Fisheries with Plankton and Certain Oceanographical Factors*

THE CO-RELATION OF THE WEST COAST (MALABAR & SOUTH KANARA) FISHERIES WITH PLANKTON AND CERTAIN OCEANOGRAPHICAL FACTORS*

BY K. CHIDAMBARAM AND M. DEVIDAS MENON

Received September 6, 1945 (Communicated by Prof. S. G. Manavala Ramanujam, v.A.sc.)

CONTENTS PAGES

o INTRODUCTION .... O .. 355 2. PHYSICAL FEATURES OF THE COAST .. 356

3. SURFACE TBMPERATURE .. Q O .. 357

4. SPECIHC GRAVITY .. 9 ~ .. 358

5. PLANKTON .. Q 9 .. 360 6. FISHERmS ...... 362 7. DISCUSSION .. .. 363

8. SUMMARY .- 6 9 t 9 .. 366 9. BIBLIOGRAPHY .. .~ 366

1. INTRODUCTION IT is well known that fishes depend either directly or indirectly upon the nature and availabilty of planktonic organisms in the seas. Animal life in the sea subsists on macro and micro plankton, consisting of small animal- cules and minute plant organisms; the latter depend for their food on various chemical substances such as phosphates, nitrates, etc. One can, therefore, partly attribute the fluctuations of the Fisheries to the hydrographical variations such as the fluctuations of the physical and chemical factors and the consequential changes in the productivity of plankton. In addition to hydrography, ecology or the study of living things in relation to their environ- ment is equally important in fisheries research. In this paper, an attempt is made to co-relate the bydrographical factors, ecological findings and fisl~e~ landings at Calicut Fishing Centre with one another 9 The scope of the study is therefore necessarily narrow but nevertheless it, perbaps, furnishes key to similar problems in other fishing centres all over the West Coast. The present investigation covers a period of 5 years from 1938 to 1942.

* With the kind permission of the Director of Industries and Commerce, Madras 9

B2 355 356 K. Chidambaram and M. Devidas Menon

2. PHYSICAL FEATURES OF THE COAST There are two rivers, one the Korapuzha emptying into the sea north of Calicut and the other, the Beypore, south of Calicut (Lat. 11-18 N. and Lovg. 73-43 E.). Calicut is taken as an indicator for the whole of the West Coast of Madras Presidency and the important physical features of this area are :-- (1) The narrow belt of low land between the s.-a and the Western Ghats and (2) The shortness of the 'rivers that run into the sea. ~0:

:)5

30 Ji -- 1938 .... 1939 -x-x- 1940 25 ...... 1941 ...... 1942

10 l

0 Jan Feb. Mar.Apr. May Jun Jul. Aug. Sep. Oct.N0v. Dec Ralnf',dl Co.RelaHon o)e West Coast Fisheries with Plankton 357 During the rainy season of the S.W. Monsoon, these rivers discharge into the sea large quantities of silt and organic matter, both in solution and in suspension. The seasonal climatic changes consist of a wet season from June to September, a short hot and dry transition period in September and October, the cool dry N.E. Monsoon period from November to February and the hot dry season characterised by calms and light breeze from March to May. The rainfall is very heavy during June and July especially on the western slopes of the Ghats from where large volumes of rainwater rush down through the short rivers, carrying plenty of nutrient salts and organic debris into the sea. The total amounts of rainfall during the years 1938, 1939, 1940, 1941 and 1942 were 117.7455, 98-382, 116.9, 118.09, and 111.8 inches respectively, the maximum being in the months of May, June and July. Again in the months of October and November there is a second peak of rainfall which though not so heavy as the other is still bad enough to create unsettled weather conditions to restrict fishing (vide graph).

TABLE I Amount of rainfall at West-Hill, Calicut, 1938-1942

I Year Jan. I Feb. March April May June July Aug. I Sept. Oct. Nov. Dec.

