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Interference of Chironomus in an open culture system for Tubifex tubifex
Aquaculture, 44 (1985) 249-251 Elsevier Science Publishers B.V., Amsterdam -Printed
249 in The Netherlands
Short Communication INTERFERENCE OF C~r~O~O~~S FOR TUBIFEX TUBIFEX
IN AN OPEN CULTURE SYSTEM
M. PETER MARIAN and T.J. PANDIAN wahoos of BioZogicaZ Sciences, ~u~urai ~am~raj ~nive~ity, (Accepted
~a$~ra~ 625 021 (India)
20 November 1984)
ABSTRACT Marian, M.P. and Pandian, T.J., 1985. Interference of Chir~nomus system for Tubifex tubifex. Aquacufture, 44: 249-251.
in an open culture
In an outdoor culture of Tubifex tubifex, occurrence of the larvae of Chironomus pulcher and C. calligaster was recorded. An increase in the density of Chironomus larvae reduced the standing biomass of tubifex and made the harvest impossible.
INTRODUCTION
Recently we have described a technique for culturing Tubifex tubifex using waste materials like cow dung and coconut mesocarp (Marian and Pandian, 1984). In our open culture system, an individual grew to a size of 7.5 mg, which is nearly two times larger than the largest size attained in another culture system (Kosiorek, 1974). However, about 16 g of cow dung was required in our system to produce 1 g of tubifex. During an effort to minimize the cow dung requirement, we observed the occurrence of the larvae of Chironomus p&her and C. culliguster (species identification confirmed by Dr NC. Pant, London), and the competitive exclusion of tubifex from the culture system. This note reports on the effect of chironomus density on the harvestability of tubifex. MATERIALS
AND METHODS
Our method of rearing Tubifex tubifex has been described in detail elsewhere (Marian and Pandian, 1984). Briefly, the worms were reared in outdoor cement culverts (150 X 15 X 15 cm each) containing the culture medium, i.e. a mixture of 75% cow dung and 25% fine sand and coconut mesocarp; continuous water flow through the culverts was maintained to keep the oxygen content of the medium = 3 mg l-‘, and 250 mg cmm2 cow dung was added once in 4 days. The culture system yielded a sustained harvest of tubifex at the rate of about 125 mg cm-’ once every 30 days during the period from October to March. However, with the occurrence of the larvae of
0044-8486/85/$03.30
0 1985 Eisevier Science Publishers B.V.
250
Chironomus calligaster from April to May, and C. p&her from April to October, the harvestable tubifex began to decrease. As the identification of Chironomus could be confirmed only from collections of emerged imagoes, it was not possible to make a species-wise estimation of the Chironomus larval density. Hence a study was undertaken considering the combined density of larvae of Chironomus spp. (see also Brinkhurst and Kennedy, 1965) as a function of the standing biomass and harvest of T. tubifex in the culture system. RESULTS
Our culture system consistently supported an average standing biomass of about 180 mg Tubifex tubifex and yielded a regular harvest of about 125 mg cm-’ once every 30 days. During the period from April to October, occurrences of larvae of Chironomus pulcher and C. calligaster and reductions in the standing biomass of tubifex were recorded. From Table I it is clear that (i) increase in chironomus density reduced the standing biomass of tubifex, and (ii) a density of two chironomus cm-’ rendered the tubifex harvest impossible. TABLE I Diminishing biomass and scope for harvest of Tubifex tubifex as a function of larval density of Chirononus spp. Each value represents the mean (+ SD) of 10 observations Chironomus density (no. cm-‘)
0
1 2 3 4 5 7
Tubifex biomass (no. cm-‘)
(mg cm-‘)
146 t 21 97 + 23 42t 6 25* 3 20+ 2 18* 3 lo? 2
181 + 16 119 + 19 512 8 33* 4 27+ 6 22+ 3 13* 4
Continuation of tubifex harvest
Possible Possible Not possible Not possible Not possible Not possible Not possible
DISCUSSION
Our observation on the competitive exclusion of tubifex by Chironomus larvae confirms the previous record of Brinkhurst and Kennedy (1965); these authors noted the elimination of Tubifex tubifex from a Canadian stream with the appearance of the larvae of Chironomus thummi thummi and C. annularius. In this stream the density of tubifex was 228 per sample during November, when the chironomus began to appear (one larvae per sample); with increasing density (117 per sample) in February, tubifex totally disappeared. Strong illumination (Ivleva, 1969) and elevation of temper-
251
ature (owing to too rapid decay of organic matter; see Kinne, 1977) are known to attract flies into the tubifex culture system. It may be noted that our tubifex culture system was invaded during the warmer period of the year; the Canadian stream attracted chironomus during winter when temperatures and light intensity were low. Hence it is not clear which environmental factor(s) facilitates the invasion of chironomus into the tubifex bed and how chironomus competitively excludes tubifex from the bed. While further work is in progress, we suggest that care should be taken to avoid oviposition of chironomus, to ensure consistent harvest of tubifex.
REFERENCES Brinkhurst, R.O. and Kennedy, C.R., 1965. Studies on the biology of Tubificidae (Annelida, Oligochaeta) in a polluted stream. J. Anim. Ecol., 34: 429-443. Ivleva, I.V., 1969. Biological Principles and Methods of Mass Culture of Food Invertebrates. Nauka Publishing House, Moscow, 177 pp. (in Russian). Kinne, O., 1977. Cultivation of animals - Research cultivation. In: 0. Kinne (Editor), Marine Ecology, Part 2, Cultivation. Wiley, London, pp. 579-1293. Kosiorek, D., 1974. Development cycle of Tubifex tubifex Mull, in experimental culture. Pol. Arch. Hydrobiol., 21: 411-422. Marian, M.P. and Pandian, T.J., 1984. Culture and harvesting techniques for Tubifex tubifex. Aquaculture, 42: 303-315.
