Jellyfish blooms pose threat to State

Jellyfish population is thriving off the Kerala coast, posing a threat to other species, messing up the food chain and jeopardising the fisheries and tourism potential of the State.

Scientists have documented the increasing presence of jellyfish blooms along the coast. Estuaries in the State are often choked with heavy swarms of jellyfish. Fishing vessels operating in the near shore waters accidentally net huge quantities of the slimy species.

Studies by the Central Marine Fisheries Research Institute (CMFRI) have shown that the blooming jellyfishes prey on other species such as sardine in their larval stage. As the jellyfish devour humungous quantities of the larvae, smaller fish species may get deprived of food, thus affecting the entire food chain.

Inland fishing hit

The proliferation of jellyfish and their blooms along the southwest coast of India is more than at any time in history, says A. Biju Kumar, Head, Department of Aquatic Biology and Fisheries, University of Kerala. Massive blooms often appear in estuaries and backwaters, affecting inland fishing.

The increased presence of jellyfish blooms in the waters off the coast of Kerala and Goa is also feared to impact tourism. Jellyfish have venomous harpoon-like structures on their tentacles which can penetrate human skin causing discomfort and even fatalities.

The construction of seawalls along large stretches of the Kerala coast is cited by marine researchers as one of the reasons for the increasing frequency of jellyfish blooms. “Granite seawalls provide the ideal structural habitat for the larvae of jellyfish to settle and grow,” explains Dr. Kumar. “Reduction of predatory species such as billfish, dolphins and marine turtles might also create a conducive environment for jellyfish.”

Influencing factors

Aquaculture, introduction of exotic species, excessive leaching of nutrients from land, overfishing and climate change are other factors influencing the frequency of jellyfish blooms.

The department has joined hands with the Centre for Venom Informatics under the university for a major research project funded by the Kerala State Council for Science, Technology and Environment (KSCSTE) to identify the species of jellyfish along the Kerala coast and characterise their venom.

The researchers will also study the climate change factors responsible for the blooms.