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Microplastics (MPs) are emergent pollutants in freshwater environments and may impact aquatic organisms, including those of nutritional value. The specific activities of digestive and antioxidant enzymes can be used as good bioindicators of the potential effects of MPs on fish in case of waterborne MP contamination. In this study, we used fluorescent polystyrene microplastics (PS-MPs) to analyze the alterations in enzyme activities in larvae of Coregonus peled Gmelin (peled or Northern whitefish), one of the most valuable commercial fish species of Siberia. Our results indicate that peled larvae can ingest 2 µm PS microspheres in a waterborne exposure model. A positive correlation (rs = 0.956; p < 0.01) was found between MP concentration in water and the number of PS microspheres in fish guts, with no significant differences between 24 h and 6-day exposure groups. The ingestion of MPs caused alterations in digestive enzyme activity and antioxidant responses at the whole-body level. The presence of PS-MPs significantly stimulated (p < 0.05) the specific activity of α-Amylase and non-specific esterases in peled larvae after 24 h. However, a pronounced positive effect (p < 0.05) of MPs on the activity of pancreatic trypsine and bile salt-activated lipase was only found after 6 days of exposure compared to after 24 h. Intestinal membrane enzyme aminopeptidase N was also stimulated in the presence of PS-MPs after 6-day exposure. We also observed a significant increase in the specific activity of catalase in peled larvae after 6 days of exposure, which indicates the MP-induced modulation of oxidative stress. Taken together, these results highlight the potential impact of environmental MPs on northern commercial fish, their importance for estimating fish stocks, and the sustainability of freshwater ecosystems.

Omnipresent microplastics (MPs) in marine ecosystems are ingested at all trophic levels and may be a vector for the transfer of persistent organic pollutants (POPs) through the food web. We fed rotifers polyethylene MPs (1–4 µm) spiked with seven congeners of polychlorinated biphenyls (PCBs) and two congeners of polybrominated diphenyl ethers (PBDEs). In turn, these rotifers were fed to cod larvae from 2–30 days post-hatching (dph), while the control groups were fed rotifers without MPs. After 30 dph, all the groups were fed the same feed without MPs. Whole-body larvae were sampled at 30 and 60 dph, and four months later the skin of 10 g juveniles was sampled. The PCBs and PBDEs concentrations were significantly higher in MP larvae compared to the control larvae at 30 dph, but the significance dissipated at 60 dph. Expression of stress-related genes in cod larvae at 30 and 60 dph showed inconclusive minor random effects. The skin of MP juveniles showed disrupted epithelial integrity, fewer club cells and downregulation of a suite of genes involved in immunity, metabolism and the development of skin. Our study showed that POPs were transferred through the food web and accumulated in the larvae, but that the level of pollutants decreased once the exposure was ceased, possibly related to growth dilution. Considering the transcriptomic and histological findings, POPs spiked to MPs and/or MPs themselves may have long-term effects in the skin barrier defense system, immune response and epithelium integrity, which may potentially reduce the robustness and overall fitness of the fish.

Striped catfish Pangasianodon hypopthalmus (Sauvage, 1878) is a flagship catfish species of the Mekong River region, a commercially valuable food fish that is important in freshwater fisheries, and a popular aquaculture species in many Asian countries. The species was assessed as “Endangered” by the International Union for Conservation of Nature (IUCN) due to range contraction and declining abundance, though the status of the species’ wild population in Cambodia, a critical habitat for the species, is not well understood. Here, we assess the population status of the striped catfish in Cambodia using multiple sources, including time-series catch data and length frequency distribution data from a commercial fishery (stationary trawl bagnet or dai) operated in the Tonle Sap River from 1998/99 to 2017/18 and larval drift data monitored in the Mekong River in Phnom Penh from 2004 to 2018. We found that there was a significant decline (R2 = 0.54, p = 0.0002) in the catch (metric tonnes) of the striped catfish from the commercial dai fishery over the last two decades. Similarly, length-based indicator analysis indicates that striped catfish mean length and abundance have both declined over the study period, raising concerns about the sustainability of river catfish fisheries. Moreover, long-term larval drift monitoring in Mekong River shows that there was a marginally significant decline in the quantity of striped catfish larvae/juvenile drifting downstream to the lower floodplain over the last decade. Changes in flood index (extent and duration of flood) in the Tonle Sap floodplain affected by the Mekong’s flow are likely key factors driving the decline of the wild populations of the striped catfish. Both larval fish abundance and floodplain fish harvests have a significant positive relationship with Mekong flow and flood extent. Indiscriminate fishing exacerbates pressures on striped catfish stocks. Therefore, actions such as maintaining natural seasonal flows (flood timing, extent, and duration) to the Tonle Sap floodplain and protecting migratory fish stocks from overharvest and habitat fragmentation are essential to the persistence of stocks of striped catfish and other large-bodied migratory fishes that utilize both the Cambodian Mekong and Tonle Sap floodplains.

The northern coast of the Iberian Peninsula is an important spawning and nursery area for several marine fish species, some of which are economically exploited by fisheries and under management plans. Larval stages of fish are highly sensitive to environmental change and anthropogenic pressures, and Marine Protected Areas (MPA) can help mitigate the impacts on fish populations. This study investigated the environmental drivers of the temporal and spatial patterns of the larval fish assemblages inhabiting a small coastal MPA along the NW Portuguese Iberian Coast. Seasonal surveys were conducted over two years at nine sampling stations distributed throughout the MPA to collect larval fish samples and water parameters. Results showed that a total of 39 different fish taxa were identified. In terms of abundance, reef-associated species, such as Parablennius gattorugine (54.6%), and marine species that use estuaries as nursery areas, such as Ammodytes tobianus (15.7%) and Clupeidae n.i. (8.8%) dominated the larval fish assemblages. The larval fish assemblages were characterized by a strong temporal pattern that, according to CCA analyses, was related to the temporal variability of water temperature, pH, chlorophyll α, TPM, and also the river flow of an adjacent river. This study showed that 47% of the fish larvae belonged to commercially exploited species, highlighting the importance of this MPA as a nursery area for the early life stages of the fish population. Overall, these new findings emphasize the role of MPAs in ensuring the connectivity of fish species between marine-estuarine habitats and enhancing the conservation of fish populations.

