A Pelagia noctiluca jellyfish in the Mediterranean, near palermo, Sicily. (Photo: Alberto Romeo)
Warnings on jellyfish proliferation in the Mediterranean and Black Sea
Thursday, May 30, 2013, 23:10 (GMT + 9)
The United Nations Food and Agriculture Organization (FAO) has warned that the rapid increase in the number of jellyfish in the Mediterranean and Black Sea may be causing the decline in fish stocks.
According to a report issued by the General Fisheries Commission for the Mediterranean, an organization that belongs to the FAO, overfishing eliminates the main marine predators and is one of the factors triggering jellyfish proliferation.
There may be a "vicious circle" in which many jellyfish feed on fish larvae and on juvenile specimens and "further reduce the resilience of fish populations already impacted by overfishing," explained the Commission in the document.
Jellyfish "might be the provervial straw that broke the camel’s back," it adds.
According to FAO, in general, the impact of the human fishing activities is taken into account to set the limits of sustainable fisheries. But it notices that the jellyfish can also have great impact on the fish eggs and larvae, either directly or by competing for the same food sources.
Hence the need to take this into account in any ecosystem approach to fisheries management.
"In the past, the system could cope with episodes of jellyfish abundance, but in the case of the early 1980s blooms, the system went in another direction and is still not back to "normal" in pre-Pelagia years," reads the report.
For some experts, the abundance of jellyfish in almost all oceans of the world would occur by a "global regime shift from a fish to a jellyfish ocean," in which the latter would have replaced the former.
In addition to overfishing, this proliferation would be influenced by:
- Global warming, which increases the species that thrive in tropical latitudes;
- Eutrophication, which causes the increase in nutrients in the water;
- The widespread use of dams to prevent coastal erosion and the large number of tourist ports, which are an ideal habitat for jellyfish undergoing a stage of polyps in their first years of life.
According to FAO, the following measures can help prevent or deal with jellyfish proliferation:
- Incorporate research on jellyfish in the fishing study;
- Develop jelly based products for food and medicine;
- Establish early warning systems given jellyfish proliferation, with protective barriers for fish farms;
- Take measures to reduce overfishing, emission of greenhouse gases and causes of eutrophication "could certainly improve the quality of the environment in general and thereby, also reduce the current prevalence of jellyfish."
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By Analia Murias