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

Greenhouse gases increased in concentrations over pre-industrial values by 257% for methane and 145% for carbon dioxide in 2016. Such increased levels are the main climate change drivers and may affect aquatic systems that accumulate and carry carbon to the ocean and the atmosphere. Additionally, these systems are sensitive to environmental changes since their physical, chemical and biological properties respond rapidly to changes. Therefore, this study focus on the greenhouse gases dynamic over an urban eutrophic tropical lagoon. Samplings were performed in the Rodrigo de Freitas Lagoon by covering four periods in 2016 (April, June, October and December). Mean diffusive flux was -1,466.8 mg m-2 d-1 of carbon dioxide and 113.7 mg m-2 d-1 of methane. Regarding the bubbling, fluxes were 58.28 mg m-2 d-1 for methane and negligible for carbon dioxide (mean value of 5.01 mg m-2 d-1). Environmental parameters such as depth, water temperature and sediment particle size were strongly related to the fluxes. In conclusion, the region is a sink of carbon dioxide and a source of methane to the atmosphere. Additionally, the rivers discharge impacts the lagoon by generating a methane hotspot emission region.

Hsp70 proteins are widely found through several species, and they are considered among the most conservative proteins in nature, in both their sequence and function. They play an important role in the response mechanism to several different kinds of stress such as temperature and pathogens among others. In some species, the variations in the sequence of the Hsp70 gene result in intra-specific differential expression, and therefore in differences in thermo-tolerance of individuals as well as other productive characteristics. The study of the potential impact of the Hsp70 gene polymorphisms represents a field of study that could greatly help the mollusk farming industry.

Fisheries interactions with non-target marine vertebrates are a worldwide problem. The impact of coastal bottom trawl fisheries on marine mammals has never been evaluated before in the Río de la Plata Estuary and the adjacent Atlantic Ocean. Our aim was estimating the bycatch per unit effort (BcPUE) and incidental mortality rates of marine mammals caused by the industrial coastal bottom trawl fisheries fleet. We evaluated the mortality of three species (i.e., franciscana dolphin Pontoporia blainvillei, South American sea lion Otaria flavescens, and the South American fur seal Arctocephalus australis); these species are facing conservation problems either at the regional or local scale. We conducted an onboard data collection program of marine mammals' bycatch involving crew members of 10 vessels (30%) of the Uruguayan coastal bottom trawl fleet between January 2009 and April 2012. A total of 102 marine mammal individuals were bycaught during 490 fishing trips involving 2,398 fishing days. Mortalities estimated for franciscana dolphin were the highest among the species affected, with values adding up to ~100 individuals for year (with scenarios of population decline in the area), followed by South American sea lion with ~77 individuals by year (0.8% of local population) and the South American fur seal with an annual mortality estimate of ~25 individuals (~0.02% of local population). BcPUE showed significant temporal variation, with franciscana dolphin BcPUE varying seasonally and those of otariids according to their breeding season. Our estimates of marine mammal bycatch by bottom trawl fisheries should constitute an important input for the sustainable management of fisheries and the conservation of marine biodiversity in the southwestern Atlantic Ocean.

Chinook salmon (Oncorhynchus tshawytscha) were recorded in two extensive areas during a survey conducted between February 2012 and June 2013 to obtain information regarding the seasonal distribution and population structure of a self-sustained salmonid population inhabiting the Palena River. A total of 83 Chinook salmon were captured, which corresponded to 8.3% of the total salmonids collected in both areas. Juveniles of less than 15 cm were recorded in the upstream section of the river, from which fry-parr were less than 5 cm, and pre-smolt ranged between 5 and 10 cm aged 0+. Smolts displaying the characteristic silver coloration with an absence of parr-markings ranged between 10 and 15 cm and were aged 1+. The diet of the juvenile salmon was composed mainly of aquatic insects. Mature salmon returning from the ocean were collected in the middle section of the river, with weights ranging between 4.6 and 28 kg and their age ranged from 4+ to 6+ years in the ocean, plus 1+ year´s growth in freshwater (stream type ecotype). All the adult salmon were devoid of food. Immature adults, with ages between 3+ and 4+, were collected from a small lake (Claro Solar), displayed a piscivorous diet mainly based on native Galaxid species. Adult salmon returning from the ocean were infested with the cestode Hepatoxylon trichuri, attached to the pyloric caeca.