Histological techniques are a traditional and essential tool for adequately comprehending cellular morphology and physiology in several scientific fields, including ecotoxicological studies. Although bioassays generally recommend using small test organisms, based on advantages such as low maintenance costs and the possibility of a higher number of replicates, the histological process of such organisms is still challenging due to the difficulty of handling them. The present study proposes an accessible protocol for performing the histology of a biological sample of 8 mm maximum length and using histopathological biomarkers in Senegal sole larvae for ecotoxicological tests. Eight-day old larvae of Solea senegalensis obtained from breeders’ natural spawns in cultivation conditions were submitted to histological processing by an adjusted protocol comprising fixation, agarose array pre-embedding, dehydration, paraffin embedding, slides’ preparation, and image analysis by light optical microscope coupled to a digital camera. Low-cost and easy-to-use alternatives were applied in the technique execution. The histological steps were detailed, and S. senegalensis morphological features were presented. This can be considered valuable background information for ecotoxicological studies where changes in cell morphology and physiology are expected.

Estuaries, as important fish nursery habitats, usually include a variety of larval fishes of different ecological guilds and exhibit complicated changing environmental conditions. We carried out a survey to examine the spatiotemporal dynamics of different ecological guild larval fishes and their relationships with environmental factors in the springs and summers from 2018 to 2020 in the Yangtze Estuary (China). The aims of the study were to provide detailed information on the characteristics of the larval fish assemblage and to explore the spatiotemporal variation in different ecological guild species and the effects of environmental variables on assemblage structure. More than 140,000 fish larvae from 26 families and 99 species were gathered during the six cruises, with the spring being the most prolific. The assemblage was dominated by a few species and was divided into three ecological guilds. Engraulidae was the most abundant family, followed by Cyprinidae and Gobiidae. Hemiculter bleekeri (freshwater), Pseudolaubuca sinensis (freshwater), Coilia mystus (brackish water), and Engraulis japonicas (marine) were the predominant species. Seasonal variations in larval fish assemblage structure were closely influenced by temperature, and the fluctuation in salinity mainly determined the spatial distribution of the larval fish community. Freshwater flows also played an important role in shaping the larval fish assemblage structure and dynamics. The conclusions improve the understanding of the ecological dynamics of larval fish assemblages in environmentally heterogeneous areas and may be applicable to other estuary ecosystems.

The early ontogeny of Triportheus albus and T. angulatus, two fish species of Triportheidae, is described using morphological, meristic, and morphometric characters. These species are exploited by subsistence fisheries and have potential as an alternative source of fish, given the decline in the natural stocks of other commercially important fish species in the Amazon. The specimens were collected in the open water limnetic zone, under of the macrophyte stands, and in subsurface areas near sandbars in the Amazon basin. Intra and interspecific morphometric analyzes were performed to evaluate growth models between species. The combination of color pattern, body morphology, morphometric proportions and myomeres number distinguishes the species from each other and from other congeners. Some morphometric relationships related to head as snout length and eye diameter as well as length from the snout to the origins of anal and length from the snout to the origins of pelvic, related with standard length were different between the two species of Triportheus, reflecting different growth models between them. An identification key for larvae and juveniles of some species of Triportheus from the Eastern Amazon is presented. Resumo A ontogenia inicial de Triportheus albus e T. angulatus, duas espécies de peixes pertencentes a Triportheidae, é descrita usando caracteres morfológicos, merísticos e morfométricos. Essas espécies são exploradas pela pesca de subsistência e têm potencial como fonte alternativa de pescado, dado o declínio nos estoques naturais de outras espécies de peixes comercialmente importantes na Amazônia. Os espécimes foram coletados na zona limnética de águas abertas, sob bancos de macrófitas e em áreas subsuperficiais próximas a bancos de areia na bacia amazônica. Análises morfométricas, intra e interespecíficas, foram realizadas para avaliar modelos de crescimento entre as espécies. A combinação do padrão de coloração, morfologia corporal, proporções morfométricas e número de miômeros distingue as espécies entre si e de outras congêneres. Algumas relações morfométricas relacionadas à cabeça, como comprimento do focinho e diâmetro do olho, assim como o comprimento do focinho à origem da nadadeira anal e o comprimento do focinho à origem da nadadeira pélvica, relacionadas ao comprimento padrão foram diferentes entre as duas espécies de Triportheus, refletindo modelos distintos de crescimento entre elas. Uma chave de identificação para larvas e juvenis de algumas espécies de Triportheus da Amazônia Oriental é apresentada.

Opportunistic microorganisms acquired through rearing water or live feed ingestion are believed to underpin high mortality rates of fish larvae, constituting a production bottleneck for the aquaculture industry. We employed 16S rRNA gene sequencing to determine whether treatment of live feed (rotifers and Artemia) with algal-derived, antibacterial metabolites could alter bacterial community structure of gilthead seabream (Sparus aurata) larvae in a larviculture facility. Owing to a large degree of sample-to-sample variation, pronounced 'legacy effects' of live feed manipulation on the total fish larvae bacterial community could not be verified. Notwithstanding, the approach induced shifts in relative abundance of specific bacterial phylotypes in both the live feed and fish larvae. Some phylotypes representing opportunistic taxa such as Stenotrophomonas, Pseudomonas and Klebsiella displayed reduced abundances in the bacterial community of fish larvae fed metabolite-treated vs. control live feed. Conversely, potentially beneficial phylotypes in the Alphaproteobacteria clade were consistently-although not significantly-promoted in the treated larval samples. These outcomes encourage future microbiome manipulation attempts to improve fish larviculture. However, successful host colonization and competition with resident symbionts are primary barriers that need to be overcome if live feeds are to be used as effective delivery systems of beneficial bacteria to fish larvae. info:eu-repo/semantics/publishedVersion

Background Considering wild inter-populational phenotypic differentiation can facilitate domestication and subsequent production of new species. However, comparing all populations across a species range to identify those exhibiting suitable key traits for aquaculture (KTA; i.e. important for domestication and subsequent production) expressions is not feasible. Therefore, proxies highlighting inter-populational divergences in KTA are needed. The use of such proxies would allow to identify, prior to bioassays, the wild population pairs which are likely to present differentiations in KTA expressions in aquaculture conditions. Here, we assessed the relevance of three alternative proxies: (i) genetic distance, (ii) habitat divergence, and (iii) geographic/hydrologic distances. We performed this evaluation on seven allopatric populations of Perca fluviatilis for which divergences in KTA had already been shown. Results We showed differences in the correlation degree between the alternative proxy-based and KTA-based distance matrices, with the genetic proxy being correlated to the highest number of KTA. However, no proxy was correlated to all inter-populational divergences in KTA. Conclusion For future domestication trials, we suggest using a multi-proxy assessment along with a prioritisation strategy to identify population pairs which are of interest for further evaluation in bioassays. Supplementary Information The online version contains supplementary material available at 10.1186/s12862-021-01937-z.

