very far from their birth-place. This then is where Johannes Schmidt found the larvae; that 

 is, in the Sargasso Sea. 



Adult albacore do not enter European waters. They range across the Atlantic in a 

 vast belt between latitudes 10" and 40''N. from the Gulf of Mexico to the entrance of the Medi- 

 terranean, living in waters with a salinity from 36 to 36..0 "/on and a high temperature varying 

 from 18° to 24°C. The westward concentrations gather in winter or at the beginning of spring 

 in the "basin" of equatorial waters, where, south of Bermuda, the isotherm for 15°C descends 

 more deeply to about 270 fathoms. Then the large hungry albacores disperse over an area 

 from the West Indies to Morocco. Fishes with spent ovaries are sometimes caught around the 

 Azores, Madeira and the Canaries. 



Development of the fry is accomplished within a perimeter extending round the Sargasso 

 Sea at a distance of about 800 miles. At the end of the first year they measure little more 

 than 9 inches in length and are the selected victims of numerous predators such as sharks, 

 swordfishes and other tunnies. When towards 3 J years of age they have reached a length 

 of about 18 inches, the immature albacores begin their travels and move towards the north- 

 east with the Atlantic transgressions, always keeping in waters with a temperature of 14°C. and 

 a salinity of 35.5 "/oq. These are the fishes that move by the Iberian coasts in April to enter 

 the Bay of Biscay from May to July and reach the Celtic Sea from August to October. In 

 autumn they withdraw to the south, swimming at the surface if the waters are still warm or 

 diving towards the depths along the isotherm to reach the groups of islands where they spend 

 the winter. 



When they are about 4 or 5 years old and measure about 27 inches they become sexually 

 mature for the first time. These fishes also move northwards but to a much lesser extent, 

 for they never leave those waters of 36 "/oo salinity and a temperature of le^C. It is probable 

 that fishes with lengths of 31, 35 and 39 inches are 8, 10 and 12 years old respectively. We do 

 not know whether they return to the Sargasso Sea each year or if there are wider intervals in 

 spawning so as to recuperate their powers, for crossing the Atlantic is an easy matter for these 

 strong swimmers. 



Albacore are not found just at the equator, but in the South Atlantic there is a population 

 that follows the southern transgressions towards Angola and the Cape of Good Mope and around 

 isolated islands hke Ascension, St Helena and Tristan da Cunha. The spawning-grounds 

 should probably be in the west above the great depths of the Brazilian basin, where the salinity 

 reaches 36 and 37 "/qo- Ehrenbaum has reported on larvae from the region of Pernambuco, 

 which could be those of the albacore. 



When on board a Canadian ship travelling between Vancouver and Hawaii. I was able to 

 ascertain the course of the Pacific transgression off California and Oregon, and to follow the 

 passage of albacore very like those of the Atlantic. Between January and May in 1937 the 

 Japanese ship " Fuji Masu " discovered a gathering of albacore to the west of the Midway Islands, 

 from 28" to 34° N. and 170° to 173° E. All sizes of fish from 9 to 31 inches were represented. 

 This grouping of fry, immature fish and adults suggests a spawning-ground ; this corresponding 

 in position with the Sargasso Sea and having the highest salinity in the Pacific. As early 

 as 1923, Kishinouye found small tunny in the stomachs of other fishes taken around the Ogasa- 

 wara Islands, 1,200 miles west of Midway. In 1937 and 1938, American ships confirmed the 

 passage of albacore shoals that I reported in 1923. Evidently this concerns a journey of imma- 

 ture fishes in the waters of the transgressions covering some 2,500 miles. The winter quarters 

 should be around the islands off the Mexican coast. Based on these data, the American scien- 

 tist, Vernon E. Brock, made precise studies on the biology of the North Pacific albacore in 1943. 



From Colombia to the East Indies on the equator there extends across the Pacific a belt 

 of low salinity water which seems to be a real barrier for tunny and separates the northern 

 populations from those of the south. Albacore are known from the Juan Fernandez and Easter 

 Island areas and they are found again round Australia and New Zealand. In the Indian Ocean 

 they occur near Reunion and Madagascar. Nothing is known of their biology, but within this 

 immense marine area there re probably at least two distinct populations with their own 

 spawning-grounds. 



HI 



