Dietary enrichment with crude protein content and feed additives (Bacillus spp. and yeast strains) improves growth performance, survival and circulating hemocytes in juvenile White shrimp, Litopenaeus vannamei: Enriquecimiento de la dieta con proteína y aditivos alimentarios (cepas de Bacillus spp. y levaduras) mejora el crecimiento, supervivencia y hemocitos circulantes de juveniles de camarón blanco, Litopenaeus vannamei

In this study the enrichment dietary effect with different  crude protein levels (CP) and feed additives on growth, survival, feed conversion ratio (FCR), feed consumption (FC) and total hemocyte count (THC) in juvenile white shrimp Litopenaeus vannamei were evaluated. The study covered two bioassays: in the first one, juveniles were daily fed for 45 days with four experimental diets containing: (1) Control, commercial feed (35% CP); (2) 29% CP; (3) 32% CP; (4) 35% CP. After the 29% CP diet was selected, juveniles in bioassay II were daily fed for 45 days with a single CP diet complemented with probiotics: (1) Control, commercial feed (35% CP); (2) 29% CP; (3) 29% CP + Bacillus mix at 1×106 CFUg–1 feed; and (4) 29% CP + yeast mix at 1×106 CFUg–1 feed. Juvenile shrimp fed with experimental diets gained significantly more weight and increased survival, FCR, FC and THC compared with control diet. However, differences among experimental diets were not significant. In bioassay II, juvenile shrimp fed with experimental diet + feed additives significantly increased survival, FCR, FC and THC compared with control diet. Growth of juveniles significantly increased with 29% CP and 29% CP + yeast mix diets, compared with control group. Complementing the diet with yeast mix showed higher survival and THC of juveniles compared with the other experimental treatments. Different CP levels in shrimp diet improved growth, survival and circulating hemocytes, and addition of mixed yeast as feed additive induced better survival and immune response in juvenile shrimp

Testing of the 4SM Method in the Gulf of California Suggests Field Data Are not Needed to Derive Satellite Bathymetry

Satellite-derived bathymetry methods over coastal areas were developed to deliver basic and useful bathymetry information. However, the process is not straightforward, the main limitation being the need for field data. The Self-calibrated Spectral Supervised Shallow-water Modeler (4SM) method was tested to obtain coastal bathymetry without the use of any field data. Using Landsat-8 multispectral images from 2013 to 2016, a bathymetric time series was produced. Groundtruthed depths and an alternative method, Stumpf’s Band Ratio Algorithm, were used to verify the results. Retrieved (4SM) vs groundtruthed depths scored an average r2 (0.90), and a low error (RMSE = 1.47 m). 4SM also showed, over the whole time series, the same average accuracy of the control method (40%). Advantages, limitations and operability under complex atmosphere and water column conditions, and high and low-albedo bottom processing capabilities of 4SM are discussed. In conclusion, the findings suggest that 4SM is as accurate as the commonly used Stumpf’s method, the only difference being the independence of 4SM from previous field data, and the potential to deliver bottom spectral characteristics for further modeling. 4SM thus represents a significant advance in coastal remote sensing potential to obtain bathymetry and optical properties of the marine bottom

Studies on the nutrition of spotted sand bass, Paralabrax maculatofasciatus. Effect of the dietary protein level on growth and protein utilization in juveniles fed semipurified diets

Two feeding trials were conducted to determine the digestibility of a casein-based semi­purified diet and the effects of different protein levels on growth and protein use of spotted sand bass Paralabrax maculatofascÜltUs juveniles. For trial 1, a semipurified diet with vitamin­free casein as the sole source of protein was fed three times a day to apparent satiation, for a period of 20 d. Feces were collected by siphoning each tank. The digestibility of the exper­imental diet was high: 97% for protein, 89% for lipids, and 84% for gross energy, whereas that of organic matter was 78%. For trial 11, seven diets were formulated using vitamin-free casein at graded levels (25, 30, 35, 40, 45, 50, and 55% protein). Triplicate tanks for each dietary treatment were stocked with fish and fed by hand three times a day to apparent satiation for 6 wk. Perfomance of fish fed the different diets was evaluated for survival, percent weight gain, specific growth rate, feed conversion ratio, and protein efficiency ratio. Survival was 100% for all treatments. Growth of spotted sand bass juveniles increased as the dietary protein increased, but no evidence of reaching a plateau was found. The daily feed intake values showed an inverse relation to the protein content of the diets. The feed conversion ratio did not differ among diets containing 40% protein or greater. The results indicate that spotted sand bass juveniles with 2.5-g mean weight need at least 55 % dietary protein for best growth when casein is the sole protein source. However, in terms of feed conversion ratio, the requirement apparently could be lower

Assessment of endemic microalgae as potential food for Artemia franciscana culture