Betta fish (Betta sp) is a freshwater ornamental fish during the pandemic that is very popular with the public. However, people tend to prefer male betta fish than female fish. To deal with the large number of requests, a sex reversal technique is carried out which applies hormonal engineering to change female to male sexual characters (masculinization) using natural ingredients, namely cow testicle flour. The purpose of this study was to analyze the dose of bovine testicular flour hormone on the process of oral male betta fish larvae. This research was conducted in Moncongloe Village, Maros Regency, from July to September 2021. The production of beef testicle flour was carried out in the Chemical Engineering laboratory, Ujung Pandang State Polytechnic. Betta fish seeds were kept each in an aquarium measuring 20 cm x 14 cm x 20 cm as many as 12 pieces. Soaking artemia with beef testicle flour with a predetermined dose of 60 mg L-1, 80 mg L-1 and 100 mg L-1, the duration of immersion is 24 hours. This study used a one-factor completely randomized design (CRD). The results obtained were the highest percentage of male genitalia at a dose of 100 mg L-1 with a percentage of 66.7%. The survival rate of betta fish during the maintenance period with different doses of cow testicles obtained data ranging from 80-100%.

Anthropogenic activities including climate change affect the development of structural complexity in seagrass and the state of environmental variables. It remains unclear whether these variables, alone or in combination, have an important influence on fish larvae assemblages. This study examined the influence of the structural complexity of seagrass meadows and various environmental variables on fish larvae assemblages in tropical coastal waters of Tanga, Tanzania. The study was conducted in four Thalassia hemprichii dominated seagrass meadows from June 2019 to January 2021. Multiple regression analysis indicated that the structural complexity of seagrass (canopy height, seagrass cover, and shoot density) and environmental variables (dissolved oxygen, temperature and salinity) were the foremost predictors for fish larvae assemblages; abundance and richness (R2 = 0.75, p = 0.0185, R2 = 0.54, p = 0.0396, respectively). Based on these findings, the structural complexity of seagrass and environmental variables are both important determinants of fish larvae assemblages in tropical coastal waters. The findings suggest that reducing anthropogenic activities that affect the development of structural complexity of seagrass and negatively impact environmental variables in seagrass meadows through more effective governance would result in increased production of fish larvae in meadows and, as a result, increased fish recruitment in tropical coastal waters.

The larval distributions of the small-sized fishes Omobranchus elegans, Erisphex pottii, Benthosema pterotum, Acropoma japonicum, Upeneus bensasi, and Apogonichthys lineatus in the East China Sea ecosystem are important due to their ecological and economic benefits. To date, however, there have been few studies describing their population distributions and dynamics. In the current study, ichthyoplankton surveys were carried out from April to July 2018 to analyze variations in the larval abundance, distribution, and development stages of these species. In addition, the spatiotemporal larval distribution was investigated in terms of measured environmental variables. It was found that larvae were mainly distributed at depths of 5.00–66.00 m, in areas with sea surface temperature of 4.40–29.60 °C, sea surface salinity of 16.54–34.60 psu, pH of 7.00–9.00, and dissolved oxygen concentration of 2.54–8.70 mg/L. Benthosema pterotum and A. lineatus migrated from 30.00–31.00° N 123.17–123.50° E in June to 30.00–32.50° N 122.22–123.50° E in July. The results of this study can help to preserve spawning and nursery grounds and contribute to sustainable coastal fisheries management.

Marine deposits of earliest Eocene age in northern Jutland, Denmark, are renowned for yielding diverse teleost assemblages that have proved central for enhancing our understanding of the early evolution of many extant actinopterygian clades. In this study, we investigate diminutive larval fish fossils from the Stolleklint Clay, Olst Formation, that retain multiple soft-tissue features preserved as distinct dark-coloured stains. To examine the elemental and molecular composition of these soft parts, we employed a combination of time-of-flight secondary ion mass spectrometry (ToF-SIMS), scanning electron microscopy (SEM) and energy-dispersive x-ray spectroscopy (EDS). Our analyses revealed that the preserved structures contain chemically identifiable eumelanin intimately associated with densely aggregated microbodies that are morphologically consistent with melanosome organelles. Thus, we conclude that the carbonaceous structures represent traces of originally melanized body parts, including the eyes and peritoneum. Comparable pigmentation patterns are seen in many extant teleost larvae that use semi-transparency as a means of camouflage in pelagic environments, to suggest a similar visual appearance of the Stolleklint Clay fish fossils. This in turn suggests that adaptations for concealment and UV-protection had already evolved by the beginning of the Eocene, notably during a time interval characterized by an extreme greenhouse climate, when the global fish fauna become increasingly modern in composition. (Less)

Accurate estimates of growth and mortality are needed to understand drivers of production and cohort success. Existing methods for estimating mortality rates, such as catch-curves, require large sample sizes, as they work by grouping individuals into age-bins to determine a frequency distribution. Yet, sampling enough larvae is often not possible at fine scales within the constraints of research projects, due to low density of larvae in pelagic environments. Here, we develop a novel method to simultaneously estimate growth and mortality rates of fish larvae as a continuous function of size using theory of size-structured populations, eliminating the need to group data into age-bins. We compare the effectiveness of our model to existing methods by generating data from a known distribution. This comparison demonstrates that while all models recover correct parameter values under ideal circumstances, our new method performs better than existing methods when sample sizes are low. Additionally, our method can accommodate non-linear growth and mortality functions, while also allowing growth and mortality to vary as functions of environmental co-variates. This increased accuracy and flexibility of our method should improve our ability to relate variability in larval production to environmental fluctuations at finer spatial scales.

Targeting in zebrafish fast growth, high survival rates and improved reproductive performance has led over the last years in variable feeding regimes between different facilities. Despite its significance on fish function and welfare, normal skeletal development has rarely been evaluated in establishing the best feeding practices for zebrafish. The aim of this study was to establish a protocol for normal skeletal development, growth and survival of zebrafish larvae through live feed-to-microdiet transition at an appropriate rate. Four feeding regimes including feeding exclusively on Artemia nauplii (A) or dry microdiet (D), and feeding on both Artemia and microdiet at two different transition rates (slow (B) or fast (C)) were applied from 5 to 24 dpf (days post-fertilization). Results demonstrated a significant effect of feeding regimes on the incidence of skeletal abnormalities (gill cover, fins and vertebral column, p

Seagrass beds provide critical nursery habitats and spawning grounds for new generations of fish. The habitats are under threat from human activities and climate change, and with that, an important ocean service is lost that limits fish production. The present study investigates patterns in the larval occurrence and abundance in seagrass meadows at two locations with varying degrees of seagrass fragmentation. Monthly ichthyoplankton sampling was conducted during the northeast monsoon (NEM) and southeast monsoon (SEM) seasons in 2019 and 2020. A total of 42 larval fish families belonging to 37 genera and 21 species were identified. Dominant families were Labridae (29.5%), Blenniidae (28.7%), Gobiidae (26.0%), Engraulidae (23.3%) and Scaridae (22.3%). Canonical Correspondence Analysis and regression analysis revealed water temperature, dissolved oxygen and pH as the most important abiotic variables driving taxonomic composition of larval assemblages, while zooplankton and chlorophyll-a were the most important biotic factors. Fish larvae were more abundant in healthy seagrass habitats as compared to degraded ones. However, despite some loss in functionality, the degraded sites equally played a role in supporting some species, including Gobiidae and Blenniidae. Seasonality influenced larval abundance at the two sites, with a peak in mean abundance coinciding with the NEM season. Interannual variability in fish larval abundance was observed at both sites, indicating that factors controlling larval production varied between the years. This study demonstrates the important role of seagrass meadows in the replenishment of fish stocks and supportive evidence for their management and conservation.

