Fish Species Research Articles

Fish oil replacement with different vegetable oils in Onychostoma macrolepis: Effects on fatty acid metabolism based on whole-body fatty acid balance method and genes expression.

To evaluate the fatty acid (FA) metabolism status and possibility as a DHA source of farmed Onychostoma macrolepis, a total of 168 fish (2.03 ± 0.23 g) were fed four diets supplemented with fish oil (FO), linseed oil (LO), soybean oil (SO), and a mixture of LO and SO oil (MO), respectively, for 70 days. Body FA compositions were modified reflecting dietary FAs. Comparing liver and intestine fatty acids with fish fed four diets, the content of ARA in fish fed SO was significantly higher than others (P < 0.05), but showed no difference in muscle. The tissue FA profile showed that the FO-fed group successfully deposited DHA, while the LO-fed group converted ALA to DHA effectively, as well as the liver and intestine EPA was notably highest in the FO group, whereas no difference between the FO and LO group in the muscle. The FA results showed that the DHA contents in the muscle of Onychostoma macrolepis are at a medium-high level compared with several other fish species with the highest aquaculture yield. Correspondingly, in the fish fed diet with LO, SO, and MO, the genes of most FA biosynthesis, transportation, and transcriptional regulation factors were increased in the liver and muscle, but no significant difference was observed in the gene expression of Elovl4b, FATP1, and FABP10 in the muscle. In addition, the enzyme activity involved in PUFA metabolism was higher in fish fed vegetable oil-based diets, corroborating the results of the gene expression. Increased in vivo elongase and desaturase (Δ5, Δ6, and Δ9) activities were recorded in fish fed fish oil-devoid diets, which resulted in the appearance of products associated with elongase and desaturase activities in fish. Besides, as the specific n-3 PUFA synthesis substrate, the dietary supplementation of ALA not only retains most of the nutrition value but also ensures the muscular texture, such as fiber diameter and density. It is concluded that farmed O. macrolepis owns strong n-3 LC-PUFA biosynthetic capacity and high DHA contents so it can be a good DHA source for the population.

Assessing Colouration in Ichthyology: Insights from the Melanophore Index Perspective

Fish colouration significantly influences various aspects of their biology, including communication, camouflage, and mate selection. Among the pigment cells responsible for generating colours, melanophores are particularly significant due to their ability to produce dark pigments called melanin. The Melanophore Index (MI) quantitatively evaluates melanophore density and distribution across different fish species. This comprehensive review delves into the significance of fish colouration, the biology of melanophores, methods for assessing MI, factors influencing MI variations, and the ecological and evolutionary implications of MI in fish populations. By synthesizing current research and highlighting gaps in knowledge, this review aims to provide a foundational understanding of assessing fish colouration through the lens of the Melanophore Index.

Myxobolus acanthogobii Hoshina, 1952 and Myxobolus selari n. sp. (Myxosporea: Myxobolidae) infecting brain of commercial fishes in Terengganu, Malaysia.

Myxosporean infection in marine water fishes has drawn less attention than in freshwater fishes, which resulted in a higher taxonomic variety in freshwater in Malaysia. This study aimed to address the gap by conducting a myxosporean survey on two commercially significant marine fish species, Nemipterus furcosus (Valenciennes) (Eupercaria incertae sedis: Nemipteridae) and Selar crumenophthalmus (Bloch) (Carangiformes: Carangidae), collected from the northeastern part of peninsular Malaysia. During the examination of the organs, two distinct Myxobolus Bütschli, 1882 species were discovered in the brain tissue of these fishes, despite the absence of any observable pathological signs. The two Myxobolus species were characterized through morphometry, morphology, and analysis of partial small subunit ribosomal RNA (18S rDNA) gene. As a result, Myxobolus acanthogobii Hoshina, 1952, which infects 2.3% of N. furcosus, is synonymous with a myxobolid species commonly found in Japanese waters, based on its morphological traits, tissue tropism, and molecular diagnostics. Furthermore, a novel species, Myxobolus selari n. sp., was described, infecting the brain of one (11%) individual S. crumenophthalmus. This unique species displayed distinctive features, placing it within a well-supported subclade primarily comprising brain-infecting myxobolids. Maximum likelihood analysis further revealed the close relationships among these brain-infecting myxobolids, underscoring the significance of tissue tropism and host taxonomy for myxobolids. This study represents the initial documentation of Myxobolus species within the southern South China Sea, shedding light on the potential diversity of marine myxosporean in this region. This article was registered in the Official Register of Zoological Nomenclature (ZooBank) as urn:lsid:zoobank.org:pub:7C400E35-7CB8-4DEE-92B7-F75FF3926441.

