Fish Species Research Articles

Insights into trophic interactions: DNA metabarcoding reveals species composition in black-tailed gull fecal samples in coastal environments of South Korea.

This study explored the algae, zooplankton, macroinvertebrate, fish, and parasitic single-celled organism communities in Larus crassirostris (black-tailed gull) fecal samples from Baengnyeongdo, Hongdo, and Ulleungdo in South Korea. The fecal samples can identify key species consumed by black-tailed gull, providing insights into their, trophic interactions, and habitat dependencies. Using DNA metabarcoding, we identified algae, zooplankton, macroinvertebrate, fish, and intestinal and single-celled parasite species in the fecal samples. Parasitic single-celled organisms, such as Rhogostoma sp., Rhogostoma schuessleri, Eimeria furonis, and Aggregata eberthi, showed differing relative abundances at each sampling location, indicating variability in parasite diversity in the fecal DNA analysis of birds at each site. Intestinal parasites showed similar site-specific variability, though Clistobothrium sp. and Tetrabothrius sp. were common at all locations. Algae species, including Heterocapsa steinii, Heterocapsa niei, and Sargassum cristaefolium, also displayed habitat-specific patterns, as did zooplankton, with Calanus sp., Corycaeus speciosus, and Caprella californica being dominant on Baengnyeongdo, Hongdo, and Ulleungdo, respectively. In the macroinvertebrate communities, Octopus sinensis was prevalent at all locations but at varying abundances. Site-specific dominant fish species were also identified, with Ammodytes personatus, Decapterus maruadsi, and Arctoscopus japonicus highly predominant on Baengnyeongdo, Hongdo, and Ulleungdo, respectively. Other fish species, such as Ammodytes hexapterus, were detected in lower frequencies, suggesting a diverse diet for the seabirds. These results offer insights into the species composition and ecological dynamics in black-tailed gull populations across disparate Korean islands.

Unravelling the intricate language of fish guts: Impact of plant-based vs. plant-insect-poultry-based diets on intestinal pathways in European seabass

The long-term sustainability of aquaculture depends on finding economically viable and environmentally friendly feed ingredients to reduce the use of fishmeal and fish oil. An optimal strategy for the industry is not to identify substitutes or alternatives, but to find a combination of complementary raw materials that together meet the specific nutritional requirements for a given farmed fish species. The study aimed to examine the effects of different diets on the pyloric caeca and distal intestine of subadult European seabass (Dicentrarchus labrax) by applying transcriptomics and transmission electron microscopy. The study examined three dietary approaches: the classic fishmeal-based diet, a plant-based diet, and a plant-insect-poultry-based diet. The distal intestine was more sensitive to dietary changes than the pyloric caeca. The differentially expressed genes in both experimental diets were mainly involved in the digestion and absorption of proteins, fats, and vitamins. The overall transcriptomic changes were greater in the plant-based group than in the plant-insect-poultry-based group and included a greater number of overrepresented metabolic and signalling pathways. In contrast to the transcriptomic results, the ultrastructural findings showed decreased inflammation and/or evidence of tissue repair in the plant-based group, particularly in the pyloric caeca. Since the nutritional quality of all fish groups in this study was previously evaluated positively, the detected transcriptome-level changes can serve as evidence supporting the efficient nutrient utilisation and adaptability in European seabass. The study provides valuable insight into the potential benefits and implications of these dietary modifications on intestinal health and pathway regulation in European seabass. This can serve as a basis for further development of sustainable European seabass aquaculture practices and optimisation of diet formulations.

Impacts of estuarine habitat degradation on the modeled life history of marine estuarine-dependent and resident fish species.