RESUMO O Parachromis dovii é um peixe carnívoro da América Central, o qual aceita facilmente rações formuladas desde o início da alimentação exógena; no entanto, seu crescimento larval é inferior ao obtido com alimentos vivos. Por esta razão, o efeito de diferentes combinações de fontes de proteína na dieta sobre o crescimento e a atividade de proteases digestivas alcalinas foi testado em larvas. As misturas proteicas de teste foram preparadas utilizando farinhas de peixe e subprodutos de aves em diferentes proporções (quatro dietas) e comparadas com um produto comercial (Artemia cysts Vitellus) e náuplios de Artemia, como controle. No final do ensaio, as larvas alimentadas com náuplios de Artemia apresentaram o melhor crescimento (taxa de crescimento específico (TCE): 17,6% PC/d). Por outro lado, a dieta Vitellus apresentou o menor TCE (12,0% peso corporal por dia (PC/d)) (LSD, P0,05). A atividade da protease aumentou até 27 DAH, sendo maior nas larvas alimentadas com Artemia do que nos outros tratamentos (P, The Parachromis dovii is a carnivorous fish from Central America, which easily accept formulated feeds since exogenous feeding starts; however, its larval growth is lower than that obtained using live food. For this reason, the effect of different dietary protein source combinations on growth and alkaline digestive proteases activity were tested in P. dovii larvae. The test protein mixtures were prepared using fish, tankage and poultry by-product meals in different proportions (four diets) and compared to a commercial product (Artemia cysts Vitellus) and Artemia nauplii as a control. At the end of the trial, larvae fed Artemia nauplii showed the best growth (specific growth rate (SGR): 17.6% BW/d), contrary the Vitellus diet presented the lowest SGR (12.0% body weight per day (BW/d)) (LSD, P0.05). The protease activity increased up to 27 DAH, being higher with larvae fed Artemia than other treatments (P, RESUMEN Parachromis dovii es un pez carnívoro de Centroamérica, el cual acepta fácilmente alimento fabricado desde el momento en que se inicia su alimentación exógena, sin embargo, su crecimiento larvario es menor cuando se usa alimento formulado que con el alimento vivo. Por esta razón, se evaluó el efecto de diferentes mezclas de proteínas en el alimento sobre el crecimiento y la actividad de las proteasas alcalinas digestivas en larvas de P. dovii. Las mezclas de proteínas en el alimento fueron preparadas con harina de pescado, carne y hueso, tortave (subproductos avícolas), y comparadas con un producto comercial (Vitelo de cistos de Artemia) y nauplios de Artemia como control. Al final del ensayo, las larvas alimentadas con nauplios de Artemia presentaron el mejor crecimiento y el menor se presentó con el Vitelo (LSD, P < 0.05). La D3 (con el mayor porcentaje de tortave) mostró la menor tasa específica de crecimiento, mientras que las otras mezclas proteicas rindieron valores similares. La sobrevivencia no fue afectada por los tratamientos evaluados (LSD, P>0.05). En general, la actividad de las proteasas digestivas alcalinas incrementó durante la ontogénesis larvaria, fue mayor con el alimento vivo, y no presentó cambios significativos entre los demás tratamientos (Vitelo y dietas formuladas). Palabras clave: larvas de peces, crecimiento, fuentes proteicas, actividad enzimática

Parachromis dovii is a carnivorous cichlid fish from Central America, which easily accepts formulated feeds since exogenous feeding starts; however, its larval growth is lower than that obtained using live food. For this reason, the effect of different dietary protein source combinations on growth and alkaline digestive proteases activity were tested in P. dovii larvae. The test protein mixtures were prepared using fish, meat and bone (tankage), and poultry by-product meals in different proportions (four experimental diets: D1-D4) and compared to a commercial product (Artemia cysts Vitellus) (VD) and Artemia nauplii as control (AD). At the end of the trial, larvae fed Artemia nauplii showed the best specific growth rate (SGR): 17.6% body weight per day (BW/d), contrary to the Vitellus diet which presented the lowest SGR (12.0% BW/d) (LSD, p0.05). The lowest alkaline digestive protease activity was found six days after hatching (DAH), and it was similar among treatments. The protease activity increased up to 27 DAH, being higher with larvae fed Artemia nauplii than with the other treatments. There were no differences in protease activity among the protein mixture diets, nor were there differences when comparing it with the Vitellus, except at 20 DAH. RESUMEN | Parachromis dovii es un pez cíclido carnívoro de Centroamérica, el cual acepta fácilmente alimento balanceado desde el momento en que se inicia su alimentación exógena; sin embargo, su crecimiento larvario es menor cuando se usa alimento balanceado que con el alimento vivo. Por esta razón, se evaluó el efecto de diferentes mezclas de proteínas en el alimento sobre el crecimiento y la actividad de las proteasas alcalinas digestivas en larvas de P. dovii. Las mezclas de proteínas en el alimento fueron preparadas con harina de pescado, carne y hueso, tortave (subproductos avícolas) (cuatro dietas, D1-D4), y comparadas con un producto comercial (Vitelo de quistes de Artemia, VD) y nauplios de Artemia como control (AD). Al final del ensayo, las larvas alimentadas con nauplios de Artemia presentaron el mejor crecimiento (tasa especifica de crecimiento (TEC): 17.6% peso corporal por día, PC/d) y el menor crecimiento se presentó con el Vitelo (12.0% PC/d) (LSD, p0.05). La actividad de las proteasas digestivas alcalinas mas bajo se encontró a los seis días después de la eclosión (DDE), y esta fue similar entre todos los tratamientos. La actividad de las proteasas se incrementó hasta los 27 DDE, siendo más alta con las larvas alimentadas con nauplios de Artemia que con los otros tratamientos. No se encontró diferencias en la actividad de las proteasas entre las dietas con mezclas de proteínas, ni tampoco hubo diferencias al compararla con la dieta Vitelo, excepto a los 20 DDE.