Assessing Diet &amp; Trophic Position of Fish in Chenderoh Reservoir, Malaysia: SCA &amp; SIA Approach

The present study assessed and compared the diet and trophic positions (TP) of two carnivorous fish H. macrolepidota and C. ocellaris from Chenderoh Reservoir, Malaysia. The focal goal of the study was to understand the effects of invasive non-indigenous species (NIS), C. ocellaris, on the native indigenous (IS) fish species, H. macrolepidota. Data were acquired from September 2014 to February 2015 within the study area. The assessment was grounded in stomach content analysis (SCA) and stable isotope analysis (SIA), which collectively clarified the feeding habits and trophic positions (TP) of these selected fish. In total, 184 fish samples (comprising 64 individuals of H. macrolepidota and 120 individuals of C. ocellaris) underwent stomach content analysis (SCA). Additionally, 24 individuals (12 of H. macrolepidota and 12 of C. ocellaris), sampled from December 2014 to February 2015, were selected for stable isotope analysis (SIA). The mean RGL values for H. macrolepidota and C ocellaris were 0.98 ± 0.18 and 1.10 ± 0.15 (Mean ± SD), respectively, aligning with known ranges for carnivorous fish. These values also clarified that both species occupy higher TP in the food web as tertiary or quaternary consumers. SCA findings also revealed that fish and crustaceans were the predominant food categories for H. macrolepidota, while C. ocellaris predominantly fed on fish. The mean stomach fullness index (MSF) and the gastrosomatic index (GSI) corroborated the differences in the foraging performance of the fishes, with C. ocellaris having a higher MSF (2.03) compared to H. macrolepidota (0.65). These implied that C. ocellaris had plentiful of food and encountered fewer diet-related challenges in the ecosystem. From SIA, δ13C values indicated that the primary carbon sources for both species are C3 plants, particularly aquatic vegetation. Further, δ15N values further ensured that both H. macrolepidota and C. ocellaris are carnivorous in nature and occupy higher TP in the ecosystem.

How to improve fishery eco-efficiency by building marine ranch in China

Based on the panel data of the province and municipality in 2010–2021, this paper measures the fishery eco-efficiency by using the SBM-DEA model and empirically analyses how China’s marine ranch construction improves the fishery eco-efficiency by using the double-difference fixed-effect model. The results show that, firstly, China’s marine ranch construction can improve the fishery eco-efficiency. Secondly, China’s marine ranch construction promotes fisheries eco-efficiency by improving the input efficiency of labor, fish species, fishing vessel, fishery technology extension, aquaculture area and by reducing pollutant outputs. Thirdly, the fishery eco-efficiency of the marine ranch construction region has increased annually since 2015, and technological changes, scale efficiency changes and technical efficiency changes can all contribute to the fishery eco-efficiency improvement, and increase in order. Based on the results of the empirical analyses, this paper proposes policy recommendations to improve the fishery eco-efficiency in the conjunction with the construction of marine ranch in China.

Leveraging relationships between species abundances to improve predictions and inform conservation

Abstract Many management and conservation contexts can benefit from understanding relationships between species abundances, which can be used to improve predictions of species occurrence and abundance. We present conditional prediction as a tool to capture information about species abundances via residual covariance between species. From a fitted joint species distribution model, this framework produces a species coefficient matrix that contains relationships between species abundances. The species coefficients allow co‐observed species to be treated as a second set of predictors supplementing covariates in the model to improve prediction. We use simulations to demonstrate the potential benefits and limitations of conditional prediction across data types and species covariance before applying conditional prediction to two management contexts with real data. Simulations demonstrate that conditional prediction provides the largest benefits to continuous data and when there is residual covariance between many species. In our first application, we show that conditioning on other species improves in‐sample and out‐of‐sample predictions of fish and invertebrate species, including Atlantic cod. In our second application, we show that the species coefficient matrix can be used to identify bird species at risk of nest parasitism by Brown‐headed Cowbirds. Synthesis and applications. We present guidelines for using conditional prediction, which can help understand relationships between species abundances, improve predictions and inform conservation in a variety of contexts.

