Marine Fish Species Research Articles

Evaluation of community science monitoring with environmental DNA for marine fish species: “Fish survey project using environmental DNA”

AbstractEnvironmental DNA is a powerful tool for community science‐based biodiversity surveys. However, the effectiveness of environmental DNA for environmental education and the time and physical costs perceived by volunteers for collecting environmental DNA remain unclear. Here, we evaluated a community science program for monitoring marine fish biodiversity using environmental DNA metabarcoding. This program aimed to investigate marine fish biodiversity in coastal areas along the Japanese archipelago. The participants were allowed to decide on the date and site to collect environmental DNA. They received a paper manual, a data sheet, and a sampling kit via a parcel delivery service. Before collecting environmental DNA, they watched a video manual for collecting environmental DNA and attended a webinar about the process and precautions for collecting environmental DNA provided by the scientists. At the sampling sites, they obtained environmental DNA samples from seawater themselves and sent the samples to the scientists via a refrigerated parcel delivery service. After collecting environmental DNA, they received fish name data from their samples and attended a webinar about survey results provided by the scientists. A cumulative total of 168 volunteers (84 pairs) participated in the program and detected 572 taxonomic groups of fish environmental DNA in the summer of 2020 and 2021. According to a questionnaire survey, more than 75% of the respondents answered that the project improved their understanding of biodiversity, marine environments, and environmental DNA. Approximately 95% of the respondents thought that environmental DNA collection work was meaningful to them. Some respondents commented on the difficulty of interpreting their fish name data, or the time and effort of selecting a sampling site. Therefore, improving the methods to communicate more information about fish name data and select sampling sites will further develop community science monitoring using environmental DNA.

Do wave exposure and drifting algae drive the functional diversity of fishes in tropical ocean-exposed sandy beaches?

Tropical ocean-exposed sandy beaches have an essential ecological function for marine fish species, which use these turbulent areas as nurseries. These habitats are characterized as homogeneous environments, but previous studies report the influence of drifting algae in providing physical structure, which increases habitat complexity and heterogeneity. This additional habitat complexity is expected to have a crucial impact on fish assemblages. Here, we analyzed the influences of wave exposure and drifting algae volume on abundance and functional diversity on two beach types: wave-dominated and tide-modified. Beach seine samplings were carried out in the rainy and dry seasons to collect the fish at each beach. Four volume categories of drifting algae were selected: bare sand, low, mid and high. A total of 97 fish species were captured. The community attributes of fishes (abundance, richness and biomass), as well as algal volume, were higher in tide-modified beaches. For abundance, three distinct patterns emerged: 1) there was a trend of decreasing herrings and anchovies compared to other species, from the bare to high-volume drifting algae in tide-modified beaches, with the opposite trend for the wave-dominated beaches; 2) L. breviceps, M. littoralis, S. naso, S. rastrifer and S. stellifer increased in abundance from the bare to high drifting algae in wave-dominated beaches; 3) P. virginicus was abundant in both beach types. These trends were accompanied by functional diversity, principally by responses in the two types of traits: diet and habitat use. The differences in habitat characteristics (wave exposure and drifting algae) among beaches affected the composition and functional diversity and consequently supported distinct fish assemblages. The presence of drifting algae in this habitat favors the attractiveness for fishes, such as larvae and juveniles, and seems to drive habitat use by tropical fishes.

DNA barcoding and misidentification of some marine fish species in Nigerian industrial trawl fishery

Identification of marine fishes across their geographical distribution is based primarily on morphological features. The ability of marine fishes to adapt to environmental changes sometimes leads to morphological differences that might give rise to wrong or misidentification of the fishes, unlike genetically based identification. Fish samples were collected with a trawl net used by demersal trawlers in Nigerian coastal waters between N 4.19823⁰ E 8.29929⁰ and N 6.18855⁰ E 3.14797⁰. The average length of the COI nucleotide sequences was approximately 584 bp. A total of 30 CO1 sequences were obtained from 18 fish species within 12 families with 97–100% identity with comparison to the Genbank database and BOLD. The average divergence within a species is 4.47%, 6.10% within a genus, and 15.94% within a family, while the maximum within a species and genus is 17.54% and 19.20% within a family. Four (4) species in the Nigerian marine environment have not been sequenced before in this study: Caranx fischeri, Pseudotolithus senegallus, Lagocephalus guentheri, and Sphyraena ensis. These findings will contribute to the barcode database of global marine fish species identification, provide baseline data for marine fishes in Nigerian waters based on the CO1 region, and serve educational purposes in universities, research institutes, fishery managers, and fish stock assessment.

