Parasite Prevention in Fish Farming

Dr Francisco E. Montero and M. Mercè Isern i Subich*, DVM, Senior Lecturer, University of Valencia, Spain

The aquaculture industry is expected to continue to expand and fulfill the increasing global needs for fish and shellfish in the coming years. However, as the industry grows and intensifies, biological plagues are becoming more critical factors affecting the profitability of aquaculture producers. All commercial aquaculture fish species worldwide suffer from a variety of parasites which often cause important economic losses. Parasites affect all fish species, including highly industrialized species such as salmon, bulk freshwater species such as tilapia, as well as new species of marine fish such as yellowtails and tuna.

Due to the complexity and diversity of parasites, including unicellular organisms, myxozoans, crustaceans and worms, the prevention and treatment of parasitic disease in fish requires focused and specific approaches. Multiple interactions with other diseases present in the farming system will also affect the choice of the most convenient preventive approach.

The traditional approach to combat fish parasites, based on the use of a wide range chemicals and other therapeutics once the parasite outbreak is detected, is increasingly hampered by the development of resistance and the increasing restrictions on the use of chemicals. Increased knowledge on the biology parasite populations affecting the different productive systems, implementation of good handling procedures adapted to the different species and production conditions, development of biological pest control measures, together with health promoting feed additives are crucial components of effective parasitic disease prevention strategies. This presentation will illustrate a number of strategies to control parasitic diseases, both established as well as innovative, based on the particular traits of the different parasite types affecting different fish species.

Health-promoting feed additives have already become a standard ingredient in premium brands of salmon feeds designed to reduce the impact of sea lice. A wide range of additives with different mode of actions are currently being offered including yeast extracts, phytobiotics, probiotics, prebiotics, organic acids and their derivates. Functional feeds containing gut health promotors deliver with every meal, an adequate concentration of natural compounds which can work through multiple mechanisms to reduce the success of the parasitic infestation. Natural compounds with anti-parasitic activity can work directly on gut parasites or reach the blood and/or mucus to affect ecto-parasites, whereas immune modulators can change the composition and thickness of the mucus.

* Business Development Manager, Aquaculture Health, Nutriad