Invasive aquatic species – or non-native species that have been introduced to new bodies of water over time – can have a wide range of different effects on fishing ecosystems.
While our natural instinct is to view anything with the word “invasive” in the title as a threat to the area being invaded and the species who reside there, it’s actually not that simple.
Perhaps the most well-known and oft-seen invasive species in the fishing world – the zebra mussel – can have drastically different impacts on different waters. Unlike some other invasive species, zebra mussels, quagga mussels, and other similar species don’t inherently attack native fish upon their arrival to a new body of water. On the contrary, zebra mussels actually go to work filtering the water of their new habitat, making fundamental chemical shifts in the composition of that water.
From chlorophyll levels to algae levels, zebra mussels alter the chemistry of a body of water, which can impact different species in different ways. Reports have surfaced over time suggesting that zebra mussels have actually helped certain fish populations while harming others. A variety of different factors – including the size and depth of the body of water, the fish that reside there, and more – impact just how detrimental or beneficial zebra mussels are in that environment.
But here’s the problem: it’s hard to know the impact that zebra mussels will have on an ecosystem before they are unceremoniously poured into it. Since arriving in the United States from Europe in the 1980s – via a ship’s ballast water – zebra mussels have taken over the Great Lakes, destroying other mussel populations in those waters, and changing the game for fish and fishermen throughout the region. From the Great Lakes, the invasive mussels have spread to other freshwater bodies all over the nation. In some places, they actively ruin fishing opportunities; in others, they posit little change.
Put simply, spreading zebra mussels is a bit like playing a game of Russian roulette: it might be harmless, but it might also be incredibly dangerous. With that in mind, anglers should do all that they can to make sure that they are not serving as the conduit through which zebra mussels get from point A to point B.
Most often, zebra mussels are transferred from lake to lake by boat owners who neglect to empty the ballast water from their vessel before navigating to a new body of water. The mussels can also latch onto boats and hitch a ride that way. The mode of transportation doesn’t matter: once in new water, zebra mussels proliferate quickly and are difficult to control. Anglers should make sure to clean their boats thoroughly and empty any water contents before moving into a new body of water.
Of course, zebra mussels aren’t the only invasive species that are taking a hatchet to freshwater fishing industries. Scientists have also been fighting to keep numerous types of foreign carp out of the Great Lakes. The fish are voracious and gobble up baitfish and other food sources before other species can get a chance, in turn leading to the decline of other fish species and the rapid growth of carp populations.