Husbandry of Aquatic Laboratory Animals

Dr. Neil Ruane

Marine Environment & Food Safety Services

www.marine.ie

Responsible use of animals

Knowledge of the biological characteristics and husbandry

requirements of the species

Animal must be suited to the research demands e.g.

particular strain, physiology, behaviour

Housing, feeding and care must be appropriate to the

requirements of the species

Presentations topics

• Housing/rearing units

• Requirements

• Feeding

• Water quality

• Stocking density

• Biosecurity

• Fish welfare and stress

Major groups of modern fishGNATHOSTOMATA

CHONDRICHTHYS OSTEICHTHYES

ELASMOBRANCHI SARCOPTERYGII ACTINOPTERYGII

CHONDROSTEI NEOPTERYGII

TELEOSTEI

Diversity of fish species

Reflects their ancient history

Ability to speciate rapidly

– In response to isolation (landlocked species)

– Wide range of habitats (deep ocean, FW, SW)

– Pelagic, benthic etc.

Most of the diversity is found in FW even though 97% of all water is in the oceans.

Physical and chemical characteristics of water impose a number of constraints on the functional design of fish – hence similar adaptations in body form and physical appearance

Fish Production in Ireland – ca 13,000t

Atlantic salmon (90%)

Rainbow trout (8%)

Others (2%)

COD

PERCHTURBOT

CHAR

Husbandry – rearing units

Rearing of fish based on life cycle – FW or marine

FW species have a less complex larval rearing cycle

– Long egg incubation periods

– Hatching of well developed larvae

– Directly on to commercial diets

Marine species are more complex

– Short incubation periods

– Larvae less well developed

– Often require live food prior to weaning on to commercial diets

– Live food: Rotifer and Artemia (which also need to be fed)

Husbandry – FW rearing (e.g. trout, salmon)

Egg incubation units

Daily removal of dead eggs to prevent spread of infections (fungal/bacterial)

Husbandry – FW rearing (e.g. trout, salmon)

22 days41 days

76 days102 days

Rainbow trout are often on-grown in pond farms

Husbandry – FW rearing (e.g. trout, salmon)

Salmon and char are on-grown in tanks or cages in a lake

Atlantic salmon, rainbow trout and Atlantic cod are reared

at sea in cages – open system.

Juvenile cod and turbot are reared in pump ashore

facilities – located on land, seawater is pumped into the

facility

Husbandry – SW rearing (e.g. trout, salmon, cod)

Recirculation Systems

Closed systems where the water is reused.

Allows better control of water quality and rearing environment.

Higher costs associated with set-up and maintenance.

Basic elements:

– Physical filters (removal of large particles)

– Biological filter (conversion of harmful waste)

– Foam fractionation / Protein skimmer (seawater)

– UV sterilisation

Physical filters

Removing solid particulate matter from the systems.

The bulk of these solids are in the form of faeces or uneaten feed. These wastes

generate the greatest amount of pollution in a closed system.

Settleable solids are those particles that will generally settle out of the water and

can be removed by well placed drains, a sedimentation tank, mechanical

filtration, or a swirl separator.

Suspended solids are those small particles that will not settle to the bottom of the

tank. These suspended solids can be removed by running the water through a

fine screen or sand filter.

Biological filters

The process of removing dissolved metabolic waste products (ammonia

and nitrite) from the water.

This process requires the water to pass through filters that have live

bacteria living in them.

The effectiveness of this process depends on the amount of bacteria

that can be grown in the filter and maintaining optimum conditions for

their survival.

Dissolved solids

Removed by a process called foam fractionation or protein skimming.

The fine and dissolved organic compounds cling to the bubbles used

in the process. This results in foam, which can then be removed, from

the system.

This fine and dissolved matter is also removed during water changes.

For most systems changing some water regularly will help avoid

problems with dissolved solids build up.

Zero discharge systems or integrated systems use animals at

different trophic levels to clean the water e.g. plants or shellfish.

Requirements - feeding

The majority of fish can be fed with commercially available diets

Marine fish larvae have a more complex feeding strategy involving live feeds such as Artemia (brine shrimp) and rotifers

Requirements - feeding

Marine larvae are too small to feed on commercial diets.

Often fed with rotifers initially before switching to the brine shrimp.

Rotifers need to feed on phytoplankton species.

Rotifers can be enriched with essential fatty acids to aid growth and development.

