The extensive paddy fields on both sides of the

backwaters and many of the connected canals in tt

the northern ports of the Travancore-Cochin State,

which are single crop lands, have been used for the

past several decades for prawn fishing

Menon, M K

CMFRI Digital Repository

/ 1?eprildeil from Sedio" II of Proceedings of Indo.Pacif)c Fisheries Caul/cil, 19Jj , ON THE PADDY FIELD PRAWN FISHERY OF TRAVANCORE-COCHIN AND AN EXPERIMENT IN PRAWN CULTURE DlOCES,\:\ PRES S, )IJ\DRAS ON THE PADDY FIELD PRAWN FISHERY OF TRAVANCORE-COCHIN AND AN EXPERIMENT IN PRAWN CULTURE I by M. K. Menon 2 The extensive paddy fields on both sides of the backwaters and many of the connected canals in tt the northern ports of the Travancore-Cochin State, which are single crop lands, have been used for the past several decades for prawn fishing. Enquiries have revealed that about 11,000 acres of such fields are being utilised for this purpose at present, the annual yields from which, judging from the figures collected, seem to vary very widely, from about 70°/ Ibs. to 1.900 lbs. per acre. Expressed in terms of dry meat, which is the form in which these prawn catches are marketed, the yields vary from 106 lbs. to 29S1bs. per acre. Practically the entire production is exported from Cochin to Rangoon, Singapore and Hong Kong. In '952, 3,825 tons of dried prawns valued at approximately 85 lakhs of rupees were / exported from this port. The owners of the fields, in most cases, do not fish the prawns themselves, but lease out the fields after the harvest is gathered to those engaged in the industry, deriving thereby, an additional income which, in recent years, has been quite considerable (about Rs. 100 to Rs. 300 per acre). The lessee's right to fish is usually limited to a period of 5 months or less, from about the 15th of November to the 15th of April. He is also required to take out a licence from the State Government. In view of the importance of this fishery in the economy of these coastal villages it was considered desirable to collect accurate data on various aspects like the annual yield per acre, the monthly catches and their fluctuations, jf any, the different species represented, their proportions and size range from month to month etc. A field of about I! acres in extent on the border of one of the main canals of this place was, therefore, taken on lease in October, 1951. It has been divided into two portions, one of which is exactly an acre in area. A sluice 7t long, 5' high and Ii' wide has been put up in each portion. The one acre portion had been used for carrying on fishing operations while the smaller portion has been devoted to experiments in prawn culture. A similar experiment has also been carried out in a portion of the fish farm belonging to the State Fisheries Department through the courtesy of the Superintendent. The farm was originally a part of a, long stretch of low-lying swampy land situated close to the sea shore and not quite suited for paddy cultivation. FISHING OPERATIONS The fishery has been described in SQJ11e detail by Panikkar3 (1937), but the operations involved may be briefly stated here. Soon after· the paddy crop is harvested in October, the bunds of the fields are strengthened and sluices are installed. The method is, in reality, simply a device for large-scale prawn fishing which does not allow any time for the prawns to grow within the fields . Enquiries, however, show that in some localit ies e.g. in and around Narakkal, the current practice is a later development and that some 25-30 years ago it was actually a process of culture that wa~ in vogue. After allowing prawns to enter the fields in the manner indicated above for some days, the sluices were finally closed and the prawns were left in the completely enclosed fields for 2-3 months after which they were fished. When letting in water at high tide, the sluice is opened only after the water has risen almost to the highest level in the canal. This is to ensure that the water flows in with the maximum force possible, since the number of prawns entering depends largely on the force and duration of the current. The time taken to bring the water in the field to the same level was 25-30 minutes. A good portion of the water is let out at low tide (this also is done when the level of water has dropped almost to the lowest) so as to allow more water to flow in at the next high tide. A lamp is hung at the mouth of the sluice at night when taking in water in order to attract prawns towards it. 1 Published with the permission of the Chief Research Officer, Central Marine Fisheries Research Station, Mandapmn Camp, S. India. " 2 Prawn Research Unit of the Central Marine Fisheries Research Statton, Narakkal, India. :J Panikkar, N. K. The Prawn industry of the Malabar Coast. JOllr. Bombay Nat. Hist. Soc. Vol. 34, 1937. 