Fish Larvae Research Articles

Seasonal Distribution of Copepods as Influenced by Physicochemical Parameters in Khanki Headworks, Pakistan

Copepods are tiny aquatic animals. Their role in aquatic food chains is very crucial as they are involved in organic matter circulation and energy transfer between different trophic levels. They are important source of food for fish larvae and zooplanktivorous fish. Objective: To assess the influence of environmental variables on the abundance, diversity and seasonal variations of planktonic copepods in Khanki Headworks, Pakistan. Methods: For the analysis of environmental variables monthly water samples from four selected sites were collected for a period of one year (February 2021 to January 2022). Environmental variables were analyzed in laboratory by following standard procedures. Month wise samples of copepods were collected with planktonic net (mesh size: 37µm) from four locations (each with 3 sub-sites). Results: In total, 7 species of Copepods belonging to 4 genera were identified from February 2021 to January 2022. Mesocyclops was observed as the most diverse genus (4 species), while Mesocyclops edax was the most prevalent copepod species. Population density and biodiversity were highest in June and minimum in January. Shannon-Weaver diversity index described greater diversity among copepod species in June. Pearson correlation and canonical correspondence analysis (CCA) revealed that electrical conductivity (EC), temperature, turbidity, pH and dissolved oxygen (DO) were important environmental variables affecting the biodiversity and density of copepods. Conclusions: This investigation elucidated that physicochemical parameters generally regulate the population dynamics of Copepods.

Mesoscale activity in the northeastern pacific water mass convergence region and its influence on fish larvae distribution by development stages (October 2022)

Based on satellite, hydrographic, and zooplankton data, the mesoscale activity, and its effect on the three-dimensional distribution of fish larvae in the northeastern Pacific water mass convergence region off Mexico during October 2022 were analyzed. Three eddies were observed during the cruise, but two were measured. An anticyclonic eddy (not crossed by the cruise) was observed by satellite data in the mouth of the Gulf of California. It formed off Mazatlán in Transitional Water and moved southeast of Cabo San Lucas. It was the smallest (10,207.4 km) and least energetic (140.7 cm2s−2) of the eddies. A parallel sampling transect to this eddy showed predominance of fish larvae in preflexion stage in the surface mixed layer with dominance of Benthosema panamense and Syacium ovale species (epi-mesopelagic and soft-bottom demersal species). A second anticyclonic eddy had formed about a month earlier in the Tropical Surface Water when this was measured. Its trajectory showed that it came from the mainland coast off Cabo Corrientes. It was the most energetic (216.6 cm2s−2) and presented the maximum anomalies of temperature (7.4 °C) and Dissolved Oxygen (>50 μmolkg−1), due to the downwelling that it produced (up to 95 m depth). It was also associated with the highest concentration of fish larvae (231.3 larvae100m−3) from ∼200 m depth to surface, observing dominance of larvae in flexion stage of B. panamense and Bregamaceros bathymaster (coastal neritic species). This eddy could also retain and transport species of soft-bottom demersal habits (Dormitator latifrons). One cyclonic eddy, located off Cabo San Lucas had California Current Water. It was the largest (26,032 km2) and oldest forming about nine months earlier off mainland coast in front of Pabellones Cove. Due to the upwelling of deeper water (up to 530 m depth), the minimum anomaly values of temperature (−5.8 °C), salinity (<−0.5 gkg−1) and Dissolved Oxygen (<−50 μmolkg−1) were present. Low abundance of species such as Vinciguerria lucetia and Diogenichthys laternatus (both epi-mesopelagic) in the postflexion stage were presented there. Results showed that mesoscale eddies affected the three-dimensional fish larvae distribution in different ways. This could broaden the vision of the mesoscale evolution of physical-biological interactions in the oceans.

