Tag Archives: freshwater fish

Could Rising Temperatures Drastically Shift Species Communities?

Image Credit: Christa Rohrbach, CC BY-NC-SA 2.0, Image Cropped

Modelling temperature-driven changes in species associations across freshwater communities (2021) Perrin et al., Global Change Biology, https://doi.org/10.1111/gcb.15888

The Crux

Species interact in many complex ways within an ecosystem. One species may prey on another, which can keep that prey species at a low density. Two species might compete for resources, keeping each other’s populations in check. These interactions are part and parcel of any ecosystem. But what happens when the climate changes in that ecosystem? If one species does better under warmer conditions, perhaps that could lead to that species completely wiping out a prey species, or even a competitor?

You’d think that monitoring this would be easy, given the extensive environmental data and species occurrence data we’re able to come up with in the digital age. Yet the problem is that when a species population drops as the climate changes, it’s very hard to tell whether that’s a direct result of the climate itself, or whether that species is being negatively affected by another species which has benefited from the change. That’s what we wanted to try and figure out.

Read more

Forecasting Foreign Fishy Futures

Forecasting the future establishment of invasive alien freshwater fish species (2021) Perrin et al., Journal of Applied Ecology, https://doi.org/10.1111/1365-2664.13993

The Crux

I know I write a lot about whether or not we should jump to conclusions about non-native species, but the fact is that there are lots of situations in which invasive species need to GO. Giving them the boot, however, can be a right pain, and more often than not it’s impossible.

But an ounce of prevention is worth a pound of cure (I don’t know the imperial system well so I assume that makes sense), and figuring out where an invader is likely to turn up means you can take measures to stop it happening in the first place. This saves a lot of hassle (and money) down the road.

So how do we figure out where invasives are likely to show up? That’s what this paper, which made up the first chapter of my thesis, aimed to find out, by looking at where invasive freshwater fish species have been popping up in Norway over the last 100 years.

Read more

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.

Read more