EVALUATION OF COMPLEX PARTICLE FEEDING BY SABLEFISH Anoplopoma fimbria AND STEELHEAD TROUT Oncorhynchus mykiss

Disease continues to be a problem in finfish aquaculture. Current disease management strategies such as vaccination often involve immersion and injection delivery methods. Injections are effective but often costly and stressful on fish whereas immersions are generally less effective. C urrent options for an oral vaccine delivery route are limited. Oral delivery methods often utilize commercial-type feed particles that are top-coated, which is necessary to obtain high and even ingestion rates in fish. Vaccines cannot be added to commercial type feeds as the high temperature of production destroys bacterial-based vaccines. In this study, we investigate n ovel complex particles which utilize the entire particle volume for vaccine delivery and are produced with a cold production method..  However, in order for these particles to be effective, the particles must be ingested and partially digested (once in the hindgut) by the target organism. For this study we investigated the rate of ingestion and level of digestion of complex particles fed to sablefish (Anoplopoma fimbria) and steelhead trout (Oncorhynchus mykiss ).

We investigated the  uptake  of these particles by each species of finfish. W e used  a  control  complex particle that contained liposomes encapsulating a saline solution added to a solution of 2% alginate. For the experimental treatment , the complex particles contained liposomes encapsulating an amino acid mix of alanine, betaine, and glycine added to a solution of 2% alginate. A significantly higher portion of sablefish and steelhead fed on the amino acid mix particles when compared  to  the saline treatment. Sablefish that were offered the amino acid mix treatment had significantly more particles in their gut when compared to the saline treatment, wh ile the steelhead did not have a statistically significant difference. We investigated the d igestion of complex particles and incorporated a third experimental treatment that included liposomes encapsulating the amino acid mix added to a solution of 6% gelatin from cold water fish  skin  and 0 .5% alginate. Fish were collected at 1, 2, 4, and 8 hours to track placement of particles in the gut and investigate level of digestion. Particles containing the 2% alginate mix with no gelatin faced minimal digestion (I mage 1) while particles  that  contained 0.5% alginate and 6% gelatin were highly digested (Image 2).