Research & Development – Research Briefs
Aquaculture Research, Vol 46, 3 Feeding activity strongly affects the variability of wild fi sh aggregations within fi sh farms: a sea bream farm as a case
study K BACHER, A GORDOA AND O SAGUÉ We tested the hypothesis that fi sh abun-
dance and species compositi on vary between feeding and non-feeding periods and diff erent bott om substrates within a Sparus aurata (L.) farm. Sampling took place during feeding and non-feeding periods on six consecuti ve days in July 2011. Visual censuses were carried out at three diff erent depths and at three sampling stati ons over rocky-sandy and sandy substrates respecti vely. In all, 33 species belonging to 17 families were observed. Total fi sh abundance, biomass and species commu- nity signifi cantly diff ered between feeding and non-feeding periods. Each depth was repre- sented by a disti nct species community and was therefore aff ected diff erently by the feed- ing acti vity. At the surface, fi sh abundance was signifi cantly higher during feeding compared with non-feeding periods. The distance from the feeding vessel signifi cantly infl uenced fi sh aggregati ons in the water column, indicati ng that plankti vorous species learnt to associate the boat noise with food availability through classic conditi oning. At the bott om, substrate type was the dominant factor explaining aggregati on variability. This study provides new informati on about the dynamics of fi sh aggregati ons within farms, emphasising the importance of considering the diff erent sourc- es of variability in future study designs.
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Journal of Fish Diseases, Vol 38, 3 Effect of hydrogen peroxide and/or Flavobacterium psychrophilum
on the gills of rainbow trout, Oncorhynchus mykiss (Walbaum) MMM HENRIKSN, PW KANIA, K BUCHMANN AND I DALSGAARD The immune response and morphological changes in the gills of rain-
Above: Tilapia; rainbow trout; sea cucumber; abalone; sea bass.
bow trout fry aft er immersion in hydrogen peroxide (H2O2), Flavobac- terium psychrophilum or combined exposure were examined. The gills were sampled 4, 48, 125 and 192 h aft er exposure, and the regulati on of expression of the following genes was investi gated using qPCR: IgT, IgM, CD8, CD4, MHC I, MHC II, IL-4/13A, TcR-β, IL-10, IL-1β, IL-17, SAA and FoxP3. Bacteria were not observed in haematoxylin-and-eo- sin-stained gill ti ssue, but the presence of F. psychrophilum 16S rRNA was detected using qPCR. The 16S rRNA levels were correlated with gene expression. Although pretreatment with H2O2 before immersion in F. psychrophilum did not signifi cantly alter the amount of bacteria found in the gill, the immune response was infl uenced: exposure to F. psychrophilum resulted in a negati ve correlati on with expression of IL-17c1, MHC I and MHC II, while pretreatment with H2O2 resulted in a positi ve correlati on with IL-4/13A and IgM. Exposure to either H2O2 or F. psychrophilum infl uenced the regulati on of gene expression and damaged ti ssue. Exposure to both combined altered the immune response to infecti on and postponed healing of gill ti ssue.
Aquaculture International, Vol 23, 1 Effects of reduced pH on the growth and survival of postlarvae
of the donkey’s ear abalone, Haliotis asinine (L.) AS TAHIL AND DT DY High atmospheric CO2 levels primarily from burning fossil fuels have
increased CO2 concentrati on in the surface water of the ocean, this in turn has resulted in a drop in seawater pH known as ‘ocean acidifi cati on’ (OA) and presents a potenti al threat to calcifying marine organisms. Up to the present, however, the impacts of OA on the early stages of tropical abalone were not known. For the fi rst ti me in the Philippines, we investi - gated the direct eff ects of reduced pH on the growth and survival of the postlarvae of the donkey’s ear abalone, Halioti s asinine L. H. Asinine is the only commercial species of halioti d in the country. We reduced the
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