— I'-'l — JOHS. SCHMIDT 



their reproduction than is found in the North Sea (thus, M. byrkehmge and elongata, 

 Giidtts Foutassoti, partly also Brosmius and Gadiculus). In the most eastern and south- 

 eastern parts the water is even so shallow that only the cod (G. callarias) and the whiting 

 {G.metiangus) of all the species are able to reproduce there in quantities', and even the 

 species which produce large quantities of young in the northern part of the North Sea 

 (e. g. haddock {G . œglefinus), coalfish (G.virens) and Norway pout {G. Esmarki)) do not 

 spawn here practically speaking. 



Just as the temperatures in spring in the more northerly parts of the North Sea recall 

 those at South Iceland, we find that the same gadoids spawn at both places in quantity, 

 namely, the cod {G. callarias), whiting {G.meiiangiis), haddock (G. œglefinus), coalfish 

 ((?. virens), Norway pout ( G. Esmarki), as also the ling (Molva molva), the last however 

 only in the northern, deeper, salter and warmer part, to which the spawning of the coal- 

 fish is also restricted and where further a small production of the fry of the torsk {Bros- 

 mius hrosme) takes place. Almost all the species mentioned, which also spawn in quantity 

 at South Iceland, mainly spawn in the spring or end of winter. 



In addition to these however there are at least three species of gadoids which are 

 known to reproduce in the North Sea (with the Skager Kak), namely, the poor cod (G. 

 minutus), pollack [G. pollachius) and hake (Merluceius vulgaris), and perhaps also the bib 

 (G.luscus). All these have their main distribution in the most southern (warmest) parts 

 of our region (Bay of Biscay, Channel), whereas the production in the North Sea is much 

 smaller. In the Atlantic waters mentioned these species spawn mainly in the spring time, 

 but in the North Sea only early or late in summer. This should certainly be considered 

 as standing in connection with the fact that the temperatures in the North Sea only then 

 reach the same height as those under which the spawning occurs in the Atlantic already 

 in the spring, a fresh example of the determinative influence of the hydrographical con- 

 ditions on the spawning of the gadoids. 



5. The Channel 



The depths in the Channel are mostly but small; it is only in the extreme western 

 part that the depth exceeds 100 meters, but even there it is nowhere greater than ca. 150 

 meters. In the eastern parts the depths are much smaller, less than 75 and even than 

 50 meters. The Channel may therefore be regarded as a bight of the Atlantic with 

 throughout much smaller depths. 



With regard to the hydrographical conditions it may first of all be stated as a rule 

 of general application that the salinity of the water from surface to bottom is practically 

 the same in the ChanneP (and this also applies to the Irish Sea and the southernmost 

 part of the North Sea). As can be seen from the Table p. 132 this holds good also for 

 the temperatures, at least except in the summer. 



As a second general rule it may be said that the western part of the water is in 

 hydrographical regard more nearly related to the Atlantic water than the eastern. At the 

 spawning time of most of the gadoids, i.e. in spring and close of winter, we find sim- 

 ilar temperatures from surface to bottom in the western part to those in 

 the neighbouring parts of the Atlantic, but these are higher than all [temp- 



* The low salinity found here for the most part also excludes the spawning of nearly all other species. 

 ^ Cf. Martin Knudsen, Publications de Circonstance No. 39, p. 7, 1907. 



17* 



