Early Ontogeny of Cichlids Using Selected Species as Examples.

The purpose of this study was to characterize in detail the reproductive strategy, course of embryogenesis, and development of larvae in three species of fishes of the genus Cichlasoma: the green terror (Andinoacara rivulatus), the red discus (Symphysodon discus), and the jaguar cichlid (Parachromis managuensis). Eggs for the study were obtained from five pairs of each species (300 eggs from each female) and incubated at 26 °C. The developing eggs were observed under a microscope (Carl Zeiss Stereo Discovery. V12 and Nikon 2000SE software (NIS-Elements F 4.30.01 64-bit) from fertilization to larval hatching until complete yolk-sac resorption. The largest average number of eggs per female was found in the jaguar cichlid (x¯ = 2991 eggs), a smaller average number of eggs was shown in the green terror (x¯ = 922 eggs), and the red discus showed the smallest average number of eggs (x¯ = 300 eggs). There were significant differences in the sizes of the eggs of the studied species: jaguar cichlid eggs were the smallest (1.060 ± 0.05 mm3), red discus eggs were larger (1.070 ± 0.07 mm3), and green terror eggs were the largest (1.365 ± 0.16 mm3). The embryogenesis time in the red discus was 2132 °H (82 Hpf), in the green terror it was 2158 °H (83 Hpf), and the longest in the jaguar cichlid was 2470 °H (87 Hpf). At the end of embryogenesis, the average size of the larvae after hatching was measured (red discus x¯ = 4.346 mm, green terror x¯ = 5.203 mm, and jaguar cichlid x¯ = 5.301 mm) and the time of yolk-sac resorption from the moment of hatching to the transition from endogenous to exogenous feeding was determined (jaguar cichlid 5 days, green terror 6 days, and red discus 3 days). The results of this study may contribute to the development of reproductive biotechnology for the studied fishes that could be used in aquaculture and, thus, help protect them in their natural habitats.

Dietary L-Lysine Requirement of Coho Salmon (Oncorhynchus kisutch) Alevins.

The suitable dietary L-lysine concentration for coho salmon (Oncorhynchus kisutch) alevins was assessed by a dose response feeding trial. Six experimental diets were made with graded L-lysine concentrations of 2.29%, 2.81%, 3.32%, 3.80%, 4.27%, and 4.78% of the dry matter, respectively, each of which was fed to triplicate groups of 100 alevins (initial body weight: 0.30 ± 0.01 g) in 18 plastic baskets (water volume 240 L). The alevins were cultured in a flowing freshwater system and fed manually to apparent satiation four times a day for 12 weeks. The survival rate of alevins did not differ significantly among the dietary groups. The specific growth rate (SGR), protein efficiency ratio (PER), and body protein deposition (BPD) increased significantly (p < 0.05) with the increase in dietary lysine concentration up to 3.80% and then reduced as lysine level further increased. The feed conversion ratio (FCR) had an inverse trend to SGR. The whole-body crude protein content of the alevins increased significantly with increasing dietary lysine level, while crude lipid content showed the opposite trend. In comparison, the contents of morphological indices, whole-body moisture, and ash were not affected significantly (p > 0.05) by the different dietary lysine concentrations. The highest contents of lysine, arginine, and total essential amino acids (EAAs) were observed in the group with 4.27% dietary lysine concentration, which did not differ significantly from those in the 3.32%, 3.80%, and 4.78% groups but was significantly higher than those in the 2.29% and 2.81% groups. Similarly, valine had the highest content in the group with 4.78%. The variations in dietary lysine had no significant impacts on other EAA and non-EAA contents except glycine, which increased with increasing dietary lysine level. Second-order polynomial model analyses based on SGR, PER, BPD, and FCR evaluated the optimum L-lysine requirements of coho salmon alevins as 3.74%, 3.73%, 3.91%, and 3.77% of the diet or 6.80%, 6.78%, 7.11%, and 6.85% of dietary proteins, respectively.

Impact evaluation of marking Salmo trutta with Alizarin Red S produced by different manufacturers.