1 The fishing usually starts with the neap tides, 4-5 days before every new and full moon and is continued for 7-8 days. The nct, about 20' long has a rectangular wooden fram t..: tied to its mouth. Its cod end is tied up with a piece of rope to which a float is attached. When the level of water in the canal is nearly at the lowest limit, the wooden frame of the net is fixed vertically inside the sluice and the shutters are removed. Water rushes out through the net with considerable force, carrying with it some of the prawns, which collect at the narrow end, which is lifted from time to time and emptied into a boat moored nearby. The time taken for completing the operation (till the level of water inside and outside the field is equal) is about the same as that taken for filling the field. If the fishing is done after dusk a light is also used. MONTHLY CATCHES AND TOTAL YIELD Operati.ons ,,,,ere started in the first week of De-cember in the 1951 -52 season, a fortnight after they had begun in many of the neighbouring fields. In '952-53 fishing was started somewhat early in the first week of November. The last fishing was done on 18-4-53 and 21-4-53. The weight of prawns (fresh) caught and the number of days on which fishing was carried out in each month are given in Table 1. On the last day cast nets were used since the ordinary method usually leaves a considerable number of prawns and some water behind in the fields. The catches of March and April, when the salinity of the canal water ranged from 26% to 33%, were on the whole better than those of other months and thjs was true in regard to several other fields also. The approximate yield per acre for the two sea-sons of a number of other fields situated at different places · was obtained for purposes of comparison and these are included in Table 2. The yield from everyone of these fields is considerably more than that of our experimental field for the corres-ponding season, probably because, owing to their Ill:uch larger size, the length of . time taken to fill them will be greater, thus allowing a larger number of prawn to pass into them. The table also tends ~o show that besides acreage some other factors like location, ~ of the bottom etc. may also affect the yield. -SPECmS OBTAINED Eight species of prawns and shrimps have been, obtained in the catches, namely Peneus indicus P. carinatus, Metapenaeus monoceros, M. dobsoni, Palaemon rudis, Leander styliferus, Caridina graci-liTostris and Acetes sp. Among them P. carinatus and the last two species have been obtained in extremely small numbers on a few days only and are, therefore, of no importance to the fishery. The percentage values of the other species for each month will be found in Table 3, which also includes tHe range of salinity of the canal water during each. f It is very likely that the fall in the percent e of M. monoceros rna be ilci.th...~ sa lfllty of t e canal water. It is also noteworthy that the maXImum numbers of P. indicus have been captured in the months of March and April, i.e. at the end of the season, in the other months its percentage value not exceeding 12. Such a low proportion of the only species of penaeid prawn that grows to a fair size in the backwaters is one of the factors that may render prawn farming in such fields hardly more profitable than by the present method. The data collected in regard to growth of penaeids in these environments, particularly Table x Monthly weight of prawn catches in 195 1-52 and 1952-53 seasons from a l·acre field 1952-53 Month No. of days I Wt. caught (wet) I No. of days I Wt. caught (wet) November · . · . .. . . '. lost lbs. December .. .. 13 78 Ibs. '5 "3 " January · . .. '3 9' " ,6 '74i " February .. .' , '3 62 " '3 I07! " March · . · . '4 '25 " ,6 '39* " April .. .. S '30 " '0 '7' " , Total · . 6, I 486 lbs. 8, I 7lIt lbs. -2 _ . . - - - - - - - -- - - - - -I I 1 \ Table a Approximate yields per acre of some other fields I , Yield per acre I Yield per acre 195 1-52 ! 195:1-53 i Acreage Situation Distance . , I Dry Fresh Dry Fresh meat prawns meat prawns II, Canal Adjoining experimental .Field 106 lbs. 690 Ibs. IJI lbs. 851 Ibs. ,6 -do- 2 Furlongs north '39 " 904 " 138 " 897 " IS Backwaters 8 miles north , I06 " 690 " .. .. 