25 September 2013

Is that true?

The expression of Silvia as a person met in Agios Spiridon, Greece, tells her that fish in the Gulf of Corinth has declined over the past decades because of... earthquakes.

That is a story we heard a few times. Has such belief been generated by some misinformed TV programme? While the Gulf of Corinth is one of several seismic areas in Greece, earthquakes in this area certainly aren't a recent phenomenon.

Fish was plentiful until a few decades ago, and earthquakes are an unlikely reason behind its decline. The majority of fishermen interviewed in the Gulf of Corinth assert the most likely candidate to explain such negative trend is overfishing by trawlers and seiners.

(Photo by G. Bearzi)

1 comment:

Sigrid Lueber said...

Anthropogenic ocean noise pollution (i.e. seismic activities) presents a direct threat to the security of this food source, and to the fishing industry. Arguably, this threat has not been given the attention it deserves thus far, despite available information.
Three decades of controlled scientific studies indicate that intense ocean noise damages fish and, consequently, fisheries. Research so far indicates adverse reactions to intense noise in 21 species of fish. Harmful effects include:
• extensive damage to fish ears and hearing
• reduced catch rates of 40-80 percent and fewer fish near seismic surveys reported for cod, haddock, rockfish, herring, sand eel and blue whiting
• disruption in schooling structure, swimming behavior, and, possibly, migration in bluefin tuna
• secretion of stress hormones in several fish species in the presence of shipping noise
• alteration of gene expression in the brain of codfish following airgun exposure
• a significant increase in heart rate in embryonic clownfish with exposure to noise
• avoidance behavior in capelin and eels when exposed to noise, potentially affecting critical life-history events
• There are harmful effects to commercial invertebrates, too. These effects include:
• a reduction in growth and reproduction in brown shrimp exposed to noise
• bruised organs, abnormal ovaries, smaller larvae, delayed development and stress in snow crabs when exposed to seismic noise
• increased food consumption and histochemical changes in lobster after exposure to seismic noise

Since anthropogenic ocean noise can travel hundreds of miles from its source, the potential impact to fisheries from unregulated noise activities is immense. This could have significant effects on national economies, commercial fisheries and local fishing communities.
An estimated 43.5 million people rely on capture fisheries and aquaculture job markets for full or part time employment. Eighty-six percent of this estimated total are citizens of Asia. An additional estimated 4 million people are occasionally engaged in the fisheries and aquaculture sector.
Around 500 million people rely (indirectly and directly) on the fisheries and aquaculture sector for employment.
Developing countries produce $24.6 billion annually from their fisheries exports.
The increasing reliance on fisheries for employment and economic growth, especially for developing countries, will continue to grow.
As this dependency develops, so will the number of overexploited fish stocks.