Spatial and Temporal Changes in the Fish Fauna of a Low-Inflow Estuary following a Mass Mortality Event and Natural and Artificial Bar Breaches

Estuaries that become closed from the ocean through the formation of a sand bar are particularly susceptible to degradation and often experience poor water quality and fish kills. Sampling was conducted seasonally for two years in the deeper waters of the Vasse–Wonnerup (southwestern Australia) after a large fish mortality event to identify the fish species present and determine if richness, abundance, diversity and faunal composition differed among regions and over time. Species richness, abundance and diversity were far greater in the downstream regions than in the upstream regions, reflecting patterns in salinity. Catch rates of two marine estuarine-opportunist mugilids (Mugil cephalus and Aldrichetta forsteri) and an estuarine-resident sparid (Acanthopagrus butcheri), which were the species most affected by the mortality event, were relatively stable. It is suggested that before sampling commenced, mugilids had entered the estuary following an artificial sand bar breach, while the loss of 0+ (new recruits) A. butcheri in the mortality event and subsequent recruitment failure prevented stocks from increasing. Temporal shifts in fish composition were driven by less abundant species, which utilized the estuary more opportunistically. Increases in the occurrences and abundances of these species coincided with an open bar and salinities close to those of seawater. The data also show how the estuary responds to differing hydrodynamic phases and artificial breaches.

Development and validation of a TaqMan-based qPCR assay for reliable detection of invasive sailfin catfishes (Pterygoplichthys spp.) through measurements of environmental DNA

Sailfin catfishes (Pterygoplichthys spp.) are a group of fishes introduced to several freshwater habitats across the globe. Sailfin catfishes are a hard-armoured fish with no economic importance as a food species. These catfishes have been reported to be affecting the growth of several economically valuable species that are native to different freshwater ecosystems. In this manuscript, we developed a TaqMan-based assay targeting the mitochondrial cytochrome c oxidase subunit 1 (COX1) gene, to specifically detect the presence of catfishes by environmental DNA (eDNA) measurements. The developed assay was screened against 16 species of fish and mussel that co-occur in the habitats along with sailfin catfishes, and the qPCR reaction did not have any non-target amplifications. The assay was further validated under laboratory conditions by measuring eDNA from tanks having different biomass of catfishes (1 and 0.5 g L−1), and the copy number of the amplified product was directly proportional to the biomass maintained in the tanks. Overall, the study provides a robust molecular tool based on eDNA measurements to facilitate detection of invasive sailfin catfishes and, in turn, contributes towards the management of the invaded habitats.

Challenges in downstream dam passage and the effect of dam removal on Atlantic salmon (Salmo salar) smolt migrations.

Migration is critical for life-cycle completion in diadromous fish species. River connectivity is vital in facilitating these large-scale movement events, but the extent of present-day river fragmentation can interfere with these migrations. Fish passage solutions (FPSs) are commonly implemented with the aim of improving river connectivity. In our study, we investigated the performance of two types of FPSs, spill regimes and complete dam removal, on Atlantic salmon (Salmo salar) smolt migrations. We used acoustic telemetry to monitor migration behavior and passage success of 120 wild smolts released in three different groups/sites: one group with two dams to pass to reach the river mouth, a second group with one dam to pass, and a control group without any barriers to pass (upstream of a recently removed hydroelectric dam). Smolt passage probabilities were similar for the two studied dams (87% and 86%) but showed variation in path choice, delay times, and loss rates. Passage success was influenced by several factors, such as body size, diel period, and water temperature, but not flow. Cumulative passage success to the river mouth was 61%, with most individuals being lost within lentic river stretches, either in the forebays of hydroelectric power stations or in naturally wide river stretches. Within the recently rehabilitated river sections (post dam removal), passage speeds were significantly faster than all other sections of the river (post-rehabilitation x¯ = 56.1 km/day) with significantly faster speeds compared to pre-rehabilitation (pre-x¯ = 28.0 km/day). Our findings provide valuable information on the benefits of dam removal and highlight the need for further rehabilitation measures in upriver reaches where barriers still affect downstream passage.