60 -do- l mile east ISS " 1,008 " 153 " 995 " 26t -do- -do- 294 " 1,91 I " 18 I " 1,1 77 " 32 -do- S miles south 97 " 630 " 13 I " 852 " Table 3 Approximate composition of prawn catches and range of salinity I November December January February March April Species I I '95' I 1952 I 1951 I 1952 1 1952 i 1953 M. dobsoni M. monoceros P. indicus al. mdis P L . sty iijerotls Range of sal. per 1,000 .. .. .. .. " I .. .. % 87·9 8.6 I.6 I.8 .. 4·9 I 14·29 % % % 74.6 82·3 81.6 14·3 ,.0 5.6 7·5 8·7 II.? 2·5 r.r 0·5 0.8 O.I 0·5 4·9 ]5·73 19·89 18.17 21.33 . 23·86 of the two species P. indicus and M. dobsoni also . tend to support this inference. % 89·8 0.6 9·0 0·5 .. 22.41 24.76 I 1952 ! 1953 I I 1952 1 1953 I 1952 \ 1953 ----_. "' % % % % % " 86.8 89·5 79·2 67'·1 84·5 45·7 7·5 2.6 2.8 I.I 0.8 2.6 8·4 , .0 12·5 29.8 2.0 48.0 0.8 0·4 1.5 I.O . . I.3 2·4 .. 3·9 . . 12.6 2·4 ' ' 25·12 24.76 26·74 28.91 31.62 \ 33 .24 t 26·74 28·73 29.63 31.26 31.98 22.05 ~ ! Unless p~_ farmi~ ca~ ~e shown to lead to ~ km.,provement In proCfiiCnon, at least 1fi respect o t osenelds of wliicli11ie presenfyiJds are com.Jl-C..-r~~ low 1. It has little ctiance of bemg adopted by those engaged in the industry. Improvement l1 could be effected if the proportion of P. indicus can be appreciably raised, or if they could be made to j ' Of considerable numbers of the fry of this saccies 1 in the canals and back-wa!~~ in .Q~tober an No-vember. - .... u_ -~ / GROWTH OF P. INDICUS AND M. DOBSONI Random samples from the catches of each fort-night have been regularly analysed and the propor-tion, sex ratio, length frequencies etc. in regard to the three species of peneids determined. The frequencies for each month in respect of P. illdicliS I grow larger than at present within the fields. Ob-servations so far made have indicated the presence 3 and 111. dobsOl1i have been plotted in order to csti~ mate whether and to ~vhat extent growth takes place in the brackish· water envIronments of th~ backwaters and canals. M. monoceros was omitted from this study because of the ipsigni6cant numbers occurring in some months. The frequency curves in respect of P. indicus illustrate a steady diminution in the percentage of prawns exceeding about 90 mm,due to intensive J fishing. Further, as the days become hotter many of them would go down into the mud at the botto o tee s may not t ere are be carried in ..... : ~e ouf-flowing...:urre~. There is clear evidence of growth, however, in regard to the $mall sized individuals. The curve for December, 1951, shows that 57.20/0 of the catch was formed of juveniles measuring not more than 50 mm while those 1?etween 50 mm and 90 mm accounted for 14010. In the succeeding months there is a steady fall in the percentage of the former group and a corresponding rise in that of the latter. In March the first group constituted . only 20.6% of the catch, while the remainder was almost entirely composed of prawns of the second· group. It cannot, of course, be claimed that the I whole of this increase in the proportion of the latter is due to growth; a part of it, no doubt, is only apparent, being the effect of the disappearance of individuals of over 90 mm in length . The majority size group of December. 1951. was 31-35 mm in length while that of March, '952, measured 7r-75 mm. The curves for .November, 1952, to March, 1953, are substantiaily similar, though the percentage of juveniles does not show any fall in December and January. It would, therefore, seem that in the conditions prevailing in the canals ~nd bac~watersl the extent ~~Of growth of thes.si!!Yeniles 0(1' . . indicus has been about 40-50 mm in tne cours~-=-of~~~h: ... montbL -In the case of .1.11. dobsoni, the frequency curves do not help in estimating the growth of the young ones. It seems fairly clear, however, that the vast I majority of prawns belonging to this species do pot grow beyond 61- 65 mm in the backwaters during these months. EXPERIMENT IN PRAWN FARMING '''hile the observations detailed above were in 'progress, an experiment in farming for a short ·period of about two months was conducted in the smaller field (about! acre in extent) mainly for the ~1Purpose of ascertaining roughly how growth is influenced by the different conditions obtaining ilL paddy nelds. I he preliminary operations of taJdng In water and letting it out \vere done exactly as -described above for a period of 10 days (from I-2-52 to 10-2-52) and the sluice was kept closed thereafter. On II-2-52 a few sheafs of paddy ' straw were introduced in order to approximate the conditions prevailing soon after harvest. A week later the water turned green owing to the abun-dant