The lionfish (Pterois volitans, P. miles) is the first known species of marine fish to invade the Caribbean and Gulf of Mexico, and it is threatening the biodiversity of the region´s coral reefs. Its success as an invasive species is due to its high predation and fertility, fast growth and lack of predators. Its first recorded appearance in Mexico was in 2009. Twenty-two sites were monitored around the reef of Banco Chinchorro Biosphere Reserve (BCBR), to estimate their abundance, during 2013. Densities from 0 to 333 ind ha-1 (97.6 ± 140.2 ind ha-1) and biomasses from 0 to 58.7 kg ha-1 (18.2 ± 29.9 kg ha-1) were recorded, the highest so far in the Mexican Caribbean. In addition, two lionfish distribution zones were detected: leeward reef (LR) and windward reef (WR). LR was 4.6 and 3.9 times higher in density and biomass than WR, respectively. The sizes found in the monitoring ranged from 5 to 40 cm of total length. Finally, a gregarious behavior was observed in 47.5% of the recorded fish. Our results suggest that to prevent the development of large reservoirs of lionfishes in the BCBR, management and control actions in areas of high lionfish abundance should be prioritized.

Many questions about the role of planktonic organisms remain unanswered because of the difficulty in obtaining a medium where bacteria and fungi are not present. Moreover, an excess load of these microorganisms in phytoplankton cultures and zooplankton organisms may cause nutrient competition or diseases and consequently the death of the organisms of interest. For this reason, we reviewed several methods that have been used to obtain axenic planktonic cultures through specific metabolic inhibitors, such as antibiotics and antifungal agents. From 1940 to 2016, most research was related to microalgae and crustacean’s cultures, with the antimicrobials: penicillin, streptomycin, chloramphenicol, oxytetracycline, neomycin and nystatin being the most frequently used. The studies that applied antimicrobials agents to planktonic cultures were mainly focused on being able to culture them and to answer questions about the role of bacteria in aquatic communities without previous testing their effectiveness or their effects on non-target organisms. Therefore, this review sought to determine the correct use of antimicrobials in cultures of planktonic organisms to prevent bacterial and fungal growth, without causing damage to non-target organisms and may assist in the implementation of ecologically-oriented scientific experiments where bacterial and/or fungal inhibition is necessary.

Passive fishing gears such as pots and traps can be constructed with a section of netting made from natural fibers. In the event the fishing gear is lost or abandoned, these fibers deteriorate which effectively disables the fishing gear and allows organisms which accidentally enter the gear, an opportunity to escape without harm. This study evaluated several twines manufactured from natural fibers for their suitability to reduce ghost fishing in pots and traps. Nine cotton and jute twines of different diameters and construction were selected from Valparaiso local market, Chile. The twines were submerged for 56 days in seawater under laboratory conditions. Measurements of breaking strength were performed every 14 days. A decrease in the mean breaking strength was observed after 56 days for all twines, ranging from 0.5 to 29.6% for jute twines and 12.8 to 71.7% for cotton twines. The time until total degradation was predicted to be 113-230 days for the twisted jute twines, 68-234 for the twisted cotton twines, and 108-205 for the braided cotton twines. Our results suggest that cotton twines are a more suitable and feasible option to be implemented. The need to perform trials of biodegradable devices under commercial fishing conditions is warranted.

