Sistema Regional de Información
en línea para Revistas Científicas de América Latina,
el Caribe, España y Portugal

For a population of locate, Thaisella chocolata, in La Rinconada, Chile, on a grid of 39 stations distributed along three 910 m-long transects at depths of 5 to 18.5 m, Moran and Morisita indices were used to evaluate whether density variations along the depth distribution are related to the stratification of larger sizes at the beginning of their reproductive process. Results indicate that before, during, and after forming reproductive aggregations, there is a T. chocolata increase in density in the shallow stratum (5 to 13 m). This finding is corroborated by the Moran index, which showed a greater autocorrelation in January-May, September-October, and January 2010, and by the Morisita index; thus, it is validated as a potentially easy-to-use indicator for assessing the reproductive process of this species. This index could also alert fishermen to the prevalence of reproductive aggregations in an area and that these aggregations should not be exploited as is currently the case to ensure the reproductive success of this species.

The free amino acids (FAAs) profile and its variations during the embryonic development and yolk-sac larvae of Pacific red snapper Lutjanus peru are described. The concentration of 15 FAAs (nine essentials and six non-essentials) was evaluated by reverse-phase high-performance liquid chromatography. The fertilized eggs of L. peru contain a small concentration of FAAs (4.77 ± 0.89 nmol ind-1). However, the variations in the FAAs pool during the early development are similar to the changes reported in other species with small pelagic eggs. The essential free amino acids are more abundant than the non-essential free amino acids throughout the studied period. During the egg stage, an increase in the FAAs was observed, and after hatching, isoleucine, leucine, lysine, and alanine were the FAAs that decreased the most during the yolk-sac larvae stage. The hatching rate was correlated with the total FAAs, the fraction of essential free amino acids, and the concentrations of glutamic acid, threonine, and valine in the egg stage, suggesting a possible role as a determinant in egg quality. Further studies are required to assess the role of FAAs in other aspects of egg development, like fertilization rate and egg buoyancy.

Artisanal fisheries in center-southern Chile targeted a large amount of southern ray bream (Brama australis), whereas other species of Bramidae are negligible in the catches. During a small-scale fishing trip targeting B. australis off the coast of Lebu Harbour (38ºS) in August 2021, two specimens of other Bramidae species were also caught, but the fishermen did not identify them. The first corresponded to a sickle pomfret, Taractichthys steindachneri, the first record of the species in Chilean waters. The second specimen corresponded to the rough pomfret, Taractes asper, already reported from the Chilean coast, but with only one previous record from the eighties. We discussed how the occurrence of T. steindachneri and T. asper provide insights regarding the B. australis demography in the south Pacific.

The crustacean hyperglycemic hormone (CHH) is a multifunctional neuropeptide that plays a central role in crustacean metabolism and physiology. Experiments were conducted to examine the metabolic and osmoionic capabilities of the white shrimp Penaeus vannamei injected with its recombinant CHH-A (rCHH-A) peptide and acutely transferred from iso- (26 ppt) to hypo- (10 ppt) and hyper-osmotic (40 ppt) conditions. Hemolymph glucose, protein, osmoregulatory capacity (OC), and ionoregulatory capacity (IC) for sodium, chloride, potassium, and calcium were evaluated at four post-injection times (0.5, 1, 2, and 24 h). The rCHH-A peptide had hyperglycemic activity in all salinity conditions, obtaining maximum values at 1 h post-injection. However, in shrimp transferred to hyper-osmotic condition, rCHH-A caused the most significant reductions in OC (2 h), chloride IC (2 h), and total proteins (0.5-2 h) compared to the phosphate-buffered saline (PBS) control. Contrastingly, in shrimp transferred to hypo-osmotic conditions, rCHH-A decreased OC significantly from 2-24 h, strongly decreased chloride and potassium IC at 1 h post-injection, and increased total protein concentration in the hemolymph (1-2 h) when compared to PBS control. Concerning calcium, the rCHH-A injection decreased calcium IC at 10 ppt (1 h) and 26 ppt (2 h), providing insight into a potential role for CHH-A in calcium regulation. The results suggest that glucose and protein mobilization could enhance energy for osmo-ionic regulation under extreme osmotic conditions. This research study contributed to understanding crustacean endocrinology in P. vannamei and related euryhaline crustaceans. Further research should be performed to understand the osmo- and ionoregulatory mechanisms of the different CHH variants in crustaceans exposed to other stress conditions and the relationship with intermediary energy metabolism regulation.