Shallow coastal and estuarine habitats play an essential role in the life cycles of many fish species, providing spawning, nursery, feeding, and migration areas. However, these ecologically valuable habitats are increasingly threatened by anthropogenic activities, causing substantial changes in both habitat availability and quality. Fish species use these shallow coastal habitats and estuaries during various life stages, leading to their categorization into guilds based on how and when they rely on these areas. This differential functional use of estuaries means that changes to these habitats may affect each guild differently. To understand the impact of estuarine habitat degradation on fish populations, it is therefore necessary to consider the full life cycle of fish and when they rely on these coastal habitats. Here, we use conceptual size-structured population models to study how estuarine habitat degradation affects two functionally different guilds. We use these models to predict how reduced food productivity in the estuary affects the demographic rates and population dynamics of these groups. Specifically, we model estuarine residents, which complete their entire life cycle in estuaries, and marine estuarine-dependent species, which inhabit estuaries during early life before transitioning offshore. We find that total fish biomass for both guilds decreases with decreasing food productivity. However, the density of juveniles of the marine estuarine-dependent guild can, under certain conditions, increase in the estuary. This occurs due to a shift in the population biomass distribution over different life stages and a simultaneous shift in which life stage is most limited by food. At the individual level, somatic growth of juveniles belonging to the estuarine-dependent guild decreased with lower food supply in the estuary, due to increased competition for food. The somatic growth rates of fish belonging to the resident guild were largely unaffected by low food supply, as the total fish density decreased at the same time and therefore the per-capita food availability was similar. These outcomes challenge the assumption that responses to habitat degradation are similar between fish guilds. Our study highlights the need to assess not only fish biomass but also size distributions, survival, and somatic growth rates for a comprehensive understanding of the effects of habitat degradation on fish populations. This understanding is crucial not only for estuary fish communities but also for successful conservation and management of commercially harvested offshore population components.

Ichthyoplankton dynamics in the Brazilian Pantanal: Contribution of an important tributary and maintenance of connectivity

AbstractIn order to investigate the reproductive dynamics of the ichthyofauna in the Brazilian Pantanal, this study examines the spatial and temporal distribution of ichthyoplankton, taxonomic composition, and its correlation with environmental factors within one of the most important sub‐basins, the Taquari River. Egg and larvae collections were conducted at 11 sampling points between October and March of 2017/2018 and 2018/2019. Significant differences were observed between collection points, months, and years, with higher ichthyoplankton densities in the Coxim and Taquari rivers, particularly between November and January. Twenty‐eight genera and/or species of fish were identified, including 10 long‐distance migratory species. Egg density showed a negative correlation with water temperature and rainfall. For larvae, water transparency and rainfall were both significant, negatively influencing larval abundance. However, different species tend to occur in environments with distinct abiotic qualities. Yolk‐sac, preflexion, and flexion larval development stages were distributed throughout the sub‐basin, especially near the Pantanal. Considering the data and analyses presented in this study, the importance of connectivity between these environments, specifically between the plateau and Pantanal, is evident, highlighting the significance of the entire sub‐basin for fish reproductive processes. Therefore, research focusing on the ecological processes influencing the distribution of ichthyoplankton offers valuable insights for ecosystem conservation and aids in effective environmental management.

Fish of Low Commercial Value in Lakes of Different Trophic Status (Poland)

In a commercial fishery, some fish are classified as low-value, but their classification varies in different countries. The aim of this study was to determine the abundance, contribution, and dominance of low-value fish species, such as Abramis brama < 1000 g, Alburnus alburnus, Blicca bjoerkna, Gymnocephalus cernua, Perca fluviatilis < 100 g, Rutilus rutilus < 200 g, and Scardinius erythrophthalmus < 200 g, in 145 Polish lakes of different areas, depths, and trophic statuses situated in the northern and central parts of Poland in 2021. Perca fluviatilis and R. rutilus were the most frequent low-value species (100% and 99%, respectively). The contribution of all low-value fish to the total biomass of caught fish was relatively high, ranging from 37% in the mesotrophic lake to 100% in the eutrophic lake (mean of 77 ± 14%). Lakes in which the contribution of low-value species exceeded 90% were relatively numerous (24 lakes, 17% of the studied lakes). Among a total of about 437.5 thousand low-value fish, 261 thousand specimens (60%) had a body weight of below 10 g. All low-value fish species, except for P. fluviatilis and S. erythrophthalmus, were related to the studied environmental variables. The relative biomass of these species increased with increasing lake productivity, while it decreased with the increasing maximum and mean depth of the studied lakes. The high contribution of low-value fish to the total biomass in many lakes indicates the need for the constant monitoring of the abundance and structure of fish communities and the use of appropriate actions (biomanipulation and stocking with piscivorous fish species) to improve the ecological condition of lakes.

