WEBVTT 00:00:14.560 --> 00:00:17.040 Hello, everyone. I hope you're doing well. And of course, Arnie does too. 00:00:17.049 --> 00:00:17.850 Now, today's video, 00:00:17.860 --> 00:00:21.340 I'll be going through five of the worst invasive fish species around the world. 00:00:21.350 --> 00:00:22.760 And for those of you who don't know, 00:00:22.770 --> 00:00:25.219 an invasive species is any plant or animal which has 00:00:25.229 --> 00:00:27.840 been introduced into an ecosystem where it doesn't belong. 00:00:27.850 --> 00:00:28.780 And in most cases, 00:00:28.790 --> 00:00:32.360 this can completely ruin an ecosystem or in some of the worst cases, 00:00:32.369 --> 00:00:35.139 it can lead to some native species becoming extinct. 00:00:35.150 --> 00:00:38.500 And our first invasive fish was originally native to Mexico and 00:00:38.509 --> 00:00:41.659 the Southern United States and it is the mosquito fish. 00:00:41.669 --> 00:00:44.419 Now, this fish is native to Central and North America. 00:00:44.523 --> 00:00:46.583 They've been introduced into many countries around the 00:00:46.594 --> 00:00:48.973 world and they were introduced to control a problem 00:00:48.984 --> 00:00:51.723 that's been plaguing humans for thousands of years because 00:00:51.734 --> 00:00:53.304 as you can probably tell from its name, 00:00:53.313 --> 00:00:55.763 the mosquito fish is very good at eating mosquitoes 00:00:55.773 --> 00:00:59.144 and mosquito larvae and mosquitoes aren't just an annoying pest 00:00:59.153 --> 00:01:01.743 as they're known to transmit malaria and malaria is one 00:01:01.754 --> 00:01:04.733 of the worst infectious diseases that has ever existed. 00:01:04.744 --> 00:01:09.124 And it's still very present today. As 409,000 people were killed by malaria 00:01:09.134 --> 00:01:13.263 in 2019 and 411,000 in the previous year. 00:01:13.274 --> 00:01:14.393 So many countries, 00:01:14.487 --> 00:01:18.388 fish were imported as a last resort and to be fair to the mosquito fish, 00:01:18.398 --> 00:01:19.867 they are quite good at their job. 00:01:19.877 --> 00:01:21.867 As in the places where they were introduced, 00:01:21.877 --> 00:01:25.888 they did reduce the spread of malaria and it worked so well in one Russian town 00:01:25.898 --> 00:01:29.867 that they even created a monument to honor the fish as it saved so many lives. 00:01:29.877 --> 00:01:33.307 And as the maximum length of this fish is around seven centimeters, 00:01:33.318 --> 00:01:36.708 you wouldn't think that it would have that much impact on a new ecosystem. 00:01:36.718 --> 00:01:40.358 But the mosquito fish doesn't only limit itself to eating mosquitoes as 00:01:40.367 --> 00:01:44.318 they're also known to eat zooplankton beetles, mayflies, mites, and other inverts 00:01:44.452 --> 00:01:47.351 spirits which leaves little food for the native species. 00:01:47.361 --> 00:01:50.512 And the mosquito fish is also a very hardy species as they can 00:01:50.522 --> 00:01:54.632 survive in almost stagnant waters with a very low dissolved oxygen content. 00:01:54.641 --> 00:01:56.671 And these areas are normally free of predators, 00:01:56.681 --> 00:01:58.671 meaning that the mosquito fish can breed without 00:01:58.681 --> 00:02:00.821 being predator on and they really can breed at a fast rate. 00:02:00.832 --> 00:02:06.321 As mosquito fish are livebearers and within 16 to 28 days of mating, 00:02:06.332 --> 00:02:08.670 a female can give birth to around 60 young. 00:02:08.681 --> 00:02:13.391 And after this, the males will reach sexual maturity within 43 to 62 days. 00:02:13.401 --> 00:02:14.341 So, if left unchecked, 00:02:14.645 --> 00:02:16.675 their numbers can soon become out of control. 00:02:16.686 --> 00:02:19.796 And as they feed on prey items that are right at the bottom of the food chain. 00:02:19.805 --> 00:02:21.455 It affects everything else above it. 00:02:21.466 --> 00:02:24.376 So, it's not just native fish that suffer even amphibians, 00:02:24.386 --> 00:02:25.916 small mammals and waterfowl. 