Fish Health Management GOALS Production of healthy high

Fish Health Management • GOALS : – Production of healthy, high quality fish – – –

Principles of Health Maintenance • Maintain conditions which are designed to optimize growth, feed conversion, reproduction and survival • Intensive aquaculture – • Enhance natural resistance –

Maintaining Health • Inverse relationship between environmental quality and disease status of fish • Changes occur over time (type of system) – – • Emphasis of Health management: – – – Physical features of facility Use of genetically improved fish “SPF” stocks Environmental control Prophylactic/preventative therapy Feed quality and quantity

Stress • Adverse situation that affects the wellbeing of individual animals • •

Stress related disease • Environmental associated – – – • Microbial diseases – Decreased resistance to pathogens – Endemic pathogens

Location of site • Soil, water and fish species must be compatible • Chose site properly • Pond aquaculture • Soil characteristics • Drainage

Avoiding exposure • Best method to control infectious disease – Water is effective at delivering pathogens to fish (endemic) –

Avoiding exposure (cont. ) • U. S. : Title 50 – – Other countries? • Quarantine – Isolate stocks for a predetermined period before contact with resident fish • Eradication of Stocks – Last resort! – Is it worth it? – Can you manage around it without introducing disease to area

Avoiding exposure (cont. ) • Example: – VHSV (1989) Washington • Destroyed adults that were found to have virus • Destroyed juveniles – Great lakes (lake trout) Epidermal epitheliotropic disease (herpesvirus) • Destroyed fish and disinfected contaminated facilities • Appears to have worked – BKD (Wyoming) (1990) • • Destruction of RBT, lake, CTT, and Br. T brood stock Based on highly sensitive detection technique (ELISA) No evidence for disease “Was the cost and consequence greater than the value of what was saved? ”

Exposing Dose • • • Once pathogen load increases (due to poor resistance) = DISEASE

Extent of contact • Infection vs Disease? – Facultative – – Obligate – require host to complete life cycle • Viruses, some bacteria, and few parasites – Route of transmission • • • – Carriers

Protection through segregation • Young fish/newly hatched fish – – – • Fingerlings – Immunity increasing – • Growout – • Approaching market/release size – Very resistant to disease – Can survive in poorest water quality

Addition of new fish • Should take needed precautions when adding new fish to existing stocks • Home aquaria or large facilities •

Breeding and Culling • Important in the development of domesticated stocks that perform well • Improve by selecting for desired traits – – – • Future possibilities (genetic engineering) – Gene manipulation – Hybridization/transgenic

Eradication/prevention/control • Eradication: • Prevention: • Control: Reduction of problem to an economically/biologically manageable level – – –

Anticipating problems • • Good health records for each pond • • • Water quality/quantity • Stay on top of things!!

Fish Health Monitoring • Early diagnosis – Know what “normal” is! – – –

Question? You are in charge of fish health monitoring at an aquaculture facility. During morning rounds you notice that a first use pond containing RBT (50 g/fish) is having some problems. Fish appear lethargic, and some dark fish are observed. 1. What possible problems may be causing this? 2. How would you narrow the possibilities down? 3. You suspect the problem to be disease related, what would you do?