An assessment of tobacco waste for control of the gastropod, Tympanotonus fuscatus (Linnaeus) in brackishwater fish ponds

S. O. Aleem

AFRICAN REGIONAL AQUACULTURE CENTRE, PORT HARCOURT, NIGERIA
CENTRE REGIONAL AFRICAIN D'AQUACULTURE, PORT HARCOURT, NIGERIA

UNITED NATIONS DEVELOPMENT PROGRAMME
FOOD AND AGRICULTURE ORGANIZATION OF THE UNITED NATIONS
NIGERIAN INSTITUTE FOR OCEANOGRAPHY AND MARINE RESEARCH
PROJECT RAF/82/009

February 1987

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AN ASSESSMENT OF TOBACCO WASTE FOR CONTROL OF THE GASTROPOD, TYMPANOTONUS FUSCATUS (LINNAEUS) IN BRACKISHWATER FISH PONDS*

S. O. ALEEM

ABSTRACT

The common brackish water gastropod, Tympanotonus fuscatus or “periwinkle” can become a serious pest in tidal fish ponds. Control of the molluscs in fish ponds can be accomplished by using tobacco waste. This paper presents the results of behavioural response and survival of T. fuscatus at varying concentrations of tobacco waste. The time taken for 50% of the animals to escape from the solution increased with increasing concentration. The median times were 23, 28, 40, 62 and 213 min. for concentrations of 0.25, 0.50, 0.75, 1.00, and 1.25 g/l. AT 2 g/l no animals escaped. Using 1, 2, and 3 day old solutions, the escape time decreased with the age of the solution.

The median lethal time for the snails exposed to lethal concentrations decreased with an increase in the concentration. At 1 g/l, median lethal time was 216 hours, decreasing to 71 hours for 2 g/l.

At concentrations less than 2 g/l, T. fuscatus will attempt to escape the solution, but at this or higher concentrations the snail will close the operculum and eventually die.

* This study is based on a thesis submitted in partial fulfilment for the award of M. Tech. (Aquaculture) degree of the African Regional Aquaculture centre/Rivers State University of Science and Technology, Port Harcourt, Nigeria.

INTRODUCTION

The common brackish water gastropod, Tympanotonus fuscatus, “periwinkle”, is valued for human consumption; however in tidal fish ponds, the gastropod can become a serious pest. In the brackish water farm of Buguma, Nigeria, concentrations of 200 – 700 animals or 1 to 1.8 kg/m² have been recorded (Aleem, 1983). They consume appreciable amounts of nutrients, particularly calcium which is lost into their shells.

Control of mulluscs in fish ponds can be accomplished by using tobacco waste (FAO, 1970). The active toxic ingredient is nicotine (C₁₀ H₁₄ N₂) (Konar, 1970). In Taiwan, tobacco waste dust is applied at 1 ton acre as a pesticide and fertilizer in fish ponds (Jhingran, 1975). Tobacco dust, a by-product of the cigarette industry, is locally available, inexpensive, easily degraded, and serves as an organic fertilizer.

This paper presents the results obtained from studying behavioural response and survival of T. fuscatus at varying concentrations of tobacco waste.

MATERIALS AND METHODS

T. fuscatus with a shell length of 25–30 mm were collected from brackish water ponds at Buguma and immediately transferred to the laboratory in a plastic basin. They were washed thoroughly and left in pond water, salinity 10 ± 2.5%, temperature 29 ± 2 °C, for an hour. Ten animals which were actively crawling were selected for each experiment.

Solutions of tobacco waste and brackish water were made in the following concentrations: 0.25, 0.50, 0.75, 1.00, 1.25, 1.50, 1.75 and 2.00 g/l. For the behavioural study, 250 ml open beakers were used, the animals were observed over 24 hours, and the time taken for them to crawl out of the beakers was recorded. For all experiments, the median escape time, or when 5C% of the snails left the beaker, was determined.

For survival studies, the same concentrations were used, but the snails were placed in sealed 250 ml conical flasks. At 2 day intervals, survival was determined by placing the snails in uncontaminated and aerated pond water. Following Fry (1971) the median lethal time, or 50% mortality, was determined.

RESULTS

It was immediately apparent that the T. fuscatus reacted strongly to the tobacco waste. There were two reactions; they would either withdraw into the shell and close the operculum, or attempt to climb out of the beaker.

The results of the experiments on the avoidance of the snails is presented in Fig. 1. The median time for escape from the beaker was 23, 28, 40, 62 and 213 minutes for tobacco concentrations of 0.25, 0.50, 0.75, 1.00 and 1.25 g/l, respectively. At the higher concentrations, the snails would remain with the operculum closed for a longer time before attempting to climb from the beaker.

At 2.00 g/l no animals were able to leave the beaker while at 1.50 and 1.75 g/l, less than 50% of the animals were able to crawl out. At these high concentrations, the snails remained with the operculum closed for a much longer time, and when they would attempt to escape, a mucous material was released, and the snails attempting to climb out would fall back to the bottom of the container. In all test solutions, after 24 hours, there was no mortality.