O presente estudo mostra os avancos obtidos na coleta de peixes e caracterizacao ambiental de riachos. Desde a publicacao em 1999 do volume VI “Ecologia de Peixes de Riachos”, da entao denominada Oecologia Brasiliensis , hoje Oecologia Australis , varios progressos ocorreram. Diversos metodos de coleta de peixes propriamente ditos, permaneceram os mesmos. Porem, em relacao ao uso da pesca eletrica, coleta de ovos e larvas de peixes, e caracterizacao de habitat fisicos em riachos, houve notavel desenvolvimento e aperfeicoamento. O objetivo deste artigo e apresentar o “estado da arte” destes aspectos da amostragem de peixes e habitat em riachos. Metodos de preparo de amostras para analises geneticas, isotopos estaveis e metais pesados sao apresentados resumidamente ao final. ADVANCES IN METHODS FOR FISH SAMPLING AND HABITAT ASSESSMENT IN TROPICAL STREAMS: This paper brings some advances in fish data sampling and stream environments. Since the publication in 1999 of volume VI “Ecology of Stream Fishes” in the former Oecologia Brasiliensis journal, today Oecologia Australis , several progresses have occurred. Several methods of collecting fish themselves, have remained the same. However, in relation to the use of electric fishing, collection of eggs and fish larvae, and characterization of physical habitats in streams, there was remarkable development and improvement. The purpose of this article is to present the “state of the art” of these three aspects of sampling fish and habitats in streams. By the end, preparation methods of samples for genetic, stable isotopes and heavy metal analyses are briefly presented.

Male betta fish are more popular and expensive than female betta fish because they have a more beautiful body shape and color. One effort to increase the male fish population is the masculinization method to reverse the sex of the fish to become male, so that the profit value is higher (Siregar, 2018). Generally, sex reversal uses a steroid hormone: 17?-methyltestosterone (MT) by the method: immersion, injection or oral through feed. However, this MT hormone has side effects that can cause pollution, liver damage in test animals and can cause death (Djihad, 2015 in Nazar, 2017). This study was conducted to determine the survival of the larvae and the increase in the percentage of male betta fish by soaking different types of honey. The method used in this study was a laboratory experiment using 3 treatments, namely A (forest honey), B (cattle honey), C (propolis) and 3 replications. Betta fish larvae as test animals were 7 days old, with honey soaked for 10 hours at a concentration of 5ml/L, then reared for 60 days. The results showed that the survival rate of betta fish larvae after honey soaking treatment (10 hours) averaged 100% and the percentage of betta fish survival during maintenance (60 days) ranged from 23-28% where the highest survival was in forest honey ( 28%). Furthermore, the average sex percentage of male sex larvae in the treatment of forest honey immersion (97%), propolis honey (90%), livestock honey (63%) and control (29%). Thus it can be concluded that forest honey is the right type of honey that plays an important role in the masculinization process of betta fish larvae.

Changing environmental conditions are influencing the seasonal timing in life history events of organisms. Such shifts in phenology are often linked to increasing temperatures that stimulate faster developments or earlier arrivals. This phenomenon has been demonstrated in terrestrial and aquatic realms, but data and knowledge are limited on how early life stages of fish are affected over long-term and broad environmental scales. Here, we analyze 2 decades (1974-1996) of size class-specific Baltic herring Clupea harengus membras L. larval data along the whole coast of Finland to expose shifts in phenology linked to changes in environmental covariates. We use a novel Bayesian hierarchical spatio-temporal hurdle model that describes larval occurrence and abundance with separate processes. Abundances are modeled with the Ricker population growth model that enables us to predict size-specific larvae groups in relation to the environment while accounting for population density dependence. We quantify shifts in phenology at multiple life stages, based on first appearances of smallest larvae (15 mm) appearing earlier than they have done historically. Our results show a strong signal in shifting phenology of the larvae toward an earlier development of 7.7 d per decade. Increasing temperature had a positive effect on the earlier development of larger larvae. Additionally, we highlight that the survival of larvae becomes more density dependent as their size increases. Our modeling framework can reveal phenological shifts of early life stages in relation to environmental change for survey data that do not necessarily cover the onset of reproduction.

Estuari adalah salah satu habitat penting bagi ikan, namun terancam akibat peningkatan aktivitas manusia. Hal tersebut dapat memengaruhi keanekaragaman ikan di sekitarnya. Tujuan penelitian ini untuk menganalisis keanekaragaman dan kelimpahan larva ikan di sekitar muara Sungai Musi Sumatra Selatan. Penelitian ini menggunakan metode survei dengan cruise track design dan lintasan survei continuous para ll el pada setiap stasiun secara swept area . Hasil penelitian menunjukkan bahwa indeks keanekaragaman (H’) di muara Sungai Musi pada Maret 2019 sebesar 0,639 sedangkan pada Mei 2019 sebesar 1,253. Kelimpahan relatif pada Maret 2019 lebih tinggi daripada Mei 2019. Kelimpahan Relatif (Kr) pada Maret 2019 antara 0,69–84,61% dan pada Mei 2019 antara 0,21–58,77%. Kelimpahan larva ikan yang ditemukan pada Mei lebih tinggi, yaitu sebanyak 456 individu dari 10 famili. Pada Maret ditemukan lebih rendah, yaitu sebanyak 143 individu dari 6 famili. Ditemukan larva ikan dari famili Engraulidae , Belonidae , Osphronemidae , Nemipteridae , Gerreidae , dan Gobiidae pada Maret. Sedangkan pada Mei 2019, yaitu Nemipteridae , Engraulidae , Scatophagidae , Chandidae , Lobotidae , Terapoinidae , Belonidae , Osphronemidae , Chanidae , Clupeidae . Abstract Estuary is one of important habitat for fish, yet is threatened by an increase in human activities. Thus affecting the diversity of fish around it. This study aim to determine the diversity and abundance of fish larvae around the mouth of Musi River in South Sumatra. This study was conducted using survey method with Cruise Track Design and continuous parallel survey track by swept area at each station. The results showed that the diversity index (H ') at the mouth of the Musi River in March 2019 was 0.639 while in May 2019 was 1.253. Relative Abundance (Kr) in March 2019 between 0.69 – 84.61% and in May 2019 between 0.21 – 58.77%. Abundance of fish larvae in May was found higher at 456 individuals from 10 families. Whereas in March it was found to be lower as many as 143 individuals from 6 families. The relative abundance in March 2019 was lower than in May. Fish larvae from the Engraulidae, Belonidae, Osphronemidae, Nemipteridae, Gerreidae and Gobiidae families were found in March. Whereas in May 2019 were Nemipteridae, Engraulidae, Scatophagidae, Chandidae, Lobotidae, Terapoinidae, Belonidae, Osphronemidae, Chanidae, Clupeidae .

