The two primary divisions of the oceans are (1) the benthic and (2) the pelagic, the former referring to the

ocean floor which supports the demersal resources and the latter, the entire column of water , accomodating the

pelagic resources. The pelagic region is a part of the marine biocycle and geographically, it is divisible into

Atlantic and Indo-Pacific. Ecologically, the pelagic realm can b e bifurcated as neritic (inshore) and oceanic (opens

e a) provinces d epending on the depth to which light penetrates and to the extent and depth of the continental slop

Antony Raja, B T

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~ straining gill apparatus for pro-.., a. emen~ of fo od which is largely planktonic in character. There is not much of selective feeding amongst the s maller pelagic fishes , the food varia-tions often depending on the variations in the avai lability of p lanktom--. The larger pelagic fishes may be se lective feeders and their movements are o ften determined by the movements of the ir feed. As compared to demersal spec ies, the pelagic fishes have a sho rter span of life, The spawning season is one of variable .natu re, e ither prolonged or restricted, Similarly, the spawning habits may a lso vary between cGmplete and fractional shedding of sexual pro-ducts . The success of spawning is largely governed by external factors like su itable temperature, salinity, oxy-gen, dissolved chemicals , turbidity , cur-rents, availability of food etc. The eggs of almost all the pelagic fishes are pelagic ( freely floating) - the notable exception being those of herring - and hence greater numbers are produced to overcome the losses inherent with this group. PRESENT HARVEST From the latest figures available (F AO Yearbook of Fishery Statistics , 1970), it is seen that the pelagic fishes constitute about 53% of the total marine fish landings of the world. Area-wise, the Pacific ocean contributes about 23 million , the Atlantic , 9 million and the Indian Ocean , 1.5 million tonnes. In the harvest from the Indian Ocean, our coast accounts for 40% . Whichever be the area, among the pelagic fishes, the c1upeoids, comprising the popularly known anchovies, herrings, sardines, sprats and menhaden occupy the top 80 position with as much as two-thirds of the total p e lagic fish harvest of ·the world oceans. No doubt, much of this importan'ce credited ' to the €lupeoid s and to the Pacific Ocean in the pelagic fish p roduction largely goes to the Peruvian anc hov y, which, as the large st single-species fis hery of the world, ac-counts for near ly 60% of eithe r the group or the ocea nic area it belongs to. From the Indian seaboard , about 600,000 to nnes , forming two-thirds of our total catch a re raised from the pelagic commu nity, o f which, all the three major fisheries, n.mely , oil-sardine, mackerel and Bombay duck , enrich the marine living resources wealth of the west coas t. Group-wise, in tune with the general feature of the world catch , the c lupeoids fo rm the bulk with 56% (332,000 tonnes ). What importance the Peruvian anchovy is to the Pacific Ocean can be rough ly likened to the oil-sardine of the Indian Ocean, where it contributes 15% of the exploited pelagic resources. Practically the entire harvest of 211,000 tonnes in India, forming 35% of the total pelagic fish production, comes from the southwest coast of India. Its sister species, the lesser sardines, constitute 8% , followed by its cousins, the anchovies, with 6% and other clupeoids with 7%. Among the scom-broids . that realise 96,000 tonnes (16%), the mackerel accounts for 79,000 tonnes (13%) and the seer fishes and tunas, the rest. The Bombay duck fishery with 76,000 tonnes and 13% comes third. The ribbon fishes (6%) , the carangids (4 %) and other miscellaneous pelagic fishes (6%5 complete the tally. The averal'le catch figures (1963-72) of the important categories of pelagic fishes, state-wise , are given in Table I. Seafood Export Journal , Table 1. Average annual pelagic fish production (1963-72) f rol1l the Indian coast, in thoustJlUi" (onnes ( The total of ver tical columns of some categories of ./ish do ~Uw u·.etl:f correspond 10 the tOTal of the west coast because of incidence of less than olle thousand tonlle ill some states which Ofe covered up under 'Others' i" the table) . c o .~ " West Bengal & Orissa Andhra Tamil Nadu & Pondicherr-y Kerala Karnataka Goa Maharastra Gujarat East Coast West Coast Total Percentage ./ 2 13 16 .!1§. 10 ~ . 