00:02:25.925 --> 00:02:29.296 And they are still a problem invasive species in many countries around the world. 00:02:29.305 --> 00:02:33.055 As they've been placed on the world's 100 most invasive species lists. 00:02:33.065 --> 00:02:35.945 And as this problem has become so large, whether you like it or not, 00:02:35.955 --> 00:02:39.235 mosquito fish will be an invasive species for many years to come. 00:02:39.246 --> 00:02:43.535 And our next fish was originally native to Europe, North Africa, and Western Asia. 00:02:43.546 --> 00:02:44.949 And it is the brown trout. 00:02:44.960 --> 00:02:48.800 Now, it might surprise many of you that the brown trout is a problem invasive species. 00:02:48.809 --> 00:02:51.500 As many people see the brown trout as a positive fish to have in an ecosystem. 00:02:51.509 --> 00:02:55.639 As they're a popular food fish and they're also very popular with fishermen. 00:02:55.649 --> 00:02:59.649 But today, the brown trout has been introduced into many countries far away from its natural range. 00:02:59.660 --> 00:03:03.000 As it now has a very large presence in the southern hemisphere, 00:03:03.009 --> 00:03:07.160 being found in the cooler parts of Australia, New Zealand, and even South America. 00:03:07.169 --> 00:03:10.960 But brown trout can have a massive impact in an ecosystem where they don't belong. 00:03:10.970 --> 00:03:14.229 As they mainly feed on aquatic and terrestrial invertebrates as well, 00:03:14.343 --> 00:03:18.884 the smaller fish and as the species can reach maximum size of around 80 centimeters, 00:03:18.893 --> 00:03:20.604 this can be a wide range of fish. 00:03:20.613 --> 00:03:24.223 If the brown trout is introduced into an ecosystem with other large predators, 00:03:24.233 --> 00:03:25.884 their numbers can be kept in check. 00:03:25.893 --> 00:03:27.524 But in places such as New Zealand, 00:03:27.533 --> 00:03:31.854 they can become a real problem as they've been known to outcompete the native New Zealand Galaxy. 00:03:31.863 --> 00:03:34.283 It's causing their numbers to drastically decline. 00:03:34.294 --> 00:03:37.083 And although the brown trout is widespread throughout the U.S. today, 00:03:37.093 --> 00:03:38.423 that wasn't always the case. 00:03:38.434 --> 00:03:40.533 As the first introduction of brown trout into 00:03:40.544 --> 00:03:44.203 a U.S. ecosystem happened in 1883 where brown trout 00:03:44.307 --> 00:03:47.348 introduced and raised in a few hatcheries in Long Island. 00:03:47.358 --> 00:03:51.608 And by 1900, 38 states and two territories had received stocks 00:03:51.617 --> 00:03:54.768 of brown trout which were eventually released into the ecosystem. 00:03:54.777 --> 00:03:57.548 And as there's such a streamlined, highly adapted predator, 00:03:57.557 --> 00:03:59.878 I don't think they'll be going anywhere anytime soon. 00:03:59.888 --> 00:04:03.307 But our next invasive fish is the walking catfish and the walking 00:04:03.317 --> 00:04:06.367 catfish is native to Southeast Asia, and it got its name for 00:04:06.378 --> 00:04:09.078 its ability to move from one water source to the other as 00:04:09.087 --> 00:04:12.197 it wriggles and rolls along the ground almost like it is walking. 00:04:12.207 --> 00:04:15.932 And to be able to do this without suffocating is an air-breathing catfish. 00:04:15.942 --> 00:04:19.031 So, it can spend a surprisingly long amount of time out of water. 00:04:19.041 --> 00:04:20.791 And in its natural habitat is an 00:04:20.802 --> 00:04:23.671 omnivorous opportunistic feeder, feeding on smaller fish, 00:04:23.682 --> 00:04:27.712 mollusks and other invertebrates as well as detritus and aquatic weeds. 00:04:27.721 --> 00:04:31.291 And the walking catfish is a very popular fish when it comes to aquaculture, 00:04:31.302 --> 00:04:33.532 they can survive in very poor water conditions 00:04:33.541 --> 00:04:35.652 and they reproduce and grow very quickly. 00:04:35.661 --> 00:04:37.671 And it turns out in the 1960's, 00:04:37.682 --> 00:04:39.451 the U.S. wanted a part of the market. 