Totoaba macdonaldi is an endemic species which has been overexploited causing its population to decrease and to be cataloged as endangered. Understanding the larval period is the most critical stage in the development of marine fish farming. Our study aims to determine the changes in digestive enzyme activities during the early ontogeny of totoaba, using biochemical and electrophoretic techniques as SDS-PAGE. The results show that the acid protease had maximum activity between days 28 and 32 days post-hatching (DPH) when the Artemia was replaced by formulated food. Alkaline protease activity was detected at 2 DPH with maximal activity between 20 and 32 DPH; trypsin activity became active from 2 DPH; chymotrypsin activity increased at 6 DPH; leucine aminopeptidase activity was detected at 3 DPH, showing its maximal level at 22 DPH; carboxypeptidase A activity increased at 3 DPH; and lipase and amylase activities were detected at 2 DPH. Acid zymogram showed only one isoform (0.72 rf) from 2 DPH and increased in intensity from 8 DPH. For alkaline proteases, four isoforms were detected from yolk absorption (1 DPH), increasing to six isoforms (77.8, 47.3, 43.5, 21.0, 19.2, and 17.5 kDa) from 8 DPH onwards. Our results demonstrate that larvae of T. macdonaldi present characteristics typical of carnivore marine fish, showing the presence of alkaline digestive enzymes prematurely and the presence of offset pepsin. According to the results obtained in the present study, T. macdonaldi can be a juvenile beginning between 24 and 28 DPH, being the most appropriate day to perform replacement by artificial food.

Larviculture is a critical stage during the production of marine fish species and it is related to highest mortalities. The production of juveniles depends on a successful larval rearing, consequently the importance to investigate all aspects related to this culture stage, such as the stocking-density which is the extreme importance to improve culture conditions and reduce stress and mortality. Therefore, the objective of this study was to evaluate the effect of three stocking densities (10, 20 and 30 larvae L-1) on growth and survival of the fine flounder larvae, an important commercial species, under laboratory conditions. The number of larvae for each treatment was distributed randomly in 12-141 L fiberglass-tanks in a static-batch system. We used one day post-hatching larvae (DPH) and first feeding began two DPH with enriched rotifers (0.5 to 4 rotifers mL-1). The standard length (mm) was determined at 1, 5, 10 and 20 DPH, and the dry weight (mg) at the beginning and end of the experimental trial. Besides, the specific growth rate (SGR) and the coefficient of variation (CV) were calculated. Our results exposed that the stocking density of 10 larvae L-1 had significantly higher growth (8.14 mm and 0.90 mg), SGR (20.71 ± 1.48% d-1) and survival (42.38%) compared to the 20 and 30 larvae L-1 stocking densities. Additionally, treatment stocked with 10 larvae L-1 resulted in the highest final weight (0.90 ± 0.25 mg) and the lowest variation in sizes (CV = 5.86 ± 1.56). In conclusion, there is a significant effect of the stocking density on the growth and survival during the larval rearing of P. adspersus, and according to the results obtained in this study, the best stocking density for this species was that of 10 larvae L-1. More research is necessary to evaluate other parameters to improve growth and survival during the larval rearing of this species.

The effect of different lipid levels (10, 15, 20 and 25%) and oil sources (fish oil: FO and soybean lecithin oil: LO) on growth, survival, digestive enzymatic activity, gene expression acetyl CoA carboxylase (ACC1) and fatty acid synthase (FAS) of Mayan cichlid larvae Cichlasoma urophthalmus were evaluated by a bi-factorial design. The larvae were fed from hatching with eight different experimental isoproteic diets (45% protein) and a commercial diet for tilapia as a control diet. The results showed that larvae fed the LO15 diet had the highest growth in weight and total length and higher trypsin activity. The lowest values in FAS and ACC1 expression were obtained exclusively with the lipid type (soybean lecithin). It is concluded that the inclusion of soybean lecithin at a concentration of 15% allows the 100% replacement of fish oil in balanced feed for the culture of Mayan cichlid larvae.