322 DISCOVERY REPORTS 



to April— suggesting spring or early summer spawning— but the data are inadequate for detailed 

 consideration.) 



The very narrow dispersion of the observed length frequencies (Fig. 32) shows that a majority of 

 any modal class less than about 38 cm. long escaped through the normal cod-end mesh, as would be 

 expected with such a small slender species. This was seen to occur and was duly recorded in the log- 

 books. Above the very pronounced mode, however, such narrow dispersion (the biggest fish taken 

 were only 49 cm. long) can only mean that little growth takes place after the fish have'' attained such 

 modal length. The absence of all trace of a higher secondary mode shows that only a very small 

 mmonty of the 41-43 cm. fish normally survive another year. It is possible, therefore that 

 M. austrahs is a short-lived fish of comparatively rapid growth. Fine-meshed trawlings to sample 

 the smaller year classes would be essential to establish the point with certainty. 



The food oi Micromesistius was noted at two stations. It consisted oi Parathemisto and Euphausians 

 In this respect, as in their deep-water habitat along the edge of the shelf, they resemble their European 

 relative (cf. Hicklmg, 1927, pp. 53 et seq.). Hickling's findings also show that the European species 

 spawns late in spring (in agreement with the season suggested as probable for the Patagonian species 

 from the seasonal shift in ponderal index) in the nearest corresponding latitudes. It is in the restricted 

 distribution in colder waters than those frequented by the local hake that the Patagonian species shows 

 the most striking difference from Micromesistius poiitassou. 



Saltlota australis (Giinther). Norman (1937, pp. 52-3) has explained how this genus is barely 

 separable from the Physiadus of Kaup, with which our species was identified in the field He has also 

 a footnote concerning the circular, unsealed, pigmented area between the bases of the pelvic fins- 

 This IS associated with a luminous gland', and gives references to Hickling's work on the subject' 

 From the latest of these (Hickling, 1931) it would seem that similar organs had long been known 

 among a variety of Macruridae, and in Physiadus japonicus Hilgendorf alone among Gadidae. Hickling 

 concluded that the gland is essentially a larval organ which may remain functional throughout life 

 in some species (loc. cit. pp. 863^5). It functions strongly in the adults of Malacocephalus laevis 

 (Lowe) (Hicklmg, 1925), but though functional in the young of Coelorhynchus coelorhynchus (Risso) 

 It becomes vestigeal in the older fish. I have found a note of E. R. Gunther's stating that with Saldota 

 ... m/« luminescence was not observed in the field, so that it is possible that the gland is vestigeal 

 or less developed from its primitive condition in the common ancestral Anacanthini) in this spedes 

 also. Gunthers first colour note (St. WS73) on the species reads: 'Evenly grey, slightly darker 

 towards the back. Ventral surface slightly violaceous, becoming almost black'at'one spot anterior to 

 he anus (this spot probably luminous). The scales suggest a faint brazen glitter.' It is therefore clear 

 that our observers knew of the possibility of lummescence m this species'from the first, but no uch 

 phenomenon was seen although numerous specimens both old and young were subsequ ntly secured 

 The gland may very probably be functional in the larvae, but it would seem to be undeveloped or 

 vestigeal in the older stages of S. australis. uiiueveiopea or 



Our records of this species, set out below, show that its seasonal and regional distribution resemble 

 those of Macrnronus It is, however, much less numerous and more widely spread, wh"h suZs 

 that it IS much less given to shoaling. suggests 



Salilota austraUs was also taken in seventeen hauls during the first autumnal survey. Only four of 

 these were situated in the intermediate region; all the rest, including the four richest hauls of ten or 

 more individuals, were in the southern region. St. WS99 provided the only record of he specie 

 m deep water over the edge of the shelf at this season ^ 



During the second survey, made in winter, the species was taken in fifteen hauls. Of these one was 

 m the northern region, eight were m the intermediate region and only six m the southern region Th" 



