cited (Anonymous 1953). The latter source 

 also gives 1.6* to 4.0° for bottom long- 

 lines, and Hachey, Hermann and Bailey (1954) 

 agree that the West Greenland cod avoid 

 temperatures below 1° . 



In Labrador waters, cod prefer waters 

 with temperatures from 1.7° to 5.6°, accord- 

 ing to Grenfell (1910), although Templeman 

 (1953a) reports the best catches on Hamilton 

 Inlet Bank in the autumn from -0.93" to 

 1.23°. Whitely, Lindsay and Thompson (1932) 

 say that above 3" is best and Rasmussen 

 (1952) agrees that there is no profitable 

 fishing below 2". 



In the Spitzbergen-Bear Island area 

 on the eastern side of the Atlantic, Ras- 

 mussen (1952) and Lee (1952) state that 

 fishing is not worthwhile below about 2", 

 and Lee elaborates that the general range 

 is 3° to 5° in the summer and about 2° to 

 3* in winter, although pointing out that 

 the fishing here is in different areas in 

 the two seasons and may be on two different 

 stocks of fish. Iversen (1934) concludes 

 for the same area that cod usually do not 

 frequent water masses below 0". 



Perhaps the best conclusion that can 

 be reached was stated anonymously (1953b), 

 that different groups of cod will live 

 under and adapt to different temperatures, 

 and that there is no one temperature suit- 

 able for cod wherever they are found. 



Salinity and oxygen 



Beauge" (1937) and Thompson (1943) 

 have implied that cod are more abundant in 

 water of a particular salinity range. But 

 the general opinion seems to be that the 

 abundance of cod in a particular area can- 

 not be related to salinity (Anonymous 1933), 

 although Poulsen (1944) speculates that 

 migrations of mature cod in the Baltic may 

 be related to salinity changes. 



However, this seems reasonable when 

 one examines the salinities in which cod 

 have been found. Dambeck's report (1879) 

 of cod living and spawning in a freshwater 

 lake in Iceland seems extremely doubtful, 

 but the occasional reports of cod straying 

 upstream in rivers (Abbot 1871, Federsen 

 1880, Phillips 1883) probably are valid. 

 Cod are found in low salinities in the 

 Baltic, about 6°/oo, according to Poulsen 

 (1931) and Alander (1952) and in full 



oceanic salinities elsewhere, about 35°/oo, 

 (Damas 1909, Bigelow and Schroeder 1953, 

 etc.). So under certain conditions at 

 least, cod are found from nearly fresh 

 water to full oceanic salinity. 



There is considerable evidence that 

 the distribution of cod in parts of the 

 Baltic is related to the oxygen concentra- 

 tion (Jensen 1954, Alander 1951, Otterlind 

 1954). These authorities do not mention 

 values, but Sundnes (1957) gives 2.7 ml. 

 per liter as the critical value for cod 

 and 0.80 as the value for asphyxia. Jen- 

 sen (1952b, 1953, 1954) says that low oxy- 

 gen concentrations may have caused the 

 large numbers of d eformed young cod found 

 in the Baltic in certain years and the 

 scarcity of mature cod in some areas. 

 Alander (1951) and Otterlind (1954) agree. 



MORTALITY 



Temperature and other factors 



In spite of the relatively great 

 range of temperatures in which cod are 

 naturally found and in which they can sur- 

 vive under artificial conditions, there 

 are high and low limits to their tempera- 

 ture tolerance. The cod is a poikilotherm, 

 with little or no internal temperature 

 regulation, and Britton (1924) has shown 

 that cod have temperatures less than 1° 

 above that of their environment, at least 

 in the range of ambient temperatures around 

 10°. 



Lumby and Atkinson (1929) report the 

 finding of dead codin otter-trawl catches 

 in the North Sea in 1929 and conclude that 

 a sudden drop in temperature was the cause. 

 A. Dannevig (1947) reports that young cod 

 in the littoral are sometimes killed by 

 severe winters, but Hermann (1951) could 

 not find a relation between cold years 

 following the year of hatching in West 

 Greenland and subsequent year class yields. 



Bigelow and Welsh (1925) state simply 

 that "freezing" is fatal. Carswell (1889) 

 agrees and gives -1.7° as the freezing tem- 

 perature. Templeman and Fleming (1956) 

 claim that below -1.0° cod could be ex- 

 pected to die of cold, although Sleggs (1932) 

 observes that scanty numbers of cod are 

 found in nature at -1.6°. In older opinions, 

 Earll (1880), Carswell (1889), and Nielsen 



