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

The objective was to evaluate the effect of DL-carnitine levels on the growth and whole body and muscle composition of Nile tilapia fingerlings. A basal plant-based diet was supplemented with 0, 500, 1000, 1500, 2000, 3000 and 4000 mg kg-1 of DL-carnitine hydrochloride in a completely randomized design (n = 3). Fish (initial weight 0.8 ± 0.01 g) was hand-feed daily into three meals until apparent satiety for 70 days. The growth parameters were not influenced (P > 0.05) by dietary DL-carnitine levels. Muscle lipid decreased (P < 0.05) in fish fed with diets supplemented with 3000 and 4000 mg kg-1 of DL-carnitine, but there was no effect (P > 0.05) on whole body lipid. These results with DL-carnitine is similar to other studies using pure Lcarnitine. Thus, the use of DL-carnitine as a source of levocarnitine in Nile tilapia diets require future studies.

Some studies have characterized and evaluated the parasitic load of the Pacific sardine. However, there are few studies related to its physiology and parasites load. This study aimed to evaluate the blood parameters and the abundance of helminth parasites of sardines obtained from two samples from Todos Santos Bay during autumn 2013. The digenea Myosaccium ecaude parasite was the only species registered. Sardines had a prevalence of 28%, an average abundance of 25 and an intensity of 7 parasites. There were no statistically significant differences (P > 0.05) in most of the analyzed blood parameters (red blood cell count, hematocrit, leukocyte cellular differentiation, mean corpuscular volume, total protein, glucose, alanine aminotransferase, osmotic pressure, Na, K, and pH) of fish with and without parasites, except in white blood cell count and in Ca concentration that showed a marked decrease. The relationship between parasite abundance and blood parameters, based on the results of this study, it is not clear due to the low parasitic load.

Loco abalone (Concholepas concholepas, Bruguière, 1789) represents the most important gastropod fishery from the central coast of Perú down to the southernmost part of Chile. International prices are attractive enough to motivate the development of an important body of research to bring the catch to commercial size under controlled conditions. In this study, we analyze whether the fattening of loco from the seed stage (between 2 and 3 cm of peristomal length) up to commercial size is economically attractive for a private investor. The results of this model, composed by biological, technological and economic submodels, shows that under current conditions cultivation is not convenient Net Present Value (NPV) = -198,179 US$ on t = 1,400, the day where the maximum biomass is reached). The negative result is explained by the high operational costs (mainly wages) and high initial investments requirements (mainly plastic boxes to house the C. concholepas). Interestingly, the model shows that feeding costs are comparatively low. At t = 1400, the accumulated disbursements for investments (US$92,209) are lower than those for the operating costs (US$299,486) and represent only 24% of the total accumulated disbursements. The latter shows that the project is not profitable due to the high operating costs other than the feed. The sensitivity analysis shows that would be required a 30- fold increase in the current biomass selling price for a positive NPV. In the future, this project would benefit if more efficient forms of production are developed, especially reducing the burden due to workers' compensation.

Artificial diets have been reported to produce suboptimal pH values in the stomach of salmonid species. Therefore, it is interesting to investigate the gastric function of different species fed commercial diets. In the present work, two groups of Atlantic salmon juveniles were either fasted or fed with a commercial diet. The gastric and duodenal pH values were measured over a 25 h post-prandial period and, dry matter, moisture and protease activity in the gastric chyme of the fed group were also determined. In the fed group, the gastric pH dropped to 3.5, and duodenal pH increased from 7.0 to 7.5 at the 4th h post-feeding, whereas fasted fish showed no significant changes in the gastric pH or duodenal pH. Fed animals showed: i) two discrete events of evacuation, before the 2nd hand after the 8th h of digestion, ii) a change in the moisture of the gastric chyme from less than 10% in the diet to 60% at the 2nd h post-feeding, and iii) a maximal gastric proteases activity of 600 U mL-1 at the 2nd h followed by a nearly constant of value of ~300 U mL-1. It can be concluded that the juveniles of the Atlantic salmon can suitably acidify a commercial diet to a value generally accepted as optimal for gastric proteases of fish, and to retain about 2/3 of the ingested diet under such conditions and at a nearly constant protease activity until the 8th h of digestion.

The understanding of the differences between living (L) and dead (D) benthic foraminiferal assemblages and all the factors that might lead their distribution should be a key to characterize the environmental and paleoenvironmental changes accurately. Population dynamics and dissimilarities of biological nature (the differences in turnover rate and seasonal alterations in standing stock) can cause significant divergences between the L and D foraminiferal assemblages. This study compares L and D foraminifera to evaluate the sediment quality of the Brazilian Saquarema Lagoon System (SLS) using biogeochemical proxies and predict how coastal ecosystems are responding to the combined effects of eutrophication and pollution pressure and areas where the paleoenvironmental studies can be performed. The SLS is a transitional environment where total organic carbon, proteins, and dissolved oxygen are the main factors controlling the distribution of foraminiferal assemblage. The high values of biopolymers (carbohydrates, lipids, and proteins) in SLS indicate a very impacted environment with long water residence time. The low values of species richness, Shannon-Weaver diversity, and evenness for both L and D foraminiferal assemblages are a consequence of fluctuating conditions in the SLS. Due to low salinities, agglutinated species and Quinqueloculina seminula can occur in the most confined areas, and Ammonia parkinsoniana, Cribroelphidium excavatum, Cribroelphidium poeyanum, and Elphidium gunteri characterized the area with the highest marine influence. Although in most of the SLS the taphonomic processes modified the original assemblage, in some regions the thanatocoenosis corresponds to the biocenosis. These areas can be considered the most suitable for future paleoenvironmental and paleoclimatic studies.

