THE HERRING FISHERIES. 29 



The herring is a very voracious feeder, and, according to 

 M. Mobins, the principal food of those found in the Baltic 

 and German Ocean consists of some kinds of minute 

 crustaceans of the order of Copepoda. 



In February, 1872, a number of herrings were caught in 

 Kiel Bay at about 240,000 herrings daily for three weeks, 

 and in almost every one that M. Mobins opened, the 

 stomach was found loaded with Copepoda belonging almost 

 entirely to one species (Temora longicornis). By careful 

 counting the number present in one case was found to be 

 60,895, and another herring contained 19,170. The upper 

 surface of the water swarmed with these animalculae, and 

 could easily have been taken with fine nets in literal 

 thousands. A very low estimate was assumed from these 

 facts, namely, that allowing each of the 240,000 herrings to 

 have devoured daily 10,000 Copepoda, this would give for 

 one day a consumption of 2400 millions, and in three 

 weeks 43,000 millions. 



The roe of an ordinary sized herring is allowed to con- 

 tain about 33,000 eggs, and the time taken for hatching 

 the eggs depends both upon the season and the tempera- 

 ture of the water. Hatching operations seldom take longer 

 than one month, and the young fry are invariably produced 

 from the eggs in three weeks' time. 



As with all our marine fish, temperature has a very 

 important function in the growth and development of each 

 species, and observation is showing a close relation between 

 large or small catches and varying temperatures. Thus a ' 

 low temperature is conducive to large catches, and a high 

 temperature to small ones, and if the thermometer registers 

 the sea temperature to be at or about 55*5, average catches 

 may be expected, other things being equal. 



One of the most serious allegations against trawlers is, 



