Lably
Skip to content

Blast fishing

Using bombs underwater to kill fish

  • 10 min read
  • 3 chapters

Related on Lably

Through Ecosystem, Africa and World War I

LabEcosystem DynamicsLabOur EnvironmentLabFood Chains ExplorerLabEcosystems & Food Webs

Description

Although outlawed in some parts of the world, the practice remains widespread in Southeast Asia, as well as in the Aegean Sea and coastal Africa. In the Philippines, where the practice has been well-documented, blast fishing was known prior to World War I, as this activity is mentioned by Ernst Jünger in his book Storm of Steel. One 1999 report estimated that some 70,000 fishermen (12% of the Philippines' total fishermen) engaged in the practice.

Extensive hard-to-patrol coastlines, the lure of lucrative, easy catches, and in some cases outright apathy or corruption on the part of local officials make enforcement of blast fishing bans an ongoing challenge for authorities.

Commercial dynamite or, more commonly, homemade bombs constructed using a glass bottle with layers of powdered potassium nitrate and pebbles or an ammonium nitrate and kerosene mixture are often employed. Such devices, ironically termed expanding bait, may explode prematurely without warning and have been known to injure or kill the person using them, or innocent bystanders.

Underwater shock waves produced by the explosion stun the fish and cause their swim bladders to rupture. This rupturing causes an abrupt loss of buoyancy; a small amount of fish float to the surface, but most sink to the seafloor. The explosions indiscriminately kill large numbers of fish and other marine organisms in the vicinity and can damage or destroy the physical environment, including extensive damage to coral reefs.

Inefficiency

Blast fishing is inherently inefficient in retrieving killed and stunned fish. For every ten fish killed, only one or two float to the surface, due to damage caused to their otherwise buoyant internal air bladders. The rest sink to the bottom.

Shells exploding in the water during naval battles also tend to kill fish with the same effect of blast fishing, only without any systematic attempt to collect the harvest.

Impact on coral reefs

Researchers believe that destructive fishing practices like blast fishing are one of the biggest threats to the coral reef ecosystems. Blown up coral reefs are no more than rubble fields. The long-term impact associated with blast tanks is that there is no natural recovery of the reefs. Coral reefs are less likely to recover from constant disturbance such as blast fishing than from small disturbance that does not change the physical environment. Blast fishing destroys the calcium carbonate coral skeletons and is one of the continual disruptions of coral reefs. In the Indo-Pacific, the practice of blast fishing is the main cause of coral reef degradation. As a result, weakened rubble fields are formed and fish habitat is reduced.

The damaged coral reefs from blast fishing lead to instant declines in fish species wealth and quantity. Explosives used in blast fishing not only kill fish but also destroy coral skeletons, creating unbalanced coral rubble. The elimination of the fish also eliminates the resilience of the coral reefs to climate change, further hindering their recovery. Single blasts cause reefs to recover over 5–10 years, while widespread blasting, as often practiced, transforms these biodiverse ecosystems into continuous unstable rubble.

Sign in to keep reading

2 more chapters are free with a Lably account.

More in Earth science

Climate changeHuman-caused changes to climate on EarthKöppen climate classificationClimate classification systemIndian subcontinentPhysiographical region in South AsiaLimestoneType of sedimentary rockTropical cycloneRapidly rotating storm systemPleistoceneFirst epoch of the Quaternary Period