Fish otolith marking with the alizarin dye is a commonly used tool in sustainable fishery management. However, the reported effects of this dye on fish health are rather controversial and are possibly linked to differences in the composition of different brands of Alizarin red S (ARS). Laboratory experiments designed to elucidate effects of different concentrations of theoretically the same ARS as indicated by the CAS (Chemical Abstracts Service) number on fish at different development stages were carried out. The acute toxicity of ARS to Salmo trutta was found to be concentration- and fish developmental stage-dependant. Our study results showed that S. trutta sensitivity to ARS varies depending on its developmental stages as follows: fry (50-days after hatching) > alevins (30-days after hatching) > alevins (1-day after hatching). One of the tested ARS brands (purchased from VWR International LLC (Matsonford Road, USA)) was found to be several times more toxic to fish than another (purchased from Sigma-Aldrich (St. Louis, USA)), although according to the certificates of analysis, the tested substances were identical. Survival and growth of the S. trutta fry, which was marked with different ARS brands and stocked in the same natural stream, was investigated for two consecutive years. The results obtained indicate remarkable differences (p < 0.05) in the effects produced by the tested ARS brands, thus confirming our laboratory findings. The performed elemental analysis of the tested ARS dyes revealed significant differences in chemical impurities that these dyes contain. This study has, for the first time, expressed concern about the probable long-term impact of some ARS brands on the marked fish and their potential to bias the results of the studies dealing with ARS-marked fish.

Immunostimulant Bathing Influences the Expression of Immune- and Metabolic-Related Genes in Atlantic Salmon Alevins.

Disease resistance of fish larvae may be improved by bath treatment in water containing immunostimulants. Pattern recognition receptors, such as TLR3, TLR7, and MDA5, work as an "early warning" to induce intracellular signaling and facilitate an antiviral response. A single bath of newly hatched larvae, with Astragalus, upregulated the expression of IFNα, IFNc, ISG15, MDA5, PKR, STAT1, TLR3, and TLR7 immune genes, on day 4 post treatment. Similar patterns were observed for Hyaluronic acid and Poly I:C. Increased expression was observed for ISG15, MDA5, MX, STAT1, TLR3, TLR7, and RSAD2, on day 9 for Imiquimod. Metabolic gene expression was stimulated on day 1 after immunostimulant bath in ULK1, MYC, SLC2A1, HIF1A, MTOR, and SIX1, in Astragalus, Hyaluronic acid, and Imiquimod. Expression of NOS2 in Poly I:C was an average fourfold above that of control at the same timepoint. Throughout the remaining sampling days (2, 4, 9, 16, 32, and 45 days post immunostimulant bath), NOS2 and IL1B were consistently overexpressed. In conclusion, the immunostimulants induced antiviral gene responses, indicating that a single bath at an early life stage could enable a more robust antiviral defense in fish. Additionally, it was demonstrated, based on gene expression data, that cell metabolism was perturbed, where several metabolic genes were co-regulated with innate antiviral genes.

Single and multiple stressor effect of road deicers and Cu on Atlantic salmon (Salmo salar) alevins from hatching till swim-up.

Road salts are frequently used for deicing of roads in the Nordic countries. During snow-melt, the road run-off containing high concentrations of road salt and various metals such as Cu remobilized from sand, silt and dust may negatively influence organisms in downstream receiving water bodies. The present work focuses on the impact of road salt (NaCl) and Cu, separately and in mixtures on Atlantic salmon alevins from hatching till swim-up. The results showed that high road salt concentrations could induce a series of negative effects in alevins such as reduced growth, deformities, delayed swim-up and mortality. For alevins exposed to all tested road salt concentrations (100-1000mg/L), mortality was significantly higher compared to control. In exposure to Cu solutions (5-20µgCu/L), no effects on growth, morphology, swim-up or mortality of alevins compared to control were observed. In mixture solutions (road salt and Cu), ultrafiltration of the exposure water demonstrated that only 20%-40% of Cu was present as positively charged low molecular mass (LMM) Cu species assumed to be bioavailable. When exposed to road salt and Cu mixtures, negative effects in alevins such as reduced growth, deformities, delayed swim-up and mortality were observed. The overall results indicated that the road salt application could seriously affect sensitive life stages of Atlantic salmon, and application of road salt should be avoided during the late winter-early spring period.