2 1 2 31 211 15 211 46 35 8 ~ v .;: o "" u c < 1 7 13 10 2.1 13 34 6 2 7 10 2 I 10 9 19 22 41 7 Between the two coasts , the west contribute s 78% of the a ll· India pelagic fish yield (470,000 tonnes), of which 59% is accou nted for by the oil·sardine , mackerel and Bombay duck. In the total fi sh harvest of the west coast, the pelagic fishes constitute 70%. Only off Maha-rashtra. the percentage of pelagic fishes is low at 40, but it fo rms 74 , 94, r- 84 and 74 in the respective total fish catches of Gujarat, Goa , Karnatataka and Kerala . In the total oil-sard ine pro-duction , Kerala accounts for 84% and Karnataka, 15%. In the mackerel harvest , Kerala takes a share of 42%, Karnataka 30%, Goa 20% and Maharastra, the remainder. In the average Bombay duck yield, Gujarat sho ws 64% and Maharastra, the balance. January. J974 2 3 31 22 15 6 5 74 79 13 1 27 48 I 75 76 13 c o .0 .0 02 1 7 10 8 6 18 15 33 5 3 9 6 5 I 12 12 24 4 3 6 14 15 7 8 4 2 23 33 56 9 10 45 75 ~ ggQ 65 -24 §l EO 130 470 600 2 7 13 43 I I 4 10 lO 22 78 100 100 On the' east coast, the yiela of pelagic fishes amounts to ' 130,000 tonnes, for m-ing 22% of the total pelagic fish catch of the country. Un like the west coast, the pelagic fishes fo rm about one-half (53%) of the east coast 's total fish production. The Tamil Nadu coast (including Pondi-cherry) contributes the best part of the pelagic yield with 58%, followea by Andhra (34%) and West Bengal and Orissa (9%). There is no d ominant single· species fishery here , as s e en on the wesl S,Qast. The clupeoids realise 55% of the east coast's pelagic fis h yield, in which the lesser sardines con-stitute the most important category with 24%. The next in order are, anchovies (l6%), ribbon fishes (l4%~nd caran-gids (8%). 81 , In the all-India catch, the largest landings ~f carangids come from the TamiiNadu coast while the next im-portant areas are Kerala and Maharastra. In the group of 'other clupeoids ' (fishes other than the sardines and anchovies), the important ones are the ....... olf herring (Chirocentrus spp .) along Anqhra and Tamil Nad u and the shad (Hilsa spp .) off Tamil Nadu and Cujarat coasts . They represent roughly one-third of the re-spective state 's tota l of other clupeoids. There is a regular sequence in the patte rn of distribution of these pe lagic fi she s around the Indian coast. The Bombay duck dominates along the Cujarat and Maharastra coasts but is re -placed by the mackerel and the oil-sardine on the southwest coast along Coa to Kerala . Witb the dec line in the strength of these two stocks around the peninsular curve, the lesser sar-dines and 10 some extent the anchovies and the r ibb on fishes form the bulk in that reg ion . The quantum of the se fishes get p rogress ively reduced as we proceed no rth along the east coast, culminating, in what can be termed as the poorest crop of pelagic fishes, from the O rissa-West Bengal waters . The commercial s eason for a ll the important pelagic fishes on both the coasts is the same , i. e , October to March , with peak catches during October to December on the west coast and January to March on the east coast. This may be attributable to a large extent to the favourable ecological con-ditions that result after upwelling in the respective post-monsoon periods . 82 POTENTIAL HARVEST Attempts to estimate, in a rough way, the potential harvest from the seas have b een approached in three ways: I) By e xtrapolating the trend line of annual production of past years, which would help only in forecasting the possible y ie ld for a fe w years ahead , 2) by .,... considering our knowledge of the un-used harve stable resources and }) by ~. calculations based on the food wej- and transfer of energy through successive trophic levels . Largely , it is the third way that is very often employed ; the other two have limitations either in terms of time . or for want of adequate know-ledqe of untapped resources. The third method invo lves calculation of ~rvest­able CroD from the net primary produc-tion which is 60% of the qross amount in terms of carbon. As a first approxima-tion , it is as sumed that at each stage beginning with the herbivores, carbon is transferred At an ecological efficiency rate of 10% of the previous level. For example, if 10.000 kg . of carbon is avail-able as net primarv production, 1000 kg. is obtained at the firs t stage, 100 kg. at the next , 10 kq . at the third and I kg. at the fourth . As these are values of dry carbon , each o f these values has to be multiplied bv a factor, 10, to ge t the wet weight of the potential resource at each stage. A gross estimate of ex-ploitable fish yield in a coastal area has been placed at 4% of the net carbon production , which means that the calcu-lation is traceable to a stage roughly midway between the second and the third trophic