Parasitism with Protozoa and Monogeneans in Fish from the Natural Waters of Romania

Parasitism by protozoa and monogenean flatworms in freshwater fish from Romania was studied by collecting and examining samples from two major river systems there: 183 fish from 17 species from the Olt River and its tributaries; and 155 fish from 16 species from the Mureș River and its tributary, Târnava Mare. The average rates of parasitism in the samples from the two rivers and their tributaries were as follows: Ichthyiophthirius multifiliis (2%), Trichodina spp. (21%), Apiosoma spp. (18%), Mixobolus spp. (8%), Dactylogyrus spp. (9%), and Gyrodactylus spp. (10%). The number of parasite species varied from one river to another. I. multifiliis was found in only 3 fish species, Trichodina spp. in 13 species, Glosatella spp. in 6 species, and Mixobollus spp., Dactylogyrus spp., and Gyrodactylus spp. in 7 different species each. The highest number of parasite species (six) were identified in the European chub (Squalius cephalus) and schneider (Alburnoides bipunctatus), which seem more susceptible to parasitic infections. The aquatic environment of these rivers may represent a source of parasites for fish from neighboring countries through which these rivers pass.

Heavy Metal Accumulation in Fish, Sediment and Water from Three Riverine Ecosystems in the South-western Bangladesh and Nexus to Human Health.

This study investigated heavy metal accumulations in fish, water and sediment from three rivers around a major urban area in Bangladesh, namely the Rupsha, the Atai, and the Bhairab with a view to assessing the ecological and human health risks. Samples were collected from 10 stations over two seasons (summer and winter) and concentrations of 11 metals (As, Se, Pb, Be, Cd, Co, Cr, Cu, Mn, Ni, V) were measured using ICP-MS. Heavy metals in water of these rivers were above the WHO higher thresholds. The Rupsha River, which runs close to industrially dense areas and the downstream part of the three-river network, demonstrated the highest As, Cu, and V concentrations during both seasons. On the other hand, As, Mn and Cr were highest in the Bhairab which is the upstream to the Rupsha and connected to several industrial setups which differ from Bhairab. The less anthropogenically connected Atai River only showed elevated concentrations of Cu and Se. Ecological risk indices indicated low pollution in the rivers during both seasons. In all three rivers and in nearly all fish species, the contamination was higher in winter than summer. Benthic and carnivorous fish species such as, Cynoglossus lingua, Glossogobius giuris, Pseudapocryptes elongatus showed higher metal accumulation compared to other species. Health risk indices like the target hazard quotient (THQ) and carcinogenic risk (CR) suggested low risks but pointed potential risks to human health. The outcomes of this research reports insights into metal contamination pattern in interconnected river systems.

Species Composition and Diversity of Coastal Trawled Fishes Landed Off the Coast of Qua Iboe River Estuary, Ibeno, Nigeria

An assessment of the specie composition and diversity of fish species from Qua Iboe River Estuary was carried out over a period of six months (March-August, 2019). A total of thirty - one (31) species representing seventeen (17) families were identified under the families Bothidae, Charangidae, Clupeidae, Cynoglossidae, Drepanidae, Eleotridae, Gobiidae, Haemulidae, Polynemidae, Soleidae, Sciaenidae, Sparidae, Sphyraenidae, Scombridae, Tetraodontidae, Trachinidae and Trichuridae. Monthly abundance was lowest in April (122 specimens; 6.21 %) and was highest in March (545 specimens; 27.72 %). The longest species was Trichirus lepturus while the shortest were Drepane africana and Selena dorsalis. Family Sciaenidae had the highest representation in terms of species and Haemulidae had the highest number of individuals. Shannon-Weiner Index of general Diversity (H) value was showing dominance of in Charangidae family. Evenness Index (E) showed all the species were not equally distributed in the waters. Assessment of the condition factor (K) revealed that 22 out of 31 fish species K values less than 5 showing good body condition and wellbeing of the fish while 11 species showed bad body condition. The estuary has a rich ichthyofauna complex. Effective exploitation measures should be used to deter the menace of local extinction in the near future.

