of the Fishery Board for Scotland. 



27 



there has been much discussion, whether this solution of the wall of the 

 gut is due to the digestive action of intestinal ferments or to putrefactive 

 processes. But when one has due regard to the rapidity in many cases 

 with which solution of the gut wall takes place, it appears to be at 

 least initiated by post-mortem digestion, although this process may 

 be accompanied by, and is certainly soon superseded by, the action of the 

 bacteria of putrefaction which abound in the gut. 



There are, however, certain factors which appear to hasten or retard 

 this process. It will always be found to take place sooner in fish which 

 have been feeding immediately before capture. Amongst the fish under 

 examination, one frequently finds, especially in dealing with herring or 

 cod, some whose stomachs were evidently packed with crustaceans or 

 small fish at time of capture, and in these cases digestion and solution of 

 wall of gut may take place in a few hours, whereas if the gut is compara- 

 tively empty the digestion may be considerably delayed. This certainly 

 takes place very rapidly in herring in the above condition, and I have 

 frequently observed it in herring in the spent condition. It hals 

 frequently been observed by fishermen that herring with stomachs packed 

 full at time of capture very rapidly undergo putrefactive changes, and 

 often have been useless for curing purposes before being landed. 



It occurred to me that possibly the kind of food might exercise some 

 influence in determining the earlier or later onset of decomposition in 

 fish. Accordingly I examined the stomach contents of a considerable 

 number of fish, as well as consulted the excellent papers that have 

 appeared in the reports of the Fishery Board for Scotland by Dr. W. 

 Fulton, Director of Scientific Investigations, Dr. T. Scott, and those of 

 other writers. But it appears to me that many fish, although they may have 

 some predilections for certain kinds of food, are on the whole indiscrim- 

 inate feeders, and that the kind of food partaken of is determined chiefly 

 by the habits and disposition of the individual fish and the condition of 

 hunger at time of feeding. One generally finds the principal food in the 

 stomach of the haddock is crustaceans. Whitings, on the other hand, 

 are rapid and agile swimmers, with keener eyesight. They hunt their 

 food, and one finds that it consists chiefly of young herrings, sand eels, 

 and small flat fish. Cod are voracious eaters and appear to feed on 

 Crustacea and smaller fish. But, on the whole, more of the former were 

 found in their stomachs than the latter, and it is possible that they prefer 

 the former to the latter when it is readily accessible. As regards saithe, 

 I. found that in the adult fish the stomach contents consisted of mixtures 

 of herrings and many varieties of smaller fish. But the younger the 

 saithe the more they seem to prefer Crustacea. 



Herrings appear to feed largely on Crustacea and sand eels. I also 

 examined the stomach contents of a few other varieties of fish, but it 

 appeared evident that no very definite conclusions could be formed from 

 this line of enquiry, since fish do not adhere to any one class of food, and 

 that what they eat depends chiefly on the exigencies of circumstances as 

 stated above. However, in order to control the conditions of feeding and 

 make this enquiry more precise, I obtained a small cargo of haddocks 

 freshly caught, brought ashore in sea water and transferred at once to 

 tanks, where they were kept in conditions approaching to their natural 

 habitat. After a few weeks, when acclimatised and feeding readily, 

 separate lots were fed for a few days on such foods as bread crumbs, 

 pieces of fish, and crustaceans. Then, on a certain day, so many were 

 taken from each tank at different times after feeding and killed, some at 

 15 minutes, one hour, two hours, etc. These were laid out in plates and 

 kept moist, and observations were made from hour to hour. 



