ABSTRACT The west coast of India (WCI) is signified by increased primary productivity during the southwest monsoon season. In this study, the bacterial counts and the cultivable communities were enumerated from water depths and sediment samples at stations, off Goa, Mangalore and Trivandrum along the WCI during the monsoon season. The results reveal that the bacterial morphotypes isolated from this study included representatives from Firmicutes (70%), Proteobacteria (20%) and Actinobacteria (5%) phylum. Phylum Firmicutes had a major representation at Trivandrum and Mangalore locations compared to those from Goa. However, the Proteobacteria phylum was more prevalent in the Goa location compared to the other two locations. The morphotypes at the genera level also showed distinct spatial variations and taxa specific to each of the three locations could also be identified through Canonical correspondence analysis (CCA). Spatial variations in hydrolytic enzyme activities were also observed, with bacterial morphotypes isolated from water samples of Trivandrum exhibiting comparatively higher activities than the Goa and Mangalore sediment samples. These findings enhance our understanding of bacterial diversity and their functional roles along the WCI, emphasizing their significance in biogeochemical cycling processes.

ABSTRACT Two types of edible jellyfish, namely ‘ball-type’ and ‘white-type’, were reported to be commercially harvested respectively from the southeast and northwest coasts of Sri Lanka, but their taxonomic identity was unknown. Therefore, medusae collected in the ‘Waya-jel-Survey’, together with specimens from museums, were examined, comparing their morphomeristic data with information from the literature. As per results, the ‘ball-type’ and ‘white-type’ jellyfish species were recognized respectively as Crambionella orsini (Vanhöffen 1888) and Lobonemoides gracilis Light 1914 for the first time from Sri Lanka, with a detailed account of morphological features. Among the four valid species of the genus Crambionella, C. orsini is distinguished by the presence of 16 velar lappets per octant, without tubercles. The two congeners of L. gracilis, namely L. robustus Stiasny 1920 and L. sewelli Rao 1931, were synonymized to L. gracilis, making Lobonemoides monospecific, thus L. gracilis is recognized by the presence of papillae on the exumbrella; 1–6 elongated velar lappets between two successive rhopalia; and the window-like openings and long, spindle-shaped appendages on the oral arms. Likewise, the present study re-describes C. orsini and L. gracilis providing a basic component for efficient management of jellyfish fishery resources in Sri Lanka as well as in other Asian countries.

ABSTRACT This explorative research aimed to elucidate the stock profile and optimum catch limit of the king mackerel (Scomberomorus guttatus) stock by collecting data in the upper Bay of Bengal. This study used three length-based methods and a catch-based method to determine the growth parameters and biological reference points (BRPs) of king mackerel. A negative allometric growth pattern (b = 2.50) was observed in the length–weight relationship. The life history parameters were estimated as L∞ = 117.35 cm, k = 0.42 year−1 and the mortality estimates were the total mortality (Z = 1.18 year−1), natural mortality (M = 0.46 year−1) and fishing mortality (F = 0.72 year−1). The results show that this fishery is currently likely to be overfished due to overexploitation (F/M = >1) and the stock’s spawning biomass (SPR = 9%) is substantially lower than the target reference point because most of the catch (70%) was found to have under the maturity level. The recommended minimum total length for the catch is >59 cm and a yearly catch limit of 2400 mt as OFL (Over Fishing Limit) for the next ten years coordinated with the existing precautionary measures such as an annual fishing ban to raise the stock’s biomass over the BMSY level for maintaining sustainable yield of 4516 mt as MSY.

ABSTRACT This study investigates the reproductive biology and otolith characteristics of Neoscopelus cf. microchir, based on 24 specimens collected in summer from the Galicia Bank, a seamount in the NE Atlantic. Specimens ranged in length from 20 to 34 cm and in gutted weight from 41 to 335 g. All gonads were dissected and histologically analysed. Sagitta otoliths were removed and measured. The northeast Atlantic N cf. microchir is an iteroparous batch spawner with asynchronous oocyte development, which shows spawning activity in summer. Length at maturity (L50) was estimated to be 23.5 cm for females. Otolith height ranged from 8.28–13.92 mm, and all otolith dimensions increased with fish length. A translucent zone, probably associated with the settlement, started 2.5 mm from the otolith’s nucleus and had a mean width of 0.34 mm. Parameters of the LT – WG relationship were a = 2.5e-06 and b = 3.2 for both sexes combined. The gonadosomatic index varied between 0.6 and 11.9%, differing significantly between maturity stages. This study provides new insights into the reproductive biology and otolith characteristics of N. cf. microchir which will be useful for future studies on the population dynamics and life history of this deep-sea fish species.

ABSTRACT Bivalves are known to be infected by filamentous fungi, many of which have pathogenic and toxicogenic properties, and may represent a risk to human health. The present study investigated the mycological characteristics of Perna perna obtained from Guanabara Bay, Brazil. The mussels were sealed individually in sterile bags, weighed and measured, and the internal organs were examined. The organs were grown in different culture media. All but one of the 31 mussels (96.7%) examined contained fungi, and a total of 84 fungal colonies were isolated. The genera identified were Aspergillus (40.5%), Didymella (35.7%), Penicillium (10.7%), Aureobasidium (1.2%), Cladosporium (1.2%) and Phaeoisaria (1.2%). The molecular sequences obtained 99.8 and 100% identity with Didymella sp., Phaeoisaria sp. and Aureobasidium pullulans, and were deposited in GenBank. This is the first record of Didymella and Phaeoisaria in a bivalve. The digestive gland was the organ with the greatest diversity of fungi genera. A number of the fungi identified here, as Aspergillus awamori, Aspergillus japonicus, Aspergillus niger, Aspergillus versicolor and Aspergillus sydowii, are known to produce mycotoxins and others are opportunistic forms, which reinforces the need for the systematic monitoring of the study area to guarantee the safe exploitation of these bivalves for human consumption.