1938 908 I9.9815 5.13 30.829 !41.245 16.267 6.54 7.233 .44

1939 QO ,. 3.21 9112 28.14 35.68 9.82 3.35 10 9624 7.23 o. 1940 !i/:: 6~ .15 8.83 22.47 47.6 20.12 1.73 I1.12 4.88 .~ 1941 :~9 Q 9 2.09 20.34 38.14 14-621 16.21 6.65 11.32 8.43 1949 Q 9 6.27 37.44 34.11 110.71 2.91 12.34 2.87 3:~s l I :i4 3.73 I

3. SURFACE TEMPERATURE The surface temperature of sea-water has been found to reach the maximum of about 31 ~ C. in March and April though occasionally in the month of May also, if the outbreak of monsoon is a little delayed. In June, July, August and September, it is low falling down to 24.8 ~ C. There is another sharp rise in October from whence the temperature is gradually in the increase (vide Table II). The lowering of the temperature during the months of June, July and August is due to the rains that break with the S.W. Monsoon and to the consequent reduction in the number of hours of sunshine. 358 K. Chidambaram and M. Devidas Menon

321

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30 29 4,i'!...... il'}! 28

24 Jan Feb. 1~lar Apr. May 3un. Jul AOg.,SepOct Nov Dec. Surface Temperature TABLE II Surface Temperature of sea-water at West-Hill 1938-42

Year f Jan. Feb. March April IMay [June [ July Aug. Sept. I Oct. I Nov. Dec.

i 938 ../27.4527.9529.75 29.7529.8 27.3525.4 25.55 26"7 127.6 29"5 27.5 939 ..[27.35 27"9 28.7 29.95 30.129. 126.7 26.25 26.55 25.85 ~28-5 29.5 27.7 940 ..127.05 28.10 128.45 30.5 28.15 25.75 24.85 26.3 t29.25129.65 28.9 941 ..}27.90..[28.45 128'65 j30.25 31.20 29.552727"30.4529.55 26.55 26.2 29.90 28.813 942 29"10 i30.25 30.5 I 26.2 25.35 25.6526"75 I: 02880 28.2(

4. SPECI~CGRAVITY The specific gravity of the inshore water is the lowest in the month of July during the quinquennium under consideration. The mean specific gravity of the sea-water in different months of the five years is given in the table annexed. Taking only the month of July when the lowest specific Co-Relation of West Coast Fisheries with Plankton 359 gravity occurs along with the heaviest rainfall in 1938 it was 1019.0 falling downwards to 1018.0 in 1939 and again to 1017.5 in 1940. In 1941 it

1027

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1017

t015 Jall. Feb. Mar, Apr. May Jt{n. Jul. At'~~ Sop 0el, Nov, "Dee Specific Gravity rose to 1018.0 and in 1942 it went down to 1016.1. From August onwards there is a gradual increase in specific gravity till May. There is a slight fall in the specific gravity in the month of November or December on account of the rain-fall caused by the N. E. Monsoon. TABLE III Specific Gravity of the sea-water at West-Hill 1938-42 I Year Jan. Feb. March April May June July Aug. Sept. , Oct. Nov. [ Dec. t t938 .. 1022.0 1022.0'1021.8 1022.1311022.0 !1022-0 1019.0 1020.0 1021.0 1022.0 1022.3 1022.~ 1939 .. 1023.0 1023.0,1023-0 1021 .s 1023.0 i 1023.0 1018.0 1021-0 1023.0 1022.0 [021.0 1023.q 1940 1020-9 lO22.OtlO23.s 1023 .C 1023-7i 1023.3 1017.5 1020-0 1023.5 1022.5 1022-0 1022.( t941 1022.5 1023.011025-6 1023.4 1023.5 1022.0 1018.0 1021-0 1022.5 1022.0 1022.5 1023.1 |942 1022.3 1024.2 1024.1 1024.13 1024-3 1023.8 1016.1 1021.2 1024.2 1024.0 1024.0 1023.(

Theoretically speaking, the rise in the specific gravity of the sea, from August to November, may be attributed to the dissolution of the mineral and organic substances emptied by rivers. From August to May there is 360 K. Chidambaram and M. Devidas Menon considerable sunshine with the result that the temperature rises pari passu with the specific gravity. It does not therefore seem unreasonable to con- dude that evaporation on account of temperature is also responsible for the parallel rise in specific gravity. 5. I~,~KTON After qualitative analysis in the laboratory the total quantity of plankton is estimated in c.c. with the help of a sedimenteer and stempel flask. For

