OF TUE HABITS AND MIGRATIONS OF THE MACKEREL. 9 



At Plymouth iu June Cunningham*' found no signs of maturity in 

 fish 22'2 to 23"5 cm. (8"7-9'2 inches) long, nor in one female of 27'4 cm. 

 (10'7 inches). The smallest ripe female, which he records, is 29*5 cm. 

 (11*5 inches), and the smallest ripe male 30-3 cm. (11'8 inches). His 

 observations are, however, far too few in number to enable any general 

 conclusions to be drawn. 



Food. — It has already been stated that the mackerel is a pelagic- 

 feeding fish ; that is to say, it feeds upon free-swimming organisms, 

 and not upon those which live on the bottom of the sea. The food 

 of this fish may be regarded as of two different kinds, and it adopts 

 two different methods for procuring it. In the first place it feeds 

 upon the smaller forms of the plankton, copepods and otlier crustaceans, 

 larvse of crustaceans, molluscs, echinoderms and worms, diatoms, and 

 even siphonophores and medusa^ obtaining its food like the herring, 

 by straining the sea- water through its gill-rakers, as it swims 

 open-mouthed through the sea. This method of feeding would appear 

 to furnish the fish with its principal food supply during the spring and 

 early summer, when it first approaches the coast. During the latter 

 part of summer, however, and in the autumn, small fish of other 

 species become abundant, and the mackerel then makes these its 

 chief article of diet. Young herring, sprats, pilchards, and rockling 

 are all devoured. These young fish are hunted by sight, the mackerel 

 darting at them and capturing them individually. The fine condition 

 of the autumn fish is due to the abundance of food which they obtain 

 in this way. 



In its early stages the mackerel lives upon the small organisms of the 

 plankton, including larval fish. Marion found in the stomachs of small 

 mackerel at Nice, taken in May, copepods, zoeas of brachyura, and 

 sardine larvse. 



Migrations. — The migrations of the mackerel have long been a 

 subject of speculation, but it cannot yet be said that much definite 

 knowledge, either as to their extent, or the causes which bring them 

 about, has been acquired. The recorded facts, sufficiently trust- 

 worthy and precise to be of practical use in the consideration 

 of the subject, are not numerous. The importance of the collection 

 of statistics showing the quantities of fish landed at various ports 

 during the different months of the year has not long been recognised, 

 and without independent knowledge as to the localities where the fish 

 have been caught those statistics which are published are very liable to 

 lead to false conclusions. 



* Journ. Mar, Biol. Assoc, N.S., ii. [i. 232. 



