Thalassas: An International Journal of Marine Sciences最新文献

The age structure, growth, mortality, and exploitation status of the Chrysochir aurea stock in West Bengal coast, India, were assessed. A sample of 618 specimens with total lengths ranging from 124 to 417 mm were collected from commercial trawlers between September 2021 and September 2022. The length-frequency distribution was analysed using the FiSAT II tool. The growth parameters asymptotic length (L_∞), catabolic coefficient (K), and initial condition factor (t₀) were determined to be 435.23 mm, 0.26 yr^-1, and -0.309 years, respectively. The total (Z), natural (M), and fishing (F) mortality rates were estimated at 1.09, 0.35, and 0.74 yr^-1, respectively. A consistent recruitment trend was seen throughout the year, with two peaks, one from February to May and the other from July to November, with a length at first capture (L_C) of 177.95 mm. The current exploitation level (E_now) and maximum exploitation level (E_max) were calculated at 0.68 and 0.60 indicating overexploitation of the stock along the coast. The yield was projected to be 160.826 t at the current fishing level (f = 1.0) and 164.866 t at the maximum fishing level (f = 0.9). To create a sustainable fishery in the future, a reduction in fishing effort is suggested.

Morphological changes during metamorphosis from larvae to juvenile stage vary considerably among teleosts. Metamorphosis in Acanthopagrus berda, a commercially important sparid, recorded using simple microscopy in captivity, revealed progressive changes in pigmentation, band formation, development of fins, and other morphological features. Larvae on 2 day post hatch [dph] (2—3 mm total length [TL]) exhibited an open mouth and pigmented eyes, and on 12 dph (6—7 mm TL), notochord flexion initiated with marked development in dorsal, anal and caudal fin formation. Larvae on 8 dph (3—4 mm TL) exhibited an initial internal pigmentation in the buccal cavity and 10 dph larvae were observed with an initial external pigmentation on the cephalic region. On 22 dph (11—12 mm TL), vertical band formation was initiated at the anterior portion of the larval body and proceeded posteriorly. The sequence of fin formation was in the order of pectoral, caudal, dorsal and anal fins, followed by the pelvic fin. On 45 dph (25—28 mm TL) miniature adult with fully formed silvery scales and lateral line emerged in captivity. TL bared a positive correlation with the larvae's vertical mouth opening and eye diameter. The coefficient of variation in body weight of the fish has reduced from 38 to 25% from larvae to juvenile. Information on the metamorphosis of the larvae of the species will help to act as an identification key for planktonic larvae collected from the natural environment.

Abstract

The genus Plectorhinchus (sweetlips) exhibits high morphological plasticity, especially in coral reef ecosystems, which is often due to response to different environments regardless of genotype. Few studies are known on the correct taxonomic identification of the species in the Persian Gulf and Gulf of Oman. In the present study, the morphometric and meristic differences between eight sweetlips from the Persian Gulf and the Gulf of Oman were investigated using traditional and geometric morphometrics. The traditional approach based on principal component analysis (PCA) and discriminant function analysis (DFA) showed significant morphological differences among morphotypes. The main features used to discriminate between morphotypes were body depth, orbital diameter, caudal peduncle depth, dorsal fin length, gill rakers, and transverse scale rows. The geometric morphometric method (GMM) gave almost congruent results with the traditional morphometric and showed a high divergence between species except for Plectorhinchus schotaf and P. flavomaculatus. The morphometric and shape variations could be related to ecomorphological variables. Species diversity was greater in the Gulf of Oman than in the Persian Gulf, which could be due to abiotic factors, geological events, and habitat structure.

The nutritional compositions of fatty acids (FAs), amino acids (AAs), polysaccharides, and phenolic compounds from brown seaweeds Cystoseira trinodis, Dictyota cervicornis, Padina gymnospora, and Turbinaria oranata were studied, and their antioxidant and antimicrobial activities were evaluated. For the assessment of phytocompounds, gas chromatography-mass spectrometry (GCMS) and high-resolution liquid chromatography (HPLC) were employed. D. cervicornis and T. oranata showed high levels of saturated FA in their lipophilic profiles (48.13 and 42.41%, respectively), mainly palmitic acid (16:0) with 38.4 and 33.79%, respectively. In contrast, C. trinodis and P. gymnospora contained the highest amounts of unsaturated FAs (51.5 and 38.15%, respectively), composed predominantly of oleic acid (18:1, n9) with proportions of 18.29 and 33.79%. Unsaponifiable lipids consist primarily of phytol, cholest-5-en-3-ol, stigmasterol, and 9Z-octadecenamide. The major phenolic compounds were gallic acid in D. cervicornis, catechin in T. oranata and C. trinodis, and kaempferol in P. gymnospora with values of 227.54, 209.63, 167.18 and 85.82 µg/g, respectively. The backbone of the polysaccharides in P. gymnospora was galactose (26.5%), ribose (38.9%) in C. trinode, mannose (49.7%) in D. cervicornis, and rhamnose (30.7%) in T. oranata. In all species, leucine and phenylalanine were the primary essential AAs, whereas proline was the main non-essential AA. The MeOH extracts of T. oranata and C. trinodis displayed mild antioxidant activity with IC₅₀ values of 26.1 and 30.5 μg/ml. FAs contents of C. trinodis and D. cervicornis possessed antibacterial properties against Staphylococcus aureus and Bacillus cereus, while FAs contents of T. oranata and P. gymnospora exhibited potent antifungal activities against Penicillium expansum and Syncephalastrum racemosum with the inhibition MIC value for both = 0.312mg/ml.

