Studying fish behaviour ?!

I know what you’re going to say… Why fish ?! And why their behaviour ?! Can’t you just try to eradicate breast cancer, leukemia, world hunger or AIDS ? These are the questions usually asked to me. Well, I understand them actually but let’s go deeper.

Pssssst … fish migration has already been written about on this blog in the post Migrating Fish : Laissez-passer ! What ? You haven’t read it ?!

Why conserve migratory fish ?

Before going any further, let’s precise the notion of “Ecosystem services“. Don’t worry, it’s easy -peasy ! It is simply the benefits that we humans get from ecosystems. These are classified into 4 categories:

  • Supply services (fresh water, food, …)
  • Regulating services (climate, disease, …)
  • Cultural services (recreation, aesthetic, …)
  • and finally support services (you know, the production of oxygen, nutrients … the basic stuff that allow us to live).

If you wanna learn more about ecosystem services, you can read this brochure from the UE.

While providing us with goods and services, some of them being … While providing precious goods and services, some of which being irreplaceable, aquatic ecosystems are probably the most endangered ecosystems (1). Migratory fish are particularly at risk and are almost twice as likely to fall whithin the “at risk” classification compared to their non-migratory comparses (2).

While this should be a sufficient reason for conservation and apart from the intrinsic value they represent, migratory fish generate many fundamental ecosystem services since they represent a link between different ecosystems (between the sea and rivers by example) and they have a regulatory role of ecosystem processes; but they also generate “indirect” services and thus play an important role in terms of food and protein production, generate recreational activities (and therefore economic!) or supply the pharmaceutical industry (and thus human health!).

In addition, they represent a significant source of information for scientists and managers regarding river connectivity and health. Consider an example that you all know: the European eel, Anguilla Anguilla. They represent a very important source of food (the EU has even banned the export to Asian markets to avoid depletion of the population), are part of an ecosystem that they help regulate and maintain biodiversity and may even have a role in biological control regarding invasive species like the blue crayfish which now raging in Europe and elsewhere (3).

But then why study their behavior ?

Mainly for two reasons. The first, purely scientific: improve our knowledge. The second, rather “applied” :  help the conservation and / or management of fish populations and / or rivers in which they occur.

It should be noted that fish movement is widely used as a variable for assessing the status of ecosystems in which they occur as fish adapt or change their behavior as they deal with physical threats (like dams), threats chemical (pollution) or other changes in their habitat.

The ultimate goal of studying their behavior is to be able, in the future, to use fish like sentinels of the rivers. Using tracking techniques at the forefront of technology (remote telemetry … we’ll see later!), we could eventually know very precisely what happens in a given river. For example, imagine that a fish is equipped with a transmitter that allows us to know its activity (if it moves or not, at what depth, etc…) and its location. If we know its normal behavior in absence of any disturbance, we can then determine, based on the behavior he exhibits, if the river is being healthy or not. One could, for example, detect early pollution incidents at a very early stage and therefore act accordingly or determine who is responsible, if responsibla there is. It is as clear as spring water now?

If you want to go further in these subjects, please see :

1 – Dudgeon, D., Arthington, A.H., Gessner, M.O., Kawabata, Z.-I., Knowler, D.J., Lévêque, C., Naiman, R.J., Prieur-Richard, A.-H., Soto, D., Stiassny, M.L.J., Sullivan, C.A., 2006. Freshwater biodiversity: importance, threats, status and conservation challenges. Biological Reviews.

2 – Reid K. 2004. Global register of migratory species – from global to regional scales. Final Report, German Federal Agency for Nature Conservation. Project 808 05 081.

3 – Musseau, C., Boulenger, C., Crivelli, A.J., Lebel, I., Pascal, M., Boulêtreau, S., Santoul, F., 2015. Native European eels as a potential biological control for invasive crayfish. Freshwater Biology.

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