For the experiments on potency of the tobacco waste, the median escape times of the different ages of solutions are presented in Fig. 2. While the solution was still an irritant the snails wouldn't remain with the operculum closed for as long a time but would attempt to climb out of the beaker much faster. In the 0.25 g/l solution, the median escape time was 23 min for the freshly prepared solution, and 14 min for the three day old solution. For the 1.25 g/l solution, the time was reduced from 213 min to 38 min for the three day old solution. The solutions had therefore lost a substantial amount of their toxicity after three days.

Results of the experiments on survival are shown in Table I. The median lethal times (LT 50) presented in Table II were determined from Fig. 3. The LT 50 decreased with increasing concentration of tobacco. At 1 g/l, the LT 50 was 216 hours, decreasing to 71 hours for 2 g/l.

TABLE I

Percentage survival of T. fuscatus exposed to various concentrations of freshly prepared tobacco/waste brackish pond water (salinity, 10 ± 2.5; temperature, 29 ± 2°C) solution at different times of exposure (values indicated are means of two separate determinations).

TABLE II

Median lethal times (LT 50) of T. fuscatus exposed to various concentrations of tobacco waste in brackish pond water (salinity, 10 ± 2.5‰); temperature 29 ± 2°C), values indicated were derived from Fig. 3.

PERCENT OF ANIMALS ESCAPING

Fig. 1. Percentage of T. fuscatus escaping from different concentrations of freshly prepared tobacco waste solutions at different times of exposure. Crosses indicate the median escape time or the time taken for 50% of animals to escape. Numbers shown for the different curves are concentrations of tobacco waste (g/l)

Fig. 2. Time taken by T. fuscatus to escape from different concentrations of tobacco waste solution. Curves for solutions of different ages (1 day to 3 day old) are shown

Fig. 3. Time survival curves of T. fuscatus exposed to variou freshly prepared concentrations of tobacco waste solution in brackishwater (Salinity 10 ± 2.5‰ and temperature 29 ± 2°C). Numbers shown for the differe curves are concentrations of tobacco waste (g/l). Crosses indicate median lethal time (LT 50).

DISCUSSION

From the behavioural studies, it is apparent that the time necessary for T. fuscatus to leave the tobacco waste solution increased with increasing concentration. At higher concentrations, the snails remained at the bottom of the container with the operculum closed for a much longer time. This was undoubtedly due to the higher concentration of nicotine. At concentrations higher than 1.00 g/l, the snails would fall back into the solutions as they attempted to climb out.

As can be seen from the shorter median escape times from the 1, 2, and 3 day old solutions at all concentrations, the toxic substances in the tobacco waste are rapidly degraded. With a 3 day old solution, even at a concentration of 1.25 g/l, the median escape time was similar to that ot 0.25 g/l indicating that much of the toxicity had been lost.

T. fuscatus survive in a low concentration of tobacco waste solution or 0.25 g/l and die at concentrations above this. The survival of the animals became progressively shorter as the concentration increased. The increasing nicotine concentration reduces the respiratory activity of the animal (Konar, 1970). With all toxicants, a threshold is reached above which there is a drastic change in the survival of the animal. Below this threshold, the animal is in the tolerance zone, above it, in the zone of resistance (Fry, 1971). In this latter zone, the toxicant kills the animal. The higher the concentration of the toxicant, the shorter the resistance time.

Compared to other toxicants and according to the classification of Spector (1956), the tobacco waste would be rated slightly toxic to the mollusc as the LT 50 at 1 g/l is 9 days. Its moderate effect, and the rapid rate of degradation make it attractive for aquaculture purposes, as a toxicant to control the pest and subsequently as an organic fertilizer.

For brackish water ponds, water should be lowered to a depth of 10 cm. The tobacco waste should be applied at the rate of 2.0 tons/ha to obtain a concentration of 2.00 g/l. The animals will die in about 3 days following the application (LT 50, 71 hours).

ACKNOWLEDGEMENTS

I would like to thank both Dr. M. N. Kutty and Mr. M. A. Afinowi of African Regional Aquaculture Centre, Port Harcourt, Nigeria, for their help and advice throughout the course of the study. Appreciation is also expressed to Mr. D. Campbell, Farm Manager, African Regional Aquaculture Centre, Port Harcourt, Nigeria, for his appraisal of the typescript.

REFERENCES

Aleem, S. O., 1983. Studies on escape (avoidance) responses and survival of the gastropod mollusc, Tympanotonus fuscatus (Linnaeus) exposed to tobacco waste. M. Tech. thesis, Rivers State University of Science and Technology/African Regional Aquaculture Centre, Port Harcourt, Nigeria. 117 pp.

FAO, 1970: Reclamation of ponds, lakes and streams with fish toxicants: A review. FAO Fish Tech. pap, No. 100

Fry, F.E.J., 1971: The effect of environmental factors on the physiology of fish. Fish physiology Vol. VI, (Eds.) W. S. Hoar and D. J. Randall, Academic Press Inc (London) Ltd. pp. 1 – 98.

Jhingran, V.G., 1975: Fish and Fisheries of India, Hindustan Publishing Corporation (India). 371 pp.

Konar, S. K., 1970: Nicotine as a fish poison: Prog. Fish Cult. 32(2): 103–104.

Spector, W. S., 1956: Handbook of toxicology, volume 1: acute toxicities of solids, liquids and gases to laboratory animals. Philadelphia, W. S. Saunders Company. 408 pp.