— 35 — KNUT DAHL 



is cnmnion to a large stretcli of coast, and vvIumi tliere is an abundance of 

 fry, Ulis abundance has been observed everywhere within the large 

 area examined. The addition of artificially hatched cod larvae to a 

 locality can nowhere be proved to have influenced the relative abundance 

 of littoral fry in a recognisable degree. 



The causes of this obvious regularity in the distribution of the fry may certainly 

 be various and complex. I deem it however justifiable to suppose that one of these 

 causes is to be found in tlie fact, that the currents possess the power of carrying eggs 

 and drifting fry and thus affect their distribution. The great difference between the 

 occurrence of littoral fry in July 1904 and July 1905 may at least become more 

 intelligible if we compare the currents in these two years. Thus in the Bulletin of the 

 International Council, surface charts have in both years been compiled for the month 

 of May, which is a very critical and important month for the drifting fry. 



In May 1904 there was only a weak current through the Gattegat and the 

 Skagerrack, and the salt water from the North Sea had penetrated far into the Mouth 

 of the Skagerrack. In May 1905 on the contrary the conditions were entirely different, 

 a strong Baltic current prevailing, and fresh water of eastern origin filling the whole 

 surface of the Skagerrack. 



The investigations on the occurrence of drifting fry are on account of the gear 

 employed and for several other reasons unfortunately not comparable, but my experience 

 in these two years leaves me no doubt, that there was a very great difference. There 

 is no doubt that the fry decreased much more rapidly in number in 1905, than it did 

 in 1904. During the months of May and June the difference was especially obvious. 

 During the whole of the early summer 1904, until July, there were great numbers of 

 drifting fry to be caught in my nets as well as to be seen^ everywhere in the sea, 

 and especially in the beginning of June they were exceedingly numerous. 



I could nearly everywhere note their presence, by direct observation, under the 

 drifting jellyfish, and easily catch them with a small hand net. I could anchor my 

 boat in the open Skagerrack off Risœr, and observe the pelagic young of cod , haddock 

 and whiting in great masses drift past under the jelly-tish with a speed of 3—4 knots. 

 The sea was quite full of jelly-fish and under nearly every one of them swam one or 

 several young fish, which were easily caught for examination. By towing my small 

 tow-net (1 m. diam.) for five minutes, I could catch up to 39 cod, haddock, and whiting 

 of 2 to 3 cm. length. 



During 1905 the conditions were entirely different. In May I obtained the number 

 denoted in the table pg. 26 but only by making enormous hauls with a large net, 

 towing the entire length of the Sandnes and Sendeled Fjords besides miles of water 

 outside the coast. But with two exceptions not a single drifting fry was to be observed 

 during the months of May and June under the drifting jellyfish. Where in the beginning 

 of June 1904 I had made the above-mentioned great catches in my small 1 m. tow-net, 

 I had in June 1905 to tow a net that was many times larger for as much as 6 hours 

 without obtaining more than a few fry. 



' During my 10 years of work in Norwegian waters I have never anywhere seen so many pelagic 

 fry as in that year. 



5* 