Comparison of Abundance and Structure of Larval Fish Assemblages between Autumn and Spring in the Waters Surrounding Taiwan Bank, Western North Pacific

The fluctuations in both time and space of larval fish assemblages in relation to hydrographic characteristics in the waters surrounding Taiwan Bank were studied in October 2021 (autumn) and March 2022 (spring). Throughout the study period, we identified a total of 149 taxa of fish larvae, encompassing 96 genera and 71 families. Engraulis japonicus, Diaphus slender type, unidentified Gobiidae, Apogon sp., unidentified Clupeidae, and Benthosema pterotum were the six dominant taxa and together constituted 47.39% of the total catch. There were no notable temporal variations observed in the abundance of fish larvae, but the species number of fish larvae was greater in spring than in autumn. Significant variations in species composition were observed between the different cruises, and the cluster analysis unveiled a distinct temporal structure of the assemblages of fish larvae. The dynamics of the prevailing currents induced by seasonal monsoons contribute significantly to the transportation of fish larvae. The distribution of fish larvae showed a good association with hydrographic characteristics, where seawater temperature and salinity emerged as the primary explanatory factors influencing the composition of larval fish assemblages in the waters surrounding Taiwan Bank. While the increased influx of nutrients from upwelling ensures abundant food availability, the hydrographic conditions may not be suitable for every fish larva.

Fish larvae: an alternative animal model for testing the toxicity of food additives

Fish larvae: an alternative animal model for testing the toxicity of food additives

Амурский чебачок Pseudorasbora parva (Cyprinidae) в водоемах и водотоках Дагестана

Information is provided on the distribution of a species alien to the ichthyofauna of Dagestan – the Amur Top-mouth gudgeon Pseudorasbora parva (Temminck et Schlegel, 1846) within the region. It was found that the species expanded its range in the region under consideration, in 2021 it was found in the rivers Manasozen (9 copies), Gamriozen (10 copies), Ulluchai (6 copies), Rubas (6 copies), Avar koisu (a tributary of the Sulak River, in the area of the Gotsatli HPP), as well as in L. Mooch. It is assumed that the widespread distribution of P. parva is associated with high ecological plasticity, migration activity of larvae and fry, their high survival rate, rapid growth and accelerated puberty. The presented morphological variability of the Amur Topmouth gudgeon population based on the study of 20 signs, including 5 meristic and 15 plastic, revealed a slight variability of morphological signs due to different habitat conditions in the region. The Amur Topmouth gudgeon is a natural focus of an infectious disease of the swim bladder, dangerous for autochthonous ichthyofauna and aquaculture facilities, and a food competitor and consumer of caviar and larvae of autochthonous fish. With high numbers and prolonged starvation, P. parva can be a serious competitor for juvenile carp and variegated carp, and exhibit a predatory reaction towards commensurate juveniles of commercially valuable fish species. To control the number of this alien in the region, it is advisable to use native predators – perch Perca fluviatilis (Linnaeus, 1758), pike Esox lucius (Linnaeus, 1758) and walleye Sander lucioperca (Linnaeus, 1758).

Effects of Cadmium and Nickel on Embryonic Development of Fish: A Review

In fish embryos, a variety of abnormalities have been found, including stunted growth, a reduced survival rate, and aberrant development. One plausible explanation is that early embryonic stages are more sensitive. Embryonic studies provide additional information regarding the various impacts of heavy metals on fish, but information on larval abnormalities caused by waterborne metals is lacking. It is found that cadmium (Cd) causes a decrease in thyroid hormone levels as well as a disruption in fish growth hormone expression. Similarly, negative health effects have been documented as a result of nickel (Ni) exposure. Some toxic effects on organs, skin irritation, skin itches or blisters and allergic reactions may occur as a result of Ni exposure. This review study focuses on the impacts of Cd and Ni, on the embryonic development of different fish species. The evidence on abnormalities in fish larvae caused by Cd and Ni was also provided in text.

