OBSERVATIONS ON THE LIFE-HISTORY OF THE INDIAN SHAD, HILSA ILISHA (HAMILTON) I BY S. JONES AND P. M. G. MENON (Central Inland Fisheries Research Station, Barrackpore) Received April 26, 1950 (Communicated by Prof. L. Rama Rau) INTRODUCTION THE life-history of the Indian Shad, Hilsa ilisha (Hamilton), began to receive the attention of fishery workers in India at a comparatively early date. Investigations were first taken up in Madras and soon after in Bengal, where attempts were also made at artificial fertilization so as to liberate the fry into the rivers to supplement the natural stocks as in the case of the Ameri- can Shad, Alosa sapidissima. Wilson 0909) succeeded in artificially fertiliz- ing the eggs of Hilsa and in liberating the hatchlings into the Co]eroon River, South India. Since then, the Madras Fisheries Department have followed his lead and liberated 10 million fry in 1916 (Raj, 1917). Similar attempts, made in Bengal, did not meet with complete success (Southwell and Prashad, 1918). In Madras, however, the collection and hatching of Hilr continued as a routine (Devanesan, 1939) resulting in valuable data being gathered on the probable breeding grounds, z but the actual spawning grounds re- mained elusive as no laid eggs or prolarvm were ever collected from the rivers. Hora (1938) made a significant contribution towards the location of the breeding grounds when he discovered the postlarv~e and young stages of Hilsa in the settling tanks and the filter beds of the Water Works of the Calcutta Corporation at Pulta, about 16 miles north of Calcutta. As the Hooghly water at Pulta was pumped into the Water Works, he inferred that the fish breeds ia the river in the vicinity of Pulta and that the Hooghly as a whole serves as one of the spawning grounds of the fish. As a result of their continued observations Hora and Nair (1940 a) concluded that the fish breeds in the Hooghly in all the months of the year except November to March; and attributed their failure to collect the eggs or the larva~ Published with the permission of the Chief Research Officer, Central Inland Fisheries Research Station, Barrackpore. = Madras Fisheries Department Administration Reports for 1930-31, p. 32 (1932); 1933-34, p. 41 (1934); 1934-35, p. 38 (1936); 1935-36, pp. 37-38 (1937); and 1936-37, p. 34 (1938). B1 101 102 S. Jones and P. M. G. Menon from the river to the unsuitability of the appliances available to them, presuming that they were to be found "near the bottom in deeper waters in the middle of the river". 3Apart from a brief statement by Southwell and Prashad (1918) on the fertilization of Hilsa egg, the only published record of developmental stages of the Hilsa is by Nair (1939), who described postlarv,-e and young stages of the fish obtained from the Pulta Water Works. In. Nair's account, however, there is some confusion in the identity of the stages from 14 to 18 mm. described and figured by him. His description and the figures of Hilsa (from 14 mm. to 18 mm.) do not tally with the diagramatic repre- sentation of the relative positions of the dorsal fin and anus to the vertebrae (Nair, op. cit., Plate V). In no stage in the development of the fish, have we found the anus or the anal fin situated in a position below the dorsal fin (Nair, op. cit., pp. 410-12). Jenkins' (1938) anticipation of the discovery of the eggs and early larval stages from the rivers has been amply justified by our collection of such laid eggs and larvae both from the Hooghly near Pulta, and from the mouth of the Daya River (Chilka Lake). Some of spawning grounds of the fish have, therefore, been definitely located for the first time (Jones and Menon, 1950 b) and the development worked out in fair detail. The following account is based on the observations carried out in the Hooghly River along a stretch of about 3 miles near Barrackpore, in the Mahanadi River at Kujang, in the Bay of Bengal at Jaunput on the Contai Coast, and in the Chilka Lake at the mouth of the Daya River. MATERIALS AND METHOD (a) Collection of larval stages from the Hooghly.