Náttúrufræðingurinn - 1954, Blaðsíða 28

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NÁTTÚRUFRÆÐINGURINN
could have been responsible for this mass slaughter of adult fulmars, a pheno-
menon otherwise unknown in Iceland. Previously the great skua was only known
to take odd young fulmars as well as the young of other seabirds (especially guille-
mots) inhabiting the “bird cliffs”.
Finally it should be mentioned that the great skua is also to a considerable
extent a scavenger, feeding on carcasses and fish offal. It often follows in the
wake of ships, snatching up anything edible which might be thrown over board.
Trawling on the rich fishing banks off the south coast of Iceland must have
a great importance as a source of food for the large colonies of great skuas in this
part of the country. It is also known that fish offal has gradually become a very
important, if not the most important, item in the diet of the great skua in these
areas. It is even likely, although this cannot be proved, that the great skua
population of the coastal plains in S. Iceland has increased considerably since
trawling started off S. and SE. Iceland shortly before the turn of the century.
This increase sems to have continued up to about 1930. From then on, according
to the statements of farmers on both sides of Skeidarársandur, a marked decrease
of the population of that area has become very conspicuous. This decrease, which
coincides with the discovery of new and very rich fishing grounds off NW. Ice-
land, can easily be explained by the reduced fishing activities off SE. Iceland.
„Blóðlausir" fiskar.
Norskum sjómönnum, sem stundað hafa hvalveiðar i Suðurhöfum, hefur lengi
verið kunnugt um þrjár tegundir fiska við Suður-Georgíu, sem þeir kalla „blod-
laus-fisk“. Nú hefur próf. Johan T. Ruud í Osló fengið slíka fiska til athugunar,
og það kom í ljós, að sjómenn höfðu talsvert til síns máls. Rannsóknin leiddi i ljós,
að í blóðvökva fiskanna eru engin lituð blóðkorn, sem svara til rauðra blóðkorna.
Er blóðvökvinn því litlaus eða með fölum gulhvitum blæ. Kemur það allmjög á
óvart, að hryggdýr skuli geta lifað án þess að hafa i æðum blóðkorn, sem binda
súrefnið á sérstakan hátt. Telur próf, Ruud, að hér sé um sérhæfingu að ræða,
sem einkennandi sé fyrir suðurheimskautshöf, en eigi sér vart hliðstæðu annars
staðar. (Eftir Nature, Vol. 173, bls. 848, 8. maí 1954). H. E.