' 180

' 160

140

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~176 40 1938 ~S "~ o 1No :: 20 P.}4]

0 ,Jan Feb Mar Apr. May .lun Jul Aug. Sel~.Oct. Nov. Dee'. Plankton facilitating the present study the average quantity of each month for the 5 years has been tabulated. As plankton varies from sea to sea, a short account of what occurs in the Arabian Sea, we venture to say may not be out of place. After an examination of a few samples of the plankton, one Co.Relation of West Coast Fisheries with Plankton 361

is struck by the variety and number of the phytoplanktonic organisms such as Coscinodiscus, Biddulphia, Fragillaria, Thallassiothrix, Pleurosignut, Nitzschfa, Rhizosolenia, Choetoceras, etc. The long ribbons of Fragillaria and Thallassiothrix are really striking objects to say nothing of the Choeto- ceras chains. Occasionally the student will be bewildered by a pure culture of that inedible Cystoflagellate, Noctiluca, which is suspected to be responsible sometimes for the local scarcity of the oil Sardines and other fishes. Amongst the zoo-plankton, copepods, arrow worms, leucifer, larval crusta- ceans, fish eggs and larva: and ctenophores are organisms of common occurrence. In this paper it is proposed to discuss the relationship of the variation of the total quantity of plankton to the fluctuation of the fisheries in general. The inter-relationships of the different varieties of the organisms in the plankton amongst themselves or their co-relation to the fisheries are so complex that they can form subjects for separate studies. It is regrettable that during the months of S.W. Monsoon in June, July and August plankton collections are not possible owing to the stormy weather conditions. The volumetric studies are therefore limited to almost nine months in the year.* The volume of plankton is at its maximum in the month of September. In October and November there is a fall with the slight increase in December followed by a subsequent poverty of plankton in the month of January. In the months of February, March, April and May the productbcity of plankton is more or less steady with a minor fluctuation occasionally. The richness of plankton in August and September is perhaps due to the combined influence of fairly long hours of sunshine. low temperature and the intermixing of the different strata of water contain- ing rich nutrient salts brought down by the floods. The comparatively high productivity during the hot dry season from February to May is caused by the intense sunlight encouraging greater photosynthetic activity and uni- form vertical mixing up of the different layers of waters of the sea.

TABLE IV Average quantity of Plankton in c.c. at West Hill, 1938-42

Vear Jan. Feb. MarchlAprill May June July Aug. Sept. Oct. Nov. Dec.

1938 m I 32.25 40.5 56.77 53.0 86.44 .~ 53.0 36.14 53.5 78.3: 58.66 1939 43.82 37.5 46.32143.22 ]41 "3 80.2 88.4 I 38.08 21.0 45 "0 1940 26.75 49-0 43.33143.07/46.15 3~:o 22.5 80.5 ~ 27.22 28.33 1941 26.25 37.0 40.0 157.3 1~2.0 77.5 ~ 77.0 4~:o 62.45 1942 70.16 63.0 79.17/18.7 169.0 9~'4 9~:1 29.9 I 41.2 24.0 19.73

* This explains the gap in the graph. 362 K. Chidambaram and M. Devidas Menon

6. FISHERIES The fishing season in the locality extends from August of one year to February of the succeeding year. The average landings amount to 1,50,000 400~)0

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32000

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= , . , , t ~ . : = Jan Feb. Mai Apr May Jul, Ju} A,,~, ,q<,~ clot Nov Dec Fisherie, maunds. The fishery reaches its peak in the months of August, September and October and then there is a gradual fall till June when due to the onset of the monsoon fishing is suspended. In July the landings are fairly good averaging about 9,000 rods. Mackerel, Oil sardine, Horse mackerel, Sharks, Soles and Ribbon fish contribute mainly to the catches during the months from September to March, In April and May fishing is restricted mainly Co-Relation o/ Wesl Coast PTsher&s w~lh Pla'nkto~z 363 to Prawns, small Soles and occasionally heavy landings of Cat fishes. The minor peak observed in the month of May 1940 is due to the landings of 15,130 rods. of Cat fish which constituted 82% of the catches in that month; similar huge landings of cat fish amounting to 7,175 mds. (70%), 18,185 rods. (98%) and 11,400 rods. (80%) are responsible for the peak in the months of March, April and May in 1938. Silver bellies and Ribbon fish are landed in huge quantities in the months of July and August whereas the fishery of Chamban (Caranx crumenophthalmus) extends from August to October. TABLE V Landings offish in maunds at Calicut, 1938--42