Graphical Abstract

The present study aimed to evaluate the effect of vitamin E (VE) supplementation on the reproductive and growth performance, hormonal profile, and biochemical parameters of female hybrid red tilapia before spawning season. Seventy-two female hybrid red tilapia were caught with an average body-weight 272.56 ± 34.84g and an average total length 24.3 ± 2.5 cm. Healthy fish were distributed equally into 4 treatments supplemented with (0, 50, 100, 200 mg/kg) of VE given for 8 weeks. VE significantly improved weight gain, length gain, specific growth rate, average daily gain, feed conversion ratio, and protein efficiency ratio. 50 mg of VE/kg diet could improve the viscerosomatic index, hepatosomatic index, and gonadosomatic index. Also, it could improve the parameters of biochemical (aspartate aminotransferase, alanine transaminase, total protein, albumin, globulin, triglyceride, and alkaline phosphatase) and haematology (total erythrocytic and leucocytic count, hematocrit and hemoglobin) and increase FSH, LH, E2 and, progesterone concentrations significantly. The conclusion revealed that the addition of 50 mg of VE /kg diet has a beneficial impact on reproductive and growth performance, hormonal profile, and biochemical parameters of female hybrid red tilapia. So, it is advisable for adding 50 mg/kg of vitamin E to the fish diet before the spawning season (pre-spawning).

Abstract

A slipper lobster species Chelarctus virgosus recently separated from C. cultrifer (Ortmann 1897) by Yang and Chan (2012) was caught by a baited trap at a depth of 30 m, from off Onagawa, Oshika Peninsula (southern end of the Sanriku Coast), northeastern Japan. This record verified the distribution of C. virgosus in Japan. Also, this is the first record of scyllarid lobsters from the coastal waters of the Kuroshio-Oyashio Mixing Zone, updating the northern limit of distribution by more than 300 km. In addition, possible Japanese records tentatively listed in the original description of C. virgosus are revisited, and the distribution on the Pacific coast at the Boso Peninsula to the Ryukyu Archipelago was confirmed.

Abstract

Small-scale fisheries represent the largest source of income and livelihood for communities along Colombia’s Pacific coast, and at least 100 fish species of commercial interest have been recorded in this fishery. The aim of this study was to estimate the Length–weight relationships (LWR) for some of the most frequently captured fish species in small-scale fisheries (SSFs) in the northern Pacific of Colombia to gain valuable knowledge for regional fisheries management and conservation of species. Length and weight measurements of 7112 specimens caught between October 2021 and December 2022 were used. Regression coefficient (b) values ranged from 2.65 to 3.34, with allometric growth being more frequent than isometric growth. No differences in LWR due to sex in bony fish species were registered. New registers of LWRs in the Tropical Eastern Pacific are presented for 17 species and new maximum values of size and weight are given for five species. Because of latitude effect on species life history characteristics (e.g., maximum length), our results provide novel information for LWRs of tropical fish species of high interest in small-scale fisheries.

This article is based on the nine specimens of milk sole, Aseraggodes kobensis (Steindachner 1896), collected from the Andaman waters. The present work happens to be the first geographical record of A. kobensis in the northeastern Indian Ocean. This record from off the Andaman coast bridges an apparent gap in the geographical distribution of milk sole in the Indo-Pacific biogeographic region. Phenotypic characters were enumerated and compared with the voucher specimens from the original description, Arabian Sea, and Malaysia hence proving the morphological identification. The key distinguishing characteristics of A. kobensis from congeners were the smaller head length and slender tendrils at the anterior tip of the snout and chin. A short standardized Mitochondrial Cytochrome c oxidase subunit 1 (COI) gene was targeted to generate the sequence for molecular taxonomy. A 629 bp long sequence was obtained and submitted to GeneBank as the first barcode from Indian waters (GeneBank accession number: OR568995). Maximum likelihood phylogenetic tree showed a distinct clade of Andaman isolate of A. kobensis with other species of the family Soleidae. A redescription of A. kobensis based on the morphological and molecular analysis has been presented in this article.

Abstract

As part of a marine ecology study aimed to discover the diversity of fish parasites, we described a new species representing Magnanchor n. gen. and provided new and supplementary morphometric information for Mexicana bychowskyi, both monogenoidean species collected from the gill lamellae of the humpback grunt Microlepidotus brevipinnis (Haemulidae) from the Pacific coast of Mexico. The new genus is proposed for its unique species, M. raris n. sp. which is characterized in having overlapping gonads (testis posterodorsal to the germarium), a copulatory complex consisting of counterclockwise coils of the copulatory organ that is unarticulated to the accessory piece, a haptor armed with two pairs of anchors (each with broad base and well differentiated roots), dorsal and ventral bars, a dextral vaginal aperture, and 6 pairs of hooks with uniform shank and upright acute thumb. Data on morphological and biometric variability of the six species of Mexicana (including illustrations of the haptoral structures of the present specimens of M. bychowskyi) previously described and/or reported parasitizing different haemulid hosts from the Pacific and Atlantic oceans in the Tropics are also provided. Due to the morphological similarities among the amphiamerican species of Mexicana, they could represent sister-species pairs in the Tropics. Magnanchor raris n. sp. and M. bychowskyi (type species of the genus) are the first dactylogyrids described and/or reported on M. brevipinnis.