Relative Abundance and Species Composition of Gram-Negative, Aerobic Bacteria Associated with the Gut of Juvenile White Shrimp Litopenaeus vannamei Reared in Oligotrophic Well Water and Eutrophic Pond Water

Gut bacteria may contribute significantly to the growth and survival of cultured shrimp, although little is known about factors that affect bacterial community structure in shrimp guts. The objective of this study was to determine the abundance and species composition of gut bacteria in juvenile white shrimp Litopenaeus vannamei reared in two different environments. Eight 120-L tanks were stocked at a density of 8 shrimphank. Two treatments were tested for 10 d and consisted of tanks receiving flow-through water from one of two sources: 1) well water pumped from a sea-water aquifer (Well treatment), and 2) pond water pumped from an intensive shrimp pond (Pond treatment). Shrimp mid- and hindguts were excised on days 1, 3, 6, and 10 for enumeration of gram-negative, aerobic bacteria by quantifying colony-forming units (CFU) using standard microbiological plating techniques. Identification of bacterial isolates was made using the Biologa® GN Microplate system. Bacterial numbers were significantly greater ( P > 0.05) in Well shrimp than in Pond shrimp on days 1 and 3. Following day 3, a decrease in bacterial numbers occurred in the Well shrimp, and no significant differences between treatments were observed on days 6 or 10. Guts from Well shrimp were dominated by Vibrio and Aero-monas , and these two genera accounted for 80–851 of the bacteria on each sampling day. Guts from Pond shrimp exhibited a greater bacterial diversity and were dominated by Vibrio, Aeromonas , and Pseudomonas. Flavobacterium were identified in the guts of Pond shrimp on days 3 and 10, but were not identified in any of the Well shrimp. A greater understanding of gut bacteria-shrimp interactions could lead to increased production and profitability for shrimp farmers through the development of more cost-effective feeds and novel disease control strategies.     

Optimization of fishmeal,fish oil and wheat in diets for juvenile sablefish,Anoplopoma fimbria

Sablefish Anoplopoma fimbria is a piscivorous fish that is highly desirable as food. To ascertain the relationship of dietary protein, lipid and carbohydrate, eleven diets containing fishmeal, fish oil and wheat flour as test ingredients at different levels were formulated. The levels were chosen according to mixture experiment methodology, which varies the proportion of each test ingredient, while keeping their sum constant across all diets. The range of levels used in the test diets were as follows: fishmeal 430–600 g kg^?1, fish oil 100–270 g kg^?1 and wheat flour 30–200 g kg^?1. The sum of the test ingredients accounted for 900 g kg^?1 of all diets, with the remaining 100 g kg^?1 accounting for mineral and vitamin premix, binders, attractant, etc. Each diet, plus a commercial feed, was fed to three tanks of juvenile sablefish by hand twice daily for 11 weeks, using a completely random design. It was found that growth and feed efficiency were maximized by the highest dietary inclusion level of fish oil and fishmeal, corresponding to the lowest wheat flour level, that is 600 g kg^?1 fishmeal, 270 g kg^?1 fish oil and 30 g kg^?1 wheat flour.     

Decreased genetic diversity and a reduced effective population size in cultured silver-lipped pearl oysters (Pinctada maxima)

Before selection programmes for aquaculture species can commence, a fundamental knowledge of how the culture process affects genetic diversity is requisite. “South Sea” pearl production, through the culture of the silver-lipped pearl oyster, Pinctada maxima, stands to gain substantially from genetic selection. Aquaculture techniques for P. maxima have progressed vastly, to a point where the majority of current operations are based on hatchery-propagated stock; however, there has been no investigation on how the culture process is affecting the genetic diversity of this species. To address this deficiency, we investigated the genetic diversity and effective population sizes (N_e) in three wild and five hatchery-produced P. maxima populations. Using six microsatellite DNA markers, cultured populations exhibited low N_e (3.5–9.2) and reduced allelic richness (29–44%) compared with their wild progenitors. Observed heterozygosities were not affected greatly, however, an increased mean pairwise genetic relatedness was observed in all cultured populations. The practice of mass spawning was identified as a major factor in the reduction of diversity, although diversity was not necessarily maintained when a more controlled spawning approach was utilised. Pedigree reconstructions revealed genetic diversity and N_e is affected by large skews in full-sib family representations (up to 40% from a single family, in a cohort using 28 broodstock), and could be due to differential survival rates amongst communally reared families. In order to maximise future selective breeding efforts, further research should be directed towards identifying critical stages of the culture process in which genetic diversity is lost.