97 



clearest and sunshine strongest, conditions most favourable to 

 the rapid growth of such plant life as diatoms. It is on this 

 flocculent scum of diatoms, a scum that is not always quiescent 

 upon the bottom but is known to rise towards the surface under 

 certain conditions of light and temperature, that I found sardines 

 feeding largely during October, November and December ns 

 shown by microscopical examination of the stomach contents 

 of fish caught at this season. Fishermen and the fish-curing 

 yard officers always describe the food of sardines as " mud " ; 

 the fish-curing returns continually contain the statement 

 " stomach contents — mud ". To the naked eye the contents of 

 the stomach and intestines of every specimen I have examined, 

 appear as a smooth homogeneous stiff greenish-grey mud ; 

 broken up in water and examined under a hand lens or low 

 power of the microscope no recognizable constituents can be 

 made out, but when viewed under a ± or J inch objective the 

 mass becomes resolved into a paste of organic debris mixed 

 with large quantities of many speoies of diatoms. Among the 

 genera represented the most numerous are Coscinodiscus, Navi- 

 cula and Pleurosigma. Considering the large quantity of 

 unrecognizable debris present, together with such things as 

 decayed fragments of the vascular tissue of plants, it appears 

 to me that much of the feeding of sardines takes place on the 

 bottom, and that they browse upon the flocculent surface of the 

 muddy sea-bottom, in analogous manner to that in which grey 

 mullet may be seen in aquaria cropping the low algal growl h 

 and slime that often gather on the sides. 



70. Not having yet had an opportunity to visit the West 

 Coast during the first half of the year, I am unable to write 

 with any certainty either of the cause which impels the sardines 

 about April to move away from the localities where they had 

 been abundant during the preceding six months or of that which 

 brings about gradual absorption of fat during the early monlhs 

 of the year. From the fact that in February strong winds from 

 the north-west set in, producing a more turbid condition of the 

 sea along shore and that from this time onwards catches of 

 sardines are made at a greater distance from the shore than from 

 September to February, it appears probable that bottom currents 

 set in with gradually increasing strength dispersing and arresting 

 the growth of that diatom scum in shallow inshore waters which 

 we know from observation is luxuriant during at least the last 

 three months of the year. With such dispersion of the main 

 food supply, sardines probably find their inshore commissariat 

 inadequate to feed their great multitudes with the two-fold 

 result (a) that much of the reserve fat in their tissues is used 

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