Puzzling parrotfishes: Radiocarbon age validation and updated longevity estimates for western Atlantic species in support of sustainable fisheries management

For management efforts to succeed in Caribbean fisheries, local fishers must support and be willing to comply with fishing regulations. This is more likely when fishers are included in a stock assessment process that utilizes robust scientific evidence, collected in collaboration with fishers, to evaluate the health of fish stocks. Caribbean parrotfishes are important contributors to coral reef ecosystem health while also contributing to local fisheries. Scientifically robust stock assessments require regional species-specific information on age-based key life history parameters, derived from fish age estimates. Evaluation of the accuracy of age estimation methods for fish species is a critical initial step in managing species for long-term sustainable harvest. The current study resulted from a collaborative research program between fish biologists and local fishers investigating age, growth, and reproductive biology of the seven parrotfish species landed in U.S. Caribbean fisheries; specifically, we validated age estimation for stoplight parrotfish Sparisoma viride and queen parrotfish Scarus vetula. This is the first study to directly validate age estimation for any parrotfish species through analysis of Δ14C from eye lens cores. Our age estimation validation results show that enumeration of opaque zones from thin sections of sagittal otoliths for a Sparisoma and a Scarus species provides accurate age estimates. The oldest stoplight parrotfish and queen parrotfish in the Δ14C age estimation validation series were 14 y and 16 y; while the oldest stoplight parrotfish and queen parrotfish we aged to-date using the Δ14C validated age estimation method were 20 y and 21 y, respectively. Fish longevity (maximum age attained/life span) is a key life history parameter used for estimation of natural mortality, survivorship, and lifetime reproductive output. Past reviews on parrotfishes from the Pacific and Atlantic concluded that most Caribbean/western Atlantic parrotfish species are relatively short-lived with estimated maximum ages ranging from 3–9 y. However, information from our collaborative research in the U.S. Caribbean combined with recently published age estimates for Brazilian parrotfish species indicate that many western Atlantic parrotfishes are relatively long-lived with several species attaining maximum ages in excess of 20 y.

Coexisting in the Surf Zone: Age and Feeding Habits of the Spotted Seabass (Dicentrarchus punctatus) and European Seabass (Dicentrarchus labrax) on the Gulf of Cádiz Beaches (Southwest Iberian Peninsula)

Various commercial fish species utilize different coastal habitats as nurseries in their juvenile stages, with surf zones being particularly crucial due to the protection and abundant food resources they offer. Among the species that rely on these areas are the spotted seabass (Dicentrarchus punctatus) and the European seabass (Dicentrarchus labrax). This study aimed to investigate the age and feeding habits of surf zone specimens of these species and explore their environmental adaptations. The average size for D. punctatus was 16.94 ± 4.05 cm, and for D. labrax, it was 23.23 ± 6.30 cm. The length–weight relationship for D. punctatus was TW = 0.013*TL2.885 (parameter a: 95% CI: 0.012–0.014; parameter b: 95% CI: 2.854–2.917), and for D. labrax, it was TW = 0.008*TL3.095 (parameter a: 95% CI: 0.006–0.009; parameter b: 95% CI: 3.040–3.151). In both D. punctatus (79.20%) and D. labrax (75.92%), the predominant age classes were 1+ and 2+. Significant variations in age class abundance were observed in D. punctatus based on the time of day, lunar phase, and season, while D. labrax showed variations only by season. A diet analysis revealed that both species primarily consume mysids and fish, with D. punctatus showing dietary variations related to the time of day, lunar phase, and season, and D. labrax showing variations with the time of day and season.

Evaluation of heavy metal accumulation and associated human health risks in three commercial marine fish species from the Aegean Sea, Türkiye

This study investigates the presence and concentrations of ten specific heavy metals in the muscle tissues and gonads of three commercially important marine fish species: Garfish (Belone belone), European barracuda (Sphyraena sphyraena), and Anglerfish (Lophius piscatorius) collected from the Aegean Sea in Türkiye. The results indicate variations in metal accumulation, both between genders and among species. The fish species tend to accumulate higher levels of heavy metals in their gonads than in muscle tissues (p&lt;0.05). While Cr, Cd, and Pb were not detected, Zn, Cu, and Fe are the predominant metals in muscle tissues due to their essential biological roles. However, within toxic elements, Hg was predominant, and L. piscatorius, a benthic fish, exceeded its recommended safety limits. A health risk assessment suggests that except for L. piscatorius, consuming these fish species from the Aegean Sea is generally safe, with estimated weekly intake (EWI) values below permissible limits. Total Hazard Quotient (THQ) values for most metals are below 1, indicating no significant non-carcinogenic health risks for consumers. This study emphasizes the critical need for regularly monitoring heavy metal levels in marine fish from the Aegean Sea, Turkiye. While overall safety in consuming these fish is highlighted, exceptions exist, notably concerning Hg levels in L. piscatorius. Therefore, persistent monitoring of heavy metal concentrations, especially in L. piscatorius, is advised to ensure ongoing safety and mitigate potential risks of metal accumulation.