Genome-wide association study for growth-related traits in golden pompano (Trachinotus ovatus)

Growth-related traits are complex and economically important traits in the aquaculture industry. Improvement of growth traits is generally considered as the main objective in breeding programs of farmed fish. The molecular basis underlying Golden pompano (Trachinotus ovatus) growth traits remains largely unknown. T. ovatus is a commercial marine fish species with a considerable market value. It is necessary to select new varieties of T. ovatus with fast growth traits, which could contribute to increased production and lower costs. In this study, the whole genome resequencing (WGS) was applied for genotyping 716 T. ovatus individuals and 4,886,850 high-quality single nucleotide polymorphism (SNP) located on 24 chromosomes were developed. A genome-wide association study (GWAS) was performed to detect SNPs and genes that are potentially related with growth traits, including body weight (BW) and body length (BL). Results indicated that 107 SNPs were significantly associated with growth traits, of which 18 SNPs were commonly shared with BW and BL traits. Furthermore, 108 genes were annotated by the identified SNPs. GO enrichment analysis suggested that the terms related with muscle growth, anabolism, and bone development were significantly enriched. Most candidate genes were known to be involved in muscle growth and bone development, some of which were reported to be associated with muscle hypertrophy in humans. This study provides useful information to understand the genetic architecture of growth-related traits and provides effective molecular markers for future genome-wide selection breeding of T. ovatus.

Fatty acids as bioindicators of organohalogen exposure in marine fish from a highly polluted estuary: First insight into small-scale regional differences

Increasing evidence has revealed the lipid-disrupting effects of organic contaminants on aquatic organisms, raising attention about the efficacy of fatty acids (FAs) as bioindicator of contaminant exposure on marine organisms. Here, we investigated the concentrations of 55 organohalogen contaminants (OHCs), 35 FAs, and their correlations in 15 marine fish species (n = 274) from the estuary outlets of the west four region (WFR) and Lingdingyang (LDY) waters in the Pearl River Estuary (PRE), respectively. Despite the similar OHC profiles, significantly higher concentrations of ∑55OHCs were detected in fish from the LDY than those in the WFR. However, FAs in the LDY fish generally contained lower proportions of polyunsaturated fatty acids than in the WFR fish. A total of 148 and 221 significant correlations between OHCs and FAs were observed in fish samples from the LDY and WFR, respectively, supporting that FAs could be efficient bioindicators of OHC stress in marine fish. However, the low overlaps (14/369) of OHC-FA correlations in fish from the two regions suggested that the bioindicators of OHCs might have spatial heterogeneity. Our results highlighted that FAs likely act as potential bioindicators of OHCs in marine fish, while the regional-specific characteristic of the bioindicators should be considered.

Growth characteristics and morphology of Paramoeba perurans from Atlantic salmon Salmo salar L. and ballan wrasse Labrus bergylta in Norway

BackgroundParamoeba perurans is the causative agent of amoebic gill disease (AGD) in Atlantic salmon Salmo salar L. and many other farmed marine fish species worldwide. The first cases of AGD in Norway were reported in 2006, and it has subsequently become established as a significant gill disease that affects the country’s salmonid aquaculture industry. Despite several decades of research on AGD, there is still a lack of knowledge of the biology of P. perurans and its interactions with its hosts and the environment.MethodsThe growth and morphology of 10 clonal isolates of P. perurans were studied. The isolates were from farmed Atlantic salmon and ballan wrasse that had been obtained from different sites along the Norwegian coast between 2013 and 2015. The morphology and population growth patterns of these clonal amoeba isolates were examined in vitro using light microscopy and real-time reverse transcription polymerase chain reaction under a range of temperatures (4, 12, 15 and 21 °C) and salinities (20, 25, 30 and 34 ‰).ResultsWe found distinct morphological differences between both locomotive and floating forms of the amoeba isolates. The locomotive amoebae of the clonal isolates varied in size (area) from 453 µm2 to 802 µm2. There were differences in the growth patterns of the clonal amoeba isolates under similar conditions, and in their responses to variations in temperature and salinity. While most of the isolates grew well at salinities of 25–34 ‰, a significant reduction in growth was seen at 20 ‰. Most of the amoeba isolates grew well at 12 °C and 15 °C. At 4 °C, amoebae grew slower and, in contrast to the other temperatures, no extended pseudopodia could be seen in their floating form. The isolates seemed to reach a plateau phase faster at 21 °C, with a higher number of smaller, rounded amoebae.ConclusionsThe differences observed here between clonal isolates of P. perurans should be further examined in experimental in vivo challenge studies, as they may be of relevance to the virulence and proliferation potential of this amoeba on gills. Potential differences in virulence within P. perurans could have implications for management strategies for AGD.Graphical

