Latin American Journal of Aquatic Research

ABSTRACT. Eastern Tropical Pacific (ETP) seagrasses are composed of three genera and four species: Halophila baillonii, Halodule beaudettei, Halodule wrightii, and Ruppia maritima. These are colonizing seagrass species and meadows in the ETP can be ephemeral. Current seagrass distribution in this region remains unknown, with verified extant presence at a limited number of locations and mapping heavily reliant on historical reports. Suitable environmental conditions for seagrasses in the ETP consist of sheltered bays <10 m depth with fine sediment, 19-35 salinity, 26-32°C temperature, and water transparency of up to 10 m Secchi depth. In this region, seagrass organic carbon (OC) biomass pools (<0.2 Mg ha-1) have been reported from three locations, while sediment bulk density (<1.4 g mL-1) and OC (<24 Mg ha-1) have been reported from eight locations, all found on the Pacific coast of Costa Rica. Recent blue carbon reports from the ETP have not been included in global assessments to date. OC sequestration and sediment accumulation rates are currently unknown. Seagrasses provide key ecosystem services yet they are also threatened by anthropogenic and natural stressors. Seagrasses have already disappeared from two locations within the ETP, with restoration efforts currently underway on the northern Pacific coast of Costa Rica. This overview of our current understanding of seagrasses in the ETP and their services highlights the need for further research in this understudied region.

ABSTRACT Penaeus vannamei, or white shrimp, is an economically significant species that dominates shrimp production and represents a rapidly growing industry. However, the culture faces challenges due to high mortality rates due to bacterial and viral diseases. Unlike vertebrates, shrimp rely solely on their innate immunity for defense against pathogens. Introducing probiotics into shrimp culture can enhance growth, survival rates, and immune responses against disease outbreaks caused by pathogenic bacteria or viruses. Common diseases affecting shrimp farms include vibriosis, white spot disease, acute hepatopancreatic necrosis and black gill disease. These diseases can cause severe infections, which lead to high mortality rates. The application of probiotics, such as Bacillus cereus, B. licheniformis, B. subtilis, Lactobacillus sp., Paenibacillus, Pseudomonas sp., Pseudoaltermonas, and yeast, either through diet or direct administration, has demonstrated positive impacts on shrimp health, including enhanced growth, increased immunostimulation, improved gut microbiota, and better water quality parameters. In recent decades, aquafeed has explored effective solutions, such as microdiets, co-feeding (combining commercial feed and probiotics), and various microdiets types, to address aquaculture disease problems. Combining microdiets containing essential nutrients with probiotics has proven to be safer than antibiotics, which can adversely affect animals and the environment. However, further studies are needed to optimize the efficiency of feeding techniques by incorporating probiotics and commercial feed for disease resistance in penaeid shrimp culture. This review discusses commercial feeds and microdiets incorporated with probiotics for P. vannamei culture for growth and disease resistance to enhancement.

ABSTRACT Integrative studies are important for a better understanding of the functional development of fish digestive systems and the consequent design of suitable feeding regimes and ad-hoc diets. To characterize the ontogeny of digestive function in larvae and juveniles of two atherinopsids from South America, Odontesthes bonariensis and O. hatcheri, morphologic, histologic, and intestinal enzyme biochemical analyses were performed. Both species showed a functional digestive system from one week after hatching (wah) with a sustained high-level activity of the cytosolic enzyme leucine alanine peptidase (leu-ala) until 9 and 13 wah in O. hatcheri and O. bonariensis, respectively. Maximum specific leu-ala activities in both species were higher compared to other agastric and most gastric fish. These results and the abundant pinocytic vacuoles in the posterior intestine suggest that cytosolic digestion is crucial for these species. It seems that their apparent anatomically simple digestive system is compensated by an uncommonly early development and function of the digestive tract and accessory organs accompanied by high intestinal cytosolic activity. The above findings contribute to the understanding of the Atherinopsidae digestive model and, for the first time, suggest that under farming conditions, these species could be weaned at an early developmental stage with an appropriate balanced diet.

ABSTRACT A stochastic model was developed to analyze Crassostrea virginica production when cultivated at three stocking densities, defined as the area occupation (50, 75, and 100%) in Nestier-type trays, using juvenile oysters with an initial size (height) of 29.40 ± 0.18 mm. A 25-week grow-out was first conducted in the Rio Lagartos lagoon, showing that final oyster size was inversely related to density (P < 0.05), ranging from 61.87 mm (100% density) to 68.00 mm (50% density). At the same time, mortality was negligible (lower than 1.0%). The environmental conditions in the lagoon were stable, and the oyster growth rate positively correlated with water temperature and pH. Low pH was associated with slow oyster growth, possibly as an adverse effect of acidic conditions on the oyster shell formation. The model indicated that, for an initial 100,000 oyster population, the maximum production (oyster dozens) is obtained after 20 weeks (8310 at 50% density) and 25 weeks (8250 at 75%, and 6670 at 100% density). There was a 100% probability of oysters reaching a minimum commercial size (MCS) of 60.00 mm when using the 50 and 75% densities and 80.6% when using 100%. The model estimated that, for the maximum density, extending the grow-out up to 32 weeks would allow reaching MCS with 100% probability, although this should be experimentally confirmed. The random variability of oyster production in 50 and 75% densities was minimal, while at 100% density, it was extremely high. A sensitivity analysis indicated that for 50 and 75% densities, the main stochastic elements influencing production, are related to oyster mortality, while at 100% density, they are related to oyster growth.

ABSTRACT Macrobrachium rosenbergii is the freshwater shrimp species of greatest economic interest, and its reproduction has been studied for commercial purposes. This study aimed to evaluate the effect of different salinities (0, 6, and 12 mg L−1) on the embryogenesis of this species. The females were observed daily according to their reproductive behavior. Upon the first sign of spawning, when their eggs were attached to the abdomen, they were collected for egg collection and transferred to the incubators at the respectively tested salinities. The eggs were collected every five days for up to 23 days, separated according to their stage of development, histologically processed, and stained for visualization of structural changes during embryogenesis using an optical microscope. From the egg's histological images at different embryonic development stages, the egg hatching time was evaluated, the changes that occurred in the eggs during embryogenesis, the total area of the eggs, the vacuole area, and the ratio between the vacuole area and the total area of the eggs. Differences were observed in hatching time, egg size, and vacuole area and area ratio. The 6 g L−1 of salinity treatment was statistically different from the other in all parameters analyzed. Therefore, it was concluded that 6 g L−1 of salinity positively influenced embryogenesis, as it presented hatches from the 15th day of embryogenesis, demonstrating that there was a greater speed of migration of vitellogenin for the formation of the embryo, accelerating embryogenesis and hatching of M. rosenbergii.