00:04:39.462 --> 00:04:42.191 As aquaculture farmers in Florida imported the fish. 00:04:42.201 --> 00:04:44.131 And within 10 years, the fish had spread to 00:04:44.235 --> 00:04:45.895 20 counties in the state. 00:04:45.906 --> 00:04:48.615 The farmers surely weren't ready for their walking abilities, 00:04:48.626 --> 00:04:52.006 meaning that the catfish could easily move from one water source to the other. 00:04:52.015 --> 00:04:55.105 And today, the walking catfish can be found in southern Florida, and as 00:04:55.115 --> 00:04:58.575 far west as California and as far north as Massachusetts. 00:04:58.585 --> 00:04:59.776 Luckily, in the U.S., 00:04:59.786 --> 00:05:03.795 there are a few large predators that can take out the walking catfish such as wading, 00:05:03.805 --> 00:05:08.756 birds like herons and egrets, predatory fish like bass, and of course alligators. 00:05:08.765 --> 00:05:12.135 But despite this, the walking catfish still has a large presence in the area. 00:05:12.145 --> 00:05:15.019 And even though it doesn't seem to threaten that many new species, 00:05:15.029 --> 00:05:18.019 it does still cause millions of dollars of damage. 00:05:18.029 --> 00:05:21.019 As they're known to venture into fish farms to feed on all the fish and eggs. 00:05:21.029 --> 00:05:22.049 And this has led to many fish 00:05:22.059 --> 00:05:25.500 farmers putting up fences to stop the walking catfish strolling in. 00:05:25.510 --> 00:05:29.040 So even though they're not an overly dangerous threat, they are a very costly one. 00:05:29.049 --> 00:05:31.589 But our next species is the northern snakehead. 00:05:31.600 --> 00:05:35.609 Now, this predatory fish species originates from China, Russia, and Korea. 00:05:35.619 --> 00:05:37.010 And like most other snakeheads, 00:05:37.019 --> 00:05:39.049 they are tough hardy and at the top of the 00:05:39.059 --> 00:05:41.160 food chain and not only is it a great predator? 00:05:41.170 --> 00:05:44.019 But it's a very adaptable fish as just like the walking cat, 00:05:44.164 --> 00:05:46.223 they are able to breathe atmospheric oxygen, 00:05:46.234 --> 00:05:48.544 meaning that they can live in very poor water quality. 00:05:48.553 --> 00:05:51.303 And it's thought that this species was originally introduced into many 00:05:51.313 --> 00:05:54.544 other countries for both food and for the aquarium trade. 00:05:54.553 --> 00:05:56.544 But some of these specimens either escaped 00:05:56.553 --> 00:05:59.424 or deliberately released into freshwater ecosystems. 00:05:59.433 --> 00:06:01.104 And as northern snakeheads are known to feed 00:06:01.114 --> 00:06:03.503 on a wide range of foods including insects, 00:06:03.514 --> 00:06:05.084 small amphibians and other fish, 00:06:05.093 --> 00:06:08.303 they can have a huge impact in an ecosystem where they don't belong. 00:06:08.313 --> 00:06:10.533 As not only do they out-compete native predators, 00:06:10.544 --> 00:06:13.503 but they can also take out threatened or endangered species. 00:06:13.514 --> 00:06:14.014 And part of the 00:06:14.127 --> 00:06:16.308 and why there's such a problem is because they make great 00:06:16.317 --> 00:06:19.037 parents as not only did the adult fish create a nest, 00:06:19.048 --> 00:06:21.747 but they also guard the young viciously from other predators. 00:06:21.757 --> 00:06:24.268 And this ensures that a lot of the fry make it to adulthood. 00:06:24.278 --> 00:06:25.868 Though, in some countries around Europe, 00:06:25.877 --> 00:06:29.787 you can still find many species of snakehead available in aquarium stores. 00:06:29.798 --> 00:06:31.328 And this is because the northern snakehead 00:06:31.338 --> 00:06:33.447 is different to most other snakehead species. 00:06:33.458 --> 00:06:34.567 As in their native range, 00:06:34.578 --> 00:06:37.287 they can be found in waters with near-freezing temperatures. 