Biology

Invasive species (VII): Black bass largemouth bass

The black bass or largemouth bass , Micropterus salmoides , is a carnivorous fish belonging to the order Perciformes. It is a native species of North America, where its fishing is widespread and it is an activity that moves a lot of money, even more than the NBA .

It is currently present in more than 50 countries around the world. Some American subspecies reach 80cm and a weight of 8Kg, while in Europe a length of 30-50cm and a weight of 3-4Kg is common. The IUCN has included this species in the list of the 100 most harmful invaders in the world .

Juvenile individuals are gregarious and form very large groups, while adults lead a solitary life. Largemouth bass inhabit clear-water rivers and lakes, where it can stalk its prey from the bottom. A distinctive feature of the species is its large mouth, which in England has earned it the nickname of “bigmouth bass”, which it uses to generate a stream of water with which it catches its prey. Their diet includes insects, fish larvae, amphibians, small mammals, and even birds.

Situation in Spain of black bass

The species was introduced in our country in 1955 for its commercial use. Since then it has spread by human action to numerous rivers and reservoirs on the Iberian Peninsula. Some sources indicate that it is present in all the Autonomous Communities except Galicia and the Canary Islands , but the truth is that in Galicia wild specimens have already been detected in the Miño and Sil rivers, as well as in the Belesar reservoir.

The reason why black bass is so widespread is because of its interest from the point of view of fishing, since the fishermen themselves have released it in different bodies of water for decades.

The species is problematic in our country due to its great voracity, which affects directly (by predation) or indirectly (by competition over food resources) other native species such as trout or salmon. It causes alterations in the composition of zooplankton in rivers and lakes, which affects the entire ecosystem.

Furthermore, in the Lagunas de Ruidera Natural Park (Castilla la Mancha) it has been found that the black bass feeds on the native population of blenny ( Salaria fluviatilis ), one of the most threatened species in the Iberian Peninsula . It is a peculiar species because it is the only one of its kind to inhabit fresh waters.

 Problems with fishing for black bass

In November 2011, the Spanish Catalog of Invasive Alien Species was updated , which included all the species that are considered invasive in our country. Among the species on the list were some with hunting or fish-farming interest, such as rump, rainbow trout, black bass or American crab.

One of the consequences of this was the immediate prohibition of all economic activity related to these species, which makes a lot of sense considering that some (those with hunting or fish farming interest) were introduced or later extended by hunters or fishermen.

The measure did not sit well with these associations, who protested until in August 2013 a royal decree modified the previous regulations eliminating these species with commercial interest from the list , and in the case of the rui, restricting those areas in which it was invasive. and others in which not.

Finally, last year the Supreme Court shelved the administrative nonsense and partially admitted the appeal of different environmental associations against the Royal Decree of 2013. If a species is invasive , it must be treated as such regardless of how rewarding its fishing is or what produce economic benefits.

As of this sentence, the sale of black bass, as well as its transport alive or dead, was prohibited in Spain. This implies that if a specimen is caught it must be killed and left on the shore, as it is not allowed to return it alive to the water .

Although it makes sense to avoid the live transport of the species, to prevent it from being introduced into another watercourse or reared, that the fish caught for consumption cannot be used is somewhat illogical.

Many fishing associations have raised their voices against current regulations for this reason. In addition to this measure, the Junta de Andalucía has carried out a campaign to eradicate exotic fish between 2006-2008 and there is an initiative framed in the LIFE + project to eliminate black bass in Lake Banyoles, the largest in Catalonia.

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