Threats to Komodo’s Biodiversity ~ Destructive Fishing

By Dian Hasan | October 12, 2009

bleachedcoral

Example of coral destruction

There are numerous threats to the biodiversity of Komodo National Park including human population pressure, tourism, the introduction of exotic species and poaching. However, the most potent threat lies in the destructive fishing practices that take place in and around the Park. These practices destroy the coastal environment at great economic costs in terms of coastal protection, fisheries and tourism.

Fishermen using dynamite to catch fish in the Philippines. Similar practices are found on Komodo. Photo by Thomas Heeger

BLAST FISHING:
Fish bombs are mostly made with artificial (chemical) fertilizers such as ammonium- and potassium nitrate (NH4NO3; KNO3), which is mixed with kerosene in a bottle. Blast fishers hunt specifically for schooling reef fish, so that only a few bombs will assure a relatively large catch. After the charge explodes, diving fishers enter the water to collect the fish, which have been killed or stunned by the shock-wave from the explosion. The size of the coral area destroyed by a single blast is dependent upon the size of the bomb and the position of the explosion relative to the coral reef. A beer bottle bomb will shatter an area of stony corals approximately 5 m in diameter.

Many blast fishing operations use “hookah” compressors to collect their catch from the reef. Blast fishing is considered one of the most destructive anthropogenic threats to coral reef ecosystems. It has been estimated that the economic costs of this practice are US$100,000 per km2 on average in terms of coastal protection, fisheries and tourism. Moreover, there has been a loss of around 85,000km2 of coral reefs creating a total loss of US$8.5 billion.

Cyanide fishing in the Philippines. Same technique found among fishermen in Komodo.

CYANIDE FISHING:
Cyanide solutions are used extensively to catch live reef fish for consumption and ornamental purposes. The concentrations of dissolved poison are not meant to kill but only to tranquilize the target fish, which facilitates their capture. The live food-fish trade concentrates on the catch of groupers and Napoleon wrasse. The aquarium fish trade concentrates on a much wider variety of species of colorful reef fishes. Live spiny lobsters, are also caught with cyanide. Cyanide fishing is done by divers, using “hookah” compressors and hoses to supply air. A diver on a “hookah” compressor-hose descends 10-40 meters until he spots a target fish. He chases the fish into a crevice in the reef and then squirts cyanide from a plastic bottle into the hole. As the fish begins to weaken, the diver breaks away the coral around the hole, reaches in, grabs the fish, and slowly escorts it to the surface. The cyanide fishery for aquarium fish destroys large areas of corals, which are broken down after an area has been sprayed with cyanide and the target fishes have fled in between the corals. The use of hookah compressors is a key factor in cyanide fishing practices.

REEF GLEANING:
The fishery for abalone (mata tuju) has destroyed large areas of coral reefs in recent years. Many fishermen are digging through the reefs, using compressors and steel bar tools (the method is called ‘meting’), in search of abalone and other marine invertebrates. The fishermen break down and turn over the corals (which are also trampled by them in the process) and leave behind them fields of near 100% dead coral rubble. Collecting invertebrates from reef flats is a traditional activity, which used to be focused on sea cucumber and carried out during very low tides. The high price for abalone and the availability of dive gear and ‘hookah’ compressors changed this into a more serious activity in the early nineties and initiated an increase in the total applied effort.

FISH TRAPS (BUBU), HOOK & LINE AND GILLNETS:
The use of bamboo mesh traps) is widespread in Indonesian reef fisheries. The process of setting and retrieving the trap is responsible for extensive destruction on the reef. To hide the traps in the reef, divers break off live coral to cover them. Traps set by simply lowering the trap from boat side via a buoyed rope are responsible for even more serious reef damage. These traps are often heavily weighted, and can destroy entire stands of corals during their installation.

The main yield category from the Park is fish (almost 95%). These fish are mostly caught by gillnets, and by trolling and bottom hook and lines. Demersal trolling lines or ‘kedo kedo’ are wiping out the coral trout stocks. Bottom hook and lines catch all predators and bottom longlines are decimating the sharks and large groupers. Gillnets kill indiscriminately, including turtles, dugong, cetaceans, and all species of reef fish. The fish stocks of the Park are seriously threatened by the use of gillnets and bottom longlines.

OVER-HARVESTING:
The target fish species in the live reef fish trade commonly aggregate at specific sites to spawn. Groupers and Napoleon wrasse migrate many miles each season to these spawning sites. Spawning aggregation sites are extremely vulnerable since experienced fishers are skilled in locating them. Wiping out the fish on one aggregation site equals the elimination of top predators from several square miles of reef. Grouper and Napoleon wrasse spawning aggregation sites

Mangroves, seagrass, lontar palms, and other species have been over harvested in the past. Seagrass is collected for use as a food source and as an ingredient for cosmetics. There is a large external market for these products. Mangrove tress are used for fire wood. The palm trees are used to make furniture and buildings locally. The decrease in the seagrass population may lead to increased coral mortality and decreases in species dependent upon them for shelter and food.

Coral fish Juveniles Humphead wrasse, Cheilinus undulatus in Hong Kong market. Photo: Michèle DÉPRAZ

LIVE REEF FISH TRADE:
The live reef fish trade has rapidly expanded from its epicenter in Hong Kong throughout South East Asia and beyond during the 1990s, and the demand for live fish is projected to grow even more in the future. By supplying the market with well over 50% of this volume, Indonesia is the largest supplier of wild-caught live fish food fish. Being an export oriented activity, the live reef fishery intensified because of the Indonesian monetary crisis. The present exploitation rate is much higher than can be sustained by Indonesia’s coral reefs.

The main target fish species of the Hong Kong-based live reef fish trade are groupers and Napoleon wrasse, but at least 30 other species are also regularly found as live food fish at the Hong Kong market. Most of these fish end up in aquariums of expensive restaurants, where they are sold to consumers for up to hundreds of dollars (US$) per serving.

The live reef fish trade is the source of three of the major threats to marine biodiversity in Komodo National Park. Namely, cyanide fishing, over fishing of adults and depletion of juveniles. As mentioned before, cyanide fishing causes chemical damage to coral reefs through the use of cyanide solutions to stun and capture target fish species. Moreover, diving fisherman cause physical damage when they break away corals around the hiding places of stunned target fish.

High exploitation rates of wild populations of market-ready fish (adults and sub-adults) render it impossible for the wild stocks to recover. The most important target fish species are extremely vulnerable to over-fishing, because these species tend to aggregate for spawning at certain sites during certain seasons. Once the commercial fishery locates a spawning aggregation site, the fishery can extract a significant portion of the adult stock with little effort.

High exploitation rates of wild populations of fingerlings of target fish is also a large problem. the fingerlings are used to supply the developing grow-out fish culture industry. Wild-caught fingerlings are kept in fish cages until they reach marketable size.

Source: Komodo National Park

This entry was posted in Biodiversity, Coral Destruction, Eco Matters, Habitat Destruction and tagged , , , , . Bookmark the permalink.

2 Responses to Threats to Komodo’s Biodiversity ~ Destructive Fishing

  1. Pingback: Threats to Komodo's Biodiversity ~ Destructive Fishing | fishfacts

  2. mike says:

    nice post, keep posting good ones

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