57 



In Fehruary — March 1905 mani/ pelagic young of fhe common Cottns ivere 

 present in all the Danish waters within the Skatv, but none in the Skager Rak. 



la April 1904 the pelagic young of the common Cottus were not so 

 abundant as earlier in the year (see Tab. 3 B). None were agaiu taken in the 

 Skager Rak in this month (see Tab. 1, Skager Rak, April 28th). Even in 3Iay 

 (6th) we found some in tlie western Baltic at Æro (see Tab. 1), and on June Tth 

 \ve took one, still small, pelagic young of the common Cottus in tlie Sound, N. of 

 Hveeu (see Tab. 1); but just as in 1902, when the occurrenee of the pelagic young 

 of the common Cottus in Fæuø Sound was followed from day to day in the months 

 of March — May, only a single straggler was taken in May, so that the occurrenee 

 of the pelagic young of the common Cottus in May and June 1904 must be 

 regarded as exceptions from the rule. It thus appears: that the young of the common 

 Cottus occur in Danish teaters in January — April tvifli a few stragglers in May 

 and June. We have found thetn in all our Danish tvaters ivith exreption of the 

 Skager Rak. 



The largest pelagic specimens of the common Cottus we have taken had 

 a length of ca. 15 mm. Coueerning those a little larger Ehrenbaum says (1. cit. 

 p. 137): "Dagegen wurden die nacbst alteren Formen von 17 bis 31 mm. Lange, 

 welche auch noch planktonisch leben, in April erst in einiger Entfernung von der 

 Kiiste (40 Seemeilen) gefangeu." We know nothing of a pelagic occurrenee of 

 such large specimens of the common Cottus in Danish waters. 



The occurrenee of the pelagic yotmg of the long-spined Cottus was not 

 regularly investigated before 1904. In that year we found its pelagic young in 

 May and June (see Tab. 1), yet only at the end of Ma}% as we took the first 

 specimens in the Great Belt on May 24th. This agrees well with the result of 

 investigations at Fænø in 1902, that the spawniug time is in April — May. Pelagic 

 young of the long-spined Cottus were taken in 1904 in the Kattegat, Sound, Great 

 and Little Belt, but not in the western and eastern Baltic, though we investigated 

 both these regions in June (see Tab. 1). 



In 1902 some pelagic specimens of the long-spined Cottus were taken in 

 the northern Kattegat and Skager Rak in June, and a single specimen in the 

 Southern Kattegat in June 1903 (in the pelagic net, therefore not included in 

 Tab. 3 A). 



The pelagic young of the long-spined Cottus thus occur in Danish waters in 

 the months of May and June. We have found them hoth in the waters within the 

 Skaiv, except the ivest&rn and true Baltic, and also in the Skager Rak. 



There is a great difference in the abundance of the pelagic yoimg of the 

 two Cottids occurriug in Danish waters; whereas the pelagic specimens of tlie common 

 Cottus belong in early spring to the commonest pelagic fish j^ouug, the pelagic 

 specimens of the long-spined Cottus are always scattered and few in numbers in 

 our catches. 



The bottoill-stages of the common Cottus have rarely been found during 

 the investigations of the Biological Station. In 1902 one specimen was taken in 

 the northern Kattegat and three in the western Baltic: 



D. 13 — 6 — 02. W. from Nordre Eonner, 5 fni. (Kattegat). Youns;fi.sh trawl on bottom: 

 1 common Cottus, 1 inch (c. 2'/o cm.). 