249 in The Netherlands
Short Communication INTERFERENCE OF C~r~O~O~~S FOR TUBIFEX TUBIFEX
IN AN OPEN CULTURE SYSTEM
M. PETER MARIAN and T.J. PANDIAN wahoos of BioZogicaZ Sciences, ~u~urai ~am~raj ~nive~ity, (Accepted
~a$~ra~ 625 021 (India)
20 November 1984)
ABSTRACT Marian, M.P. and Pandian, T.J., 1985. Interference of Chir~nomus system for Tubifex tubifex. Aquacufture, 44: 249-251.
in an open culture
In an outdoor culture of Tubifex tubifex, occurrence of the larvae of Chironomus pulcher and C. calligaster was recorded. An increase in the density of Chironomus larvae reduced the standing biomass of tubifex and made the harvest impossible.
INTRODUCTION
Recently we have described a technique for culturing Tubifex tubifex using waste materials like cow dung and coconut mesocarp (Marian and Pandian, 1984). In our open culture system, an individual grew to a size of 7.5 mg, which is nearly two times larger than the largest size attained in another culture system (Kosiorek, 1974). However, about 16 g of cow dung was required in our system to produce 1 g of tubifex. During an effort to minimize the cow dung requirement, we observed the occurrence of the larvae of Chironomus p&her and C. culliguster (species identification confirmed by Dr NC. Pant, London), and the competitive exclusion of tubifex from the culture system. This note reports on the effect of chironomus density on the harvestability of tubifex. MATERIALS
AND METHODS
Our method of rearing Tubifex tubifex has been described in detail elsewhere (Marian and Pandian, 1984). Briefly, the worms were reared in outdoor cement culverts (150 X 15 X 15 cm each) containing the culture medium, i.e. a mixture of 75% cow dung and 25% fine sand and coconut mesocarp; continuous water flow through the culverts was maintained to keep the oxygen content of the medium = 3 mg l-‘, and 250 mg cmm2 cow dung was added once in 4 days. The culture system yielded a sustained harvest of tubifex at the rate of about 125 mg cm-’ once every 30 days during the period from October to March. However, with the occurrence of the larvae of
0044-8486/85/$03.30
0 1985 Eisevier Science Publishers B.V.
250
Chironomus calligaster from April to May, and C. p&her from April to October, the harvestable tubifex began to decrease. As the identification of Chironomus could be confirmed only from collections of emerged imagoes, it was not possible to make a species-wise estimation of the Chironomus larval density. Hence a study was undertaken considering the combined density of larvae of Chironomus spp. (see also Brinkhurst and Kennedy, 1965) as a function of the standing biomass and harvest of T. tubifex in the culture system. RESULTS
Our culture system consistently supported an average standing biomass of about 180 mg Tubifex tubifex and yielded a regular harvest of about 125 mg cm-’ once every 30 days. During the period from April to October, occurrences of larvae of Chironomus pulcher and C. calligaster and reductions in the standing biomass of tubifex were recorded. From Table I it is clear that (i) increase in chironomus density reduced the standing biomass of tubifex, and (ii) a density of two chironomus cm-’ rendered the tubifex harvest impossible. TABLE I Diminishing biomass and scope for harvest of Tubifex tubifex as a function of larval density of Chirononus spp. Each value represents the mean (+ SD) of 10 observations Chironomus density (no. cm-‘)
0
1 2 3 4 5 7
Tubifex biomass (no. cm-‘)
(mg cm-‘)
146 t 21 97 + 23 42t 6 25* 3 20+ 2 18* 3 lo? 2
181 + 16 119 + 19 512 8 33* 4 27+ 6 22+ 3 13* 4
Continuation of tubifex harvest
Possible Possible Not possible Not possible Not possible Not possible Not possible
DISCUSSION
Our observation on the competitive exclusion of tubifex by Chironomus larvae confirms the previous record of Brinkhurst and Kennedy (1965); these authors noted the elimination of Tubifex tubifex from a Canadian stream with the appearance of the larvae of Chironomus thummi thummi and C. annularius. In this stream the density of tubifex was 228 per sample during November, when the chironomus began to appear (one larvae per sample); with increasing density (117 per sample) in February, tubifex totally disappeared. Strong illumination (Ivleva, 1969) and elevation of temper-
251
ature (owing to too rapid decay of organic matter; see Kinne, 1977) are known to attract flies into the tubifex culture system. It may be noted that our tubifex culture system was invaded during the warmer period of the year; the Canadian stream attracted chironomus during winter when temperatures and light intensity were low. Hence it is not clear which environmental factor(s) facilitates the invasion of chironomus into the tubifex bed and how chironomus competitively excludes tubifex from the bed. While further work is in progress, we suggest that care should be taken to avoid oviposition of chironomus, to ensure consistent harvest of tubifex.
REFERENCES Brinkhurst, R.O. and Kennedy, C.R., 1965. Studies on the biology of Tubificidae (Annelida, Oligochaeta) in a polluted stream. J. Anim. Ecol., 34: 429-443. Ivleva, I.V., 1969. Biological Principles and Methods of Mass Culture of Food Invertebrates. Nauka Publishing House, Moscow, 177 pp. (in Russian). Kinne, O., 1977. Cultivation of animals - Research cultivation. In: 0. Kinne (Editor), Marine Ecology, Part 2, Cultivation. Wiley, London, pp. 579-1293. Kosiorek, D., 1974. Development cycle of Tubifex tubifex Mull, in experimental culture. Pol. Arch. Hydrobiol., 21: 411-422. Marian, M.P. and Pandian, T.J., 1984. Culture and harvesting techniques for Tubifex tubifex. Aquaculture, 42: 303-315.