The objective of this study was to evaluate two Streptomyces spp. probiotic strains (RL8 and N7) and four highly-diluted bioactive compounds (HDBC) in the growth, survival, and modulation of the microbial content in culture water and hepatopancreas of juvenile white shrimp Penaeus vannamei. An experimental design was applied with five treatments in triplicate, including T1: (RL8+N7); T2: [(ViP-7C+ViA-7C) + (PhA-7C+SiT-7C)]; T3: [(ViP-7C+ViA-7C) + (PhA-7C+SiT-7C) + (N7)]; T4: [(ViP-7C+ViA-7C) + (PhA-7C+SiT-7C) + (RL8)] and T5 as the control without actinobacteria or HDBC. T2 showed significant differences (P < 0.5) in height increase compared to the other treated and control groups. The organisms in T2, T3, and T4 recorded higher weight gain compared to T1 and T5. A survival rate from 94.13 ± 2.12 to 99.01 ± 2.45% was obtained with a significant difference (P < 0.05) between T1, T2, and T3, concerning the untreated control (T5). A significant decrease in Vibrio spp. the content was observed in water and shrimp in T1 and T2 concerning the control. The heterotrophic bacterial count in hepatopancreas increased with all treatments compared to T5. Our results suggest a positive synergy between the HDBC mixture [(ViP-7C+ViA-7C) + (PhA-7C+SiT-7C)] and N7 Streptomyces sp. strain, whose probiotic action has been previously demonstrated by improving culture conditions for P. vannamei juveniles in terms of growth, survival, and reduction of potentially pathogenic bacteria.

Ractopamine is a drug used as an additive in animal production to improve growth, body composition, and production efficiency, although its use in fish is still poorly known. This study aimed to evaluate ractopamine hydrochloride (RAC) effects at increasing levels (0, 10, 20, and 40 mg kg-1) in Nile tilapia (Oreochromis niloticus) diets during 40 days by considering growth performance, body composition, and muscle fiber morphometry. One hundred and twelve fish (mean initial weight 518.63 ± 5.49 g) were housed in 16 circular tanks (450 L), following a completed randomized design with four treatments and four replicates. Body composition was significantly affected (P < 0.05), and the content of lipids in fish fillets dropped 26.7% (20 mg kg-1 RAC) and 26.1% (40 mg kg-1 RAC), as well as the amount of unsaturated fatty acids C14:0 and C18:0 in fish fillets (P < 0.05) by treatment with 10 mg kg-1 of RAC. Results demonstrate that fish fed 20 mg kg-1 RAC for 40 days changed Nile tilapia fillet chemical composition, decreasing lipid levels, altering the fatty acid profile, and increasing protein levels. RAC did not affect any productive performance parameters evaluated for muscle fiber morphometry.

Environmental temperature can act as a positive or negative modulator of the physiology and metabolism of poikilothermic organisms. As a general rule, larvae and juveniles are more sensitive to temperature stress than adults, which represents a key factor that partly determines their development and growth in aquaculture. Therefore, this study analyzed the effect of exposure to temperatures of 21, 24, and 27°C on the respiratory metabolism (RM) of Totoaba macdonaldi in different developmental stages. For this purpose, eggs, larvae with 4, 6, 8, 14, and 22 days post-hatch (dph), and juveniles of 25 dph were exposed to the experimental temperatures for 5 h. After the exposure time, oxygen consumption measurements were performed. The results clearly show that temperature (21 to 27°C) has the greatest effect on RM in eggs and larvae at 4 and 22 dph (3.1 ± 0.3 to 4.3 ± 0.3 μmol O2 h-1 egg-1, 2.9 ± 0.3 to 10.5 ± 1.2 μmol O2 h-1 larvae-1 and 102.0 ± 6.4 to 189.8 ± 15.3 μmol O2 h-1 larvae-1, respectively). This thermal sensitivity was not observed from 6, 8, and 14 dph larvae and juveniles at 25 dph, where morphological development was the main factor that influencing the RM. Therefore, this study shows that temperature affects RM in different development stages of totoaba, beginning in the egg stage and intensifying once the larvae hatch until 22 dph. Understanding how temperature affects energy expenditure by measuring RM is essential to establish culture conditions that allow better physiological performance and growth in the early life stages of T. macdonaldi.

