When Is A Fish Really Native?

Image Credit: Alexandre Roux, CC BY-NC-SA 2.0, Image Cropped

Image Credit: Alexandre Roux, CC BY-NC-SA 2.0, Image Cropped

In the summer of 2019 I spent a week driving around south-east Norway with my Master’s student Bastian. The plan was to speak to local freshwater managers and get their take on invasive fish species in Norway. I’d never conducted this sort of research before, but I thought I knew what I was in for. Invasive bad, native good, right? More nuanced approaches are for those who are disconnected from the problem, academics like me who could watch from a distance and comment airily.

First interview. What does the term “invasive species” mean to you?

Obviously I expected some combination of “alien to the region”, “brandishes halberds and horned helmets” and “outcompetes the native trout” (trout and its fellow salmonids are really quite popular here). What I got instead (abridged) was a contemplative shrug and a reminder that there are almost no native populations of trout left anywhere in Norway.

Insert confused ecologist.

My masters student confirmed this later – brown trout (Salmo trutta) have been moved around so much throughout the Nordic countries that it’s almost impossible to find a ‘native’ population anywhere. Most populations are the result of extensive translocation and/or restocking.

How we choose to define ‘native’ here is of course important. Many of these populations which are apparently not native would have had brown trout in them since they were formed, as receding sea levels but them off from the open ocean. Yet those lakes may have been stocked with more trout in the more recent past, or overfished and then restocked, to the point that the genetic makeup of the original population is lost. In this case, ‘native’ refers not only to the species, but to the original population, and its genetic makeup.

This isn’t a phenomena unique to the trout. Many freshwater fish were spread around the area in a seemingly haphazard fashion by the church early last millenia, in order to have stocks nearby when Lent hit. In the late 1800s, the Norwegian government started stocking whitefish (another local salmonid) into lakes almost everywhere. Both of these events included plenty of lakes which had no native fish species whatsoever beforehand. Even the Arctic charr, the world’s northernmost salmonid species and the one perhaps most threatened by climate change, inhabits many lakes in Norway that it isn’t really ‘native’ to on a longer timescale.

Yet this is a very specific definition of native. You’d be hard-pressed to convince locals that these species don’t belong in the lakes they’ve resided in for so long. As I’ve mentioned before, terms like ‘native’ and ‘invasive’ are far from neutral or objective, and semantics do matter here. You can talk all you want about how 1,000 years is a blip on an ecological timescale, but it doesn’t mean that you could, or should, exterminate a fish species from a lake in order to restore a more ‘historically accurate’ food web.

Discrepancies like this are obviously not endemic to Norway, or to fish. You can read a piece by my colleague Lara Veylit here which mentions several instances in which non-native species have become important icons, while others are hated. In my home country of Australia, European carp have run rampant, and attracted the ire of everyone from far-right politicians to concerned conservationists. Yet though the brown trout has also relatively recently taken up residence in Australia following introduction by Europeans, many fishers don’t even recognise it as non-native, for the simple reason that it’s more desirable to fish for.

The situation in Australia (in my opinion anyway) is different – the brown trout does damage to unique local fish species, many of which are endemic to only part of Australia. They’re not going anywhere anytime soon though, as public opinion is more in favour of restocking this particular non-native species than eliminating it.

The common carp may not be a desirable food source in Australia and North America, but it’s a popular food fish in parts of Eastern Europe (Image Credit: John Morris, CC BY-NC-SA 2.0)

That desirability for a species as a fishing object, does it waver? Absolutely. Take the carp, for starters. While it’s seen as an undesirable, bottom-dwelling species to Australians and many western Europeans, in parts of Eastern Europe it’s a delicacy. Countless times during the thesis research I heard perch (Perca fluviatilis) or pike (Esox lucius) referred to as bad food fish, yet in France, (and even as close as southern Norway in the case of the perch) both are considered delicacies.

Should this apparent capriciousness with regards to a fish’s taste be taken into account when planning policy? Take the pink salmon (Oncorhynchus gorbuscha), a species that is flooding into Norway at the moment. While the verdict is still out on the salmon’s ecological impact, the species is widely derided as being a poor fish for eating, yet they’re sold as a delicacy across Russia and the USA. If familiarity breeds acceptance, do we simply wait it out and watch Norwegian cookbooks fill with pink salmon recipes, or spend tens of millions of Norwegian Krone attempting to control a species which seems to be an inevitability in Nordic waters?

Ultimately there’s no golden rule for any of this. Local perspectives will always be important, and are always going to have to be weighed up against environmental damage. Even if brown trout are in trouble in parts of Europe, that doesn’t mean they shouldn’t be seen as a threat in Australia. Arctic charr might not have been in some lakes in Norway for very long, but their threatened status means they definitely should stay there. And while getting support for conserving more palatable fish may be easy, it doesn’t mean we should be able to wipe out native species for their sake.

I don’t envy policymakers a bit, especially areas in which the desires of fishers directly contrasts with the conservation benefit of local species. And thanks to a bit of time around them, I gained a renewed appreciation for the nuance of what ‘native’ really means in a local context.


Dr. Sam Perrin is a freshwater ecologist who completed his PhD at the Norwegian University of Science and Technology who realises he just spent hours writing a piece that undermines his research and honestly isn’t sure how he feels about it. You can read more about his research and the rest of the Ecology for the Masses writers here, see more of his work at Ecology for the Masses here, or follow him on Twitter here.

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