Characterization of Fish Skin Hydrolysates Exhibiting Dipeptidyl Peptidase IV Inhibitory Activity

Dipeptidyl peptidase IV (DPP-IV) inhibitors are antidiabetic drugs that can lower blood sugar levels. There are still few reports on the DPP-IV inhibitory activity of peptides obtained from discarded fish skin. Therefore, we prepared various enzymatic hydrolysates using the skins of six fish species and investigated their DPP-IV inhibitory effects. As a result, it was found that the DPP-IV inhibitory activity of yellowtail hydrolysate by Alcalase was higher than that of other enzymes. In addition, the IC50 after ethanol fractionation was found to be lower in yellowtail and eel skin hydrolysate. Amino acid composition analysis showed that the hydrolysate obtained from the skin of the yellowtail contained the highest amount of Gly, followed by Pro, Hyp, and Ala, indicating that it was a peptide derived from type I collagen. Fractionation with ethanol showed that the DPP-IV inhibitory components were contained in the low molecular weight fraction. The artificial digestion test observed no DPP-IV inhibitory activity or average molecular weight change. The DPP-IV inhibitory peptide obtained from fish skin has the potential to be applied as a food material to various food products.

Antibiotic resistance profiles of sentinel bacteria isolated from aquaculture in Cambodia

ABSTRACT The misuse of antibiotics and the emergence of antimicrobial resistance (AMR) is a concern in the aquaculture industry because it contributes to global health risks and impacts the environment. This study analyzed the AMR of sentinel bacteria associated with striped catfish (Pangasianodon hypophthalmus) and giant snakehead (Channa micropeltes), the two main fish species reared in the pond culture in Cambodia. Phenotypic and genotypic characterization of the recovered isolates from fish, water, and sediment revealed the presence of bacteria, such as 22 species belonging to families Aeromonadaceae, Enterobacteriaceae, and Pseudomonadaceae. Among 48 isolates, Aeromonas caviae (n = 2), Aeromonas hydrophila (n = 2), Aeromonas ichthiosmia (n = 1), and Aeromonas salmonicida (n = 4) were detected. Both A. salmonicida and A. hydrophila are known as fish pathogens that occur worldwide in both fresh and marine water aquaculture. Antibiotic susceptibility testing for Enterobacteriaceae and Pseudomonadaceae species and six antibiotics for Aeromonadaceae species revealed antibiotic resistance patterns of 24 (50%) isolates among the 48 isolates with higher multiple antibiotic resistance index scores (&amp;gt;0.2). All the isolates of Enterobacteriaceae were susceptible to ciprofloxacin. Ciprofloxacin is a frontline antibiotic that is not recommended for use in aquaculture. This study expands our knowledge of the AMR status in aquaculture farms, which is very limited in Cambodia.

Ecological Flows Assessment of Significant Fish Species in Iril River, Northeast India Through PHABSIM

Background: Freshwater fishes are facing alarming threats due to various anthropogenic activities. The present study estimates the ecological flow requirements for Bangana dero and Wallago attu fish species in the Iril River through a habitat modeling approach. Methods: The habitat suitability modeling of the target species was carried out using the physical habitat simulation model (PHABSIM). PHABSIM model was developed for the river stretch extending about 6,000 m in Iril River. 11 cross-sections at a distance of about 500 m were specified in the model. In the model, habtae was set to run and weighted usable area (WUA) was obtained as output from the habitat model. Result: The highest WUA for the two fish species is estimated at 21 cumecs of discharge. The mean flow of the Iril River is about 27.7 cumecs, which is 6.7 cumecs higher than the optimal ecological flow requirements. The estimation of ecological flow requirements is required to have a better understanding of Weighted Usable Area (WUA) for planning and management strategies. This information may enable stakeholders to develop ameliorative strategies and adopt meaningful measures suitable for the conservation of significant fish species.