ABSTRACT We show in this study that the population of Chthamalus dentatus along the Atlantic coast of Africa displays a genetic division into four clades, namely: the South African, the Namibian-Angolan, the Cameroonian and the West African clade. This division is based on four genes – two mitochondrial genes, cytochrome c oxidase subunit I (COI) and the control region (D-loop), with the addition of two nuclear genes, the elongation factor (EF1) and the sodium-potassium ATPase (NaKA). The unique morphological feature of C. dentatus – dentated sutures between the shell compartments – is apparent in the specimens of the four clades, thus we define these clades as cryptic species of C. dentatus. The present work extends previous studies on the population genetics of C. dentatus that were based on COI only, by adding more genes and expanding the range of collection sites. In addition, the availability of new specimens from West Africa also enabled us to increase the northern limit of this species’ range to include Northern Senegal.

ABSTRACT We show in this study that the population of Chthamalus dentatus along the Atlantic coast of Africa displays a genetic division into four clades, namely: the South African, the Namibian-Angolan, the Cameroonian and the West African clade. This division is based on four genes – two mitochondrial genes, cytochrome c oxidase subunit I (COI) and the control region (D-loop), with the addition of two nuclear genes, the elongation factor (EF1) and the sodium-potassium ATPase (NaKA). The unique morphological feature of C. dentatus – dentated sutures between the shell compartments – is apparent in the specimens of the four clades, thus we define these clades as cryptic species of C. dentatus. The present work extends previous studies on the population genetics of C. dentatus that were based on COI only, by adding more genes and expanding the range of collection sites. In addition, the availability of new specimens from West Africa also enabled us to increase the northern limit of this species’ range to include Northern Senegal.

ABSTRACT Four closely related Echinometra species exist in the Indo-Pacific region, but little is known about their population genetics in Taiwan, an area rich in marine biodiversity. Echinometra dominates the Douziping coral reef off Liuqiu Island, where urchin barrens are also present. To understand the relationship between Echinometra species and urchin barrens, we investigated the genetic diversity of Echinometra species in Taiwan by using a nondestructive DNA extraction method on the spines of sea urchins. Mitochondrial DNA results showed that E. sp. C is the dominant species in Taiwan, with relatively high interspecific genetic distance. The E. sp. C is the only species in Douziping, and its population is expanding in accordance with the significantly low R2 value, the significantly negative Fu’s Fs values, and mismatch distribution analysis results. Gene flow estimates between the urchin populations in Taiwan and those in the neighbouring waters of Okinawa suggested that the Kuroshio Current could play an important role in Echinometra dispersal. This implies strongly connectivity between these populations. This study reports the first case of E. sp. C-associated urchin barrens in the tropics.

ABSTRACT Four closely related Echinometra species exist in the Indo-Pacific region, but little is known about their population genetics in Taiwan, an area rich in marine biodiversity. Echinometra dominates the Douziping coral reef off Liuqiu Island, where urchin barrens are also present. To understand the relationship between Echinometra species and urchin barrens, we investigated the genetic diversity of Echinometra species in Taiwan by using a nondestructive DNA extraction method on the spines of sea urchins. Mitochondrial DNA results showed that E. sp. C is the dominant species in Taiwan, with relatively high interspecific genetic distance. The E. sp. C is the only species in Douziping, and its population is expanding in accordance with the significantly low R2 value, the significantly negative Fu’s Fs values, and mismatch distribution analysis results. Gene flow estimates between the urchin populations in Taiwan and those in the neighbouring waters of Okinawa suggested that the Kuroshio Current could play an important role in Echinometra dispersal. This implies strongly connectivity between these populations. This study reports the first case of E. sp. C-associated urchin barrens in the tropics.

ABSTRACT This study was conducted in Shizugawa Bay, located on the north-eastern coast of Japan, to determine phytoplankton assemblages. Metabarcoding with the PsbA gene and environmental surveys were conducted from May 2021 to January 2022. PCA results showed that phytoplankton assemblages changed with the environmental parameters, such as water temperature and salinity, indicating a clear seasonal pattern. The relative abundance was dominated by Chlorophyta (annual mean 34.9%) > Bacillariophyta (29.1%) > Haptophyta (17.8%) > Dinophyceae (11.7%). It is suggested that many species of Chlorophyta remain without being filtered by shellfish because the dominant representatives were pico-prasinophytes, which are of small size and are difficult for shellfish to capture. Bacillariophytes are thought to have been consumed preferentially since they are known to be a good food source for adult shellfish. Among Dinophyceae, Dinophysis spp. (causing diarrheal poisoning) were dominant throughout the period, while Alexandrium spp. (causing paralytic poisoning) showed relatively low abundance. Phaeocystis spp. (including some toxic species) were the dominant haptophytes. Cyanobacteria tended to appear particularly in summer although their mean relative abundance was less than 3%. Although the data are limited, they provide a useful snapshot of phytoplankton assemblages in Shizugawa Bay and the environmental factors that affect them.