3o8 DISCOVERY REPORTS 



THE FOOD AND FEEDING OF MERLUCCIUS HUBBSI 

 Owing to the wide scope of the survey programme it was not possible to carry out such detailed 

 observations on this subject as have been found desirable by European specialists working on single 

 species of fish (e.g. Hardy (1924) on herring, Hickling (1927) on hake). On our first survey 191 

 stomachs were examined and on the second 186. On the third survey forty-six notes on stomach 

 contents were made in the field, but owing to pressure of other work the numbers of fish examined in 

 this way were not always recorded. It was evident, however, that the proportion of fish containing food 

 was least in summer, which accords with the known habits of European hake (Hickling, 1927, p. 49). 

 A general loss of appetite just prior to spawning is known among many diverse species of fishes. ^ 



Our first survey (autumn) and second survey (winter) results show that a slightly higher proportion 

 of Patagonian hake were found to contain food in winter, but I do not believe this indicates more 

 extensive feeding during that season. From notes on the size and numbers of food organisms in 

 individual stomachs it is evident that feeding was heaviest in autumn. The apparent anomaly is due 

 partly to a seasonal change in diet, partly, no doubt, to the limitations of the data. 



The number of times that food of recognizable categories was recorded, and the percentage occur- 

 rence of each category, during each survey are set out in Table 27. From this it is at once apparent that 

 the feeding habits of M. hubbsi art essentially similar to those of M. merluccius, and perhaps even closer 

 to those of M. bilinearis (Bigelow and Welsh, 1925, pp. 389-90). It feeds chiefly upon other fishes, 

 mcluding even its own species, squids and more or less planktonic Crustacea. This last constituent 

 was chiefly found in the stomachs of the smaller and younger fish. 



The list of fishes eaten includes the commonest species of the area. Falkland herring {Cliipea 

 fiiegensis) was by far the most important forage species, especially in winter, but other species are 

 preyed upon with equal voracity when readily available. Thus as many as sixty-seven individuals of 

 the small scald-fish Thysanopsetta naresi have been taken from the stomach of a hake less than 56 cm. 

 long. Merluccius hiibbsi, like other species of hake, are known to devour individuals of their own kind 

 more than half their own length. Had we been able to obtain more food records during the offshore 

 phase of the seasonal migration there is little doubt that such instances would have been commoner. 

 There is one peculiar difference from the feeding habits of European hake that makes the paucity 

 of deep-water observations during winter the more regrettable.^ Although the distribution of M. 

 hubbsi overlaps that of Micromezistiiis australis to the southward, the latter was not recorded as a 

 constituent of the hake food. This is extraordinary because M. australis is very closely related to our 

 own blue whiting M.poutassou (Norman, 1937, p. 51), which Hickhng (1927, p. 42) had shown to be 

 such an important constituent of the food of European hake. It seems that M. australis keeps more 

 exclusively to deeper water and higher latitudes than its European counterpart, and therefore its 

 habitat— during the warmer months of the year— does not coincide with that of the hake to anything 

 like the same extent. In winter the southern blue whiting may move northwards as well as offshore, 

 as will be shown in the section dealing with that species. Possibly the hake then feed upon them as we 

 should have expected ; but the fact remains that there was no evidence of this at the few stations where 

 we did locate the two species together. 



It will be noted that the list of food organisms includes several bottom-living fishes and a little 

 benthos. The slightly more benthic tendency in choice of food is doubtless occasioned by the uniformly " 



hv^H^t^'^T t° this phenomenon in Quinat salmon (Jordan), silver eels (Petersen) and pleuronectids (Todd), are quoted 

 by H.ckhng (1927), and he was further able 'to suggest that the blue whiting {Micromezistius poutassou) also feeds much le7s 

 ? olmrilerv.Thr'^?" -h'™'" behaviour among Labrador cod ^o^uld seem to belplied ly Harold TZmpson 

 seasoA^' ^ ^ ^^ "P°" ''P'" ^°' '^^ P'™'^ °^ S'"'' ^""'^'"g ^"'^ recuperation which succeeds the spawning 



season . 

 2 



I must reiterate that this was due to the precipitous slope preventing trawling, and not to any lack of endeavour. 