Database construction and comparative genomics analysis of genes involved in nutritional metabolic diseases in fish

Nutritional metabolic diseases in fish frequently arise in the setting of intensive aquaculture. The etiology and pathogenesis of these conditions involve energy metabolic disorders influenced by both internal genetic factors and external environmental conditions. The exploration of genes associated with nutritional and metabolic disorder has sparked considerable interest within both the aquaculture scientific community and the industry. High-throughput sequencing technology offers researchers extensive genetic information. Effectively mining, analyzing, and securely storing this data is crucial, especially for advancing disease prevention and treatment strategies. Presently, the exploration and application of gene databases concerning nutritional and metabolic disorders in fish are at a nascent stag. Therefore, this study focused on the model organism zebrafish and five primary economic fish species as the subjects of investigation. Using information from KEGG, OMIM, and existing literature, a novel gene database associated with nutritional metabolic diseases in fish was meticulously constructed. This database encompassed 4583 genes for Danio rerio, 6287 for Cyprinus carpio, 3289 for Takifugu rubripes, 3548 for Larimichthys crocea, 3816 for Oreochromis niloticus, and 5708 for Oncorhynchus mykiss. Through a comparative systems biology approach, we discerned a relatively high conservation of genes linked to nutritional metabolic diseases across these fish species, with over 54.9 % of genes being conserved throughout all six species. Additionally, the analysis pinpointed the existence of 13 species-specific genes within the genomes of large yellow croaker, tilapia, and rainbow trout. These genes exhibit the potential to serve as novel candidate targets for addressing nutritional metabolic diseases.

Buoyancy control and air breathing in royal knifefish (Chitala blanci) and a new hypothesis for the early evolution of vertebrate air-breathing behaviors.

We present the first description of inspiration-first air breaths in royal knifefish, Chitala blanci, a ray-finned fish known to use four-stroke air breaths. Four-stroke breaths are used by nearly all ray-finned fish species that use their gas bladder to breathe air and are the ancestral breath type of ray-finned fishes. Interestingly, one such species, Amia calva, is known to perform two distinct breath types. Amia use four-stroke breaths when they need more oxygen and performs inspiration-first breaths to restore buoyancy. We observed that C. blanci also performs inspiration-first breaths and tested whether the two breath types are performed for the same functions in C. blanci as they are in Amia. We recorded the frequency of each breath type when exposed to aquatic hypoxia and two conditions of oxygen availability. We found that C. blanci performed more four-stroke breaths (81% ± 15% of total breaths) than inspiration-first breaths when exposed to aerial normoxia but performed more inspiration-first breaths (72% ± 40%) than four-stroke breaths when exposed to aerial hyperoxia. These patterns match those described for Amia and indicate that C. blanci performs four-stroke breaths in response to oxygen depletion and performs inspiration-first breaths to maintain buoyancy. Few studies have examined the role of air-breathing in buoyancy regulation. Decreasing buoyancy, rather than oxygen availability, to stimulate air breaths may reveal that inspiration-first breaths are more common among fishes than we are aware. We consider this possibility and present a new hypothesis for the origin and early evolution of air breathing in vertebrates.

Implications of Heavy Metal Accumulation in Fish Feed, Water, Sediment, and Different Fish Species in a Polyculture System.

Heavy metal bioaccumulation in organisms is primarily a result of dietary uptake. The current study examines the concentrations of heavy metals (Pb, Cd, Cr, and Cu) in fish feed, water, sediment, and three fish species (Catla catla, Labeo rohita, and Cyprinus carpio) from different feeding zones in a polyculture pond system. Furthermore, associated human health risks were also evaluated. The fish samples (n = 25 for each species) were collected from 10 different fish ponds in the Kohat district, Pakistan. Heavy metals were determined using an atomic absorption spectrometer. Results revealed higher concentrations of heavy metals in sediment, followed by water. However, the concentration of heavy metals in fish feed was lower than the standard limits. In the case of fish, the bottom feeder (C. carpio) notably exhibited higher (P < 0.05) levels of heavy metals than the column feeder (L. rohita) and surface feeder (C. catla) fish. Moreover, in the liver of all fish species, the bioaccumulation of heavy metals was higher, followed by the gills. Principal component analysis (PCA) demonstrated a strong correlation of heavy metals in C. carpio gills, flesh, feed, and pond water, while the heavy metals in the liver correlated with the detected metals in sediment. The human health risk analysis shows that bottom feeder fish had higher estimated daily intake (EDI), target hazard quotient (THQ), and hazard index (HI) values (> 1). Consequently, the exposed population may experience adverse health effects. The findings of this study suggest that the bottom feeder (C. carpio) bioaccumulates a higher concentration of heavy metals than column (L. rohita) and surface feeder (C. catla) in the polyculture system.