Nivel óptimo de proteínas en la dieta para alevines de Prochilodus mariae / Optimal dietary protein levels for Prochilodus mariae alevins

The purpose of this work was to determine the optimal protein level to feed alevins of coporo (Prochidolus mariae) fish. Four diets were formulated with growing levels of crude protein (15, 25, 35 and 45%) with similar energy values (between 19,6 and 20,4 KJ g-1). Three trials were performed for each diet. The animals were acclimated and fed a commercial diet during one week and after that time the test diets were administered ad libitum three times a day during 41 days. Fifty five frys per fishbowl were placed with an initial mean weight of 0,32 ± 0,04 g. Three periods of fourteen days each were registered and at the end of each period weight gain (GP) and food consumption per fish tank was determined. The zootechnical parameters, final mean weights (PMF), total weight gain (GTP), specific growth rate (TCE) and daily growth index (ICD) of the fish did not show significant differences between the diets with protein levels of 35% and 45% proteins, indicating that a diet with 35% protein is adequate for a good development of the fish in this stage.

El propósito de este trabajo fue determinar el óptimo proteico en la alimentación de alevines de coporo (Prochidolus mariae). Se formularon 4 dietas con niveles crecientes de proteína cruda (15, 25, 35 y 45%), y valores energéticos similares entre 19,6 y 20,4 KJ g-1, de manera que sean isocalóricas. Se realizaron tres repeticiones por cada dieta (n=3). Los alevines fueron aclimatados y alimentados con una dieta comercial durante una semana y luego de este tiempo se le suministraron las dietas a ensayar ad libitum tres veces al día durante 41 días. Se colocaron 55 alevines por pecera con peso medio inicial de 0,32g ± 0,04. Se llevó un registro durante tres períodos, de catorce días cada uno, al final de cada período se determinó la ganancia de peso (GP) y el consumo de alimento por pecera. Los parámetros zootécnicos, pesos medios finales (PMF), ganancia total de peso (GTP), tasa de crecimiento específico (TCE) e índice de crecimiento diario (ICD) de los peces, no presentaron diferencias significativas entre las dietas con 35 y 45% de proteínas, lo que indica que una dieta con 35% de proteínas, es adecuada para un buen desarrollo del pez en este estadio.

Valoración de dietas para alevines de Colossoma macropomum utilizando como fuentes proteicas harinas: de lombriz (Eisenia foetida), soya (Glycine max) y caraotas (Phaseolus vulgaris) / Evaluation of diets for Colossoma macropomum alevins, using earthworm (Eiseniafoetida) flour, soybean (Glycine max) and beans (Phaseolus vulgaris) as proteins sources

The current study was carried out with the purpose of evaluating two alternative diets in the feeding of Colossoma macropomum alevins using earthworm flour (Eisenia foetida), soybean (Glycine max) and beans (Phaseolus vulgaris) as the protein source and as fishmeal substitute and was compared with a control diet. The diets were formulated with a crude protein with a theoretical 32% protein. The body composition of C. macropomum fed the different diets showed that protein was between 47,3%% and 48,6% and the lipid content was found between 21,2% and24,3% not showing significant differences between diets (p>0,05). According to the results obtained there is a reason to think that a total substitution of fishmeal by earthworm meal, soybean and beans would be successful in feeding C. macropomum alevins.

El presente estudio se realizó con el objetivo de valorar dos dietas alternativas en la alimentación de alevines de cachama negra (Colossoma macropomum), utilizando como fuentes proteicas harinas de lombriz (Eisenia foetida), soya (Glycine max) y caraotas (Phaseolus vulgaris) como sustituto de la harina de pescado, comparándolo con una dieta testigo. Las dietas se formularon con un porcentaje teórico de proteína bruta de 32%. En cuanto a la composición corporal de las cachamas alimentadas con las dietas, el % de proteína se determinó entre 47,3 y 48,6 y % de lípidos entre 21,2 y 24,3; sin presentar diferencias significativas (p>0,05). De acuerdo a los resultados se puede concluir que una sustitución total de la harina de pescado por harina de soya- lombriz, y de soya-caraota conduciría a buenos resultados para la alimentación de alevines de cachama negra.