00:06:37.298 --> 00:06:39.567 So even in places where snakeheads are legal, 00:06:39.578 --> 00:06:41.477 the northern snakehead is not. 00:06:41.488 --> 00:06:43.898 One of the worst infected areas for the snakehead invasion, 00:06:44.092 --> 00:06:45.752 is the USA and unfortunately, 00:06:45.761 --> 00:06:47.962 one native species has taken the brunt of the anger. 00:06:47.971 --> 00:06:50.261 As the snakehead looks very similar to the bowfin. 00:06:50.802 --> 00:06:52.671 And this has led to the native bowfin being 00:06:52.682 --> 00:06:55.511 killed by many people thinking that they were snakeheads. 00:06:55.522 --> 00:06:58.511 So, because of their hardiness and the fact that they're great parents, 00:06:58.522 --> 00:07:01.272 they are very hard pests to get rid of. 00:07:01.282 --> 00:07:03.671 Our next species is one that I'm sure many of you will be very familiar with. 00:07:03.682 --> 00:07:05.191 And it is the Common Pleco. 00:07:05.201 --> 00:07:07.992 Now, the common Pleco native range is South America, 00:07:08.002 --> 00:07:10.332 where it's quite widespread throughout many countries. 00:07:10.342 --> 00:07:13.951 But today, they're found in many other tropical regions around the globe. 00:07:14.286 --> 00:07:18.075 And this was almost completely created by the aquarium trade because 00:07:18.085 --> 00:07:18.536 as I'm sure many of you know, 00:07:18.545 --> 00:07:21.855 these fish are normally sold very small, and they grow very large. 00:07:21.865 --> 00:07:25.855 As they're thought to reach a maximum size around 50 centimeters or 20 inches, 00:07:25.865 --> 00:07:28.026 which means they outgrow most aquariums. 00:07:28.036 --> 00:07:31.476 And if you're faced with the problem of a fish that's growing too big for its tank, 00:07:31.485 --> 00:07:34.075 you can either do the responsible thing and try and rehome it or you 00:07:34.085 --> 00:07:37.096 can do the lazy thing and try and release it into your nearest river. 00:07:37.105 --> 00:07:38.795 And if you do choose the second option, 00:07:38.805 --> 00:07:41.585 it can have disastrous consequences on the ecosystem. 00:07:42.105 --> 00:07:43.915 Pleco's are known as armored catfish as they have 00:07:44.019 --> 00:07:45.920 tough, rigid scales along their body. 00:07:45.929 --> 00:07:49.079 And this means that they're a very difficult prey item for many predators. 00:07:49.089 --> 00:07:51.119 And although Pleco aren't predatory fish, 00:07:51.130 --> 00:07:53.779 they can still threaten native fish species as they're 00:07:53.790 --> 00:07:56.339 famous for feeding on algae and other microfoods. 00:07:56.350 --> 00:08:00.149 But this means that there's less food to go around for the native algae-eating fish. 00:08:00.160 --> 00:08:03.100 But of course, the pleco is limited because it needs warmer water. 00:08:03.109 --> 00:08:05.920 So, it's not going to be invasive in the colder parts of the world. 00:08:05.929 --> 00:08:07.399 In places such as Florida, 00:08:07.410 --> 00:08:09.350 they have become a real problem as they've been 00:08:09.359 --> 00:08:12.209 known to annoy manatees like raising the algae which grow 00:08:12.220 --> 00:08:14.273 on their body and they don't just rasp away the 00:08:14.283 --> 00:08:17.023 algae also take out parts of the manatee skin. 00:08:17.033 --> 00:08:19.134 And as there are not many predators that go after Pleco's 00:08:19.454 --> 00:08:21.644 in Florida, they have become a real problem, 00:08:21.653 --> 00:08:24.243 but they only alligators really limiting their numbers. 00:08:24.253 --> 00:08:25.884 So, if this goes to show us anything, 00:08:25.894 --> 00:08:29.123 it's that you really shouldn't release your aquarium fish into the wild. 00:08:29.134 --> 00:08:30.713 But that's about it for this video. 00:08:30.723 --> 00:08:33.513 If you have any other suggestions for problem invasive species 00:08:33.523 --> 00:08:36.383 and let me know down in the comments below and I might make a part two. 00:08:36.393 --> 00:08:38.364 But thank you for watching. I hope you enjoyed. 00:08:38.374 --> 00:08:40.633 If you liked it, please leave a like, and subscribe if you want to 00:08:40.643 --> 00:08:43.804 see more videos like these and until next time, goodbye.