0:00:14.560,0:00:17.040 Hello, everyone. I hope you're doing well. And of course, Arnie does too. 0:00:17.049,0:00:17.850 Now, today's video, 0:00:17.860,0:00:21.340 I'll be going through five of the worst invasive fish species around the world. 0:00:21.350,0:00:22.760 And for those of you who don't know, 0:00:22.770,0:00:25.219 an invasive species is any plant or animal which has 0:00:25.229,0:00:27.840 been introduced into an ecosystem where it doesn't belong. 0:00:27.850,0:00:28.780 And in most cases, 0:00:28.790,0:00:32.360 this can completely ruin an ecosystem or in some of the worst cases, 0:00:32.369,0:00:35.139 it can lead to some native species becoming extinct. 0:00:35.150,0:00:38.500 And our first invasive fish was originally native to Mexico and 0:00:38.509,0:00:41.659 the Southern United States and it is the mosquito fish. 0:00:41.669,0:00:44.419 Now, this fish is native to Central and North America. 0:00:44.523,0:00:46.583 They've been introduced into many countries around the 0:00:46.594,0:00:48.973 world and they were introduced to control a problem 0:00:48.984,0:00:51.723 that's been plaguing humans for thousands of years because 0:00:51.734,0:00:53.304 as you can probably tell from its name, 0:00:53.313,0:00:55.763 the mosquito fish is very good at eating mosquitoes 0:00:55.773,0:00:59.144 and mosquito larvae and mosquitoes aren't just an annoying pest 0:00:59.153,0:01:01.743 as they're known to transmit malaria and malaria is one 0:01:01.754,0:01:04.733 of the worst infectious diseases that has ever existed. 0:01:04.744,0:01:09.124 And it's still very present today. As 409,000 people were killed by malaria 0:01:09.134,0:01:13.263 in 2019 and 411,000 in the previous year. 0:01:13.274,0:01:14.393 So many countries, 0:01:14.487,0:01:18.388 fish were imported as a last resort and to be fair to the mosquito fish, 0:01:18.398,0:01:19.867 they are quite good at their job. 0:01:19.877,0:01:21.867 As in the places where they were introduced, 0:01:21.877,0:01:25.888 they did reduce the spread of malaria and it worked so well in one Russian town 0:01:25.898,0:01:29.867 that they even created a monument to honor the fish as it saved so many lives. 0:01:29.877,0:01:33.307 And as the maximum length of this fish is around seven centimeters, 0:01:33.318,0:01:36.708 you wouldn't think that it would have that much impact on a new ecosystem. 0:01:36.718,0:01:40.358 But the mosquito fish doesn't only limit itself to eating mosquitoes as 0:01:40.367,0:01:44.318 they're also known to eat zooplankton beetles, mayflies, mites, and other inverts 0:01:44.452,0:01:47.351 spirits which leaves little food for the native species. 0:01:47.361,0:01:50.512 And the mosquito fish is also a very hardy species as they can 0:01:50.522,0:01:54.632 survive in almost stagnant waters with a very low dissolved oxygen content. 0:01:54.641,0:01:56.671 And these areas are normally free of predators, 0:01:56.681,0:01:58.671 meaning that the mosquito fish can breed without 0:01:58.681,0:02:00.821 being predator on and they really can breed at a fast rate. 0:02:00.832,0:02:06.321 As mosquito fish are livebearers and within 16 to 28 days of mating, 0:02:06.332,0:02:08.670 a female can give birth to around 60 young. 0:02:08.681,0:02:13.391 And after this, the males will reach sexual maturity within 43 to 62 days. 0:02:13.401,0:02:14.341 So, if left unchecked, 0:02:14.645,0:02:16.675 their numbers can soon become out of control. 0:02:16.686,0:02:19.796 And as they feed on prey items that are right at the bottom of the food chain. 0:02:19.805,0:02:21.455 It affects everything else above it. 0:02:21.466,0:02:24.376 So, it's not just native fish that suffer even amphibians, 0:02:24.386,0:02:25.916 small mammals and waterfowl. 