levels. Based on the above consideration _~. and based on the values of organi<;: pro-ductivity given by Jones and Banerji (1973) , the state-wise potential fish yield is given in Table II along with the Seafood Export Journal ., .". ); Table II. Region-lVise potential fish y ield (as 4% of net organic production of carbon). in thousand IOnizes . Region up to 50 to Poten- Pre-50 m 200 m tial sent depth depth yield yield (1968· 72) West Bengal 105 54 160 I 25 Orissa 18 1 27 208 Andhra 176 61 237 79 Tamil Nadu (east) } 164 & Pondicherry 238 48 286 Tamil Nadu (west) 10 22 32 Kerala ~ j.!. ~ 354 Ka rnataka 75 29 104 93 Goa 27 12 39 27 Maharastra 270 83 353 184 Gujarat 687 36 723 84 East Coast 700 190 890 268 West Coast 1203 233 1436 742 --Total 1903 423 2326 1010 average yield of the last 5 years. No d oubt, it is not correct to do such state-wise dissection for the simple fact that fis~s know no state boundaries and m igra te dver wide areas , especia lly the pelagic ones, utilising the food of their entire migratory route . However , two important features stand out s trikingly from the tabfe. One is that , at the respec-tive northernmost areas of the two coasts, the potential yield is fantastically higher than the present yield. The other is, in the area between ~ncLXeJil la (considered as a contlgggtis !i'SlieTy zone of similar character), the present harvest is twice of the potential yield of the nearshore belt up to 50 m depth ! Th.e mosf important reaso n for this anomalous situation is in considering the yield at a stage in between the second January, 197-1 and third trophic levels, wherEas the .. most abundant pelagic fi sh , \!JE! pil- _ sardine , belongs mainly to the first ttophic level and the next important, the mackerel , to the second . Hence, if we consider the transfer of energy at a stage lo wer down , in between the first and the second, the potential fish biomass would b e ten times than what is shown in the table fo r that area. In addition to the difficulty of assign-ing a prope r trophic level to many o rga-nisms (i n fac t, a given organism may operate a t more than one tr ophic level) , the difference of assump tio n over the percentage ecological efficiency a t which carbon is transferred from one trophic leve l to the next and the diver-gence of opinion on the harvestable portion of the total potential biomass under the existing fish capture methods , can result in differences in the estitnates arrived by differe nt authors . Schaefer (1965) is of the vie w that the effective ecological efficiency ma y be higher than 10% and that 15% would be a reasonable guess although 20% is a possibility . An attempt is made herein to project the availaBle fish potential (pelagic and demersal combined) of the Indian coast, based on our present knowledge of the tr ophie level the important fishes belong to, and their percentage contribution in the current exploited state. The Indian coast, for this purpose, is considered as broadly divisible into three regions , namely , I) the northwest (Gujarat and Maharashtra), 2) the southwest and 3) the east . The basic assumptions for the calG,ulations are: For region (1),33% of potential biomass to come from trophic level II and 67% fr om level III, for region (2), 40% fr om leve l I, 50% from II and 10% from III and fo r region (3), 6% from level I, . 50% from II and 44% from III. 81 The estimated figures of 6 to 10 million t01'l nes up to 50 m depth and an additional 2 million in the region beyond would appear as a set of unbelievable numbers in the context of the present average yield of just over one million tonne. Of course, only . a part of this vast potential could be brought ashore because oi several limiting factors, like diffused distribution of fish that cannot form a basis for economically viable e xploitation and loss due to predation by other inhabitants of the sea . The q uestion, then, would be at what level could our potential be harvested? It would appear from Table HI that. at m depth around the Indian coast. a much higher percentage would be justified. especially because the present yield itself is more than the above 'per centages on the west coast. There is already an. opinion that in intensively e xploited areas. man can take 50% of the potential and yet maintain the resource (Graham and Edwards. 