Clima e pesca intensiva alterano pesci e biodiversità marina

pesca cambiamenti climatici biodiversità pesciDa uno studio effettuato in Australia è stato dimostrato che i cambiamenti climatici e la pesca intensiva, commerciale con reti a strascico, stanno alterando la biodiversità marina con particolari effetti sui pesci. Da una generazione all’altra i pesci divengono sempre più piccoli e perciò più vulnerabaili ai predatori. Forse la selezione naturale sta preservando dalle reti dei pescatori i pesci più piccoli che riescono a fuggire, ma in questo modo non può proteggerli dai pesci predatori.

I pesci stanno divenendo sempre più piccoli di dimensioni, e anche di quantità. E’ quanto emerge da una ricerca condotta dall’ente australiano Csiro, “Ricchezza degli oceani”, dalla biologa marina Asta Audzijonyte in collaborazione con alcuni studiosi finlandesi. L’equipe ha preso in esame 56 gruppi di organismi marini, tra cui alghe, pesci, crostacei e balene pescate con reti a strascico. Nell’arco di 50 anni queste specie si sono adattate all’uomo e ai cambiamenti climatici diminuendo le loro dimensioni in lunghezza. La riduzione delle dimensioni dei pesci e dei mammiferi marini è stata del 4%, ma la loro vulnerabilità ai predatori ha fatto aumentare la loro mortalità del 50%. Gli effetti sulla biodiversità sono notevoli, così come sull’indutria ittica. La quantità del pesce pescato è difatti diminuita del 35%. Come spiega la studiosa su Biology letters

Anche piccole diminuzioni di dimensioni possono avere gravi effetti sulla mortalità naturale. La pressione inoltre può  causare un’evoluzione delle specie verso minori dimensioni. Se i pesci maturano tardi possono essere catturati e non riprodursi, quindi vi è una pressione evolutiva verso una maturazione anticipata.

In sintesi, conferma la biologa marina, la pesca eccessiva e i cambiamenti climatici stanno alterando gli ecosistemi marini globali ma l’industria ittica continua ad ignorare questi aspetti segnalati e resi noti dai ricercatori di tutto il mondo. La pesca eccessiva e l’uso delle reti a strascico potrebbe, a lungo termine, “decimare le specie ittiche”.

[Fonte: Ansa]

[Photo Credit | Thinkstock]

51 commenti su “Clima e pesca intensiva alterano pesci e biodiversità marina”

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