Optimising species detection probability and sampling effort in lake fish eDNA surveys

Environmental DNA (eDNA) metabarcoding is transforming biodiversity monitoring in aquatic environments. Such an approach has been developed and deployed for monitoring lake fish communities in Great Britain, where the method has repeatedly shown a comparable or better performance than conventional approaches. Previous analyses indicated that 20 water samples per lake are sufficient to reliably estimate fish species richness, but it is unclear how reduced eDNA sampling effort affects richness, or other biodiversity estimates and metrics. As the number of samples strongly influences the cost of monitoring programmes, it is essential that sampling effort is optimised for a specific monitoring objective. The aim of this project was to explore the effect of reduced eDNA sampling effort on biodiversity metrics (namely species richness and community composition) using algorithmic and statistical resampling techniques of a data set from 101 lakes, covering a wide spectrum of lake types and ecological quality. The results showed that reliable estimation of lake fish species richness could, in fact, usually be achieved with a much lower number of samples. For example, in almost 90% of lakes, 95% of complete fish richness could be detected with only 10 water samples, regardless of lake area. Similarly, other measures of alpha and beta-diversity were not greatly affected by a reduction in sample size from 20 to 10 samples. We also found that there is no significant difference in detected species richness between shoreline and offshore sampling transects, allowing for simplified field logistics. This could potentially allow the effective sampling of a larger number of lakes within a given monitoring budget. However, rare species were more often missed with fewer samples, with potential implications for monitoring of invasive or endangered species. These results should inform the design of eDNA sampling strategies, so that these can be optimised to achieve specific monitoring goals.

Chronicles of Kyphosus in the Mediterranean Sea: new records and complete mitogenomes support the scenario of one expanding fish species

The Mediterranean Sea is a biodiversity hotspot, being home to a vast array of marine species. Furthermore, seawater warming is facilitating the arrival and spread of new thermophilic species, posing a severe threat to biodiversity. Among the species currently extending their range and increasing in abundance in Mediterranean waters, sea chubs (genus Kyphosus) are one of the most enigmatic. One challenge arises from the high phenotypic similarity between the two congeneric species documented in the basin: Kyphosus vaigiensis and Kyphosus sectatrix. Their resemblance has often led to identification challenges, resulting in incorrect or omitted species-level classifications. Therefore, despite the growing presence of these fish in the Mediterranean, it remains unclear whether only one or both species are experiencing a demographic increase and range extension. To date, there have been 26 reports of Kyphosus individuals in the Mediterranean Sea, documented in 24 separate papers. Here, we reviewed the history of the genus in the basin and provided 13 new records of these fish from multiple localities along Mediterranean coasts. In addition, we sequenced the entire mitogenomes of two specimens, assessed their phylogenetic relationships with published Kyphosus mitochondrial DNAs from around the world, and conducted detailed morphological and meristic analyses on one of them, allowing us to provide accurate species-level identifications. Our results indicate that K. vaigiensis is the species currently expanding its range in the Mediterranean Sea, while K. sectatrix is still very rare and only sporadically reported. Notably, our mitogenome data indicate that Mediterranean K. vaigiensis individuals most likely came from Atlantic waters, while there is no evidence to support an entrance through the Red Sea or any other anthropogenic vector. Finally, the potential ecological and fishing impacts associated with the proliferation of these fish in the region are discussed.

ASSESSMENT OF BIOACCUMULATION FACTORS OF TRACE METALS FOR UPPER GANGETIC FISH

Abstract The River Ganga basin is home to over 520 million people and 2500 species of flora and fauna, including several fish species. This study determines the bioaccumulation factors of fish for five trace metals, namely Cu, Fe, Zn, Mn, and Cr, in a stretch of the River Ganga in the upper Gangetic alluvial plain with limited industrial activities. The abundance of different trace metals in the water follows the order Fe > Zn > Mn > Cu > Cr. The concentrations in fish show a slightly different pattern and follow the relative quantitative order as Zn >≈ Fe >Mn > Cu >Cr. The trace metal levels in fish are well below the permissible limits set by various regulatory agencies. The bioaccumulation factor values are in order Zn>Cr>Mn>Cu>Fe. This stretch of the Ganga has not been extensively investigated for bioaccumulation by aquatic organisms. These values, therefore, represent site-specific baseline data for future anthropogenic activities that may affect the trace metal profile in this part of the Gangetic aquatic system. The study is also significant due to the presence of the Narora nuclear power plants, as the bioaccumulation factors of stable elements help predict the behavior of their radioactive counterparts and homologous elements in the environment.