Genotypic Characterization of Infectious Spleen and Kidney Necrosis Virus (ISKNV) in Southeast Asian Aquaculture

Infectious spleen and kidney necrosis virus (ISKNV) is a species within the genus Megalocytivirus (family Iridoviridae), which causes high mortality disease in many freshwater and marine fish species. ISKNV was first reported in Asia and is an emerging threat to aquaculture with increasing global distribution, in part due to its presence in ornamental fish with clinical and subclinical infections. The species ISKNV includes three genotypes: red seabream iridovirus (RSIV), turbot reddish body iridovirus (TRBIV), and ISKNV. There is an increasing overlap in the recognized range of susceptible fish hosts and the geographic distribution of these distinct genotypes. To better understand the disease caused by ISKNV, a nucleic acid hybridization capture enrichment was used prior to sequencing to characterize whole genomes from archived clinical specimens of aquaculture and ornamental fish from Southeast Asia (n = 16). The method was suitable for tissue samples containing 2.50 × 104–4.58 × 109 ISKNV genome copies mg−1. Genome sequences determined using the hybridization capture method were identical to those obtained directly from tissues when there was sufficient viral DNA to sequence without enrichment (n = 2). ISKNV genomes from diverse locations, environments, and hosts had very high similarity and matched established genotype classifications (14 ISKNV genotype Clade 1 genomes with >98.81% nucleotide similarity). Conversely, two different genotypes were obtained at the same time and location (RSIV and ISKNV from grouper, Indonesia with 92.44% nucleotide similarity). Gene-by-gene analysis with representative ISKNV genomes identified 59 core genes within the species (>95% amino acid identity). The 14 Clade 1 ISKNV genomes in this study had 100% aa identity for 92–105 of 122 predicted genes. Despite high overall sequence similarity, phylogenetic analyses using single nucleotide polymorphisms differentiated isolates from different host species, country of origin, and time of collection. Whole genome studies of ISKNV and other megalocytiviruses enable genomic epidemiology and will provide information to enhance disease control in aquaculture.

Ecological adaptation in cod and herring and possible consequences of future climate change in the Baltic Sea

The Atlantic herring and Atlantic cod are two marine fish species that have successfully adapted to the brackish Baltic Sea, and the former is able to spawn in near-freshwater conditions in the inner Gulf of Bothnia. Here, we review the state of current knowledge concerning ecological adaptation in the two species and make an attempt to predict how they will be able to cope with future climate change. Previous whole genome sequencing studies in Atlantic herring have revealed hundreds of genetic loci underlying ecological adaptation, including several loci that show very strong associations to variation in salinity and temperature. These results suggest the existence of standing genetic variation available for adaptation to a changing environment. However, although Atlantic herring probably has the genetic potential to adapt, its future status also depends on how climate change will affect plankton production and competing species, such as sprat and three-spined stickleback. In cod, the situation is challenging, as there is only one true Baltic population, spawning east of Bornholm and then dispersing towards the east and north. This Baltic cod population is threatened by overfishing, low oxygen levels in benthic waters and generally bad physiological condition of individual fish, in addition to being completely isolated from gene flow from nearby cod populations at the entrance of the Baltic Sea.

Development and Evaluation of Recombinant B-Cell Multi-Epitopes of PDHA1 and GAPDH as Subunit Vaccines against Streptococcus iniae Infection in Flounder (Paralichthys olivaceus).

