Invasive species

Introduced by man, invasive species are more common. They create imbalances within ecosystems and threaten biodiversity and the survival of some species.

An invasive species or invasive alien species can be defined as:
“an allochthonous species whose introduction by humans (voluntary or fortuitous), implantation and spread threaten ecosystems, habitats or native species with negative health or environmental or economic consequences” (IUCN 2000, McNeely et al. 2001 McNeely 2001).
All introduced species are therefore not considered invasive. Thus, for example, a large number of fish species in the Lake of Cazaux-Sanguinet correspond to introduced species, more or less long ago: mosquitofish, catfish, perch, Ruffe, common carp, black bass, Pike, perch, etc. However, all are not considered invasive species.
It is the threat of these species on the ecosystem, health or the economy that actually turn them into invasive species.

The introduction of a foreign species within an ecosystem produces changes that can lead to a imbalance. According to the upheavals caused by the introduced species and according to the resilience of the ecosystem capacity it can regain a balance more or less close to the initial state.
These imbalances often stem of new competition between invasive species and one or several native species. The introduced species may, in particular, consume resources needed for native species or feed directly on them.

How to explain their proliferation

Invasive species today are extremely numerous and constitute a major challenge to fight against the reduction of biodiversity at the national and global level. Overall, their explosion is due to the development of transport and trade (in all their forms).
It may be trade or the introduction may be involuntary or voluntary (for food, new pets, ornamental plants, etc…) but also individual introductions following trips for example.

If the fight against these species once installed can limit their proliferation, it is often an expensive solutions in energy and financial (weeding, harvesting, trapping, etc.). Prevention remains the most effective method. In this sense, it is important to remember that the introduction, picking or movement of species can have dramatic consequences.

July 13, 2016, the European Union has published the list of invasive alien species threatening biodiversity and economic activities, and which aims to be updated every 6 years. This list includes:
  • plant: baccharis sheets to stereotypical, Giant Hogweed from Persia, Hogweed Sosnowski, cabombe of Carolina, fake arum, great lagarosiphon, feverfew, pennywort false Buttercup, water hyacinth, jussie with large flowers, creeping jussie, kudzu, the Brazil milfoil, renewed perfoliee;
  • mammals: Red coati, squirrel in red belly, Fox squirrel, Gray Squirrel, Java Mongoose, various of Reeves, coypu, raccoon, Siberian Chipmunk;
  • amphibians: frog Bull;
  • a reptile: turtle in Florida;
  • bird: Raven familiar (or Crow of the India), Ruddy, ibis, sacred;
  • an insect: Asian Hornet.
  • fish: Asian Stud, Stud of love;
  • crustaceans: Chinese River crab, crayfish, crayfish of California, Louisiana crayfish, the swamp crayfish, virile crayfish.

This is a list necessarily not exhaustive, but we can wonder at the absence of certain species such as mink of America, for example, that competes with mink in Europe, protected.

Several species in the European list are present in and around the Lake of Cazaux-Sanguinet, while other species are not listed here, but represent a danger at a lower level (local, regional or national).

Lagarosiphon major

Name: Big lagarosiphin – Lagarosiphon major
Description: plant aquatic especially present in the nutrient-rich environments. It is found in the ponds, channels and ditches, edges of water to low summer flows, etc. By its capacity for growth and multiplication, the great lagarosiphon rapidly forms dense mono-specific meadows that prevent the development of local species and leads to the filling of the habitat by accumulation of litter produced by the plant.
Origin: South Africa

Pectinatella Magnifica

Name: Pectinatelle – Pectinatella Magnifica
Description: Presents in the form of colonies, slimy to the touch but firm, fixed to the substrate. It is formed by a common jelly, around which are distributed individuals called zooids. It likes low-flow, hot and polluted waters. Media recovery is likely to harm native species, and it could be competing microphages filter-feeding. Its recent arrival on the Lake of Cazaux-Sanguinet and its accelerated dispersion represents a risk not assessed to monitor.
Origin: North America
Pectinatella magnifica is an invasive species that has recently appeared on Lake Cazaux - Sanguinet.

Pectinatella magnifica is an invasive species that has recently appeared on Lake Cazaux – Sanguinet.

Creeping Jussie

Name: Creeping Jussiê – Ludwigia peploides
Description: Plant herbaceous creeping, its leaves are shiny green and bright yellow flowers. In the form of very dense, submerged or emergent aquatic weed, it enjoys very sunny, stagnant waters or low-flow and was introduced to bloom ponds and aquariums. It competes with the aquatic flora immersed in preventing the penetration of light and taking all of the ecological niche. Very sensitive to the quality of the water, it demonstrate a great capacity for adaptation. It can lead to an acceleration of the filling in the environment by accumulation of organic matter and impede the good functioning of irrigation and drainage systems.
Origin: South America
The Creeping jussie can prevent the light from penetrating and promote the accumulation of organic matter.

