and present levels of abundance are listed according 

 to three major runs — spring, summer, and fall. 



572. Effects of lamprey larvicides on inverte- 

 brates in streams, by Richard L. Torblaa. 

 August 1968, iii + 13 pp., 2 figs., 11 tables. 



ABSTRACT 

 The study was conducted on five streams tribu- 

 tary to Lake Superior and four tributary to Lake 

 Michigan. Samples of the bottom fauna before and 

 after chemical treatment revealed that most groups 

 of aquatic organisms were not adversely affected 

 by exposure to larvicides. The total number of in- 

 vertebrates was smaller 1 week after treatment than 

 before treatment, increased somewhat by 6 weeks 

 after treatment, and had returned to pretreatment 

 levels 1 year after treatment. Aquatic insects were 

 affected less than other organisms, and invertebrates 

 were more severely affected and recovered more 

 slowly in areas of sand and detritus than in riffle 

 areas. 



573. Physical, chemical, and biological ocean- 

 ography of the entrance to the Gulf of Cali- 

 fornia, spring of 1960, by Raymond C. Grif- 

 fiths. December 1968, iii + 47 pp., 40 figs., 

 1 table. 



ABSTRACT 



The whole area at the entrance to the Gulf of 

 California and off southwestern Lower California 

 in the spring of 1960 was underlain by Intermediate 

 Water (marked by a salinity minimum of about 

 34.5 ppt at about 800 m) and, above that, by 

 Subtropical Subsurface Water (marked by a sa- 

 linity maximum of 34.80 ppt at about 200 m). 

 Above these waters were: to the northwest, Cal- 

 ifornia Current Surface Water (marked by a shal- 

 low salinity minimum of about 34.10 ppt at about 

 100 m) ; to the northeast. Gulf Surface Water 

 (marked by high surface salinities that obscure the 

 maximum of the Subtropical Subsurface Water) ; 

 and, to the south, Subtropical Surface Water 

 (marked by intermediate salinities and high tem- 

 peratures). 



The most important oceanographic feature of the 

 area was a strong front between California Current 

 and Gulf Surface Waters. At Cape San Lucas this 

 front was roughly vertical, but to the south and 

 west it became more sinuous and much weaker and 

 was formed more and more by California and Sub- 

 tropical Surface Waters. At the Cape tl.>i stronger 

 flow of the California Current Water seemed to 

 hold back the Gulf outflow at the surface, and to 

 the south of the Cape it penetrated Gulf Surface 

 Water at depths between 50 and 100 m, spreading 

 horizontally or affecting in some way the entire 

 Gulf entrance, often in a complicated manner. The 

 vertical front at Cape San Lucas thus became a 

 horizontal one offshore at depth. The frontal sys- 



tem was very clearly shown in the distributions of 

 temperature and salinity in the upper 100 m, but 

 only between 50 and 100 m in the oxygen distribu- 

 tion. 



The Subtropical Subsurface Water was in the ex- 

 tensive oxygen minimum of the eastern Pacific, and 

 the oxygen content of the surface waters was af- 

 fected by upwelling and probably by phytoplankton 

 activity. 



The second important feature of the area was 

 upwelling. Distributions of temperature, salinity, 

 and oxygen showed it to be strong off western Lower 

 California and weaker off Cape Corrientes and 

 other parts of the eastern side of the Gulf entrance. 

 The water upwelled off Lower California was ini- 

 tially low in oxygen content, but this content in- 

 creased as the water moved south. The distribu- 

 tions of temperature and, particularly, salinity 

 showed this transport. The standing crop of zoo- 

 plankton was generally highest in the areas in 

 which upwelled water occurred. 



574. Some operational aspects of the Hawaiian 

 live-bait fishery for skipjack tuna (Katsuwon- 

 us pelamis) , by Vernon E. Brock and Richard 

 N. Uchida. September 1968, iii -I- 9 pp., 1 

 fig., 5 tables. 



ABSTRACT 



An analysis of detailed operating records of two 

 Hawaiian skipjack tuna vessels during 1952 and 

 1953 indicated consistent patterns of time utiliza- 

 tion and activities that probably were representa- 

 tive for the Hawaiian skipjack tuna fleet during 

 these 2 years. Availability of skipjack tuna appears 

 to be lowest during the winter; hence, the vessels 

 are drydocked and repaired then. The pattern of 

 fishing was marked by a period of bait collection 

 lasting a day or more, followed by a period of fishing 

 that lasted from 1 to 5 days, but generally was 3 

 days or less. Baitfish mortality rates were so high 

 that it was difficult to maintain a large quantity of 

 live bait, or to fish successfully for more than 3 days. 

 The design of the skipjack tuna vessels and their 

 operating procedure reflected these constraints in 

 the use of bait. Long-range vessels with refriger- 

 ation, possibly able to fish more efficiently during 

 the winter, would be impractical without the devel- 

 opment of methods to reduce baitfish mortalities. 

 A fishery for live bait, independent of the tuna fish- 

 ing vessels, would require the same techniques to 

 be successful. 



Much of the time at sea was spent in searching 

 for fish rather than in fishing. A reduction in time 

 spent searching would reduce the loss of baitfishes 

 in the baitwells and increase the catch of skipjack 

 tuna for baitfish used. Hence, knowledge of areas 

 where skipjack tuna are concentrated would be of 

 substantial value to the fishery. 



575. Length relations of some marine fishes 



12 



