50 FISH AND GAME COMMISSION 



been provided to the industry through the publication of the results of 



the investigation on the proper methods of refrigerating the fish on vessels, 



which resulted in a marked decrease in losses from rejected fish due to 



poor preservation. 



MACKEREL 



The mackerel fishery was especially successful in 1940, with 120,503,- 

 612 pounds landed ; but it decreased in 1941 to 78,167,200 pounds. Scoop 

 boats dominated the fishery and landed over two-thirds of the catch in 

 the 1941-42 season. The success of this simple form of fishing requires no 

 expensive gear, for almost any type of motor-propelled vessel is suitable ; 

 consequently the fisher}^ has attracted large numbers of fishermen. As a 

 result, competition between the various fishermen has meant a low indi- 

 vidual return in spite of the fact that this method of fishing has produced 

 a good total catch. The Navy 's acquisition of many purse-seine boats has 

 further increased the importance of the scoop boats. 



Besides the loss of the purse-seine boats, many mackerel fishermen 

 haA'^e entered the armed forces, and even more left the fishery to take part 

 in the defense industries. Elimination of the enemy aliens also curtailed 

 the productivitj^ of this fishery. Port restrictions in Los Angeles Harbor 

 have been particularly difficult for the scoop boats, since the delay in their 

 daily passage in and out of port has restricted their fishing time. 



Mackerel investigations of the Bureau of Marine Fisheries have con- 

 sisted of tagging, sampling of the catch, and racial and age studies of the 

 fish. During the biennium 42,401 mackerel were tagged and 4,486 tags 

 have been recovered. Although the movements of the tagged fish indicate 

 that the fish are migratory to some extent, the concentration of the fishery 

 in one section of the range of distribution makes it very difficult to inter- 

 pret the tagging results. The investigations of the possible occurrence 

 and distribution of various races, and the studies of abundance of different 

 age-classes of mackerel have been carried out to assist in measuring the 

 rates of change of the various populations. There is little doubt that 

 more extensive w^ork will be necessary off the coast of Mexico in the future 

 years before definite interpretation of the fluctuations in the local catch 

 will be possible. 



CENTRAL VALLEYS INVESTIGATIONS 



Central Valleys investigations are designed to find ways and means 

 to provide for the continued existence of the salmon runs which will be 

 affected by the various units of the Central Valleys Water Development. 

 So far the problem has been to try to salvage as much spawning area as 

 I)ossible and make it accessible to the fish. In each case where the fishery 

 and agricultural or engineering interests conflict, the resultant solution 

 of the problem has been decided largely on the basis of supposed relative 

 values, and the difficulty of arriving at a proper evaluation of the salmon 

 runs in the various streams has been a major handicap. Investigations 

 have therefore been directed on the one hand to devising ways and means 

 for caring for the fish, and on the other to reach some idea of the size and 

 value of the runs currently affected, or that will eventually be affected 

 by immediate developments of the Central Valleys water plan. 



Care of the salmon on the spawning grounds involves provision of 

 adequate passage upstream to suitable gravel beds. Ladders must be 