--Collections of Clupied prolarv~e and postlarv~e were made from the Hooghly in the neighbourhood of Pulta from September, 1949 onwards. They consisted of 2 different types of larvae. One was that of the Gangetic Anchovy, Setipinna phasa (whose eggs were also obtained), and the other was that of the Hilsa (Jones and Mellon, 1950). During the same time postlarvze and juvenile Hilsa were present in large numbers in the ' Bhin-jals' (conical bag nets) operat- ing in the river. The Hilsa larvae showed a remarkable peak occurrence during the second week of November, when yolked larva~ and postlarvae were collected in exceedingly large numbers in both surface and sub-surface hauls; but the eggs of Hilsa did not occur in these collections. In the col- lections made during the following December and January, the yolked larvae 3 See the addendum at the end of the paper. Life.ftistory of the Indian Shad, Hi!sa ilisha (ttamillon) 103 of Hilsa were absent, but Setipinna phasa was breeding as was evident from the regular occurrence of its eggs.4 (b) Collection of Hilsa eggs from the Hooghly.--Yowards the end of January, 1950, the presence of stray adult Hilsa in the river was observed. On the 2rid of February, 1950, we succeeded for the first time in collecting the eggs of Hilsa along with larval stages in our plankton net hauls and thereafter fairly regularly except for a few days (from 12th to 16th of Febru- ary) when a cold spell prevailed. (c) Collection of the eggs and the larvte from the River Daya.--IBlsa eggs and larvte were collected by one of us (S. J.) from the mouth of the River DayaFone of the deltaic branches of the Mahanadi--on the 16th and 17th of September, 1949, near the villages of Jagadal and Garasaguda respectively during one of the investigational tours to these places. This stretch of the river is situated close to its point of discharge into the Chilka Lake. The exact identity of these eggs was determined only after working out the deve- lopment of the Hilsa from the collections in the Hooghly. (d) Method.--Collections of eggs and larwe were made from a 3-mile stretch of the Hooghly below the Pulta Water Works up to the Titaghur Paper Mills. A bolting silk net (course) was tied to a country boat by means of a rope and towed against the current. Hauls were made at different depths along the river generally up to a distance of 50 to 75 yards away from the shore and occasionally across the river. The plankton net was usually lowered to the desired depth with the aid of a punting pole. The flow of the current served to keep the net straight and its mouth open. Eggs and larvae were present in larger numbers nearer the banks than in the middle of the river where the current was stronger. We collected both larvae and eggs from shallow regions of about 18 inches depth. The post- larvte were obtained in greater numbers in the hauls nearer to the surface than to the bottom, whereas the eggs were present usually in the sub-surface and bottom collections. Due to the upwelling of the water caused by the swirl of the current, the eggs were sometimes obtained in the surface hauls also, even though they are demersal in still water. The embryonic and larval stages described and figured up to the 5th day are from the laid eggs collected from the Hooghly which were reared in the laboratory, and the later stages from the collections made from the river. For whole mounts and myotome counts, they were stained in 4 A detailed account of the life-history and bionomics of Setipinna phasa (Ham.) is being published elsewhere. 104 S. Jones and P. M. G. Menon Eosine (aqueous), and for observing the skeletal parts, they were stained in Alizarin Red. All the diagrams were executed by the junior author (P.M.G.M.) under the supervision of the senior author. SPAWNING HABITS There is a fair amount of literature on the spawning habits of Hilsa. The ascent of Hilsa, first recorded by Hamilton (1822), far above the tidal limits of flooded rivers, is now well known. The available records indicate that the main breeding season is during the monsoons (Day, 1878, Hora and Nair, 1940 a and Chacko and Ganapati, 1949), from June to Sep- tember and October to December, and in the Hooghly River, where detailed investigations were carried out (Hora and Nair, op. cit.) the breeding extends almost throughout the year with a peak period during the rainy season. Our own observations in the Hooghly show that the breeding is very restricted, if not at a stand still, during the winter months of December and January, for, in the routine plankton hauls, the prolarv~e and the postlarv~e were scanty or absent. However, it is quite possible that the fish may even then be breeding lower "down in the estuary where the temperature is higher. Detailed investigations in the Chilka Lake indicate that the fish there breed mainly during the monsoon months (July to October) when the Daya River and its connected branches are in floods. As stated by Day (-1878), the rapidity of the current is probably an imlSortant factor amongst others in stimulating the spawning migration.