1962). Hence, if the entire belt up to 50 m depth around both the coasts of India could be exploited as intensively as it is done in the present traditional grounds , a modest consider-ation of 40% of the potential at 10% ecologica l e fficiency and of 20% at 15% efficiency level wou ld not be unrealistic, ./ . Table III. Potential hiomass of fish, ill million ton lies, compared IO the current y ield of /.0 / mil/ion tonnes (average of 1968-72). up to 50 m depth 50 10 200 m depth Region Potential allO% Current efficiency yield (%) Gujarat to Maharastra 0 .96 28 Goa to west Tamil Nadu 2.81 18 West Coast 3.77 20 East Coast 2.00 12 Total 5 .77 18 present, comp aratively greater per-centage of available resources is exploited on the west coast than on the east and that even on the west coast, the northern areas are taking more ad-v antage of the resources level than the south. This may probably be a reflection of the differences in the extent of the areas actively fished. Schaefer (1965) visualised a general harvestable yie ld of 19% of the potential biomass at 10% efficiency and 8% at 15% e fficie ncy levels. For shallower regions up to 50 84 Potential Potential Potential at 15% Current all0% at 15 % efficiency yield (%l efficiency efficiency 2.16 12 0. 12 0.27 4.37 11 1.29 1.97 6.53 II 2.09 1.56 3.80 7 0.63 1.20 10.33 10 2.72 1.76 maybe rather conservative . Even then, the harvestable potential would be about 2.3 million and 2.1 million tonnes at the respective e fficiency levels with an average of 2.2 million tonnes . If we add to this the possible harvest from the 50-200 m depth zone. anticipating only half of the earlier exploitable p ercentages at the respective ecological efficiencies , the resultant figure would b e 2.6 million tonnes. The present estimate, thus, is rathe r very close to that of Prasad et ai. (1970) , Jones and &afood Export Journal Banerji (1973) and Nair et al. (1973) who h.ve placed the pote n tial yield as 2.3 or 2.4 million tonnes. Within 50 m area, where our im-mediate concern is, out of 2.2 million tonnes, the share of the west and east coasts wo uld be 1.4 and 0.8 million tonnes respectively. Apportioning the amo unt to the current ratio between the p elag ic and demersal resources, it a p pears that about 1,000,000 tonne from the west coast and 400.000 tonnes from the east coast could come from the pelagic s tocks as against the average current landings of 470,000 tonnes from the wes t and 130,000 tonnes from the east coast. In short, in the light of present explo ita tion as confined to about one-half o r even less of the e nvisaged area , about twice the present catch is the potential harvest of pe lag ic resources from the west and three times from th e eas t coast. Bane r ji (1 973) has estimated the optimum yield from the pelagic resour-ces of the pres,ent fish ing area as 620,000 tonne s which is about the annual a verage of the last 10 ye ars and which has been s light ly e xceeded in the average of last 5 years. Added to this, the fact that, although , he average ann ual rate of increase in pelagic fish production in Indi a d ur ing the last 20 years (1952-72) is 6.3% , it is almost zero during the last 5 years, would show that the present belt of exploitation has yielded the max imum benefit to our efforts . A fishery which is confined wi thin c ertain traditio-nallimits would be incapable of yielding more than a certain amount of fish however intense the e ffort is. As January, 1974 Schaefer (1965) has rightly observed, whateve r ecological efficiency lactor is operative and whatever be the e s timate made, an obvious way of increasing the harvest is by fishing on the stocks at lower trophic levels, that is , at stages I and II. To this level belong our ma jor _ pelagic fisheries of sardines and mackerel. Hence, we have to shoot our nets yonder still and the mod est expansion up to 50 m de pth should be largely orien ted tcwards rapid develop-ment of purse seine and pelagic trawl fisheries. A cknOldedgemcnl The author expresses his than ks to Dr. K. V . Sekha ra n for going through the manuscript and sugge sting improve-ments and to Mr. P. V. Ramachandran Nair fo r the benefit of discussion. REFERKNCES Banerji. S. K. 1973 . Proc. Symp. LMnr reJOll rcu 01 th~ Sf!QS around India, SpJ. PUb. CMFRI. 114-1 35. Graham, H. W. and R. L. Edwards. 1962. Fish ;1I nulrit;on. Fishing News (Books) Ltd., London, 3- 8. Jones, S. and S. K. Bancrji . 1973. Proc. Symp. U.-;nl "sources of th . seas around India . SpJ. Pub. CMFRI. 1-17. Nair, P. V. R. t S. Samuel, K. J. Joseph and V. K. Balachandran. 1973. I bid . 184-198. Prasad, R. R., S. K. Banerji and P. V. R . Nair. 1970. Indian J. ~n;m. Sci . 40 (I), 73-98. Schaefer, M. B. 1965. Trans. Am-..Fish. Soc .. 94 (2), 123-128. • 115 

Our pelagic fishery resources Present and potential harvest

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Our pelagic fishery resources Present and potential harvest

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