0:02:25.925,0:02:29.296 And they are still a problem invasive species in many countries around the world. 0:02:29.305,0:02:33.055 As they've been placed on the world's 100 most invasive species lists. 0:02:33.065,0:02:35.945 And as this problem has become so large, whether you like it or not, 0:02:35.955,0:02:39.235 mosquito fish will be an invasive species for many years to come. 0:02:39.246,0:02:43.535 And our next fish was originally native to Europe, North Africa, and Western Asia. 0:02:43.546,0:02:44.949 And it is the brown trout. 0:02:44.960,0:02:48.800 Now, it might surprise many of you that the brown trout is a problem invasive species. 0:02:48.809,0:02:51.500 As many people see the brown trout as a positive fish to have in an ecosystem. 0:02:51.509,0:02:55.639 As they're a popular food fish and they're also very popular with fishermen. 0:02:55.649,0:02:59.649 But today, the brown trout has been introduced into many countries far away from its natural range. 0:02:59.660,0:03:03.000 As it now has a very large presence in the southern hemisphere, 0:03:03.009,0:03:07.160 being found in the cooler parts of Australia, New Zealand, and even South America. 0:03:07.169,0:03:10.960 But brown trout can have a massive impact in an ecosystem where they don't belong. 0:03:10.970,0:03:14.229 As they mainly feed on aquatic and terrestrial invertebrates as well, 0:03:14.343,0:03:18.884 the smaller fish and as the species can reach maximum size of around 80 centimeters, 0:03:18.893,0:03:20.604 this can be a wide range of fish. 0:03:20.613,0:03:24.223 If the brown trout is introduced into an ecosystem with other large predators, 0:03:24.233,0:03:25.884 their numbers can be kept in check. 0:03:25.893,0:03:27.524 But in places such as New Zealand, 0:03:27.533,0:03:31.854 they can become a real problem as they've been known to outcompete the native New Zealand Galaxy. 0:03:31.863,0:03:34.283 It's causing their numbers to drastically decline. 0:03:34.294,0:03:37.083 And although the brown trout is widespread throughout the U.S. today, 0:03:37.093,0:03:38.423 that wasn't always the case. 0:03:38.434,0:03:40.533 As the first introduction of brown trout into 0:03:40.544,0:03:44.203 a U.S. ecosystem happened in 1883 where brown trout 0:03:44.307,0:03:47.348 introduced and raised in a few hatcheries in Long Island. 0:03:47.358,0:03:51.608 And by 1900, 38 states and two territories had received stocks 0:03:51.617,0:03:54.768 of brown trout which were eventually released into the ecosystem. 0:03:54.777,0:03:57.548 And as there's such a streamlined, highly adapted predator, 0:03:57.557,0:03:59.878 I don't think they'll be going anywhere anytime soon. 0:03:59.888,0:04:03.307 But our next invasive fish is the walking catfish and the walking 0:04:03.317,0:04:06.367 catfish is native to Southeast Asia, and it got its name for 0:04:06.378,0:04:09.078 its ability to move from one water source to the other as 0:04:09.087,0:04:12.197 it wriggles and rolls along the ground almost like it is walking. 0:04:12.207,0:04:15.932 And to be able to do this without suffocating is an air-breathing catfish. 0:04:15.942,0:04:19.031 So, it can spend a surprisingly long amount of time out of water. 0:04:19.041,0:04:20.791 And in its natural habitat is an 0:04:20.802,0:04:23.671 omnivorous opportunistic feeder, feeding on smaller fish, 0:04:23.682,0:04:27.712 mollusks and other invertebrates as well as detritus and aquatic weeds. 0:04:27.721,0:04:31.291 And the walking catfish is a very popular fish when it comes to aquaculture, 0:04:31.302,0:04:33.532 they can survive in very poor water conditions 0:04:33.541,0:04:35.652 and they reproduce and grow very quickly. 0:04:35.661,0:04:37.671 And it turns out in the 1960's, 0:04:37.682,0:04:39.451 the U.S. wanted a part of the market. 