growth of microscopic algae! and a scum appeared on the surface, which persisted in patches till about 9-3-52. During this period the tempe-rature of the water rose to a maximum of 35°C during the day and the salinity was 28.73 % on 5-3-"52. Many of the prawns were seen swimming at the surface at daybreak and remained there for about a couple of hours, exposing themselves to the attacks of crO\vs and kites. A little water was there~ fore let in on some days and this proved effective in preventing the prav-ms from remaining at the surface long. They seemed to be otherwise unaffected by the conditions induced in the field by the fertiliser and temperature. They were fished in the first week of April, thus allowing about two months for growth. The length freguencies : .f;ndicated that substantial rowth had t ce, a oug e met od adopted to stock the field with prawns makes it difficult to determine their initial length frequencies. . The differences in the frequencies of most of the groups of P. indiclls were reduced ~ppreciably, probably because of their unequal" growth rates, the smaller groups growing more rapidly than the larger. The increase in the proportion of groups . between 75 and 95 mm would also seem to show that g~owth has been more rapid than in the back-waters and canals. . The second experiment similar to the one des-cribed above was conducted in a Pilrt of ~he Govern-ment fish farm, about two acres in extent. Its location and the nature of the land have been re-ferred to in the introduction. \Vater was let in, as in the former experiment, for about I I days (from 10-3-52 to 21-3-52) and was stopped only after making sure that' a good number of prawns had entered. Two days later some sheafs of paddy straw were put in, mainly to stimulate algal growth, which gave rise to the same changes as were noticed in the . first experi-ment. The salinity of the water in the farm rose 1 According to Dr. F. Thivy, Algologist. there are two dominant species, one a blue,green alga belonging to the genus -Anabaellopsis and the othtr a species of diatom of the genus Chaetoceros. I ~ to 33.06% in the fl.rst week of April. As in the previous experiment most of the prawns used to . swim at the surface in the morning during the period, but kept to the bottom after allowing some water to pass in occasionally. They were apparent-ly quite healthy as long as the experiment lasted and hardly any mortality occurred. Fishing was done on 8-5-52 and the following day, but some prawns, mostly smal1, were still left behind. T he total quantity fished was 767 lbs. In addition, a few pearl spotsJ catfish and mullets were also caught. On one day one of the bunds was slightly breached and a few pra\'ms may have escaped before the breach was closed. Making an allowance for this, it would not be wrong t9 assume that about 800 Ibs could I) have been fished, i.e about 400 Ibs per acre. During the period November to May, at least two and probably three crops of prawns could be raised. The annual av~rage yield per acre could'il therefore, be estimated at approximately 800 to 1,200 lbs. As such land is not usually used for rice cultivation and as prav·;ns in the surrounding canals had ,become very scarce after the monsoon started, the farm was stocked with some young ------......- ... --mullets and chanos in the last week of May. No-thing was done to influence their growth and they were fished on the 17th and 19th, October, 1952. The catch consisted of:~ Mullets Chanos Pearlspots Other fish 79 527 26 73 lbs. .. .. .. The total weight of the catch is thus 705 lbs and the net yield was about 350 lbs. per acre. Though the number of mullets originally stocked was more than the number of ehanos, the number actu-ally caught was remarkably few. T he experiment would thus seem to show that farms developed in such coastal tracts with facilities for taking in '\vaterJ If,y tidal action from backwaters and canals could e expected to yield benveen 1,000 and 1,500 Ib~ of valuable food per acre annually. My thanks are due to Dr. N. K. Panikkar, Chief Research Officer of the Central l\1arine Fisheries Research Station, for his helpful suggestions in the planning of the work and in the preparation of the paper. ---- - --

On the paddy field prawn fishery of Travancore-Cochin and an experiment in prawn culture

http://eprints.cmfri.org.in/7214/1/218-PROCEEDING_INDO_PACIFIC_FISHERIES_COUNCIL_1954.pdf

On the paddy field prawn fishery of Travancore-Cochin and an experiment in prawn culture

Abstract

Similar works

Full text

Available Versions

CMFRI Digital Repository