Meta-Analysis of the Causality of Deformations in Marine Fish Larvae Culture

The development of deformities in farmed fish is largely the result of abiotic, biotic, and xenobiotic factors, information deficiencies in optimizing nutrition, and the genetic background to which the fish are exposed in their early life stages. In general, skeletal anomalies are considered to have significant adverse effects on animal welfare, biological performance of farmed fish, product quality, and production costs. In the data obtained by the meta-analysis method, the presence of negative effects on the formal structures of fish was found, regardless of the region, duration, stage, factor, stock density, and method used to detect deformation. In this regard, in the studies considered within the deformation region/type, 46% of deformities were found in the spine, 37% in the head, and 16% in the total skeleton. In turn, the results of the meta-analysis showed that the percentages of the apparent value were 35.82% in the spine, 33.12% in the skeleton, and 31.06% in the head. The deformation rate had an overall negative effect on the functional characteristics of the fish, regardless of the variables considered. In addition, all statistically significant individual response variables had a negative effect size. In the future, advanced statistical tools such as Bayesian meta-analysis, network meta-analysis, and meta-regression analysis can be used to explore more complex data structures. The rapid development of artificial intelligence techniques will increase the efficiency of data collection and the robustness of results for meta-analysis studies in aquaculture and other fields.

Microfeed Incorporated with Probiotic for Aquaculture: A Review

Ensuring the availability of high-quality larvae in sufficient quantities remains a significant bottleneck for the grow-out phase of aquaculture. Over the past century, various alternative dietary solutions for larval stages have been explored, encompassing bacteria, microalgal pastes, yeasts, and various inert microparticles, though with inconsistent outcomes. This review aimed to discuss the innovative integration of probiotics into microfeeds, highlighting encapsulation, coating, and fermentation techniques to propel aquaculture productivity. Microfeeds, which are often nutrient-rich and easily assimilated in powdered or liquid form, play a crucial role in larval fish nutrition. These can be classified into microencapsulated, dry, liquid, and live feeds. The choice of microfeed is pivotal, ensuring appeal, digestibility, and water stability tailored to each larval stage. As probiotics gain popularity in aquaculture for their potential to enhance growth, bolster disease resistance, and improve water quality, their administration methods have diversified. The probiotics can be administered through direct immersion and bath treatments to biofloc systems and feed additives. The results indicated that microfeed incorporated with probiotics showed a positive result impact on the aquaculture industry.

Sarcomere level mechanics of the fast skeletal muscle of the medaka fish larva.

The medaka fish (Oryzias latipes) is a vertebrate model used in developmental biology and genetics. Here we explore its suitability as a model for investigating the molecular mechanisms of human myopathies caused by mutations in sarcomeric proteins. To this end, the relevant mechanical parameters of the intact skeletal muscle of wild-type medaka are determined using the transparent tail at larval stage 40. Tails were mounted at sarcomere length of 2.1 μm in a thermoregulated trough containing physiological solution. Tetanic contractions were elicited at physiological temperature (10°C-30°C) by electrical stimulation, and sarcomere length changes were recorded with nanometer-microsecond resolution during both isometric and isotonic contractions with a striation follower. The force output has been normalized for the actual fraction of the cross section of the tail occupied by the myofilament lattice, as established with transmission electron microscopy (TEM), and then for the actual density of myofilaments, as established with X-ray diffraction. Under these conditions, the mechanical performance of the contracting muscle of the wild-type larva can be defined at the level of the half-thick filament, where ∼300 myosin motors work in parallel as a collective motor, allowing a detailed comparison with the established performance of the skeletal muscle of different vertebrates. The results of this study point out that the medaka fish larva is a suitable model for the investigation of the genotype/phenotype correlations and therapeutic possibilities in skeletal muscle diseases caused by mutations in sarcomeric proteins.NEW & NOTEWORTHY The suitability of the medaka fish as a model for investigating the molecular mechanisms of human myopathies caused by mutations of sarcomeric proteins is tested by combining structural analysis and sarcomere-level mechanics of the skeletal muscle of the tail of medaka larva. The mechanical performance of the medaka muscle, scaled at the level of the myosin-containing thick filament, together with its reduced genome duplication makes this model unique for investigations of the genotype/phenotype correlations in human myopathies.

