David GuestWritten by

How Does a Fish Species Go Extinct?

Conservation| Views: 1631

“A reprehensible and irreparable loss.” This is how one scientist from the Chinese Academy of Fishery Sciences described the news that one of the country’s oldest fish species has been declared extinct. As reported by National Geographic and many others, the Chinese paddlefish – a large freshwater fish with distinctive long sword-like snout that resided mainly in the Yangtze River – has been declared extinct, after not being spotted for more than 17 years. This fish has lived in the rivers of China since the time of the dinosaurs, so how did we get to this? What in the heck happened?

It’s a depressingly predictable story – human beings have played a major role in the demise of this species. Since the 1970s, overfishing had started to dent the populations of Chinese paddlefish, but then came the human need to alter our surroundings to make life more convenient and comfortable. Dam construction on the Yangtze stopped the paddlefish being able to reach its breeding grounds and drove a huge concrete nail into the already near-sealed coffin of this majestic fish.

It’s a story we see all too often – human beings have witnessed the extinction of an estimated 60% of mammals, birds, fish and reptiles since 1970, according to a major report from the WWF in 2018. Fish in particular have suffered and are suffering at the hands of human beings, and there are examples all around the world, but it’s not all just about eating too much sushi. Here are some other ways fish have either disappeared off the face of our blue planet, or been pushed very close, for one reason or another.

Dam projects, like the Three Gorges Dam here, were a major factor in the extinction of the Chinese paddlefish.

Species: European sea bass

Status: Recovering

What happened: The European sea bass’ problem seems to be that it’s just too damn tasty. This species has suffered from being an ‘en vogue’ dining option throughout Europe and the world and was commercially fished to perilously dangerous levels in the 2000’s and into the 2010’s – in 2013 the stocks in the North Sea were the lowest they had been for 20 years due to our insatiable appetite for them. The European Union stepped in and brought in incredibly strict measures, which you may have already heard about as they also affected recreational anglers, who were only allowed catch-and-release fishing for sea bass for some time (in fact catch-and-release only is still enforced in February, March, November and December). Some of the restrictions seemed controversial at the time (many felt recreational anglers had little effect on sea bass numbers), but overall stocks are now recovering – the fish is now officially listed as ‘low concern’ on endangered species lists. 

Species: Atlantic halibut

Status: Endangered

What happened: Atlantic halibut are the largest flatfish in the sea and have been affectionately targeted by recreational anglers for many years. Unfortunately, they are also regarded as good seafood and commercial fishing has blighted the population over the last 200 years. Things have gotten so bad in recent times that they are now not really targeted by commercial fishermen and only really caught as bycatch when targeting other species. The reason that halibut have struggled under fishing pressure is they are slow. Slow to breed and slow to grow – a halibut reaches maturity at around seven years old for males and as late as 11 years old for females. This means they simply cannot repopulate at the rate they are being caught. A new meaning to slow love.

Species: Yellowfin cutthroat trout

Status: Extinct (early 1900’s)

What happened: A subspecies of the cutthroat trout, the yellowfin cuttie was first discovered and named in American waters back in 1891. They mainly resided in the Twin Lakes in what is now Colorado alongside another trout subspecies known as the greenback. The populations of these two trout remained healthy and isolated in the Twin Lakes until rainbow trout were inadvertently introduced at the start of the 20th Century. They began interbreeding with both yellowfin and greenback cutthroats and eventually erased the traits of the yellowfin, leaving only rainbows behind after just a few generations. Greenbacks have survived, but they are listed as a threatened species by the US Fish and Wildlife Service.

Species: Blue Pike

Status: Extinct (1960’s)

What happened: A very close relative of the walleye (so close that some studies have revealed very little genetic difference between the DNA), the blue pike was a fish that once swam free in the waters of New York State and Ontario. Blue Pike were a little smaller than regular walleye and inhabited deeper waters. Lake Erie, Lake Ontario and the Niagara River were all once guaranteed places to catch what many veteran anglers still claim was the best eating freshwater fish there ever was.

Overfishing began the downfall, but then in places such as Lake Erie, pollution became a major issue, drastically affecting the oxygen levels in the waters where blue pike lived. They disappeared almost overnight during the 1960s, and were officially declared extinct in 1975.

Species: New Zealand grayling

Status: Extinct (sometime in the 1930’s)

What happened: The New Zealand grayling was a native fish species in the country, closely related to smelts, which only grew to around 15 inches in length. It thrived in the clean and clear waters of New Zealand’s lowland rivers and streams and fed on greenery that grew on rocks – its silvery torpedo-like body was a common sight until the early 1900’s. Not long after Europeans arrived in the country, their numbers started to decline and by about 1930, they were on the verge of extinction. Nobody can be certain, but the two major factors in their demise appear to have been brought by those European settlers. One was the introduction of trout, which unsettled the food chain and also sometimes preyed on the grayling fry. Second was rapid deforestation that came with the building of towns and roads, which damaged the food supply to these tiny, but beautiful fish.

You can keep track of endangered species via the US Fish and Wildlife Service. Many of the fish might be threatened, but that doesn’t mean we can’t save them.

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