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Usages and Impacts of Quinalphos in Commercial Aquaculture in Rajshahi, Bangladesh

Md. Mokhlesur Rahman*
Institute of Environmental Science, University of Rajshahi, Rajshahi-6205, Bangladesh

M. Nazrul Islam
Department of Zoology, University of Rajshahi, Rajshahi-6205, Bangladesh

Abstract/ Executive Summary:

Fish farmers involved in commercial aquaculture in northwest Bangladesh is striving for ruthless efficiency of the system. In this process they have been selective poisoning the undesired species (!) by using quinalphos pesticides while keeping their desired species (Indian and Chinese major carps) seemingly unaffected. The study was conducted to know the impact of the use of quinalphos on zooplankton, aquatic insects and benthos population in commercial aquaculture ponds. To know the bioaccumulation phenomena, fish were collected pre and post-treatment and analyzed for residual content of quinalphos. Zooplankton, aquatic insects and benthos sample were collected and counted at pretreatment and after 1 day, 2 days, 5 days, 10 days, 15 days, 21 days and 28 days after the treatment. Quinalphos was found to be bioaccumulated in fish till 10 days after the use. Zooplankton were found to be impacted for short duration and were able to regenerate within 5 days of the use of quinalphos. Aquatic insects and benthos were also affected but the loss of insect diversity was observed till the end of the observation period.

Keywords: Quinalphos; Selective poisoning; Aquaculture; Bioaccumulation; Zooplankton; Aquatic insects.

Location: Hatgodagari area of Poba Upazilla of Rajshahi.

Start Date:

End Date:

Program Area: Pest Management

Commodity: Aqua Drugs

Objectives:

This phenomenon of quinalphos is exploited by the commercial fish farmers in northwest Bangladesh and quinalphos is being used as a weapon (selective poison) to kill and wipe out the undesired (!) fish species like Chanda sp., Pseudambasis sp. and Glossogobius sp. Though the author failed to find any reference for LC50 value of Pseudambasis sp. and Glossogobius sp. for quinalphos but that is defiantly much lower than that of Indian major carps in commercial aquaculture ponds. The study was conducted to know the unintended consequences of use of quinalphos in commercial aquaculture ponds on fish, zooplankton, aquatic insects and benthos population.

Methodology:

The study was conducted in 3 different ponds (each of which were 2 to 3 acres in size) under commercial aquaculture located in Hatgodagari area of Poba upazilla of Rajshahi. During the survey in the region the author came to know about this practice by the farmers. Therefore, farmers were communicated early to inform the author when they intend to use quinalphos in culture ponds. Accordingly, the author was present during the treatment in last week of November 2018. Total quantity of quinalphos pesticide was diluted in a big aluminum pot and then was broadcasted manually over the entire body of water of the pond. Based on the uses the doses were back calculated using the following formula: Concentration (mg/liter) = total amount of pure quinalphos (in mg) / volume of the water (of the pond in liter). Accordingly, the doses of quinalphos were found to be 0.02 mg/liter which is little less than 1/6th of the (lowest of Indian major carps) 96-hour LC50 value of Cirrhinus mrigala (LC50 value is 0.128 mg/l). The study was repeated using similar doses of quinalphos (brand name Deviqueen 25 EC quinalphos marketed by ‘The Limit Agroproducts Ltd’) with two additional farmers at different times and each one/pond was considered as one replication. Sampling of zooplankton, aquatic insects and benthos was done just before the treatment and 1 day, 2 days, 5 days, 10 days, 15 days, 21 days and 28 days after the treatment. In addition, fish and water sample were also collected pretreatment and after 1 day, 2 days, 5 days and 10 days of the experiment for testing the residue level of quinalphos. For each sampling approximately one to one and half kg fish (Labeo rohita) were caught using cast net, put in a plastic bag and immediately transferred into the freezer. Water samples were collected from 18 inches below the surface of water level, at least from four different locations of the pond to make totaling of 1 liter. The water sample was put in nontransparent plastic bottle and immediately put into the freezer. Both the fish and water samples were coded with numbers and transferred to the ‘Pesticide Analytical Laboratory’ located in Entomology Division of Bangladesh Agricultural Research Institute (BARI). The lab then analyzed the sampleusing GCMS-MS machine (level of detection of organophosphate insecticides ranged from 0.003 to 0.009 mg/liter) for quinalphos residue and delivered the report.

Source of Information: Rajshahi University Journal of Environmental Science, 8: 71-78, 2019

Article Link (Online Journal): www.ru.ac.bd/ies

Funding Source:

Budget:

Total Budget (Tk.) :

Achievement/Findings:

Aquatic insect count showed that the number got down moderately around 5th days after the treatment and then 10th day onwards remain almost static. On the other hand, benthos count showed that the number got down moderately one day after the treatment and slight increased and almost continued to stay the same till the end of the observation period, 28 days except increased number was observed (like a spike), on the 10th day. The author has no logical explanation for this spike except the possibility of sampling error.

The diversity of the aquatic insect was greatly affected than the total counts of insects due to the quinalphos treatment in pond water. One day after the treatment insect types found to be three as opposed to the seven types that was recorded at pre-treatment. Of the aquatic insects may fly and Gerris sp. were not found The diversity of the aquatic insect was greatly affected than the total counts of insects due to the quinalphos treatment in pond water. One day after the treatment insect types found to be three as opposed to the seven types that was recorded at pre-treatment. Of the aquatic insects may fly and Gerris sp. were not found.

Knowledge Management: Journal