Urbanization effects on growth and otolith asymmetry in Chrysichthys nigrodigitatus and Oreochromis niloticus within tropical coastal lagoon watersheds

In this study, we investigated the growth dynamics and otolith shape asymmetry of two fish species, Chrysichthys nigrodigitatus (CN) and Oreochromis niloticus (ON), within urbanized watersheds of the southern lagoon system, Nigeria. Using the von Bertalanffy growth model (VBGM), in addition to sediment metal concentration indices such as the average shale content, index of geoaccumulation (Igeo), contamination factor (CF), pollution load index (PLI), and potential ecological risk (PER) index, contamination levels were classified, and ecological risks were assessed. Notably, a lower growth potential (t0) was observed in CN at Ikorodu than at Epe, with similar trends for ON in the Epe during the dry season. Otolith asymmetry patterns, particularly in the CN at Ikorodu and ON in the Epe during the dry season, exhibited distinct ecological variations, indicating heightened stress levels at Ikorodu. Sediment analyses revealed moderate to strong contamination (Cd, Pb, Ni, and Cr) in both Lagos Lagoon (Ikorodu) and Epe Lagoon, with Ikorodu exhibiting notably high to moderate contamination levels according to the CF index. Elevated PLI values for Cd and Pb in Ikorodu, in addition to greater PER, indicated increased risk, with Cd posing a high risk (61.42%) and Pb posing a moderate risk (49.50%). Additionally, the reduced asymptotic length in the Epe during the dry season suggests that Chrysichthys nigrodigitatus is adaptable to seasonal variations, while divergent growth patterns in both areas indicate the existence of trade-off mechanisms in response to changing conditions. Habitat-specific otolith asymmetry and metal contamination underscore species adaptability, with wider stressor variability in Lagos than in Epe. Furthermore, multidimensional scaling analysis highlights the intricate relationship between otolith shape variables and environmental factors, emphasizing the need for tailored conservation efforts in urbanized watersheds.

A comparative study of tissue protein synthesis rates in an Antarctic, Harpagifer antarcticus and a temperate, Lipophrys pholis teleost

The affect of temperature on tissue protein synthesis rates has been reported in temperate and tropical, but not Antarctic fishes. Previous studies have generally demonstrated low growth rates in Antarctic fish species in comparison to temperate relatives and elevated levels of protein turnover. This study investigates how low temperatures effect tissue protein synthesis and hence tissue growth in a polar fish species. Groups of Antarctic, Harpagifer antarcticus and temperate, Lipophrys pholis, were acclimated to a range of overlapping water temperatures and protein synthesis was measure in white muscle (WM), liver and gastrointestinal tract (GIT). WM protein synthesis rates increased linearly with temperature in both species (H. antarcticus 0.16–0.23%.d−1, L. pholis, 0.31–0.76%.d−1), while liver (H. antarcticus 0.24–0.27%.d−1, L. pholis, 0.44–1.03%.d−1) and GIT were unaffected by temperature in H. antarcticus but increased non-linearly in L.pholis (H. antarcticus 0.22–0.26%.d−1, L. pholis, 0.40–0.86%.d−1). RNA to protein ratios were unaffected by temperature in H. antarcticus but increased weakly, in L.pholis WM and liver. In L.pholis, RNA translational efficiency increased significantly with temperature in all tissues, but only in liver in H. antarcticus. At the overlapping temperature of 3 °C, protein synthesis (WM 26%, Liver, 39%, GIT, 35%) and RNA translational efficiency (WM 273%, Liver, 271%, GIT, 300%) were significantly lower in H. antarcticus than L.pholis, while RNA to protein ratios were significantly higher (WM 270%, Liver 170%, GIT 186%). Tissue specific effects of temperature are detectable in both species. This study provides the first evidence, that tissue protein synthesis rates are constrained in Antarctic fishes.