The Creeping jussie can prevent the light from penetrating and promote the accumulation of organic matter.

Louisiana crawfish

Name: Louisiana crawfish – Procambarus clarkii
Description: Usually dark (from black to dark orange) color, omnivore, resistant to polluted waters poor in oxygen, it can also travel great distances on Earth to join a new environment. It is in direct competition with native crayfish. Healthy carrier of crayfish plague, it promotes its transmission to local populations. It also digs burrows nearly 2 meters long weakening banks and disturbing the water.
Origin: Mexico and United States South
The Louisiana crayfish is an invasive species that competes with native species and can create riverbank damage.

The Louisiana crayfish is an invasive species that competes with native species and can create riverbank damage.

Coypu

Name: Nutria – Myocastor coypus
Description: Introduced in the nineteenth century for its fur, this large rodent (up to 10kg) with a brown coat, herbivore and swimmer (webbed hind legs), is easily recognized by his large orange incisors. It lives mainly in stagnant waters and low flow. The construction of burrows and galleries promotes the erosion of the banks and its strong consumption of aquatic plants may threaten some species. It can also transmit diseases (liver fluke, leptospirosis).
Origin: South America
The Coypu participates in the weakening of the banks by the construction of burrows.

The Coypu participates in the weakening of the banks by the construction of burrows.

Florida turtle

Name: Florida turtle – Cuban scripta elegans
Description: Olive green color, with a yellow striped shell and Red temples, the Florida turtle can reach 2 kg. Present mainly in stagnant waters and low flow. The biggest nuisance concerns the European pond turtle (Emys orbicularis) with which it shares the living environment and is competing. Bigger, more opportunistic (omnivore), it can also transmit parasites to local species.
Origin: America North and central

Pumpkinseed

Name: Sun – Lepomis gibbosus
Pole Description: Fish that measure up to 15 cm and was introduced for aquariums. Multicolored predominantly blue and green on the back, the sides are yellow orange, it attendesd calm waters. The female deposits 1500 to 3000 eggs in a nest built and defended by the male. Carnivorous, it gladly consumes the eggs and fry of other fish and figure on the list of species likely to cause biological imbalances.
Origin: North America
Susceptible to imbalances, the populations of pumpkinseed seems today stable in the lake.

Susceptible to imbalances, the populations of pumpkinseed seems today stable in the lake.

Black bullhead

Name: Catfish – Ameiurus melas
Description: Fish without scales, about 20 cm, the first individuals would have broken away of the aquariums in the natural history Museum in Paris. Particularly resistant and enduring lack of oxygen it presents a great adaptability and a strong potential for colonization. Reproduction takes place on a nest prepared by the parent couple. Spawning and fry, grouped into balls, are then protected by the male. Omnivore and competitor, it limits food resources of other species.
Origin: North America

Mosquitofish

Name: Mosquitofish – Gambusia affinis
Description: Introduced to combat the proliferation of mosquitoes, is a small fish of rather dull, slightly grey, brown or greenish color. The female is larger than the male (7cm vs 3cm). It is known for his ability to adapt: it supports water very low in oxygen and very high salinity. Ovoviviparous, it has a strong reproductive power. Predator of mosquitoes and invertebrates, it also appreciates the eggs of other fish species it can jeopardize. It is host potential of helminth parasites, transferable to other species.
Origin: North America

American mink

Name: American mink – Mustela vison
Description: The American mink were introduced in Europe for the operation of its fur. Morphologically very close to the European species, it occupies the wetlands and built their dens on the edge of water. Depending on resources, space may be 1 to 6 km of water courses. It is an opportunistic predator that eats small mammals, waterfowl, small invertebrates, amphibians, reptiles and fish. Occupying the same ecological niche, it threatens the European Mink (competition for food and habitat).
Origin: North America

Cordbicula Fluminea

Name: Cordbicula Fluminea
Description: A small, round, yellow, 20-30 mm shell that feeds on phytoplankton using two siphons to filter water. A hermaphrodite species, each individual can release up to 40000 larvae that will quickly colonize their environment. Originally from Asia, where it is sometimes consumed, Corbicula appeared in France in the 80s and has now colonized a large part of the territory.
Origin: Asia
Appearing very quickly, the population of Asian bugs seems to have stabilized.

Appearing very quickly, the population of Asian bugs seems to have stabilized.