Streptococcus iniae is a severe Gram-positive pathogen that can infect a wide range of freshwater and marine fish species. In continuation of our earlier studies on the development of S. iniae vaccine candidates, pyruvate dehydrogenase E1 subunit alpha (PDHA1) and glyceraldehyde-3-phosphate dehydrogenase (GAPDH) were highly efficacious in protecting flounder (Paralichthys olivaceus) against S. iniae. In the present study, to investigate the potential of multi-epitope vaccination strategy to prevent flounder against S. iniae infection, the liner B-cell epitopes of PDHA1 and GAPDH proteins were predicted using a bioinformatics approach and were identified by immunoassay, and recombinant B-cell multi-epitopes of PDHA1 and GAPDH (rMEPIP and rMEPIG) containing immunodominant epitope-concentrated domains were expressed in Escherichia coli BL21 (DE3) and were used as a subunit vaccine to immunize healthy flounder, while recombinant PDHA1 (rPDHA1), GAPDH (rGAPDH) and formalin-inactivated S. iniae (FKC) served as controls. Then, the immunoprotection efficacy of rMEPIP and rMEPIG was evaluated by determining the percentages of CD4-1+, CD4-2+, CD8β+ T lymphocytes and surface-IgM-positive (sIgM+) lymphocytes in peripheral blood leucocytes (PBLs), spleen leucocytes (SPLs) and head kidney leucocytes (HKLs), as well as total IgM, specific IgM, and relative percentage survival (RPS) post immunization, respectively. It was found that fish immunized with rPDHA1, rGAPDH, rMEPIP, rMEPIG and FKC showed significant increases in sIgM+, CD4-1+, CD4-2+, and CD8β+ lymphocytes and production of total IgM and specific IgM against S. iniae or recombinant proteins rPDHA1 and rGAPDH, which indicated the activation of humoral and cellular immune responses after vaccination. Moreover, RPS rate of the multi-epitope vaccine rMEPIP and rMEPIG groups reached 74.07% and 77.78%, higher than that of rPDHA1 and rGAPDH (62.96% and 66.67%) and KFC (48.15%). These results demonstrated that B-cell multi-epitope protein vaccination, rMEPIP and rMEPIG, could give a better protective effect against S. iniae infection, which provided a promising strategy to design the efficient vaccine in teleost fish.

Sea temperature is the primary driver of recent and predicted fish community structure across Northeast Atlantic shelf seas.

Climate change has strongly influenced the distribution and abundance of marine fish species, leading to concern about effects of future climate on commercially harvested stocks. Understanding the key drivers of large-scale spatial variation across present-day marine assemblages enables predictions of future change. Here we present a unique analysis of standardised abundance data for 198 marine fish species from across the Northeast Atlantic collected by 23 surveys and 31,502 sampling events between 2005 and 2018. Our analyses of the spatially comprehensive standardised data identified temperature as the key driver of fish community structure across the region, followed by salinity and depth. We employed these key environmental variables to model how climate change will affect both the distributions of individual species and local community structure for the years 2050 and 2100 under multiple emissions scenarios. Our results consistently indicate that projected climate change will lead to shifts in species communities across the entire region. Overall, the greatest community-level changes are predicted at locations with greater warming, with the most pronounced effects at higher latitudes. Based on these results, we suggest that future climate-driven warming will lead to widespread changes in opportunities for commercial fisheries across the region.

Olfactory cueing responses in the early stages of a marine estuarine-dependent fish species in South Africa

Many marine fish species depend on estuaries as nurseries for their vulnerable life stages. Consequently, successful recruitment into estuaries by the larvae and juveniles of marine estuarine-dependant fish such as Rhabdosargus holubi (Sparidae) is vital to completing their lifecycles and thus maintaining populations. This species is known to be attracted to the water of riverine and estuarine origin, potentially via olfaction of chemical cues. However, the specific cues and cueing mechanisms involved in these recruitment responses have yet to be fully elucidated for many species utilising estuaries as nursery areas. In this study, choice chamber flume experiments were used to test the chemical attraction of fish to water from different sources to understand further the mechanisms and cues involved. Rhabdosargus holubi juveniles were attracted to the water of riverine and estuarine origin, as the larvae were previously shown to do. These fish were also attracted to exudates from seagrass that occur naturally in their preferred estuarine habitats. The results of the study highlight both the importance of conserving vegetated habitats and managing adequate freshwater flow into estuaries, as well as the need for more research on fish cueing into nursery areas.

