Innovative Solutions for Tracking the Health of our Fish

Sometimes we just have to stop and think about what we’re doing, why we’re doing it, and if there might be a better way to accomplish our goals.

Take, for example, the environmental monitoring programs designed to evaluate potential environmental impacts from Canada’s metal mines and pulp and paper mills. Both industries must collect data to determine whether existing environmental regulations are effectively protecting against their potential effects and then must report that data to Environment and Climate Change Canada.

The monitoring program under which industry collects this data is called Environmental Effects Monitoring (EEM). One of its cornerstones is the wild fish survey in which fish are collected from reference areas (unaffected by industry) and compared to fish captured downstream from industrial activity.

The fish populations at the different sites are compared based on their weight, length and size at a given age, but liver and gonad (testes or ovary) sizes are also compared as indicators of the health and reproductive potential of the fish. While weight and length can be measured using catch-and-release methods, determining liver and gonad size requires killing and dissecting fish.

In fact, the EEM program stipulates that in order to provide accurate results, 20 males and females must be collected at each location for valid comparisons. Considering that there are approximately 78 metal mines and 16 pulp and paper mills in Canada, that is a lot of fish being killed just to measure their livers and gonads. Surely, there has to be a better way?

Here at IISD Experimental Lakes Area (IISD-ELA), we are working in collaboration with Dr. Lynn Weber of the Western College of Veterinary Medicine at the University of Saskatchewan to develop ultrasound methods to measure liver and gonads in fish. Ultrasound technology has changed over the last decade so that it now is able provide high-resolution images in smaller, more affordable units that can be used right in the boat!

A video of the liver is obtained using a portable ultrasound instrument. A series of liver images are then digitized using image analysis software and the images are spliced together to reconstruct a 3-dimensional image of the liver, which has been animated here so that it appears to emerge out of the ultrasound video. Estimates of the volume and shape of the liver using ultrasound have been shown to be remarkably accurate in a test species of fish.

We have already had some promising results using these techniques in the laboratory, and, by continuing to test our methods using wild fish at IISD-ELA this fall, we hope to refine the methods to allow us to accurately and reliably measure these organs and their seasonal fluctuations over time. Hopefully, we will ultimately be able to provide guidance and methods so that ultrasound can reduce the need to kill fish in EEM programs across Canada.