Requirements - feeding

General rules: maintenance levels for feeding are 1% body weight per day. Can be increased to 3 – 5% for growth. Growth trials require more complicated calculations e.g. allometric growth.

Fish can be fed by continuous belt feeders or divided into meals – never feed more than the fish can eat.

Regular observation of feeding is necessary (sick fish do not eat)

Feeding level can be adjusted by weighing fish and readjusting the feeding level.

Requirements - feeding

Terms:

Food conversion ratio: ratio of weight gain to feed (optimal is an FCR of 1 or less i.e. 1 g food equals 1 g increased weight)

Feed intake: actual amount of feed digested by the fish

Growth rate: weight gain by fish e.g. Xg per day

Requirements – water quality

As fish are in intimate contact with their environment a reduction or sudden change in the quality of the water can have serious implications for the health and welfare of the animal

Important parameters to monitor include:

pH, temperature, salinity, oxygen, ammonia, nitrite, water flow

carbon dioxide, turbidity, aluminium, water depth

Water quality: pH

Water pH is essential as it affects the acid/base balance within the

fish.

Sudden changes in pH can lead to fish kills from hydromineral

imbalance (fish lose minerals e.g. Na, Cl, maintaining acid/base

balance).

High dissolved CO2 levels can lead to blood acidosis.

Seawater has a higher buffering capacity than freshwater.

Generally pH levels should be slightly basic, but can range from

6 – 8.5

Water quality: temperature

Fish are poikilothermic, therefore temperature regulates all aspects

of life – development, metabolism, oxygen levels.

Sudden changes in water temperature are stressful – need to keep

temperatures stable.

Each species will have a different optimal temperature range:

Atlantic salmon: 4 – 15oC

Rainbow trout: 4 – 20oC

Zebrafish: 18 – 24oC

Carp 4 – 25oC

Water quality: salinity

Stenohaline – tolerate a narrow range of salinities (carp, cod)Euryhaline – tolerate a wide range of salinities (salmon, tilapia)

Marine fish operate hypo-osmotically, maintaining blood osmolarity at 33% of seawater – drink seawater and excrete ions.

FW fish operate hyper-osmotically, excrete water (dilute urine) and actively take up ions.

Water quality: oxygen

Dissolved oxygen (DO) is probably the most critical factor in maintaining good water quality.

Expressed as mg/L or % saturation.

DO levels decrease during active periods (feeding) and oxygen dissolves better in cold water.

Cyprinids are more tolerant than salmonids.

DO must be > 5 mg/L, levels below 2 mg/L can lead to death

Water quality: ammonia

Ammonia is a natural product of fish metabolism, majority is

excreted through the gills.

High levels cause stress, damage gills, increase susceptibility to

pathogens and cause fish kills.

Ammonia occurs in two forms: un-ionized (NH3) and ionized

(NH4+). NH3 is highly toxic.

Nitrogen Cycle

Calculating Un-ionized Ammonia

Calculating Un-ionized Ammonia

Requirements – stocking density

Stocking density refers to the number of fish per tank i.e. g fish / L water.

Loading density: g fish / L water per hour (i.e. includes the flow rates.

High densities affect water quality and fish behaviour.

Some species like high densities (catfish), some are solitary (grouper, tilapia when reproducing).

Salmonids – high and low densities lead to stress.

Requirements – biosecurity

Defined as a set of management practices to prevent the introduction of a disease causing pathogen into the rearing system.

Prevent pathogen entry – External barriers

Prevent pathogen spread – Internal barriers

+ Ensure the health and welfare of animals at all times

Biosecurity – external barriers

All equipment and vehicles should be cleaned and disinfected before entering the site.

Fish coming in to the site should be certified as disease free, it is not allowed to move sick fish.

Other aspects – visitor logbook, clear signs indicating procedures

Biosecurity – internal barriers

Clothing and equipment should be cleaned and disinfected, before and after use.

Wash hands after handling fish.

Regular cleaning schedules for rearing system.

Logs of disinfectants and cleaning agents.

Cleaning Protocol

1. GROSS RINSE/REMOVE SOILING

2. APPLY DETERGENT *

5. RINSE WITH CLEAN WATER & DRY

4. APPLY DISINFECTANT *

3. RINSE WITH CLEAN WATER & DRY

* Used according to the manufacturers instructions

Examples

Detergents -

Chlorine based – HalamidIodine based – FAM30, BuffodinePeroxy compounds – Virkon AquaticPeracetic acid/acetic acid/hydrogen peroxide – Vanodox, Proxitane