In this study, five microalgal strains were isolated from Bahía de La Paz, Baja California Sur, Mexico and identified as Grammatophora sp., Navícula sp., Rhabdonema sp., Schizochytrium sp., and Nitzschia sp., and their evaluation as potential food for Artemia franciscana. The isolated strains were cultured outdoors and harvested after four days. Chaetoceros muelleri was cultured under laboratory conditions and used as control. The protein, lipid, and carbohydrate composition and the fatty acid profiles of the strains were determined by gas chromatography. To assess the effect of microalgal strains on A. franciscana, decapsulated cysts were cultured at outdoor conditions in 15 L containers. The experiment was conducted for twelve days. Samples from the five different feeding treatments were taken at the beginning and end of the experiment to assess number, size, and weight of Artemia larvae. Treatment with Rhabdonema sp. showed larvae with a lower percentage of polyunsaturated fatty acids (PUFAs) while Grammatophora sp. showed those with the greatest PUFA proportion, even more than those fed Chaetoceros muelleri (control). Larvae consuming Schizochytrium sp. had no docosahexanoic (DHA) nor eicosapentaenoic (EPA) fatty acid content. Growth and survival of A. franciscana did not show significant differences among feed treatments, except when it was fed Nitzschia sp., showing lower survival and dry weight. Treatment based on Schizochytrium sp. and Rhabdonema sp. had a greater A. franciscana size but reduced dry weight; additional tests including two or more algal species for every treatment should be carried out to determine the best yield

Anomalías positivas de temperatura del 2014-2016 en Bahía Magdalena: el caso de Phyllospadix scouleri

Trabajo presentado en el XXI Congreso Nacional de Oceanografía y la III Reunión Internacional de Ciencias Marinas, celebrados en Ensenada (Baja California) del 20 al 25 de septiembre de 2021.Investigaciones y monitoreos recientes han documentado disminución de pastos marinos a gran escala tras eventos climáticos extremos; por lo que el propósito de este trabajo fue conocer la distribución temporal y la estructura de la comunidad de Phyllospadix scouleri en Bahía Magdalena después de eventos climáticos extremos. Para ello, se realizaron seis salidas de campo entre 2015 ¿ 2016 y se visitaron 11 sitios en donde se recolectaron cuadrantes de 12.5 x 12.5 cm para obtener datos de densidad y biomasa de P. scouleri en la zona intermareal. Se obtuvieron imágenes de satélite de la base de datos de ERDDAP, satélite Aqua MODIS (resolución espacial= 1km, temporalidad= mes, años= 2005-2017) para extraer promedios mensuales de temperatura superficial del mar (°C); además, obtuvimos valores del Índice Multivariado ENSO3 (MEI) de la página de la NOAA y se recabó información de la Comisión Nacional del Agua de los ciclones tropicales que afectaron el área de estudio entre 2008 y 2015. Para la temperatura superficial del mar, los resultados obtenidos muestran temperaturas máximas de 26.1°C en 2013, 29.6°C en 2014, 29.1°C en 2015 y 25.9°C en 2016 que coincide con anomalías positivas de temperatura ocasionadas por El Blob (2013-2015) y El Niño (2015-2016), este último con MEI de 2.5. Con respecto a los ciclones tropicales, durante el 2014 los huracanes Norbert (categoría II) y Odile (categoría III) afectaron a Bahía Magdalena. En cuanto a la distribución temporal se observa que hasta el verano de 2014 se registraron praderas de P. scouleri en la zona de estudio, su desaparición a partir del 2015 y una recuperación en noviembre de 2016, con valores de densidad de 17,984 haces m-2 en El Star y 8,448 haces m-2 en El Huesito. Los valores de biomasa fueron de 2,639.36 gr PS m-2 en la localidad de El Star y de 1,488 gr PS m-2 en El Huesito. Así en el área de estudio coincidieron en el tiempo anomalías de temperatura positivas conocidas como ¿El Blob¿ (2013-2015), los huracanes Odile y Norbert en 2014 y el fenómeno de El Niño en 2015 con la desaparición de Phyllospadix scouleri en el intermareal de Bahía Magdalena, por lo que se presume que el conjunto de estas perturbaciones pudo ocasionar la desaparición de dichas praderas de pastos marinos del área de estudio durante 2015 y parte de 2016

Effect of isolated bacteria and microalgae on the biofloc characteristics in the Pacific white shrimp culture

At present, the Pacific white shrimp Litopenaeus vannamei Boone, 1931, is one of the species with the greatest potential to be reared under biofloc Technology (BFT). Although BFT presents promising culture methods, some of these require improvements in efficiency by the use of native microalgae and bacteria (BFNO) as an alternative to commercial organism probiotics (BFCO). This experiment was developed using a culture system for the shrimp L. vannamei to a stocking density of 400 in./m3 for 44 days. Schizochytrium sp. and recently isolated Latobacillus plantarum (class: Bacilli), a probiotic strain (used as experimental biofloc), were incorporated to geomembrane tanks holding 28 m3 seawater to evaluate if these presented bioregulating effects influencing water quality and growth performance of L. vannamei. These microorganisms were compared with the BFCO. Results showed that both promoted bioflocs maintained optimal concentrations of total ammonium, nitrites, and nitrates for L. vannamei cultures. However, the BFCO required to be supplied every 10 days, whereas the experimental biofloc only required an initial stocking and maintenance of sodium carbonate levels >100 mg L−1 and pH > 7.5. Additionally, the load of Vibrio spp. in experimental biofloc was less than that observed for BFCO. Furthermore, the results of growth performance did not demonstrate differences between both treatments. Therefore, it is suggested that Schizochytrium sp. and the bacterial strain of L. plantarum should be used as initiator and basic constituents of the biofloc-based culture systems for L. vannamei, maintaining good water quality and avoiding periodical probiotic supplementation in cultures. Keywords: Induced biofloc, B. plantarum, L. vannamei, Microalga