Role of Mangroves as Fishery Resource: A Systematic Review

Mangroves are valuable for their fishery resources, coastline stabilization abilities, water quality and clarity benefits, provision of habitat to economically profitable and ecologically important species, carbon sequestration services, and climate regulation capabilities. For centuries, mangroves have contributed significantly to the socioeconomic lives of coastal dwellers; especially in coastal fishery by providing nursery grounds for finfishes. Fishery resource services provided by mangrove ecosystem play an important role as the habitat, nursery ground, feeding ground, and spawning ground for various marine fish species. Despite their enormous socio-economic value and ecological significance, mangrove ecosystems are under severe threat such as large scale clearing, small scale harvesting and grazing, and industrial threats. The productivity of mangrove ecosystems has been linked to the well-being of valuable fisheries because of the role mangroves play as nursery habitat for a variety of marine and estuarine species. Many species of mangrove-related fish and crab have served the coastal communities as a natural, cheap and balanced nutritional source. Mangroves provide vital ecosystem services to coastal fishing communities through the enhancement of fisheries production. Due to their economic and ecologic significance, it is important to look to the future of these systems in the face of ‘fishery resource’ so that policy makers may act quickly to preserve and protect these ecosystems. Present review provides recent information on role of mangroves as fishery resource by studying the updated published literature and the threats faced by the mangroves. It is suggested that strategies should be prepared and rigorously implemented for the conservation and restoration of mangrove ecosystem.

Novel lytic bacteriophage AhFM11 as an effective therapy against hypervirulent Aeromonas hydrophila

Several farmed fish species, including carps, tilapia, salmon, and catfish, have experienced significant economic losses in aquaculture due to motile Aeromonas septicemia caused by Aeromonas hydrophila. In the present study, a novel lytic bacteriophage infecting hypervirulent Aeromonas hydrophila (vAh) was isolated and characterized. This is the first report of a phage against vAh. Phage AhFM11 demonstrated lytic activity against both vAh strains and the A. hydrophila reference strain ATCC 35654. The AhFM11 genome was sequenced and assembled, comprising 168,243 bp with an average G + C content of 41.5%. The genome did not harbor any antibiotic resistance genes. Genomic information along with transmission electron microscopy revealed that phage AhFM11 belongs to the Straboviridae family. Therapeutic application of monophage AhFM11 in fish showed 100% survival in injection, 95% in immersion and 93% in oral feeding of phage top-coated feed. Fish and chicken meat spiked with A. hydrophila and phage showed significant reduction of A. hydrophila. These findings support that phage AhFM11 can be used as a biocontrol agent against vAh as an alternative to antibiotics.

OMSACC-SGRAN: an implementation of hybrid Optimized Multi-Scale Atrous Convoluted CNN with Self Guided Residual Attention Network for fish species classification

OMSACC-SGRAN: an implementation of hybrid Optimized Multi-Scale Atrous Convoluted CNN with Self Guided Residual Attention Network for fish species classification

Extraction and characterization of collagen from the skin of Pterygoplichthys spp. (armored catfish) from Chiapas