Jaw malformations imply an important problem during the commercial production of Seriola lalandi larvae and juvenile fish in Chile and New Zealand. Since the rate of malformations in other fish species has been associated with the content of long-chain PUFA (LC-PUFA) in neutral lipids of the diet, the relationship between body LC-PUFA and the rate of malformations, together with a transcriptomic analysis of genes related to the metabolism and transport of lipids in commercially produced S. lalandi larvae have been investigated in the present work. A total of 10 batches of S. lalandi larvae were obtained and cultured at about 22 °C following the protocols of a Chilean commercial hatchery during the spawning season. There were three larval batches that were collected in August (austral winter), three batches that were obtained in October (spring), and finally four spawning events that were obtained in December-January (spring-summer). The rate and type of jaw malformations, the profile of long-chain PUFA (LC-PUFA) of total lipids during larval culture, and the distribution of LC-PUFA were analyzed. Additionally, a transcriptome analysis related to lipid metabolism in 40-day-old larvae was performed. As a result, a decrease in the rate of malformations was recorded from August to December. DHA showed a steep decrease between days 1 and 10 of culture, probably due to the consumption of yolk sac lipids, but a higher proportional change was noted in larvae that hatched during August. The DHA content in polar lipids (PL) and neutral lipids (NL) of 40-day-old larvae increased from August to December, so that the abundance of DHA was higher in PL in larvae that hatched in December, but it was higher in NL in those larvae that hatched in October. In conclusion, the rate of jaw malformations was associated with the rapid decline in DHA during early larval life and the highest abundance of DHA in neutral lipids at the end of the larval life.

The review briefly addresses the mechanisms underlying micro- and macromolecular transport of proteins, fats and carbohydrates in the fish intestines. A special focus is on the differences between some mechanisms of micromolecular transport of peptides, amino acids and hexoses, as well as craniocaudal transport gradients, in fish compared to mammals. Transport proteins emerge at the earliest stages of fish ontogenesis, before the transition of fish larvae to exogenous feeding. The reasons behind the differences in the intestinal transport systems are analyzed.

Of the five nominal species in the genus Caranx Lacepède 1801 distributed throughout the Eastern Central Pacific, Caranx caballus and Caranx sexfasciatus are the only two that have formal fish larval descriptions based on diagnostic characteristics (morphology, meristics and pigmentation). In this study, the diagnostic characteristics of three Caranx species larvae were validated using DNA barcoding analysis cytochrome c oxidase subunit I (COI; 651 bp). For the first time, the morphological taxonomic assignation of C. caballus fish larvae was confirmed using COI gene partial sequences of adults, with a genetic similarity between 99.8–100%. However, molecular evidence demonstrated that fish larvae previously described as C. sexfasciatus had high genetic similarity (99.7–100%) and low genetic distance (Caranx caninus adults. An undescribed larval morphotype collected in the present study genetically matched (100%) with COI sequences of C. sexfasciatus adults. The diagnostic characteristics of this new morphotype were a lack of pigmentation in the supraoccipital crest, over the gut, and at the terminal region of the gut. The combination of diagnostic characteristics and DNA barcoding evidence allowed the discrimination and validation of C. caballus, C. caninus and C. sexfasciatus larvae. The diagnostic characteristics and COI sequences of Caranx lugubris and Caranx melampygus larvae, which are also distributed in the Eastern Central Pacific, remain to be investigated.

The role of small prey (Clupea harengus) as a case study, as it is a key species with high commercial and ecological importance. In autumn and winter, the potential PZP and MZP prey was dominated by cells Pronoctiluca pelagica,Tripos spp. and Strombidium spp.), while copepod nauplii and copepodites where more abundant in autumn than in winter. Based on their trophic enrichment (∆15 N), larvae preferentially grazed on small MZP 15N but different δ13C). Growth rates (based on RNA/DNA estimates) were similar in autumn and winter, suggesting that growth was not affected by station-specific differences in the composition of the prey field. Our results not only underscore the important role of MZP on larval herring diets both in autumn and wintertime, but also emphasize the limitations of bulk stable isotope analysis. Given the current low recruitment in North Sea herring, these results provide significant information for future monitoring approaches relevant to stock assessment of this species.

The semah fish (Tor douronensis) is an Indonesian endemic fish that has a long growth, which takes 4 years to grow from larvae to broodstock. This study aims know of Daphnia sp. pelet fed with effective doses to increase the growth of semah’s fish larvae. The study was conducted from March 25 to April 13, 2020 at the Instalasi Riset Plasma Nutfah, Cijeruk, Bogor, West Java. The experimental design used completely randomized design (CRD) 4 treatments and 3 replications, namely treatment A (Daphnia sp.+pelet feed 0 gr/ L), treatment B (Daphnia sp.+ pelet feed 1 gr / L), treatment C (Daphnia sp. + pelet feed 2 gr / L), treatment D (Daphnia sp. + pelet feed 3 gr / L). The larvae of 9 days in age were randomly stocked into 12 aquariums measuring 60x30x35 cm with a density of 50 fish/aquarium and fed in the form of Daphnia sp. enriched pelet feed according to the treatment of 50 ind/larvae by giving 3 times a day which is maintained for 20 days. The test parameters measured are absolute growth in length and weight, survival rate, and water quality. Based on the results of statistical analysis (Anova), the results showed that the treatment D gave the highest influence on the growth of semah’s fish larvae (P

Understanding the cues that drive larval fish settlement is critical for managing reef systems under stress. Reef sound is increasingly reported to influence fish recruitment, yet the physical and acoustic environment in which larval fish settle varies in space and time. Accordingly, testing potential settlement cues under different conditions is vital for understanding their ecological importance. We conducted 2 sets of field playback experiments in St. John, US Virgin Islands, one nearshore (10 m depth) and the second ‘offshore’ (25 m depth), to assess the effects of reef soundscape playback on settlement rates of multiple reef fish families. In each experiment, nightly currents were quantified and we replicated the diel soundscape cycle using high, low, and control (silent) amplitude recordings from nearby reefs. The first experiment revealed significant current-based, down-stream reduction in larval fish catches in subsurface light traps and a significant effect of increasing amplitude of reef playbacks on larval lizardfish (Synodontidae) catches. In the second, offshore experiment which had no current effect, increasing reef playback amplitude led to a significantly greater catch of parrotfish (Scaridae) larvae and decreased larval pelagic fish catch. Total reef fish larvae only showed attraction to reef playbacks at the most nearshore site. This work demonstrates that while sound can play a role in the settlement of certain reef fishes, responses are influenced by multiple factors, including larger-scale physical processes, underscoring the need to consider the scale of soundscape cues for reef fish settlement within an oceanographic context.

