of the Fisher II Board for Scotland. 9 



the mortality was owing, not to the low temperature, but to deficient 

 aeration. At the request of the iSlew Zealand authorities, these 

 experiments are being continued, and it is hoped that it will be 

 possible to devise an apparatus which will enable the difficulties 

 referred to to be surmounted. 



The Food of the Halebut. 



An extensive research on the nature of the food of this important 

 fish was made by Dr. Thomas Scott, who contributes a paper to the 

 present Eeport setting forth the results of the investigation. The 

 stomachs of 1076 halibut were examined, the fish ranging in length 

 from 18 inches to five feet; they were caught at various parts of the 

 North Sea and North Atlantic and landed at Aberdeen. About one- 

 third of the stomachs, or nearly 34 per cent., were found to be empty, 

 or contained food in such a condition that identification of the 

 organisms composing it could not be made. A very considerable 

 proportion of the food of the halibut was shown to consist of fishes, 

 of which twenty species were determined, the most common being 

 the haddock and the whiting, and it was found that the larger 

 halibuts were more prone to a fish diet than the smaller ones. 

 Crustaceans, and in particular the Norwegian lobster {Ne]-ihrops) and 

 hermit crabs, were common in many of the stomachs examined, and 

 cuttle-fishes of several species were not infrequent, but echinoderms 

 were sparingly represented, and annelids hardly at all. 



Diseases of Fishes. 



The subject of the diseases to which fishes are liable is now 

 receiving more attention than was the case previously. In the 

 present Eeport, Dr. A. G. Anderson, now the Medical Officer of 

 Health of Kochdale, describes a bacteriological investigation which he 

 made of an outbreak of disease among the fishes at the Marine 

 Laboratory. Some haddocks and whitings which were caught in the 

 neighbourhood of a sewer were conveyed to the Laboratory 

 to replenish the tanks, and a few of them were observed 

 to have small ulcerations on the skin. Within a few days the 

 healthy fish which were previously in the tank became affected in 

 like manner, and shortly afterwards they all died. The outflow from 

 those tanlcs was into the large pond, in which live plaice were con- 

 tained, and later on a number of these fish became also affected and 

 subsequently died. The bacteriological investigations made at 

 Marischal College by Dr. Anderson revealed the presence of various 

 bacteria, including bacillus coli communis, which made it probable 

 that the fish had died from a form of septicemic poisoning, possibly 

 caused by infection from the sewage-borne micro-organisms. A few 

 years ago a similar outbreak of disease was observed to have occurred 

 among the fishes in the pond at the Marine Laboratory, Port Erin. 

 It appears that marine fishes are not so susceptible to microbal 

 attacks as are fresh-water fishes, and that amongst the former flat- 

 fishes are less susceptible than round fishes, as haddocks and whitings. 

 The evidence, moreover, indicates that fish do not suffer readily from 