Because of its biocompatibility and safety, collagen is a valuable biomaterial that is used in various industries. While traditionally sourced from terrestrial mammals, collagen extracted from fish waste is a promising alternative due to its chemical properties and low cost. In Mexico, Pterygoplichthys spp. is considered an invasive species, inedible, and of limited commercial importance due to the low muscle content and skin covered with rigid bony plates. This study aimed to extract and characterize collagen from the skin of Pterygoplichthys spp. obtained from two communities in Chiapas, Mexico. Our results show that the extracted collagen is type 1, with a yield of 43.0% (dry weight). Sodium dodecyl sulfate polyacrylamide gel electrophoresis analysis revealed the presence of two alpha chains (α1, α2) and a beta and gamma component, consistent with type 1 collagen. Liquid chromatography coupled to mass spectrophotometry analysis identified peptide sequences homologous to those reported in other species. This study highlights the potential of Pterygoplichthys spp. skin collagen as a viable alternative to mammalian collagen. The efficiency of the extraction process and the identification of peptides resembling those of the other species underscore the feasibility of utilizing collagen from the skin of Pterygoplichthys spp. in industrial applications, offering a sustainable solution to environmental and economic challenges. Practical Application: Collagen extracted from the skin of Pterygoplichthys spp., an invasive fish species, can serve as a sustainable alternative to mammalian collagen, offering a cost-effective biomaterial with properties suitable for various industrial applications.

Molecular identification of Mymarothecium viatorum and Anacanthorus penilabiatus in extensive native fish farming systems of the Peruvian Amazon

Piaractus brachypomus (Pacú) is the main native fish species cultivated in Peru and holds great potential for growth in aquaculture from the Peruvian Amazon. Between October 2021 and January 2022 in two fish producing farms in the Amazon region of San Martín in Peru, P. brachypomus individuals were examined for parasite evaluation. A total of 6366 monogeneans were isolated from the gills of 30 fish, revealing a prevalence of 100%, with an abundance and mean intensity of 212 parasites per fish. Monogeneans were morphologically identified as Mymarothecium viatorum and Anacanthorus penilabiatus. The genetic divergence in the 28S rDNA gene found among A. penilabiatus sequences was 0.1% and among Anacanthorus spp. it ranged from 0.9% to 7.5%. The genetic divergence found among the M. viatorum sequences was 0.3%. These finding represents the first molecular data of M. viatorum and A. penilabiatus in Peru using the 28S rDNA gene of these monogeneans. The new sequences obtained will contribute to future studies on the phylogenetic relationships among dactylogyrids. However, further research with a broader range of host-parasite samples and additional genetic markers is needed to clarify these relationships and provide stronger support for the phylogenetic positions.

A Baseline Assessment of Contamination in the Sacramento Deep Water Ship Channel

The Sacramento Deep Water Ship Channel (SDWSC) in the San Francisco Estuary, which is an active commercial port, is critical habitat for pelagic fish species including delta smelt (Hypomesus transpacificus), longfin smelt (Spirinchus thaleichthys), and Sacramento perch (Archoplites interruptus). Pelagic organism decline has been attributed to covarying factors such as manipulation of habitat, introduction of invasive species, decrease in food production, and contaminant exposure. Quantification of bioavailable toxicant loads in the SDWSC is limited despite previous surveys that have detected elevated contaminant concentrations in the sediments. Therefore, the focus of the present study was to characterize the bioavailability of the contaminants in the SDWSC from six sites along the channel. At each site, organochlorine pesticides (OCP), pyrethroid insecticides, polyaromatic hydrocarbons (PAHs), and polychlorinated biphenyls (PCBs) were quantified in sediment, zooplankton, and suspended solids. In addition, Tenax extraction was used to measure the bioaccessible fraction of sediment-associated contaminants freely dissolved in the water. Bioaccessible contaminants in the sediment provided an uptake route for these stressors into invertebrates and fish with bioaccessible OCPs being found at all sites, particularly 4,4’-dichlorodiphenyldichloroethylene (DDE). Bifenthrin was the only pyrethroid to be detected in the chosen matrices and it was found at concentrations below levels of concern. Bioaccessible PAHs were found at all sites, with highest detections for phenanthrene and pyrene. No PCBs were detected in sediments, but were detected in both suspended solids and zooplankton. Contaminant concentrations overall were significantly higher in suspended solids, followed by zooplankton and sediments. The highest sediment concentrations of DDE, fluoranthene, pyrene, and dibenzo[a,h]anthracene exceeded sediment quality benchmarks which suggested potential risk to sediment-dwelling species. Finally, elevated contaminant levels were found in both suspended solids and zooplankton, suggesting additional risk to pelagic species in the SDWSC.

