Overstocking, overfeeding of ‘bangus’ eyed in Dagupan fish kill

DAGUPAN CITY, PANGASINAN, Philippines — Aside from changing weather conditions and neap tides, human practices, such as overstocking and overfeeding may have contributed to the massive fish kill that struck the city’s rivers over the weekend, fisheries experts said Tuesday.

Sudden rainfall on Saturday, Oct. 10, following several days of hot weather, may have triggered water stratification or the rapid mixing of water layers, according to Luisito de Guzman, head of the City Fisheries and Aquatic Resources Management Council (CFARMC).

As cooler, denser surface water sinks, warmer water from the bottom—potentially depleted of oxygen and laden with toxins—may rise to the surface, he added.

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READ: Massive fish kill hits Dagupan City

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According to De Guzman, this sudden mixing can further reduce the oxygen available to fish, causing “bangus” (milkfish) to suffocate and die. This may explain the reported death of about 70 percent of the bangus being raised in Dagupan.

The CFARMC, however, has yet to determine the volume of losses and the number of affected fish pens.

Pangasinan produced 109,893.50 metric tons of milkfish in 2019, accounting for about 27 percent of the country’s total production of 409,906.56 MT, according to records.

In this city about 2,639 MT of bangus are harvested annually from 910 hectares of fishponds and fish cages, according to the city government’s website.

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De Guzman said the city’s rivers may also have suffered from overcrowded fish pens, some of which reportedly encroach on navigational lanes.

Under a city ordinance, only 1,000 fish pens are allowed in the rivers, with local residents given priority in owning and operating the structures, he said.

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However, some operators from other towns reportedly use local residents as fronts for their businesses, De Guzman added.

‘Joint ventures’

Fish pen operators who spoke on condition of anonymity said some local growers were at the mercy of financiers who dictated how many fingerlings they should stock and how much feed they should use, often exceeding recommended levels.

One operator said these arrangements were presented as “joint ventures,” with financiers providing inputs, such as fingerlings and feeds, while the fish pen owners served as caretakers of their own facilities.

Upon harvest, the cost of the inputs is deducted from the proceeds, and the remaining income is divided between the financier and the fish pen owner.

Another operator, however, said financiers often dictated stocking densities and feeding rates regardless of recommended practices.

“For example, a 10-by-10-meter pen should hold only 10,000 bangus, but they stock it with 30,000 to 35,000. Then the financiers insist on feeding rates that are way above the normal feeding requirements of bangus. Uneaten feeds cause water pollution,” the operator told the Inquirer.

The operator also alleged that some financiers inflated the price of feeds. A bag that normally costs P750, for instance, could be charged at P900, allowing the financier to earn from the sale of supplies even before the fish were harvested.

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When disasters strike, such as during a fish kill, financiers are reportedly shielded from losses because the agreements require fish pen owners to settle their debts from their next harvest. /cb