0:04:39.462,0:04:42.191 As aquaculture farmers in Florida imported the fish. 0:04:42.201,0:04:44.131 And within 10 years, the fish had spread to 0:04:44.235,0:04:45.895 20 counties in the state. 0:04:45.906,0:04:48.615 The farmers surely weren't ready for their walking abilities, 0:04:48.626,0:04:52.006 meaning that the catfish could easily move from one water source to the other. 0:04:52.015,0:04:55.105 And today, the walking catfish can be found in southern Florida, and as 0:04:55.115,0:04:58.575 far west as California and as far north as Massachusetts. 0:04:58.585,0:04:59.776 Luckily, in the U.S., 0:04:59.786,0:05:03.795 there are a few large predators that can take out the walking catfish such as wading, 0:05:03.805,0:05:08.756 birds like herons and egrets, predatory fish like bass, and of course alligators. 0:05:08.765,0:05:12.135 But despite this, the walking catfish still has a large presence in the area. 0:05:12.145,0:05:15.019 And even though it doesn't seem to threaten that many new species, 0:05:15.029,0:05:18.019 it does still cause millions of dollars of damage. 0:05:18.029,0:05:21.019 As they're known to venture into fish farms to feed on all the fish and eggs. 0:05:21.029,0:05:22.049 And this has led to many fish 0:05:22.059,0:05:25.500 farmers putting up fences to stop the walking catfish strolling in. 0:05:25.510,0:05:29.040 So even though they're not an overly dangerous threat, they are a very costly one. 0:05:29.049,0:05:31.589 But our next species is the northern snakehead. 0:05:31.600,0:05:35.609 Now, this predatory fish species originates from China, Russia, and Korea. 0:05:35.619,0:05:37.010 And like most other snakeheads, 0:05:37.019,0:05:39.049 they are tough hardy and at the top of the 0:05:39.059,0:05:41.160 food chain and not only is it a great predator? 0:05:41.170,0:05:44.019 But it's a very adaptable fish as just like the walking cat, 0:05:44.164,0:05:46.223 they are able to breathe atmospheric oxygen, 0:05:46.234,0:05:48.544 meaning that they can live in very poor water quality. 0:05:48.553,0:05:51.303 And it's thought that this species was originally introduced into many 0:05:51.313,0:05:54.544 other countries for both food and for the aquarium trade. 0:05:54.553,0:05:56.544 But some of these specimens either escaped 0:05:56.553,0:05:59.424 or deliberately released into freshwater ecosystems. 0:05:59.433,0:06:01.104 And as northern snakeheads are known to feed 0:06:01.114,0:06:03.503 on a wide range of foods including insects, 0:06:03.514,0:06:05.084 small amphibians and other fish, 0:06:05.093,0:06:08.303 they can have a huge impact in an ecosystem where they don't belong. 0:06:08.313,0:06:10.533 As not only do they out-compete native predators, 0:06:10.544,0:06:13.503 but they can also take out threatened or endangered species. 0:06:13.514,0:06:14.014 And part of the 0:06:14.127,0:06:16.308 and why there's such a problem is because they make great 0:06:16.317,0:06:19.037 parents as not only did the adult fish create a nest, 0:06:19.048,0:06:21.747 but they also guard the young viciously from other predators. 0:06:21.757,0:06:24.268 And this ensures that a lot of the fry make it to adulthood. 0:06:24.278,0:06:25.868 Though, in some countries around Europe, 0:06:25.877,0:06:29.787 you can still find many species of snakehead available in aquarium stores. 0:06:29.798,0:06:31.328 And this is because the northern snakehead 0:06:31.338,0:06:33.447 is different to most other snakehead species. 0:06:33.458,0:06:34.567 As in their native range, 0:06:34.578,0:06:37.287 they can be found in waters with near-freezing temperatures. 