107 



fish and cause them to dash upon the net and become meshed ; 

 hence the name thathu vala. 



This form of fishing is of comparatively recent origin and 

 has not been more than 15 years in use at such centres as 

 Tellicherry, Badagara, and Calicut, and is viewed with great 

 disfavour by the peru vala fishers. Its alleged demerits should 

 receive attention, and the effects of its employment in the 

 centres where most used carefully investigated. 



94. Reference to the diagram facing page 100 shows graphi- 

 cally how variable is the catch of mackerel from year to year ; 

 how in some years there is absolute dearth and in others 

 enormous abundance. It is very noteworthy that mackerel and 

 sardines are scarcely ever abundant in the same year ; a good 

 year for the one is usually coincident with an unsuccessful 

 fishery for the other. What may be the factors at work we do 

 not know ; the food and feeding habits of the two when fully 

 known may afford the needed enlightenment. For the present 

 all we can say, from the examination of the stomach contents of 

 mackerel taken within \\ mile from shore is that this fish 

 during November on the Malabar coast, feeds almost wholly 

 upon those minute crustaceans which at that season constitute 

 so large a bulk of the surface plankton of inshore water. Frag- 

 ments of copepods and daphnise form the principal constituents 

 of the stomach contents with a fair number of dinoflagellates 

 ( Oeratium chiefly) and diatoms. If we compare this with the food 

 of sardines in the same localities and at the same season, which 

 is characterized by an almost complete absence of small Crustacea 

 and is made up of diatoms and organic debris, we may infer 

 that whereas the sardine is largely a bottom. feeder, the mackerel 

 feeds some distance above the bottom following the shoals of 

 minute crustaceans according as they rise towards the surface or 

 sink some distance below. In this the ludian mackerel agrees 

 in habit with the English species which is considered so essen- 

 tially a surface swimmer that mackerel drift nets are made only 

 half the depth of herring nets. The sardine may be described 

 as phytoplanktonic, the mackerel as zooplanktonic in feeding. 



95. The prospects of improving the mackerel fishery seem 

 decidedly good. The present method of prosecuting it is 

 limited to the netting of a very narrow zone of shallow water 

 and a waiting upon Providence to send the shoals close inshore. 

 No effort is made to seek the shoals although there is good 

 reason to believe both from analogy and observation that they 

 move up or down the coast at some seasons and at others migrate 

 towards deeper water. No effort is ever made to follow them 

 when they begin to move away from a particular locality ; 



