmetrical were found in all sample, females and males. The regressions of total length against otolith sizes (otolith lengt, otolith width otolith perimeter and otolith area of D. kurroides follow a power function. The growth patterns showed dominant allometric growth in total length–otolith sizes relationships of D. kurroides from Kema Bay, Key Words: size, shape index, otolith, Decapterus kurroides, Kema Bay.

Biometric relationships between body size and otolith size in 15 demersal marine fish species from the northern Brazilian coast

ABSTRACT The relationships between fish size and sagitta otolith measurements were calculated for the first time for 15 species belonging to six families from the northern Brazilian coast. A total of 220 fish were sampled from the bycatch landed by the bottom-trawl industrial shrimp-fishing fleet between August and September 2016. All species had strong relationships between otolith measurements and fish total length with the coefficient of determination (r 2) ranging between 0.71 and 0.99. The variable most strongly related to fish total length was found to be the sagittal otolith length (OL) with 98% of the variability. These relationships are a useful tool to estimate length and mass of preyed fish from otoliths found in stomach contents of marine predators.

Relationships between fish length, otolith size and otolith weight in Sperata aor (Bagridae) and Labeo bata (Cyprinidae) from the Ganga River, India

The present study was conducted to investigate the relationships between fish length, otolith size and otolith weight. A total of 180 Sperata aor and 171 Labeo bata specimens were collected monthly during January 2016 to March 2017 from the River Ganga at the Narora site. Student’s t-test showed no significant differences in the size of right and left otoliths in the selected fish species, therefore, a single linear regression based on the left otolith was carried out. Fish length was plotted against otolith weight, otolith length and otolith height. Moreover, otolith length was plotted against otolith weight and otolith height. The linear regression model was found to fit the data well for fish length to otolith size in both selected fish species. A strong relationship between otolith length and weight was found in both species (r2 > 0.8). Furthermore, the study revealed that fish length is potentially related to otolith size and a strong relationship between fish length and otolith size exists in S. aor (mean r2 = 0.89) as compared to L. bata (mean r2 = 0.70). Such relationships should be determined for the fish species that are ecologically and socio-economically important in order to understand their trophic relationships, population dynamics and yield estimates.

Otolith biometry analysis of betong fish, Selar crumenophthalmus (Bloch, 1793) (Teleostei: Carangidae) in Manado Bay, North Sulawesi

This study aims to examine whether there are differences in the size and shape of otolith both between sexes and between the sampling times of bigeye scad Selar crumenophthalmus in Manado Bay, North Sulawesi. Most of the otolith sizes and the otolith shape indices do not show any significant differences between left and right, some of which show statistically significant differences such as the otolith length and the indices of the roundness, ellipticity and aspect ratio of female fish at August 2017 and otolith length, otolith width and otolith perimeter of male fish at November 2017. The otolith sizes and shape indices do not differ between sexes but differ between sampling times ie August 2017 and November 2017. Otolith sizes such as length, width, area and perimeter and shape indices such as circularity and rectangularity can be used as indicators of stock determination. Other shape indices of otolith such as form factor, roundness, ellipticity and aspect ratio are not well used as stock determination. Most of the samples showed a negative allometric growth pattern, except in the sample of female fish sampled in November 2017 which showed an isometric growth pattern for all otolith size variables. There is no statistically significant difference in the regression line of the otolith sizes - total length between sexes, but there is a statistically very significant difference in the regression line between sampling times (months) where the otolith size is greater in November 2017 or in other words at the same length of fish, otolith sizes bigger in November 2017 than in August 2017. The otolith sizes and their relationship with the total length of the fish can be used for determining (separating) the stock of bigeye scad Selar crumenophthalmus. There is a possibility that the sample for August 2017 is a different stock with samples from November 2017.Key words: Selar crumenophthalmus, otolith, morphometry, stock identification, Manado Bay ABSTRACTPenelitian ini bertujuan untuk menguji apakah terdapat perbedaan ukuran dan bentuk otolit baik antar seks maupun antar waktu pengambilan sampel ikan selar betong Selar crumenophthalmus di Teluk Manado Sulawesi Utara. Sebagian besar ukuran serta indeks bentuk otolit tidak menunjukkan perbedaan yang nyata antara kiri dan kanan, beberapa di antaranya menunjukkan perbedaan yang nyata secara statistik misalnya ukuran panjang otolit serta indeks bentuk otolit ‘roundness’, ‘ellipticity’ dan ‘aspect ratio’ pada ikan betina Agustus 2017 dan ukuran panjang otolit, luas otolit dan keliling otolit pada ikan jantan November 2017. Ukuran dan indeks bentuk otolit tidak berbeda antar jenis kelamin tetapi berbeda antar waktu sampling yakni Agustus 2017 dan November 2017. Ukuran otolit seperti panjang, lebar, luas dan keliling otolit serta indeks bentuk seperti ‘circularity’ dan ‘rectangularity’ dapat digunakan sebagai indikator penentu stok. Indeks bentuk otolit lainnya seperti ‘form factor’, ‘roundness’, ‘ellipticity’ dan ‘aspect rasio’ kurang baik digunakan sebagai variable penentu stok. Sebagian besar sampel menunjukkan pola pertumbuhan alometri negatif, kecuali pada sampel ikan betina yang disampling pada November 2017 yang memperlihatkan pola pertumbuhan isometrik untuk semua variabel ukuran otolit. Tidak terdapat perbedaan garis regresi ukuran otolit - panjang total antar seks, tetapi terdapat perbedaan yang sangat nyata garis regresi tersebut antar waktu sampling (bulan) di mana ukuran otolit lebih besar pada bulan November 2017 atau dengan kata lain pada panjang ikan yang sama, ukuran otolit lebih besar pada bulan November 2017 dibandingkan dengan pada bulan Agustus 2017. Ukuran otolit serta hubungan regresi dengan panjang total ikannya dapat digunakan untuk penentuan (pemisahan) stok ikan selar betong Selar crumenophthalmus. Ada kemungkinan sampel bulan Agustus 2017 merupakan stok yang berbeda dengan sampel bulan November 2017.Kata kunci: Selar crumenophthalmus, otolit, morfometri, identifikasi stok, Teluk Manado