Year Jan. Feb. IMarch I April May June July Aug. Sept. Oct. Nov. Dec

1938 16310 9737 10835 18450- 14435 4650 5330 17810 11725 18265 9370 10590 1939 5110 5210 3130 5715 5970 3040 7380 38380 1091e 38635 14789 27320 1940 12630 3036 2933 3390 18380 3576 8970 12250 25318 12174 11967 26390 1941 21345 6375 6600 4479 3040 4805 13195 13090 23685 16470 9290 8790 1942 18890 1975 3415 1485 4560 3390 9105 33150 35280 24530 22504 2034

7. DISCUSSION Changes in temperature, rates of evaporation during the different seasons and the rainfall in different months give rise to regular variations in the conditions under which marine fishes live; in Indian waters this variation has been reported to have "a period of approximately 6 months the temperature and salinity of the upper layers of the waters having two maxima in May and September respectively. Again the rotation of the earth and the influence of the winds of the monsoon season give rise to internal 'seiches' that produce oscillating changes in salinity and temperature of the water at definite levels" (R. B. S. Sewell, 1925). In the sea opposite West-Hill the surface temperature of sea-water exhibits a bimodal curve with a major peak in the month of April and a minor peak in the month of November. During the S.W. Monsoon the temperature falls down to as low as 24.85 ~ C. (in August 1940). The second fall to about 28 ~ C. is in the months of December and January when the effect of N.E. Monsoon is felt slightly on the West Coast. The rise in temperature in the month of April is mainly due to the effect of the sun's rays striking vertically from above and increased biological reactions of the developing planktonic organisms even though there may be a little cooling down owing to the increased evaporation at that time. Consequent on the increase in temperature, the specific gravity is high at the two different seasons and the temperature also is high. The fall in 364 K. Chidambaram and M. Devidas Menon

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2 Co-Relation of I4Test Coast Fiskeries with Plankton 365 the specific gravity in July is caused by the influx of fresh water from the rivers and from the rains. The relationship between surface temperature and specific gravity is direct. But the rains during the monsoons, when sometimes the average rainfall is about 40" in June, effect the marked changes in specific gravity and surface temperature and again the showers of the N.E. Monsoons cause the second fall in temperature and specific gravity in the month of November. As indicated above the planktonic organisms are very rich in the months of July, August and September, when the surface temperature and specific gravity are low. The rains which commence late in May or early in June wash into the sea plenty of nutrient salts for enriching "the pasture of the sea". The statement, that "the supplies of nutrients brought up from below by the S.W. Monsoon support a large but short-lived outburst of phytoplankton which develops in the increasingly stable conditions following the change of wind and subsequently provides food for a rich zoo-plankton" made by Thompson and Gilson in connection with the South-Eastern section of the Arabian Coast holds equally good in this area. During the later period of the monsoon, i.e., in August and September, the rise in plankton productivity is contributed by the intermingling of the various salts in the upper layers of the sea and the prevailing calm and settled conditions of weather whereas in the earlier period the development of planktonic organisms is arrested partly by the lack of sunshine and partly by the unstable conditions of the different strata of water. There is a gradual fall in the productivity of plankton till November when the supplies of nutrient salts perhaps become exhausted. In December there is a slight rise in the productivity due to lowering in surface temperature, the renewal of the supply of nutrient salts owing to the occasional outbursts of rain caused by the N.E. Monsoon and the upwelling of the waters. In the months of February, March, April and May there is a steady appearance of plankton in the surface waters due to the reappearance of calm weather, stability in surface waters and a steady though not rich supply of nutrient salt from the Bay of Bengal brought by the change in the current system during that period. The landings of fish is directly proportional to the quantity of plankton thus indicating the direct relationship of plankton as food to fishes. The fishery in general coincides with the major peak in the plankton productivity. The comparatively low catches in the months of March, April and May are due to the increase in temperature, in the inshore waters which result in a temporary migration of fish to the cooler off-shore regions. 366 K. Chidambaram and M. Devidas Menon