Methamphetamine Shows Different Joint Toxicity for Different Types of Microplastics on Zebrafish Larvae by Mediating Oxidative Stress.

The coexistence of polystyrene (PS) and polypropylene (PVC) microplastics (MPs) and methamphetamine (METH) in aquatic systems is evident. However, the joint toxicity is unclear. Here, zebrafish larvae were exposed to single PS and PVC MPs (20 mg L-1) and combined with METH (250 and 500 μg L-1) for 10 days. The results indicated that acute exposure to PS and PVC MPs induced lethal effects on zebrafish larvae (10-20%). Treatment with MPs markedly suppressed the locomotion of zebrafish, showing as the lengthy immobility (51-74%) and lower velocity (0.09-0.55 cm s-1) compared with the control (1.07 cm s-1). Meanwhile, histopathological analysis revealed pronounced depositions of MPs particles in fish's intestinal tract, triggering inflammatory responses (histological scores: 1.6-2.0). In the coexposure groups, obviously inflammatory responses were found. Furthermore, the up-regulations of the genes involved in the oxidative kinase gene and inflammation related genes implied that oxidative stress triggered by MPs on zebrafish larvae might be responsible for the mortality and locomotion retardant. The antagonistic and stimulatory effects of METH on the expression changes of genes found in PVC and PS groups implied the contrary combined toxicity of PS/PVC MPs and METH. This study for the first time estimated the different toxicity of PS and PVC MPs on fish and the joint effects with METH at high environmental levels. The results suggested PS showed stronger toxicity than PVC for fish larvae. The addition of METH stimulated the effects of PS but antagonized the effects of PVC, promoting control strategy development on MPs and METH in aquatic environments.

Nutritional values of Artemia salina (brine shrimp) enriched with microalgae Chlorella vulgaris grown in banana stem compost extract medium

ABSTRACT Artemia salina enrichment is limited by the high cost and availability of commercial microalgae culturing media. This study was conducted to evaluate the nutritional value of Artemia salina nauplii enriched with Chlorella vulgaris grown in Bold’s Basal Medium (BBM, commercial media) and banana stem compost extract (BSCE) as the alternative low-cost media. The C. vulgaris was cultured in the laboratory and fed to Artemia nauplii hatched as per standard protocols and, after that, analyzed for nutritional values. Artemia fed BSCE-cultured C. vulgaris had significantly (p < .05) higher carbohydrates, total polyunsaturated fatty acids (PUFAs), and monounsaturated fatty acids, but lower saturated fatty acids (SFAs), while protein and lipids were the same as those fed BBM-cultured C. vulgaris. It was concluded that BSCE can replace BBM as an alternative microalgae culturing media and produce an ideal enrichment diet for fish larvae nutrition because of high PUFAs and lower SFAs.

Optimization of Selenium Inclusion Level in the Larval Diet of Labeo rohita.

The nutritional requirement of fish larvae remains a limiting factor in advanced aquaculture. Micronutrients are crucial for early development, but their dietary inclusion level in the larval feed of carps has not been standardized. The present study was executed to determine the optimum dietary inclusion level of organic and inorganic selenium in the larval feed of Rohu, Labeo rohita. A 35-day feeding trial in triplicate under semi-control conditions was conducted in 21 troughs divided into seven groups. Each trough (capacity 4.0 L) contained 200 larvae (average body weight 0.4mg). The first group (control) was reared on nano-particulate basal diet (CP 50%), while three groups Se-Na(0.5), Se-Na(1), and Se-Na(1.5) were fed basal diet supplemented with graded levels (0.5-1.5mg/kg diet) of inorganic form of Se, sodium selenite (Se-Na). The last three groups (Se-Met(0.5), Se-Met(1), and Se-Met(1.5)) were fed organic form of dietary Se, selenium methionine (Se-Met) at the same inclusion level as Se-Na. Results indicated the curvilinear relationship of dietary Se levels with body weight, activity of digestive enzymes (protease, amylase, lipases, and trypsin), and antioxidant enzymes (SOD, CAT, POD, and GSH-Px) activity, intestinal villi, width, and absorptive area. A positive correlation was observed with up to 0.5 and 1mg/kg diet of Se-Na and Se-Met, respectively; however, above these levels, a negative impact was observed. The upregulation of growth hormone mediator (IGF-1) and downregulation of heat shock protein (HSP-70) also followed a similar trend in response to Se-Na and Se-Met inclusion. Based on the results, 1mg/kg diet Se-Met could be considered the optimum level and is recommended for the early rearing of rohu larvae.