Physalia physalis is one of the jellyfish believed to be responsible for a significant proportion of jellyfish attack cases in the world. As one of the most dangerous members of the Cnidarian in the sea, P. physalis has a sting that can paralyze their prey. To humans, the sting can cause cardiotoxic, neurotoxic, musculartoxic, and hemolytic effects. P. physalis has different biological characteristics than most organisms. For example, an individual of P. physalis actually is a colony consisting of four groups of individuals who have different structures and functions. The arrangement of the colony has a complex structure and shows a polymorphism. P. physalis is a pleustonic organism because they live on the surface of the water. P. physalis still leaves many mysteries to scientists. For example, the life cycle of a P. physalis is not yet fully known. Besides, the diversity of P. physalis also still leaves questions among scientists. Some believe that P. physalis is monotypic, while others suspect there is cryptic diversity. Therefore, the study of P. physalis is very interesting, especially under the issue of climate change. Many scientists believe that jellyfish get benefit from increasing sea temperatures, so the population is predicted to increase. The high population of P. physalis threatens the sustainability of fish stocks in the ocean, mainly due to P. physalis are productive predators of fish larvae. This paper aims to provide information on the biological aspects of P. physalis, which are still limited in Indonesia.

Four algal species (Isochrysis galbana, Chaetoceros muelleri, Tetraselmis suecica and Nannochloropsis oculata) were tested experimentally as food for the calanoid copepod Gladioferens imparipes, which could be a potential food for marine fish larvae. Each of the algal species was used at four separate concentrations (5 × 104, 1 × 105, 2 × 105 and 4 × 105 cells/ml). The results illustrated that I. galbana and C. muelleri were the most suitable diets for the copepod species, promoting high survival of the adults and shortening the maturation time. With both algal species, intensive successful rearing of nauplii to mature adults was conducted at all concentrations of the algal species, resulting in high number of ovigerous females. Meanwhile, I. galbana was the best diet enhancing the production of egg sac in the cultivated copepod. In addition, the fatty acids in the copepod species were affected by the algal diets, resulting in variable amounts of the HUFA (DHA, EPA and ARA) in the copepod relative to the algal diets.

Most coastal fish species spend their early life stages in the pelagic environment, before settling in coastal habitats. The variability in the arrival of larvae to coastal habitats provides information on the species’ biology and recruitment potential. To explore the dynamics of larval fish supply to coastal habitats in the NW Mediterranean Sea, 13 sites were monitored using light-traps, from July 2012 to December 2015. Most variation in catches per unit effort (CPUE) among topographic basins and species were statistically significant for high (quantile 75%) and very high (quantile 90%) catches only. At the yearly scale, CPUE displayed strong seasonality, and 3 main species assemblages were detected in late spring-early summer, summer and late autumn-early winter. At the monthly scale, CPUE were higher around the new moon for all quantiles and temporally autocorrelated at a lag of ~28 d. Larval supply also varied spatially with site-specific associations and with riverine influence. Altogether, these results confirm that the previously described patterns of larval supply observed in tropical and subtropical environments (e.g. the high variability at all spatial and temporal scales and the strong influence of the moon) also apply to Mediterranean fish assemblages. Our quantile-based approach demonstrated that the larval supply in the NW Mediterranean Sea is a solid candidate for monitoring the state of the marine ecosystems, highlighting the need to continue such time series.

The alternation of the classic and microbial food-webs in spring and winter, respectively, and the trespass towards higher trophic levels represented by fish early stages, are not well understood in Patagonia. These trophic routes were investigated in the inner Sea of Chiloe, an estuary of high ecological relevance in northern Patagonia. The isotopic values of δ13C and δ15N of ichthyoplankton and particulate organic matter were analyzed in late winter and spring 2017 to evaluate whether seasonal changes (e.g. in the composition of the freshwater discharge) were reflected in the isotopic signals of fish larvae. For this purpose, larvae of dominant fish species with contrasting feeding strategies were collected up to 100 m depth. The inshore zone of northern Patagonia was characterized by a dominance of marine carbon production, with increasing input of terrestrial organic matter during winter. δ13C values < -25 ‰ at the outermost estuary stations indicated the influence of allochthonous carbon exported from the inshore area in spring. The δ13C-larval signature of the species of the lightfish Maurolicus parvipinnis, the pipefish Leptonotus blainvilleanus, and the rockfish Sebastes oculatus followed the isotopic signature of the particulate organic matter in both seasons, at inshore and the exchange (outer) zone. Food partitioning was detected between species, with Merluccius spp. at the highest trophic position and L. blainvilleanus at the lowest. The fish larval community reached more diverse and higher δ15N values in winter, when larvae likely fed on prey items of higher trophic level, or instead when the food-web was partly sustained by microbial sources. Our results showed seasonal variations in δ13C values, suggesting differences in the source of organic carbon incorporated by the studied fish larvae. Moreover, trophic plasticity at larval stages may be an important characteristic of this type of estuarine environment.

For much of their pelagic larval dispersal (PLD) stage, larval perciform fishes are able to directly influence their dispersal by horizontal swimming, but it is unclear which means of measuring swimming ability is most appropriate for modelling dispersal and studying demographic and genetic connectivity. Most studies use critical speed (Ucrit), a laboratory flume measure derived by increasing flow until larvae can no longer maintain their position. Most swimming ability data on fish larvae are Ucrit, usually for larvae nearing the end of PLD. Recognizing that a forced laboratory measure is inappropriate for dispersal, researchers have used decreased Ucrit values, usually by 50%, and have argued that Ucrit is strongly correlated with more relevant swimming measures. Here I examined the suitability of Ucrit versus in situ speed (ISS), wherein speed of larvae is measured by divers following them in the ocean with a flow meter. Considerations of dispersal require inclusion of swimming ontogeny. Swimming speed regressions of speed on size of 10 species in 8 families showed that Ucrit and ISS are not well correlated. The Ucrit:standard length (SL) slope was greater than the ISS:SL slope in 6 species, and did not differ in the other 4 species. No overall metric, e.g. X% of Ucrit = ISS, was appropriate for conversion of Ucrit to ISS. Conversion of Ucrit to ISS is not straightforward. Ucrit measures swimming potential, not what larvae do in the ocean, whereas ISS directly measures larvae swimming in the ocean. Ucrit ontogeny is less variable, but ISS ontogeny is more relevant to dispersal. Ucrit may be useful for other purposes.