The southern rays bream (Brama australis) is a highly migratory, epi-mesopelagic species supporting an important artisanal fishery off central-southern Chile. Despite its importance, several questions exist about this species's demography and migratory routes. The first step in understanding the migratory behavior of B. australis is to test the feasibility of a conventional tagging program, a standard mark-recapture method, to infer migration in fish. Between February 2020 and December 2021, conventional tagging was conducted during 21 fishing trips on board artisanal vessels off Lebu harbor (Biobío Region, Chile) using gillnets, longlines, and handlines. Three thousand nine hundred forty-six individuals of B. australis between 30 and 55 cm fork length were tagged using external T-anchor bar labels (commonly known as "spaghetti"). Approximately 100 and 200 fish were tagged per fishing trip using longlines and gillnets, respectively. The size distribution of the tagged individuals was consistent with those retained in the catch, with 90% of tagged fish being longer than the fork length at 50% maturity. Eight tags have been recovered off the coast of Lebu up to May 2022. With times at liberty between 50 and 537 days. These preliminary recaptures are also analyzed in the context of the conceptual model for demography and migration proposed for this species in Chile. The main conclusion of this research is that a conventional tagging program is feasible for B. australis in Chile.

Quarterly collections of demersal fish were conducted between 2014 and 2018 on the adjacent continental shelf and in the Paranaguá Estuarine Complex (PEC). Univariate and multivariate statistical analyses were used to determine the abundance, richness, and composition of demersal fish assemblages and to list predictor variables responsible for the variability in these ecological descriptors by applying generalized linear models. The collected specimens of demersal fish (n = 25,179) were distributed across 19 orders, 31 families, and 72 species. Fish richness was explained by the following predictor variables: the percentage of fine sand in the sediment, the richness of the benthic megafauna, and sampling sites. The abundance was associated with the predictor variables of the percentage of very fine sand in the sediment, percentage of silt in the sediment, salinity, and sampling sites. Canonical correspondence analysis showed that the fish assemblage composition was strongly associated with the salinity gradient and positively correlated with benthic megafaunal species richness. As it is one of the last remnants of the Atlantic Forest, declared by UNESCO as a Natural Heritage of Humanity, the patterns observed in this study will support PEC's coastal management of current developmental demands, particularly related to port activities.

The present study evaluated the effect of different energy levels (15.07, 15.91, 17.17, 18.00, and 19.68 kJ g-1 of diet) on isoproteic practical diets for Macrobrachium amazonicum during the nursery phase on the zootechnical performance and proximate composition of the whole body. Postlarvae with a mean weight of 0.043 ± 0.01 g were stored in 25 experimental units, at 150 animals per m2, in a completely randomized design with five treatments and five replicates. The post-larvae were evaluated at the end of the experimental period according to the pre-established performance parameters. The analysis of variance for regression (α = 0.05) allowed us to estimate that the maximum final weight was observed in the treatment with 16.74 kJ g-1. In contrast, the lowest apparent feed conversion was observed at the 16.43 kJ g-1 level. The best values were found in 17.29 and 17.50 kJ g-1, respectively, for the energy and protein retention rates. As the best fit of the equation was presented for the energy retention ratio (R2 = 0.63), which approached the treatment of 17.17 kJ g-1, this energy level is recommended in postlarvae diets.