Review of Central-Eastern European Propagation and Larvae Nursing Method for Common Carp (Cyprinus carpio L.).

Common carp (Cyprinus carpio L.) as a cultivated fish species has huge importance all over the world. According to FAO statistics, carp is the third most widely bred freshwater pond fish species; only two other Cyprinids (silver carp and grass carp) are bred in higher amounts. Carp is native all over Asia and in a large part of Europe. As a result of human intervention, at present, carp are widespread all over the world, except for the Arctic region. Carp breeding was launched in the antique period, in the ancient Chinese Empire and the Roman Empire. The presently applied method of breeding of common carp has a long evolution. From the effectiveness point of view, the propagation and early-life nursing are crucial parts of carp production, as they provide seed stocks for the further growing section. Without effective propagation, there is no intensive carp production. Nowadays, more advanced propagation methods are available all over the world; however, in the current review, only the main milestones and production efficiency of the propagation and nursing method used in the ponds of Eastern Central Europe are discussed. In the historical overview of carp reproduction, first the natural reproduction, then the semi-extensive and intensive hatchery propagation are presented and investigated in detail. The analysis focuses on the advantages and disadvantages of the method. In particular, the different important milestones of the advanced hatchery method are shown and explained. The effectiveness is proven even with practical calculations. Not only the reproduction, but the pond nursing method is also presented and discussed, concentrating on the management of evolutionarily adapted natural feeds (Zooplankton) and their effect on the survival of fish larvae.

First Record Sparus aurata Larvae in Teluk Penyu Beach Cilacap, Indonesia, revealed by DNA Barcoding

Morphological identification often fails to reveal the taxonomic status of fish larvae. DNA barcoding using particular DNA segment is frequently successful in solving the faulty and might reveal overlooked species, including species outside their recognized geographic ranges, such as Eastern Atlantic seabream Sparus aurata. This study aims to assess fish larvae diversity in Teluk Penyu Beach, Cilacap Central Java, Indonesia, through the cytochrome c oxidase 1 barcoding. Fish larvae were collected using a larva net with a diameter of 60 cm and height of 150 cm and horizontal towing during the field trips in March and April 2021. Larvae morphotypes were determined based on their general morphological performance observed under a magnification lens according the available references. Eighteen larvae morphotypes were successfully barcoded, and 5% genetic distance was used as a species border. Fourteen fish larvae species were revealed, with intraspecific genetic distances between 0.00% and 4.12%, while intrageneric genetic distances ranged from 5.50% to 19.29%. An interesting finding was that one larva morphotype was barcoded as S. aurata with high genetic identity (99.19% to 99.68%) and low genetic distance (0.32% to 0.81%). The discovery provides the first new data on S. aurata in Teluk Penyu Beach Cilacap, Central Java, outside its recognized geographic range. Overall, this study provides information about fish larvae in Teluk Penyu Beach, essential for estimating the number and species of fish recruited in the southern Cilacap, which is vital for fisheries management. Nevertheless, new research requires further clarification of S. aurata in Teluk Penyu Beach.

