202 BULLETIN OF THE BUREAU OF FISHERIES 



Land have been found full of shelled pteropods (Limacina) ; and a large series of 

 small fish examined by Vinal Edwards contained copepods, shrimps, crustacean 

 and molluscan larvre, annelids, appendicularians, squid, fish eggs, and fish fry 

 such as herring, silversides, and launce. In short, practically all the larger floating 

 animals except the Medusas and 'ctenophores regularly serve for the nourishment 

 of mackerel, and a diet list for any given locality would include all the local pelagic 

 Crustacea and their larva?, Sagittre, pteropods, etc. 



In Swedish waters mackerel feed to a considerable extent on the younger 

 stages of prawns (Pandalus and Pasipha?a) though we have no record of this in 

 the Gulf of Maine. They have often been seen to bite the centers out of large 

 Medusas, but, as Nilsson suggests, they probably do this for the amphipods (Hy- 

 peria) that live commensal within the cavities of the jellyfish, not for the sake of 

 the latter. Side by side with these comparatively large objects mackerel are 

 also known to take various microscopic organisms, chiefly the commoner peri- 

 dinians and diatoms, but they never feed extensively on these as menhaden do 

 (p. 123). Mackerel also eat all kinds of small fish, to a greater or less extent accord- 

 ing to circumstances. In the Gulf of Maine they devour large numbers of small 

 herring, launce, and even smaller mackerel. They likewise feed on pelagic fish 

 eggs when available, oftenest on those of their own species. 



In the British Channel, according to Allen, 50 mackerel turn more and more 

 to a fish diet as the summer and autumn advance and the young fry of the herring 

 tribe become more and more abundant. This does not apply to the Gulf of Maine, 

 however, where they have been found feeding more often on pelagic Crustacea 

 than on fish throughout the season, nor, says Nilsson, to Swedish waters. Probably, 

 the extent to which mackerel feed on fish depends entirely on the local supply. 

 Nevertheless, while it can not be said that the mackerel feeds more on fish or on 

 any other given prey at one time of year than another over its whole range, it is 

 fully established that its diet varies from month to month, as is indeed inevitable 

 because of the seasonal variations in the pelagic communities both of plants and 

 of animals in all northern seas. No precise observations have yet been made on 

 this phase of the diet of the mackerel of the Gulf of Maine. 



Mackerel caught in the English Channel and examined by Bullen had fed 

 indiscriminately (by filtration) and largely on unicellular plants in March, but more 

 and more on animals, and, it seems, by selection as the spring progressed. Cope- 

 pods are so plentiful in the Gulf of Maine, and the vegetable plankton swarming in 

 April has so largely disappeared over most of the Gulf of Maine before the mackerel 

 appear in spring, that we doubt if they are ever reduced to a vegetable diet there 

 or, for that matter, anywhere in American waters. 



Mackerel are also known to feed on bottom animals to a small extent. Nilsson, 

 for example, reports various worms and hydroids and even small stones from their 

 stomachs, but all experience in the Gulf of Maine is to the effect that this would be 

 quite exceptional there, if it happens at all. 



w Journal , Marine Biological Association of the United Kingdom, Vol. V, New Series, 1S97, pp. l-to. Plymouth. 



