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Invasive aquatic species

invasive aquatic species
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In this section you will learn about how aquatic invasive species impact on the ecosystems they introduced into issues like food, web disruptions, competition for food and habitat. And also the co- introduction of parasites and diseases are all impacts that can have serious effects on the river ecosystem. It can also result in local extirpation of native species inhabitants. Hi, everyone. I’m Dr. Bonnie Holmes from the University of the Sunshine Coast in Queensland, Australia. And I’ve spent part the past several years involved in a range of freshwater invasive species programmes across Australia. Now today, I’m going to introduce you to a few of the biggest threatening exotic invasive fish and crustacean species.
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And how they get into an establishing habitats that they didn’t actually naturally evolve in, will then discover what can happen to these ecosystems once these species establish and what can we do about it. So first, let’s look at some of the world’s most invasive and destructive fish hailing from the central and southern Africa are the tilapiine fishes. Now these guys are a family of warm water fish that employ a range of ecological traits that make them incredibly successful. They’re able to tolerate a range of water temperatures from around 12 degrees Celsius, up to a really warm 36 degrees Celsius. So that’s a huge number range.
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And this thermal tolerance makes them successful across a broad range of warm temperate to tropical freshwater ecosystems. Secondly, they also invest heavily in their young, with some spaces employing mouth brooding as a reproductive strategy, where the fish fry hatch and are protected by hiding and growing within the mouths of their parents. This provides much more protection of the young from predators, which results in greater fry survival. The adults are also very fecund, meaning they can produce 1000s of eggs each breeding season. Now in Australia, it’s the Mozambique tilapia, Oreochromis mossambicus because that successfully established after deliberate release from home aquaria into our native environment in the 1970s.
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And this has caused the most widespread impact in our tropical waters across the country. Now as a popular food fish in other countries, it’s often deliberately released into farm dams to create local fisheries, which can become a huge problem. Fish aren’t the only successful invaders in aquatic waters. freshwater crayfish, like those from the procambarus family, are also extremely successful adapters and invaders. Species like the red swamp crayfish or procambarus clarkia are a native crayfish from northern Mexico and Southern USA. And they are a rapidly growing crustacean that can quickly dominate new waterways and out compete other species for resources and available habitat.
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Now they are also able to reproduce via pathogenesis, which means that they don’t require sexual reproduction to reproduce, they just make a complete copy of themselves. Now like many procambarus species, these crayfish also can carry the deadly crayfish plague disease, which is a water mould that presently doesn’t exist in Australia and kills their crustacean hosts within weeks. Also, our popular aquarium species, we know this species has actually been imported into Australia before, but there are currently no reported wild cases yet. So what happens when these species are released into the wild in these non native environments?
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Well, first of all, there needs to be enough propagule pressure for them to establish now essentially, that means there needs to be enough males and females, except if you’re parthenogenetic, to produce viable young in the new ecosystem. Now often if the location of the incursion is a climatic match for the invasive species, species that a good invaders can actually establish within weeks. Now because these animals are establishing in an aquatic environment, it’s very hard for us to even identify that they’re there. And once established in an open waterway, most invasive fish and crustaceans are almost impossible to eradicate.
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Now once established, the species has moved itself into a novel food web for the very first time, it’s likely that it will need to feed upon the same resources as a range of our other native fish or crayfish. mainly that they will be depriving our native species of their traditional food sources and putting extreme pressures on our natives to survive. Alternatively, sometimes unexpected interactions like invasive species changing the biome of larger mammals, also occurs like in the case of the invasive pleco fish.
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pleco fish have been introduced in Florida, USA for many years and these suckerfish have now in such numbers that they’ve been reportedly mobbing manatees, and grazing all of the natural algal cover and other epibionts that live on this skin. The cost of these interactions to the manatees are still unknown. And this is just one example of a whole range of impacts that invasive species can have. Now another seriously and mostly invisible consideration is that of disease and also parasite introduction. These are also a significant threat, and unfortunately, much of the research in this space is still in its infancy.
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As mentioned before, we know that crayfish plague disease is caused by a highly infectious fungus that causes 100% mortality, and could wipe out an entire river system of native crayfish. And this was documented back in Great Britain and Ireland back in the 1980s. And there’s still today no evidence of resistance developing your local crayfish population since that time, so the risk to Australia is huge. So how do we protect against the introduction of non native invasive species, given the global network of animal trade? Well, strict biosecurity is one way but also education about the dangers of keeping species like these ornamentally which increases the risk of deliberate or incidental release into native waterways.

In this video we will learn about the impact invasive species can have on aquatic ecosystems. We will focus on the effect that Tilapia and other species introductions have had on the local ecosystems.

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Life Below Water: Conservation, Current Issues, Possible Solutions

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