Micropterus salmoides is a centrarchid native of North America, introduced in Europe at the end of 1800s and observed for the first time in Bracciano Lake in 1998, as a consequence of unauthorized introduction. To estimate the impact caused by the black-bass on the lake ecosystem, an ecology study on this species was carried out. From October 2001 to September 2002, 162 individuals were caught, measured, aged and submitted to biopsy (stomache and gonads were extracted). The gonads were weighed and histological slides were prepared. The individuals were divided into 4 age classes, from 0+ to 3+. An analysis of their diet highlighted that predatory activities was high in June; 55.7% of the prey was composed of fishes (Atherina boyeri – over 50% –, Lepomis gibbosus, Salaria fluviatilis and Perca fluviatilis, Coregonus lavaretus, Micropterus salmoides and Esox lucius juveniles), Palaemonetes antennarius for 37.5% and insects and molluscs, for 4.5% and 2.3% respectively. A trophyc overlap with the autochthonous or historically introduced species, such as Esox lucius or Perca fluviatilis, is possible. Moreover, a demographic decrease in concomitance with the black-bass introduction was observed. The I.G.S. values showed that the Micropterus salmoides breeding period occurred from December to February, rather than in the summer, and could be spread over more than three months as commonly described. During this period, ovaries and testes showed the maximum maturation level; it was possible to observe eggs with yolk and lipidic drops and totally matured spermatozoa. Also, from May to September females showed an unexpectedly high level of testes activity maturation while males showed high testes activity during all the year. Moreover, sexual maturity is reached by the second year (1+) both by males and females. A more detailed analysis on the effects caused by this species to the Bracciano Lake fish community can contribute to improving the freshwater fish management and conservation. The effects of the recent introduction on the lake community cannot be foreseen, but its predation and reproduction success along with the absence of natural predators can increase the naturalisation process of the black-bass in freshwater habitats of Central Italy.

Marinelli, A., Scalici, M., Gibertini, G. (2005). The largemouth bass (Micropterus salmoides) in Bracciano Lake (Rome, Italy). In Biological Invasions in Inland Waters (pp.54). Firenze : Università di Firenze.

The largemouth bass (Micropterus salmoides) in Bracciano Lake (Rome, Italy)

SCALICI, MASSIMILIANO;GIBERTINI, Giancarlo
2005-01-01

Abstract

Micropterus salmoides is a centrarchid native of North America, introduced in Europe at the end of 1800s and observed for the first time in Bracciano Lake in 1998, as a consequence of unauthorized introduction. To estimate the impact caused by the black-bass on the lake ecosystem, an ecology study on this species was carried out. From October 2001 to September 2002, 162 individuals were caught, measured, aged and submitted to biopsy (stomache and gonads were extracted). The gonads were weighed and histological slides were prepared. The individuals were divided into 4 age classes, from 0+ to 3+. An analysis of their diet highlighted that predatory activities was high in June; 55.7% of the prey was composed of fishes (Atherina boyeri – over 50% –, Lepomis gibbosus, Salaria fluviatilis and Perca fluviatilis, Coregonus lavaretus, Micropterus salmoides and Esox lucius juveniles), Palaemonetes antennarius for 37.5% and insects and molluscs, for 4.5% and 2.3% respectively. A trophyc overlap with the autochthonous or historically introduced species, such as Esox lucius or Perca fluviatilis, is possible. Moreover, a demographic decrease in concomitance with the black-bass introduction was observed. The I.G.S. values showed that the Micropterus salmoides breeding period occurred from December to February, rather than in the summer, and could be spread over more than three months as commonly described. During this period, ovaries and testes showed the maximum maturation level; it was possible to observe eggs with yolk and lipidic drops and totally matured spermatozoa. Also, from May to September females showed an unexpectedly high level of testes activity maturation while males showed high testes activity during all the year. Moreover, sexual maturity is reached by the second year (1+) both by males and females. A more detailed analysis on the effects caused by this species to the Bracciano Lake fish community can contribute to improving the freshwater fish management and conservation. The effects of the recent introduction on the lake community cannot be foreseen, but its predation and reproduction success along with the absence of natural predators can increase the naturalisation process of the black-bass in freshwater habitats of Central Italy.
2005
non disponibile
Marinelli, A., Scalici, M., Gibertini, G. (2005). The largemouth bass (Micropterus salmoides) in Bracciano Lake (Rome, Italy). In Biological Invasions in Inland Waters (pp.54). Firenze : Università di Firenze.
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11590/271350
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