Juvenile fish communities in coastal soft-bottom and shallow water habitats at the Tolo Harbour and Channel in Hong Kong, South China

Coastal soft-bottom and shallow water habitats are often key nursery grounds for marine fishes, which are important not only in supporting a rich biodiversity, but also of social-economic importance in terms of ecosystem services and fishery resources provided by these habitats. Tolo Harbour and Channel (the Tolo Area) at north-eastern Hong Kong in South China has been previously recognised as a nursery ground of marine fish species, including those that are commercially important. However, marine biodiversity and fisheries resources in this area have been jeopardized by various anthropogenic threats such as coastal development and pollution. This study aimed at providing up-to-date ecological information of juvenile marine fishes in the Tolo Area, and identifying locations with a high conservation priority. A three-year study, using beach and purse seining, was carried out to assess the current status of the juvenile fish community in coastal soft-bottom and shallow water habitats throughout the Tolo Area. A total of 171 species/taxa were recorded, including the IUCN-red-listed vulnerable species of seahorse Hippocampus kuda. Juvenile individuals were found in 155 of the recorded species/taxa. Juvenile fishes were dominated by small and/or fast-growing species. Significant spatial and seasonal variations in juvenile fish assemblages were recorded in the Tolo Area. Diel differences in juvenile fish assemblages were also recorded in sites where additional night-time surveys were conducted. Species richness was generally higher in outer Tolo Harbour and inner Tolo Channel, and priority should be given to the coastal soft-bottom and shallow water habitats in these areas to protect the species diversity and fishery resources. The results of this systematic study provide an ecological baseline of juvenile fishes in the Tolo Area for future monitoring and conservation of the marine fish communities.

Intestinal Fatty Acid Binding Protein Gene Variation in European Sea Bass (Dicentrarchus labrax)

Fatty acid binding proteins (FABPs), which belong to the multigene family, play an important role in homeostasis, lipid uptake and transport in tissues. Intestinal fatty acid binding protein (I-FABP) is a small cytosolic protein and is highly active in intracellular fatty acid metabolism in fish gut. The European Sea bass (Dicentrarchus labrax) is an important commercial marine fish species in the Mediterranean region. In the present study, the partial I-FABP gene region of European sea bass was sequenced for detecting single nucleotide polymorphism (SNP) using DNA sequencing. We identified one SNP (g.2450T>C) in the noncoding region of the I-FABP gene in European sea bass. In this study, the relationship between the g.2450T>C locus of the I-FABP (fabp2) gene and body length, post-anal length, body weight and fillet weight was found significant (PC locus in I-FABP which could affect growth and muscle fat content, can be used for marker-assisted selection (MAS) studies in European sea bass.

Nutritional composition, heavy metal contents and lipid quality of five marine fish species from Cameroon coast

The nutritional value, heavy metal content and lipid quality of five marine fishes from, Cameroon coast were be investigated. Fish samples from Ilisha africana, Sardinella, maderensis, Cyprinus carpio, Arius parkii and Ethmalosa fimbriata were collected at, the Douala sea port, carried to the laboratory, washed with distilled water and, processed. Proximal composition, minerals, lipid quality and heavy metal analyses, were performed using AOAC standard methods. Results show that proteins (18.43%), and lipids (3.69%) contents were higher in Ilisha africana. Cyprinus carpio had the, highest ash content (4.59%). Contents of minerals and heavy metals were found as, follows: P > Mg > K > Ca > Na > Fe > Zn > Cu > Mn and Hg > Pb > Cd > As. Oils extracted from C. carpio, A. parkii and E. fimbriata were semi-siccative while those of I. africana and S. maderensis were siccative. Thus, these fish species are good sources of proteins and, minerals that can be used for managing mineral deficiencies in humans and animals.