Current disease treatments for the ornamental pet fish trade and their associated problems

AbstractThe trade in live ornamental fishes to be held as companion animals or displayed in public aquaria has an estimated global annual value of US$15–20 billion. Supply chains for ornamental pet fishes often involve many more parties than for fish farmed as food fishes, and at each stage, fishes are exposed to stressors including handling, confinement, crowding, mechanical disturbance, and poor water quality. If chronic, these stressors can compromise their immune system, making fishes more susceptible to pathogens. Mortality and morbidity from infectious disease can result in considerable welfare impacts and massive economic losses for the industry, and the range of infective agents seen in ornamental species is well documented. However, treating these diseases is not straightforward with practices varying greatly across the trade and with several approaches having unintended consequences, such as the emergence of resistant strains of pathogens. While disease treatments for a handful of fish species (e.g., koi, goldfish) have received focused research attention, for the home aquarium owner, there is an increasing reliance on products based on natural compounds which have received far less scientific attention. This review aims to highlight the gaps in our knowledge surrounding the range of disease treatments used across the ornamental pet fish trade, with a particular focus on freshwater tropical species destined for home aquaria. Consideration is given to the potential problems arising from these treatments, including microbial resistance and effects of treatments themselves on fish health and welfare.

Occurrence of microplastics in commercial fish species from the Ethiopian rift valley's Lake Hawassa, Ethiopia.

Microplastics (MPs) have recently been detected as emergent pollutants in the Ethiopian rift valley lakes located close to rapidly expanding towns. We provide the first study of MPs ingestion of commercial fish species from Lake Hawassa, Ethiopia: Catfish (Clarias gariepinus) and Nile Tilapia (Oreochromis niloticus). A total of 60 individual fish species was collected from three sampling sites of lake Hawassa in October 2020. Across all sampling sites, there was a significant difference in ingested MPs between benthic omnivore catfish and pelagic phytoplanktivorous Tilapia (χ2 = 15.864, p < 0.001). The most common size of ingested MPs (84.6%) was 0.5-1mm, with fragments (59.5%) dominating, followed by fibers (25.4%). On average, 4.03 ± 1.33 MPs with sizes ranging between 60μm and 10.53mm were detected per individual. White and yellow MPs were particularly numerous, accounting for 36.8% and 26.4% of the total, respectively. Because Lake Hawassa's fishery is so significant, the potential impact of MP pollution on the lake biota in general, and economically valuable fish species in particular, deserves attention, additional research, and, if possible, early mitigation.

UV-absorbing mycosporine-like amino acids in the eyes of temperate marine and freshwater fish species

Ultraviolet radiation (UVR) is the photochemically most reactive waveband of incident solar irradiation. Despite high absorption in aquatic environments, UVR causes numerous biochemical, genetic, and cytotoxic effects in aquatic organisms. To counteract UVR stress, many of those species are able to synthesize, accumulate, or acquire UV-sunscreen compounds for photoprotection from their diet. The most abundant UV sunscreens in marine and freshwater organisms are mycosporine-like amino acids (MAAs), which exhibit high molar extinction coefficients in the UVR range along with a strong photo- and heat stability. In this study, we investigated the qualitative and quantitative MAA distribution patterns in the eyes of 39 fish species, mainly from the temperate northern hemisphere (Baltic Sea, Northern Atlantic), using state-of-the-art analytical methods. The fish eyes of the most investigated species (33 taxa) contained MAAs, between one and seven different compounds. The MAAs palythine, asterina-330, palythene, and usujirene were present (as previously reported), and three new compounds, aplysiapalythine A, porphyra-334, and shinorine, were identified. Total MAA concentrations covered a wide range from trace amounts to &amp;gt; 4.2 mg g−1 dry weight, thereby providing the first quantitative data on MAAs in fish eyes. The highest MAA contents were measured in Sprattus sprattus, which are comparable to those of intertidal red seaweeds. The trophic transfer of MAAs from primary producers via zooplankton to the fish is discussed, along with the localization in the fish eye as well as possible additional functions.