8. SUMMARY 1. There are two peaks of rainfall, the major one in July to August due to S.W. Monsoon and the minor one in October effected by N.E. Monsoon. 2. The surface temperature is high in April and low in August followed by a gradual increase up till November when again there is a slight fall. 3. The changes in specific gravity are parallel to the changes in surface temperature. 4. The maximum productivity of plankton takes place in the months of July, August and September followed by a rise in December due to the showers of the N.E. Monsoon and again a period of steady production. 5. The landings of fish are directly proportional to the quantity of plankton produced in the different months of the year. The fishery has invariably been found to be good after heavy rains when they bring plenty of' indispensable food substances ', thus enriching the "pasture of the sea" and increasing the food of fishes.

9. BmLioGg.~m'

1. .. Administration Reports of the Madras Fisheries for the years 1937-38, 1938-39, 1939-40, 1940--41, 1941--42 and 1942-43. 2. Bigelow, B. Henry "Studies of the waters on the continental shelf; Cape Cod to Chesapeake Bay, I. Cycle of Temperature," Papers in Physical Oceonography and Meteorology, published by Massachussets Institute of Technology and Woodshole Oceanographic Institution, 1933, 2 and 4. 3. Calvin, O. Easterly .. Reactions of Various Flankton Animals with J~eference to Their Diurnal Migrations, Summary and Interpretation of the Hydrographic observations made by the Scripps Institu- tion for Biological Research, 1919, 15, No. 1. 4. Gardiner, J. Stanley .. The Fauna and Geography oJ the Maldive and Laccadive Archipelagoes, 1905, 2, Supplement I ; 1906, 2, Supplement II ; 1904, 2, Part III ; 1905, 2, Part IV. 5. Hornell, J., and Ramswami "Notes on the plankton of Malabar Coast," Madras Fisheries Naidu, M. Department Report, No. 5, 1923. 6. James Paton .. "Report on the Meteorological observationsmJohn Murra) Expedition, 1933-34," Scientific Reports, 2~ No. 1. 7. Johnstone .. Introduction to Oceanography. 8. -, Scott and Chadwick Marine Plankton. 9. Lucas, C.E. .. "Ecological investigations with the continuous plankton recorder. The Phytoplankton in the Southern North Sea, 1932-37," Hull Bulletins of Marine Ecology, March 1940 1, No. 3, Co.Relation of t4,"esl Coast Fisheries wttk Plankton 367

10. Marshall, S. M., and On,, "Relation of the plankton to some chemical and physical A.P. factors of the Clyde Sea Area," Journal of the Marine Biological Association, 1927, 14, No. 4. 1I. .. Meteorological Registers of the West-Hill Biological Station for the Years 1937-;38, 1938-39, 1939-40, 1940-41, 1941-42 and 1942-43. 12. McEwen, F. George "Summary and Interpretation of the Hydrographic Observa- tions made by the Scripps Institution for Biological Research, 1908-15," University of California Publications in Zoology, 1916, 15, No. 3. 13. 9 Report on the Preliminary Expedition for the Exploration of the Red Sea in the R.R.S. Mabahith, Publications of the Marine Biological Stations, Ghardaqua (Red Sea), Decem- ber 1934 to February 1935. I4. Sankara Menon, K, 9 "A preliminary account of Madras Plankton," Rec. Ind. Mus., 1931, 33, Part IV. 15. Sewell, R. B. S. "Temperature and salinity of the deeper waters of Bay of Bengal and Andaman Sea," Memoires of Asiatic Society oJ Bengal--Geographic and Oceanographic Research in Indian Waters, 1932, Part VI. 16. .. "Oceanographic Research in Indian Waters," ibid., 1925-29, 9, Nos. 1-5. 17. .. Statistical Registers of Madras Fisheries Department for the Years 1937-38, 1938-39, 1939-40, 1940-41, 1941-42 and 1942-43. 18. Thompson, E. F. .. "Chemical and Physical Investigations IntroductionsmJohn Murray Expedition. 1933-34," Scientific Report, 2, No. 2.