Navigating the scales of diversity in subtropical and coastal fish assemblages ascertained by eDNA and visual surveys

Environmental DNA (eDNA) metabarcoding emerges as a powerful method, allowing a more exhaustive investigation of fish fauna than any other methods. Yet, the general use of eDNA as a replacement of traditional methods such as visual surveys or physical sampling remains debatable. Therefore, a prior understanding of eDNA’s spatial resolution is necessary. This study aimed to compare the assessments of fish diversity at three spatial scales by eDNA, underwater visual census (UVC), and diver-operated video (DOV) surveys across 21 reef sites in northern Taiwan. The specific objectives were to explore the regional species pool (γ-diversity), reveal spatial patterns of fish assemblages (β-diversity), and disentangle the relationships between fish assemblages and benthic composition (α-diversity). At the γ-diversity level, a total of 438 marine fish species were detected across methods. eDNA exhibits an extraordinary power to explore the regional species pool given sufficient replication, a power which is unachievable by DOV and UVC. At the β-diversity level, all the methods successfully revealed the same spatial patterns of beta diversity and the distance decay of similarity in fish assemblages. At the α-diversity level, none of the methods is capable of investigating the entire resident fish fauna, but visual surveys are more suitable for scrutinizing interactions between fish and benthos. Instead of undiscriminatingly recommending a combination of eDNA with traditional survey methods, we suggest implementing specific surveys in accordance with the ecological questions of interest.

Estimation of ecological carrying capacity of small-scale fish in marine ranch of the Pearl River Estuary, China

Small-scale marine fish are a critical part of the food chain and energy flow of the marine ecosystem. The ecological carrying capacity (ECC) is important to better understand the marine fishery ecosystems. However, few studies have focused on the ECC of small-scale marine fish species. This study proposed the estimation model of the ECC for small-scale fish species, and estimated the ECC of 18 small-scale fish species in the targeted sea areas (artificial reef area near Wanshan Island, WAR; non-artificial reef area near Wanshan Island, N- WAR; artificial reef area near Miaowan Island, MAR; non-artificial reef area near Miaowan Island, N- MAR; and control area near Wailingding Island, C-WLD) in the Pearl River Estuary (PRE), China. The result shows that the ECC of the 18 small-scale fish species in the marine ranch of the PRE is ranged from 85.92 t/km 2 to 551.33 t/km 2. In terms of magnitude: WAR > MAR > N- WAR > N- MAR > C-WLD, and their ECCs accounted for 50.68%, 16.89%, 13.74%, and 10.79% and 7.90% of the total ECC, respectively. These findings show that artificial reefs can improve the fishery resource carrying capacity and can therefore be beneficial both ecologically and economically.

Water temperature explains part of the variation in basal plasma cortisol level within and between fish species.

Within the thermal tolerance range of fish, metabolism is known to escalate with warming. Rapid thermic changes also trigger a series of physiological responses, including activation of the stress axis, producing cortisol. Fish have adapted to their environment by producing a low level of plasmatic cortisol when unstressed (basal), so that thriving in their natural temperature should not impact their basal cortisol levels. Yet, surprisingly, little is known on how temperature affects cortisol within and between fish species. Here, we conducted a phylogenetic meta-analysis to (1) test whether temperature can explain the differences in basal cortisol between species and (2) evaluate the role of temperature on differences in cortisol levels between individuals of a same species. To do this, we retrieved basal plasma cortisol data from 126 studies, investigating 33 marine and freshwater fish species, and correlated it to water temperature. Intra-species variability in basal plasma cortisol levels was further investigated in two species: the European sea bass Dicentrarchus labrax and the Nile tilapia Oreochromis niloticus. Factors such as life stage, sex and weight were also considered in the analyses. Overall, our phylogenetic analysis revealed a clear positive correlation between basal cortisol level and the temperature at which the fish live. The role of temperature has also been confirmed within D. labrax, while it failed to be significant in O. niloticus. In this paper, the influence of habitat, life stage, sex and weight on basal plasma cortisol levels is also discussed. Since some abiotic parameters were not included in the analysis, our study is a call to encourage scientists to systematically report other key factors such as dissolved oxygen or salinity to fully depict the temperature-cortisol relationship in fishes.