Within the Gulf of California, the Midriff Islands Region (MIR) is characterized by mixing conditions of water masses that lead to high primary productivity, which fosters the presence of sardines, anchovies, and their predators. Using acoustic tools, we analyzed the presence and characteristics of schools detected in three surveys carried out in late spring of 2012 and 2013 and early summer of 2014. We sought to relate changes in the geographical distribution of schools with Sea Surface Temperature (SST) and Net Primary Productivity (NPP). The largest number of schools was observed in 2012, coinciding with the highest and most extensive NPP, while the following years were associated with lower NPP coupled with a lower number of detections. During the study period, the Ballenas-Salsipuedes Channel and its area of influence showed the lowest SST and higher NPP even toward the summer as compared to the rest of the MIR, favoring the presence of fish schools and supporting the importance of this site as a feeding center for these species. As for their vertical distribution, it was found that during the day schools reach greater depths, while during the night these are concentrated in surface waters. However, no differences in size, density, or other characteristics were detected either between periods or between years. Finally, we found a high proportion of schools during the night (61%), which departs from the typical nocturnal dispersal behavior described for similar species in other areas.

The gar, Atractosteus tropicus is a native fish distributed in fluvial systems of the Mexican southeast, which presents aquaculture potential in the food industry and as ornamental species. However, it is necessary to deepen the knowledge for the optimization of its culture. The present study examined the effect of three feeding frequencies on the growth, survival, and condition of juveniles. The fish (90) were placed in nine 35 L tanks, (n = 10; three replicates per treatment). The feed (44% protein, 15% fat) was supplied to 2% of the biomass, divided into 2, 4 and 6 servings throughout 10 h for eight weeks. After eight weeks the standard length, wet weight, survival, Fulton K, specific growth rate, nitrogen carbon rate, the coefficient of variation and size heterogeneity were recorded, which were analyzed with a one-way ANOVA. There were no significant differences among treatments for any of the response variables. The overall results indicated that in general both the culture conditions and the three food frequencies tested were adequate for the species. The results indicate the high flexibility of the species to be cultured with minimum requirements of the food supply, which can translate into the optimization of production costs.

The increasing degradation of freshwater ecosystems has demanded the development of methods that allow us to evaluate the ecosystem alterations. The Indexes of Biological Integrity (IBI) are a methodological approach to assess the condition of aquatic ecosystems. The objective of this study was to estimate the biological integrity and to validate the Index of Biological Integrity based on macroinvertebrate assemblages (IIBAMA) in 33 study sites rivers in the Lerma-Chapala and Pánuco river basins, in central Mexico. The Family-Level Biotic Index (FBI) was used to estimate the water quality and the Visual-Based Habitat Assessment (VBHA) was used to estimate the habitat quality. Spearman correlation analysis among IIBAMA, FBI, VBHA and water characteristics were made for validation of the IIBAMA. Besides, all variables were evaluated together by multivariate analyses. The rivers were classified in three of four biotic integrity categories, poor, regular and good, being poor the most common (88% of the study sites). We did not find study sites with excellent biotic integrity. The rivers of the Lerma-Chapala River Basin showed a worse ecological condition compare with the Pánuco Rivers Basin. We validated and recommended the using of the IIBAMA to assess the biological integrity of these two basins and rivers in central Mexico. This research represents the first efforts to validate an IBI based on aquatic invertebrate communities in a broad scale in Mexico and provide a general framework for their widespread use and to approach the validation and implementation of IBIs in other regions with similar conditions.

The behavior of the Argentine shortfin squid (Illex argentinus) in reaction to a trawl net is reported from images obtained during one fishing tow operated by a commercial trawler in May 2015 in slope grounds off southern Brazil (depth 370-361 m; 33°37’S, 50°49’W). Video analysis utilized criteria to classify the horizontal and vertical distribution of squid in the field of view of the camera, posture (pitch and yaw), squid color patterns, escape reaction, swimming time and use of the tail fin. The monitored bottom trawl operation intercepted dense and patchily distributed schools of I. argentinus that could be observed for brief periods of time swimming ahead of the mouth of the trawl. Individuals were evenly distributed in the water column but concentrated on the center and right sectors of the trawl mouth. Most squids in the path of a trawl tended to swim by jet-propulsion for 10-20 s, tail-first and with regularly spaced fin flaps. Estimated speed (1.24 m s-1) was higher than cruise speed recorded for other ommastrephid squids in nature (0.3 m s-1), possibly reflecting an emergency escape reaction. After a period of sustained swimming ahead of the trawl, squid reacted in different ways including: a) slowing down and swimming into the net tunnel, b) shifting directions to escape through the trawl mouth sides, and c) swimming up, trying to escape over the top trawl panel, sometimes turning around pointing the tail towards the trawl mouth.

In fish feeding studies, stomach related parameters are mainly measured in order to have biometric relationships. To determine those parameters a direct and straightforward method for measuring real maximum stomach volume in fish based on Archimedes' principle was tested and compared against a traditional method. The new method is based on the measure of the real maximum stomach volume when fish are fed ad libitum. By contrast, the traditional method measures the forced expanded capacity of the stomach under an arbitrarily assigned hydraulic pressure head of a 50 cm column of water. The two methods were assayed in juvenile rainbow trout Oncorhynchus mykiss, and the results displayed significant different stomach volume and related indices. The best relationships for potential regression were obtained using the Archimedes’ principle method, being between fish weight and stomach volume (R2 = 0.68), and stomach content and stomach volume (R2 = 0.95). These results indicate that the measurement of real maximum stomach volume in fish using the Archimedes’ principle method could be a useful method of estimation of how much stomach can expand; this can be a suitable tool to improve fish feeding research by regulating the amount of feed that can be ingested by animals.