Background. The Gulf of Gabès supports an important fishery which is characterized by a great diversity of fish species. Despite this importance, there has been no attempt to examine the whole larval fish assemblage in this area. The aim of this study was to investigate the larval fish communities during summer and winter seasons in the Gulf of Gabès. Materials and methods. Two multidisciplinary surveys were carried out aboard the R/V Hannibal in 2009. A total of 80 and 70 stations were sampled during winter and summer surveys, respectively. Stations were arranged in a regular sampling grid of 10 × 10 nautical miles. Ichthyoplankton was sampled by oblique tows with a Bongo net of 60 cm mouth diameter, fitted with 335 µm mesh nets. Zooplankton dry weight was obtained by drying aliquots of the zooplankton sample in an oven at 60ºC, for 72 hours. Results. In summer 34 taxa representing 24 families, were collected, whereas in winter 35 taxa, representing 16 families, were collected. Larval fish communities were dominated by small pelagic species: sardinella and anchovy in summer and sardine in winter. The results also highlight the Gulf of Gabès as an important spawning ground for many large and medium pelagic fishes, both highly migratory (Thunnus thynnus) and resident species (Auxis rochei, Euthynnus alletteratus). The summer/winter differences observed in species composition and abundance of the larval fish communities reflected the seasonality in fish species spawning in the Mediterranean Sea, likely influenced by the highly contrasting environmental conditions between seasons. Thus, the seasonal changes in the hydrographic conditions of the Gulf of Gabès result in different scenarios that provide suitable spawning environments for a variety of fishes, allowing them to share the Gulf as spawning habitat. Conclusion. The Gulf of Gabès is an important fish spawning area for demersal, small pelagic, medium pelagic, and large pelagic (tunas). Larval species composition differed considerably between summer and winter surveys., Sí

This research has been done in the larvae fish pond in Lumbung Village, Tabanan regency. Surya cell is device consists of solar cell, charge controller, and batterei that change sunlight to be electric. Fish like many living organisms have specific tolerant range of various environmental parameters, thus fish larvae ponds of specific types of fish species requires certain conditions that have to be reached. Larvae that have hatched, should be raised in a special place, when their ages are 5-7 days. And it becomes threat if in interval 3 – 4 weeks happen cold weather that make the larvae will be died. To avoid the cold weather occurs, warming can be done with heater or halogen lamps. Solar Energy is produced by the Sunlight is a non-vanishing renewable source of energy which is free from ecofriendly. The highest intensity of sunlight occurs at 11.00-14.00 with the value of the intensity of sunlight is around 96.000 - 112.500 lumen and average power about 24 – 28 W. Monitoring and taking actions to maintain the habitat’s sustainable environment for certain larvae inside of fish larvae ponds. Halogen lamps give the warmth to the water with the intensity of the light in cash, so that the water temperature is located between 27 – 30 oC at the night.

The keurling fish (Tor soro) is a freshwater fish that has an economical value, with a thick, delicious texture of the flesh. so much popular community. It is indicated by the high demand for the keurling fish meat at a higher price. This research aims to determine how the behavior of the fish larvae in responding to feed supply when the egg yolk starts to thinning and which type of feed is more responded to by the fish larva keurling. The design used in this research is a mixed method design with embedded design with a single container of three treatments, i.e. feeding (artemia), polar red and feed paste. The observed Parameter is the response of a keurling fish larva to feed. The results showed that the feed was very well responded by the fish larva keurling was well-reviewed polar red artemia and the feed paste was not responded at all by the larva of keurling fish.

Investigating goby fish is vital to perform an integrated and comprehensive study in order to maintain the roles of the fish, thus providing balanced ecosystem functions and services, as well as contributing to fish biodiversity. Local societies simply recognize fish species by their local names, which are not common. This condition, in turn, causes hitches in conducting further studies. Nike, the name of a local fish, refers to the schools of goby fish larvae whose adult phase has not been fully confirmed. This study aimed to reveal the species that categorizes as nike fish through tracing adult goby inhabiting freshwater. Two fish samples, i.e., Unknown 01 and Unknown 02, were taken from two sites in Bone River, Gorontalo, Indonesia. These samples were captured purposively using a hand net by considering the morphological similarity between the two target samples and the general characteristic of goby. Furthermore, the samples were analyzed genetically through the PCR sequencing method using the Mitochondrial Cytochrome Oxidase Subunit 1 (CO1) gene. Based on the NCBI database, Unknown 01 had the highest similarity to Belobranchus belobranchus (99.54%), while Unknown 02 was identical with Awaous ocellaris (100%). Unknown 01 and Unknown 02, compared to the BOLD database, the similarity level, had the highest percentage of similarity with B. belobranchus (99.85%) and A. ocellaris (100%), respectively. Therefore, A. ocellaris and B. belobranchus were strongly alleged as two species making up the goby schools in the adult stadia that reach freshwater during their migration.

Connectivity of nurseries and spawning habitats for young of the year life stage is essential for successful recruitment of fish populations and therefore provides a key indicator for river restoration measures. Models for dispersal offer the potential to draw conclusions regarding restoration scenarios and to fill knowledge gaps about possible implications for fish populations. A newly developed rheoreaction‐based correlated random walk model (RCRW), in combination with a three‐dimensional numerical model and a non‐steady‐state particle tracing model, was applied for nase carp larvae (Chondrostoma nasus) before and after a restoration project on the river Danube, Austria. Spatio‐temporal patterns of dispersal of virtual larvae, attached with rheoreactive behaviour, were analysed within both scenarios. In comparison to the heavily modified river reach, the restored reach enabled a greater amount of upstream movement from the release site and showed a generally higher variability of spatio‐temporal distribution patterns. In contrast, estimated total settlement of rheoreactive larvae was substantially higher for the situation prior to the restoration measure. By comparing model results with a previously field experiment it was found that model simulations including rheoreaction as a single behaviour for navigation could not explain the whole pattern of larval dispersal. Therefore it is highly recommended for future studies to develop larval dispersal models by considering other factors (i.e., behaviour, bio‐energetics and environmental factors) of existing and future individual‐based models, which could serve as a tool to analyse the effect of restoration measures for recruitment of riverine fish populations.

Betta fish (Betta splendens) is one type of freshwater ornamental fish that has the potential to be cultivated because it has high economic value. This study aims to determine the appropriate substrate for hatchability of betta fish eggs. This study uses a non factorial Completely Randomized Design (CRD) with 4 treatments and 3 replications. The treatments were control (treatment A), dried ketapang leaf substrate (treatment B), dried coconut leaf substrate (treatment C) and dried banana leaf substrate (D). The container used is a jar with a volume of 10 l and filled with water as much as 5 l, dense stocking of betta fish eggs as much as 50 grains / liter. Observation parameters included hatching time, hatchability and survival rate of betta fish larvae. The results of this study were analyzed using the one way Anova test. The results showed that the use of different substrates significantly affected the egg hatchability and survival rate of betta fish (P