Impacts of marine fishing ban on the ecology of hilsa In the Nijhum Dwip Seascape in Bangladesh

Bangladesh government has imposed a 65-day marine fishing ban since 2015 to conserve marine fisheries, particularly to boost hilsa (Tenualosa ilisha) production. However, the ecological impacts of the marine fishing bans on water quality and hilsa’s growth are not assessed yet. Thus, this study aims to contribute here using data from coastal waters and fish from pre-contacted fishers in the Nijhum Dwip seascape during and outside the fishing ban in 2021 – 2022. Data were analyzed using R software. The measured mean dissolved oxygen, temperature, pH, electrical conductivity, total dissolved solids, and transparency of the sample water were 7.1 ± 1.13 mg/l, 31.1 ± 0.71°C, 8.45 ± 0.07, 40000 ± 2828 μS/cm, 18000 ± 1414 mg/L and 63.5 ± 2.12 cm at 1 week prior to the ban ends (July) and 8.45 ± 0.21 mg/l, 22.35 ± 0.49°C, 8.45 ± 0.07, 20500 ± 1060.66 μS/cm, 10350 ± 212.13 mg/l and 63.5 ± 7.78 cm before the ban starts (February). The values might be varied due to seasonal differences. The mean length (38 cm) and weight (601 g) of sampled hilsa during the ban periodwere comparatively larger than the mean length (29 cm) and weight (229 g) of hilsa which were sampled during the outside fishing ban period. Therefore, this study concludes that the marine fishing ban has positive impact on the growth and size of hilsa. This study suggests that further research is required to assess the fishing ban’s impact on the growth and production of other coastal and marine fish species across the Bay of Bengal. Dhaka Univ. J. Biol. Sci. 32(1): 33-43, 2023 (January)

DNA Barcodingof Commercial Fish Sold in MuarFish Market, Johor

Due to the high demand in the fisheries market, species identification is vital for commercial fish to avoid mislabeling and fraud in marketplaces. The increasingly threatening human activities like overfishing, blast fishing, poison fishing, and trawling have become the major threats to fish and caused an urgent need for documentation of both marine and freshwater fishes. Commercial fish products sometimes are sold by their parts, such as fins which further create confusion for identification purposes.Morphological identification also requires highly skilled ichthyologists to avoid misidentification. Thus, identification through DNA barcoding can be utilized as it holds the potential for accurate and rapid identification. Here we identified the commercial marine fish species sold in Muar Fish Market, Johor, using the Cytochrome Oxidase subunit I (COI) gene of mitochondrial DNA (mtDNA). A 700 base-pair sequence of the COI region was targeted by amplifying extracted DNA from 28 fin samples collected from the fish market. From 28 samples, we successfully sequenced 16 samples, and by using phylogenetic analysis, (Neighbor-Joining (NJ), Maximum Parsimony (MP) and Bayesian Inference (BI)) we successfully identified the samples belonging to nine families (Scombridae, Platycephalidae, Carangidae, Ariidae, Polynemidae, Coryphaenidae, Sphyraenidae, Muraenesocidae, Engraiulidae), 12 genera and 16 species. This study reports the first documentation of commercial fish sold in Muar through the DNA barcoding technique. This technique should be expanded further to identify any species with important conservation implications, such as endangered species, for improved management of fisheries in Malaysia

Length–weight Relationships of 19 Marine Fish Species from the Southern Coast of Black Sea Associated with Small-Scale Fisheries

This study presents the length-weight relationship (LWRs) estimates for 19 marine fish species belonging to 12 families from the southern coast of the Black Sea. The species were sampled using small-scale fishing gears such as gillnets and trammel nets at depths of 0-120 m from 2010 to 2021. The LWRs were calculated by the linear regression of natural log-transformed data concerning W = a × TLb. Growth type was evaluated according to Pauly’s t-test. The slope (b-value) ranged between 2.5643 and 3.5745, corresponding to the commonly expected range (2.50–3.50) except for Spicara flexuosum. The coefficient of determination values (r2) were above 0.90 except for Chromis chromis, Gobius niger, Neogobius melanostomus, Sardina pilchardus and Uranoscopus scaber. This study targeted specimens from small-scale fisheries-related gears; therefore, the results are primarily of interest to local fisheries management. The new LWRs cover substantially larger TLmax values than any previous study, and thus we can assume that all size classes of the species are adequately represented, and the new LWRs are more significant and species-specific than any previous estimate. This paper offers new insights into LWRs for the Umbrina cirrosa from the southern coast of the Black Sea.