http://www.nytimes.com/2016/09/23/science/discarded-goldfish-invasive-species.html 2016-09-22 22:46:28 In the Wild, Goldfish Turn From Pet to Pest Your pet goldfish may seem tiny and harmless. But in the wild, they can take down entire ecosystems. === Two decades ago, someone dropped a handful of unwanted pet goldfish into a creek in southwestern Researchers from Murdoch University believe this scenario, or something like it, is the cause of a feral goldfish invasion in Australia’s Vasse River. Since 2003, they have been running a goldfish tracking and control program that involves catching fish along the length of the river, freezing them to death and studying them in the lab. Despite this program, goldfish in the Vasse are thriving, with some fish growing as long as 16 inches and weighing up to four pounds — the size of a two-liter soda bottle. Goldfish are one of the world’s worst invasive aquatic species, with outbreaks also having been reported in Goldfish invasions start with a disconnect between how people view goldfish and what goldfish are like in the wild, Dr. Beatty said. “Once you introduce something into a new environment — even if it’s a cute, cuddly aquarium fish — it can have quite unexpected, serious biological consequences.” The goldfish is a domesticated carp, first bred in ancient China for ornamental gardens. For centuries, goldfish were prized symbols of luck and fortune. Shortly after they made their way to the United States in the mid-1800s, however, they transitioned from the exotic to the mundane. The U.S. government played a large role in this, according to Katrina Gulliver, a historian who has In a Times This, and the later practice of giving out goldfish at carnivals, spawned the harmful notion that goldfish are disposable and inconsequential. In fact, when tossed into waterways — particularly warm, nutrient-rich and relatively stagnant ones like the Vasse — goldfish behave in unexpected ways. For one, they look different. Freed from the constraints of a tank, goldfish balloon to the size of footballs. Within a few generations, they revert to natural yellow and brown colors, in place of the bright orange breeders try to achieve. . They’re also an ecological nightmare. Goldfish swim along the bottom of lakes and rivers, uprooting vegetation, disturbing sediments and releasing nutrients that trigger excess algal growth. They feed broadly, eating algae, small invertebrates and fish eggs. To add insult to injury, they transmit exotic diseases and Females produce up to 40,000 eggs each year — much more than most freshwater fish species — and are capable of interbreeding with other species of wild carp. With no natural predators, a large portion of goldfish offspring survive to reproductive age, continuing a cycle of rampant overpopulation. So how do you get rid of them in a lasting way? Once they’re established somewhere, eradicating goldfish is a notoriously difficult undertaking — which is why Murdoch scientists recently spent a year tracking the movement of the fish in the Vasse. For starters, goldfish are long-distance swimmers — Dr. Beatty’s team saw goldfish routinely travel the length of multiple footballs fields in a day, and even observed one fish that traveled more than 140 miles in a year. For another, goldfish migrate to spawn. That’s right, the same fish that are often kept in tiny bowls, swimming in circles, navigated in droves to an off-channel wetland during breeding season. It’s perhaps a surprising finding for a domesticated species, but the behavior seems to be innate, Dr. Beatty said, and points to goldfish having complex cognitive abilities. “We think of goldfish as not being very intelligent — more like furniture or home accessories than sentient creatures,” said Dean Pomerleau, an engineer from Pittsburgh. But his family has trained pet goldfish to perform complicated A better understanding of goldfish behavior can inform management strategies, Dr. Beatty said, such as trapping fish en masse after they’ve migrated to their breeding grounds. Meanwhile, to ensure goldfish invasions don’t get worse, it’s crucial that pet owners get rid of unwanted fish responsibly, said The best strategy is to give healthy fish away, to a responsible aquarium, pet store or hobbyist, Dr. Walters said. In Florida, the Fish and Wildlife Conservation Commission also takes unwanted exotic pets off people’s hands on regularly scheduled If your fish is sick, the most