Two experimental feeding trials were conducted during four weeks to evaluate the use of Ulva lactuca in shrimp culture: (1) for wastewater bioremediation, and (2) using different inclusion levels of U. lactuca meal in shrimp feed. In feeding trial 1, shrimp reared under seaweed U. lactuca water exchange in a re-circulation system (SWE) resulted in similar growth and feed utilization as shrimp reared with clean water exchange (CWE). Shrimp under no water exchange (NWE) resulted in significant lower growth and higher feed conversion rate (FCR) compared to the other treatments (p < 0.05). Nitrogen compounds and phosphate in water from SWE and CWE treatments did not present significant differences during the experimental trial (p > 0.05). In feeding trial 2, U. lactuca biomass produced by wastewater bioremediation in SWE treatment were dried and ground to formulate diets containing 0, 1, 2, and 3% U. lactuca meal (0UL, 1UL, 2UL, and 3UL). Shrimp fed the 3 UL diet resulted in a significant (p < 0.05) improvement of growth and FCR, and enhanced whole shrimp lipid and carotenoid content by 30 and 60%, respectively, compared to control diet. Seaweed U. lactuca is suggested as a desirable species for wastewater bioremediation in integrated aquaculture systems, and its meal as a good feed additive for farmed shrimp.

Aims This study describes the physicochemical and genomic characterization of phage vB_Vc_SrVc9 and its potential for phage therapy application against a pathogenic Vibrio campbellii strain. Methods and Results A lytic phage vB_Vc_SrVc9 against Vibrio campbellii was isolated from shrimp farm sediment, and characterized physicochemical and genomically. The use of vB_Vc_SrVc9 phage increased the survival in Brine shrimp Artemia franciscana and reduced presumptive Vibrio campbellii to non‐detectable numbers. Genomic analysis showed a genome with a single contig of 43.15 kb, with 49 predicted genes and no tRNAs, capable of recognizing and generating complete inhibition zones of three Vibrio species. Conclusions To our knowledge vB_Vc_SrVc9 is a lytic phage that could be used against Vibrio infections, reducing vibrio presence without any apparent impact over the natural microbiota at the family level in 28 libraries tested. Significance and Impact of Study vB_Vc_SrVC9 is a novel phage and ecofriendly alternative for therapeutic applications and biotechnological purposes because is stable at different environmental conditions, has a potential to eliminate several strains, and has a short latent period with a good burst size. Therefore, the use of phages, which are natural killers of bacteria, represents a promising strategy to reduce the mortality of farmed organisms caused by pathogenic bacteria.

Aims This study describes the effect of phage therapy on hatching of longfin yellowtail (Seriola rivoliana ) eggs challenged with Photobacterium damselae subsp. damselae . Methods and results A lytic phage (vB_Pd_PDCC‐1) against P. damselae subsp. damselae was isolated and characterized. The use of phage vB_Pd_PDCC‐1 increased the hatching rate of eggs, and reduced presumptive Vibrio species to non‐detectable numbers, even in non‐disinfected eggs. High‐throughput 16S rRNA gene sequencing analysis revealed that phage vB_Pd_PDCC‐1 caused significant changes in the composition and structure of the associated microbiota, allowing that members (e.g. those belonging to the family Vibrionaceae) of the class Gammaproteobacteria to be displaced by members of the class Alphaproteobacteria. Conclusions To the best of our knowledge, this represents the first study evaluating phage therapy to control potential negative effects of P. damselae subsp. damselae during hatching of longfin yellowtail eggs. Significance and Impact of the Study The Seriola genus includes several important commercial fish species due to its rapid growth and easy adaptability to confinement conditions. However, bacterial infections (especially those caused by Vibrio and Photobacterium species) are among the main limiting factors for the intensification of marine fish aquaculture, particularly during early development stages. Therefore, the use of phages, which are natural killers of bacteria, represents a promising strategy to reduce the mortality of farmed organisms caused by pathogenic bacteria.