0:06:37.298,0:06:39.567 So even in places where snakeheads are legal, 0:06:39.578,0:06:41.477 the northern snakehead is not. 0:06:41.488,0:06:43.898 One of the worst infected areas for the snakehead invasion, 0:06:44.092,0:06:45.752 is the USA and unfortunately, 0:06:45.761,0:06:47.962 one native species has taken the brunt of the anger. 0:06:47.971,0:06:50.261 As the snakehead looks very similar to the bowfin. 0:06:50.802,0:06:52.671 And this has led to the native bowfin being 0:06:52.682,0:06:55.511 killed by many people thinking that they were snakeheads. 0:06:55.522,0:06:58.511 So, because of their hardiness and the fact that they're great parents, 0:06:58.522,0:07:01.272 they are very hard pests to get rid of. 0:07:01.282,0:07:03.671 Our next species is one that I'm sure many of you will be very familiar with. 0:07:03.682,0:07:05.191 And it is the Common Pleco. 0:07:05.201,0:07:07.992 Now, the common Pleco native range is South America, 0:07:08.002,0:07:10.332 where it's quite widespread throughout many countries. 0:07:10.342,0:07:13.951 But today, they're found in many other tropical regions around the globe. 0:07:14.286,0:07:18.075 And this was almost completely created by the aquarium trade because 0:07:18.085,0:07:18.536 as I'm sure many of you know, 0:07:18.545,0:07:21.855 these fish are normally sold very small, and they grow very large. 0:07:21.865,0:07:25.855 As they're thought to reach a maximum size around 50 centimeters or 20 inches, 0:07:25.865,0:07:28.026 which means they outgrow most aquariums. 0:07:28.036,0:07:31.476 And if you're faced with the problem of a fish that's growing too big for its tank, 0:07:31.485,0:07:34.075 you can either do the responsible thing and try and rehome it or you 0:07:34.085,0:07:37.096 can do the lazy thing and try and release it into your nearest river. 0:07:37.105,0:07:38.795 And if you do choose the second option, 0:07:38.805,0:07:41.585 it can have disastrous consequences on the ecosystem. 0:07:42.105,0:07:43.915 Pleco's are known as armored catfish as they have 0:07:44.019,0:07:45.920 tough, rigid scales along their body. 0:07:45.929,0:07:49.079 And this means that they're a very difficult prey item for many predators. 0:07:49.089,0:07:51.119 And although Pleco aren't predatory fish, 0:07:51.130,0:07:53.779 they can still threaten native fish species as they're 0:07:53.790,0:07:56.339 famous for feeding on algae and other microfoods. 0:07:56.350,0:08:00.149 But this means that there's less food to go around for the native algae-eating fish. 0:08:00.160,0:08:03.100 But of course, the pleco is limited because it needs warmer water. 0:08:03.109,0:08:05.920 So, it's not going to be invasive in the colder parts of the world. 0:08:05.929,0:08:07.399 In places such as Florida, 0:08:07.410,0:08:09.350 they have become a real problem as they've been 0:08:09.359,0:08:12.209 known to annoy manatees like raising the algae which grow 0:08:12.220,0:08:14.273 on their body and they don't just rasp away the 0:08:14.283,0:08:17.023 algae also take out parts of the manatee skin. 0:08:17.033,0:08:19.134 And as there are not many predators that go after Pleco's 0:08:19.454,0:08:21.644 in Florida, they have become a real problem, 0:08:21.653,0:08:24.243 but they only alligators really limiting their numbers. 0:08:24.253,0:08:25.884 So, if this goes to show us anything, 0:08:25.894,0:08:29.123 it's that you really shouldn't release your aquarium fish into the wild. 0:08:29.134,0:08:30.713 But that's about it for this video. 0:08:30.723,0:08:33.513 If you have any other suggestions for problem invasive species 0:08:33.523,0:08:36.383 and let me know down in the comments below and I might make a part two. 0:08:36.393,0:08:38.364 But thank you for watching. I hope you enjoyed. 0:08:38.374,0:08:40.633 If you liked it, please leave a like, and subscribe if you want to 0:08:40.643,0:08:43.804 see more videos like these and until next time, goodbye.