Larval fish assemblages in selected Brazilian estuaries: Species-environment relationships under different anthropogenic influences

We investigate the effects of spatial changes in environmental conditions and anthropogenic influences on larval fish communities in two tropical estuaries with varying levels of human impact. Our findings revealed a distinct structure of larval fish assemblages between the two estuaries located in northeastern Brazil, and we observed that eutrophication, characterized by high concentrations of nutrients, had adverse effects on the abundance and richness of larval fish assemblages. Additionally, we observed that a decrease in rainfall had an impact on larval fish assemblages, particularly during the dry season, when intermittent upstream rivers lead to changes in salinity and species composition within the estuaries. This study contributed to evaluating the community descriptors of two tropical estuaries under different levels of human influence, providing insights into the vulnerability of larval fish assemblages to climate change, specifically in relation to human influences and hypersalinity and the effects of marinization in shallow tropical estuaries in this region.

Anchovy boom and bust linked to trophic shifts in larval diet

Although massive biomass fluctuations of coastal-pelagic fishes are an iconic example of the impacts of climate variability on marine ecosystems, the mechanisms governing these dynamics are often elusive. We construct a 45-year record of nitrogen stable isotopes measured in larvae of Northern Anchovy (Engraulis mordax) in the California Current Ecosystem to assess patterns in food chain length. Larval trophic efficiency associated with a shortened food chain increased larval survival and produced boom periods of high adult biomass. In contrast, when larval food chain length increased, and energy transfer efficiency decreased, the population crashed. We propose the Trophic Efficiency in Early Life (TEEL) hypothesis, which states that larval fishes must consume prey that confer sufficient energy for survival, to help explain natural boom-bust dynamics of coastal pelagic fishes. Our findings illustrate a potential for trophic indicators to generally inform larval survival and adult population dynamics of coastal-pelagic fishes.

Time of day-dependent effects of heat treatment on thermal tolerance and sex differentiation in Nile tilapia (Oreochromis niloticus)

The present research aimed to determine the influence of the time of day at which heat treatment (HT) is applied to sexual differentiation and thermal tolerance mechanisms in Nile tilapia (Oreochromis niloticus). To this end, fish larvae were subjected to HT (36 °C) for 12 days at different times of the day during the thermosensitive period (i.e. 11–23 days post-fertilization, dpf). The heat treatment was applied during the light phase (L-HT); during the dark phase (D-HT), or during both light-dark phases (LD-HT). A control group maintained at constant rearing temperature (28 °C, CTRL) was also used. At 25 dpf, thermal tolerance was determined (survival) and whole larvae samples were collected for the mRNA expression analysis (qPCR). There after, all the groups remained at constant temperature until 270 dpf, when some fish were sacrificed and each individual's gonadal lobules were collected for histological and qPCR analyses. At the same time, each experimental group was subjected to acute heat shock (HS; 36 °C for 2 h) in either the mid-light (ML) or the mid-dark (MD) phase. When HS exposure finished, adults' brains were extracted to determine the HS response by qPCR. The expression of the genes involved in female (cyp19a1a, foxl2, era) and male (amh, ara, sox9a, dmrt1) sexual differentiation and thermal tolerance (hsp70, hsp90a, hsp27) in the 25 dpf larvae and adults was studied. The results revealed that all the HT-treated larvae showed an up-regulation of testicular differentiation gene expression and inhibition of ovarian differentiation gene expression, which resulted in a higher percentage of males. The time of day of HT during development influenced thermotolerance in the larval and adult stages, with the lowest survival and highest cellular stress (higher HSPs expression) observed in the larvae of the D-HT and LD-HT groups. These findings reveal the need to further investigate the link between sexual differentiation and thermotolerance daily rhythms in thermal biology research. These results may be useful for optimizing masculinization protocols in the tilapia industry, while ensuring animal welfare and minimizing negative HT effects on fish physiology.

