BC CAHS exists to support healthy aquatic ecosystems and thereby promote economic stability, cultural values and environmental integrity in coastal communities.

Laboratory Services - ATPase Testing

Rationale

To biological organisms, internal salt balance is a lifelong challenge. This challenge becomes especially dramatic in the life of a salmon during the time they migrate between freshwater and saltwater environments. The salt content of the ocean at 50°N latitude is 30-35% ("R.E. Thomson, Oceanography of the British Coast, DFO, 1981, Ottawa") while that of rivers and streams is considerably less. The internal salinity of the salmon must all the while remain constant. How does the salmon achieve this? Through osmoregulation. The kidneys and gills are the two main osmoregulatory organs. Gill physiology, in particular, changes to maintain internal salt balance.

At the beginning of its life in freshwater, the salmon has a high salt content relative to the surrounding stream environment. Thus, water diffuses IN along the osmotic gradient. During migration to seawater, the salt content of the salmon is low relative to the surrounding environment; therefore, a concentration gradient is established whereby the direction of flow is in favour of bringing salt into the salmon. To maintain internal salt balance, the salmon must constantly pump OUT salts against the concentration gradient via active transport. Active transport requires energy. This energy is in the form of ATP and is performed by sodium-potassium (Na+/K+) pumps that line the secondary lamellae of the gills.

ATPases are enzymes that catalyze the reaction of ADP --> ATP and so will be found where active transport is occurring. During smolting (the physiological changes which occur in salmonids during migration between freshwater and saltwater environments), there is increased active transport occurring across the gill surface and therefore more ATPase enzymes present.

With this knowledge of the salmon natural life cycle, we are able to farm salmon by growing them in freshwater hatchery facilities then timing their entry into seawater net pens. To reduce stress and mortality, this timing must be precise. Historically, behavioural cues and visual appearance have been used to time saltwater entry. Visually, salmon change colour from greenish-brown, which helps them stay camouflaged in the stream, to a shiny silver which helps them remain unseen by predators in the ocean. More recently, the saltwater challenge has been used to gauge seawater readiness. This method uses measurements of plasma ion levels or osmolality as an indicator of smolt readiness after the fish are immersed in saltwater for a 24- or 48-hour period.

The Na+/K+ ATPase assay has been developed in an attempt to time more precisely the window of saltwater entry in a humane manner. Along with behavioural observations, visual cues, and chloride determination, this data provides the most accurate measure of smoltification to date.

 

Sample Collection

Gill tissue sampling is done on-site at a hatchery. The Centre can provide a technician to perform the sampling, and if a long-term arrangement is made, then the Centre can train your personnel to sample. Samples must be stored in a buffer on dry ice, both available from the Centre's lab. Most clients sample 10-20 fish per pen. Fish weights, lengths, and other observations are recorded on a data sheet supplied either by the Centre or the client. Sample processing takes approximately 8 hours for 60 samples.

 

Procedure Description

Enzymes in the gill are extracted by chemical and physical means. A measure of enzyme activity is recorded. Collection of several data points over time gives information on trends in enzyme activity in the population.

 

Report

A full report of test results can be sent out by email or fax.