Fifty-year study of microplastics ingested by brachyuran and fish larvae in the central English North Sea

Microplastics (MPs) are ubiquitous pollutants in marine environments. Among the many detrimental consequences of microplastic pollution, its consumption by marine biota is of particular relevance for human health, due to exposure through the food web. Long-term time-series biotic samples are overlooked sources of information for microplastics research. These collections are extremely valuable for the detection and monitoring of changes in marine environments. However, there are very few long-term studies (>10 years) of the uptake of microplastics by biota. Here, we used Dove Time Series planktonic samples (from 1971 to 2020) to assess the presence and prevalence of microplastics in the English North Sea coast over time. Fish and brachyuran larvae were selected due to their commercial importance and consequent implications for human health. A custom enzymatic digestion method was used to extract microplastics for FTIR-ATR polymer identification. An increasing cumulative trend in MP ingestion was identified. Cellophane and polyethylene terephthalate were the polymer types found most frequently in both taxa. Although a total higher microplastics uptake was observed in fish, consumption was not significantly different between taxa over time. Equally, results were not clearly related to microplastics shape or polymer type. This work did not find significant long-term evidence on the increasing uptake of microplastic particles by zooplankton over time. However, the results of this report identified additives, plasticisers, and other more complex and hazardous compounds that should not be released to the environment (e.g., bis-(2-hydroxyethyl) dimerate, propylene glycol ricinoleate) inside marine biota. The study detailed herein provides a case study for the use of long-term time-series in providing accurate assessments of microplastic pollution in marine biota.

Barcoding a glass eel migration: a snapshot of taxa migrating upstream in the Palu River, Central Sulawesi, Indonesia

Eels of the genus Anguilla are high value food fish with a catadromous life cycle. As tropical anguillid glass eels migrate to freshwater in multi-species schools, effective management of these and other diadromous resources requires reliable data. Previous research using two morphological methods concluded that between three and five anguillid eels recruit to the Palu River in Central Sulawesi, Indonesia with interannual and seasonal variations in species composition, size structure, and co-migrating taxa. Some glass eels and other taxa could not be identified based on external morphology. To clarify the taxonomic uncertainty regarding species recruiting to the Palu River this study applied DNA barcoding using the Cytochrome Oxidase I (COI) mitochondrial DNA (mtDNA) molecular marker. Taxa identified from the first sampling of glass eels and other taxa recruiting in these mixed schools included three anguillid eels, five other fishes, two crustacea and one mollusc, presenting a snapshot of taxa migrating upstream in the Palu River. Current GenBank accessions did not enable species level identification of two fish larvae (families Eleotridae and Tetraroginae). The sequences will add to Indonesian accessions in the GenBank repository and inform resource management, including the use of environmental DNA (eDNA) methods for monitoring Indonesian anguillid eels.

Successful Rearing of Nutritionally Supplemented Rotifers (Brachionus plicatilis) at Reduced Salinity for Zebrafish (Danio rerio) Polyculture.

Rotifers, Brachionus plicatilis, are a valuable first exogenous feed for zebrafish because they can provide continuous nutrition for growing zebrafish larvae when used in a rotifer-zebrafish polyculture. Typically cultured at high salinities (>10 ppt), B. plicatilis are temporarily immobilized when moved to lower salinities (5 ppt) used for polycultures, decreasing their accessibility and attractiveness to the larvae. The nutritional value of rotifers varies based on their diet, typically live algae, which has limited nutritional value and may pose biosecurity risks. After confirming that rotifers consume and can reproduce when fed an irradiated, processed larval fish diet (PD), they were reared at 5 or 15 ppt, and fed various combinations of an algae mix and/or PD. Population densities and percentages of egg-bearing rotifers were quantified daily until the population density plateaued, and then their nutritional value was assessed. Results indicated that rotifers thrived at both salinities. Those fed PD were successfully maintained at >500 rotifers per mL and contained a greater ω-6/ω-3 fatty acid ratio. Our findings indicate that enriching rotifers with PD raised at 5 ppt can potentially eliminate rotifer immobilization in polyculture, while providing a nutritious, attractive diet for zebrafish larvae and decreasing biosecurity risks.