were similar in the different years and were related 

 closely to trends in air temperature. Average water 

 temperatures were lowest (about 13° C.) in Jan- 

 uary and February and highest (about 31° C.) in 

 July. The rate of warming and cooling was directly 

 related to the magnitude of the annual temperature 

 difference between the warm and cool months. 



Salinity ranged from 0.1 to 23.7 p.p.t. (parts per 

 thousand) and was related inversely to stream flow 

 and precipitation. Variations in rainfall resulted 

 in fluctuations in stream flow and these, in turn, 

 were reflected by variations in salinity. 



Dissolved organic nitrogen ranged from 23.5 to 

 171.5 tig. at./l. microgram atoms per liter) and 

 averaged 66.4 ,ig. at./l. Total phosphorus ranged 

 from 1.7 to 26.3 /ig. at./l. and averaged 8.2 /ig. at./l. 

 Phosphorus values increased markedly in July 1966. 

 No correlation existed between nitrogen or phos- 

 phorus and stream flow or rainfall. 



Dissolved o.xygen ranged from 3.8 to 19.3 p.p.m. 

 (parts per million). 



579. Published in 1968. 



580. Maturity and spawning of skipjack tuna 

 (Katsioronus pelamis) in the Atlantic Ocean, 

 with comments on nematode infestation of the 

 ovaries, by David C. Simmons. January 1969, 

 17 pp., 6 fig-s., 3 tables. 



ABSTRACT 



Ovaries were examined from 537 fish collected in 

 the eastern tropical Atlantic, western tropical At- 

 lantic, and off New York. The reported incidence 

 of larval and juvenile K. pelamis was also reviewed. 

 The minimum fork length of skipjack tuna at ma- 

 turity was 435 mm. in the eastern tropical Atlantic, 

 and 410 mm. in the western tropical Atlantic. All 

 ovaries collected off New York were in an early 

 stage of development. The percentage of skipjack 

 tuna near spawning or recently spawned was greater 

 in the western tropical Atlantic than in the eastern 

 tropical Atlantic. Skipjack tuna spawn throughout 

 the year in the areas studied in the tropical Atlantic. 

 The number of eggs per spawning for fish 465 mm. 

 to 809 mm. long was 262,000 to 1,331,000. 



Nematodes identified as Philometrn sp. and 

 Spiruroidea infested the ovaries of about 90 percent 

 of the mature skipjack tuna. Both taxa were found 

 in the ovaries of tuna collected in all three areas. 



581. Zooplankton volume off the Pacific coast, 

 1960, by James R. Thrailkill. March 1969, 

 50 pp., 13 figs., 5 tables. 



ABSTRACT 

 Basic data on volumes of zooplankton are given, 

 together with data for all plankton hauls taken on 

 survey cruises of the California Cooperative Oceanic 

 Fisheries Investigations. Distribution charts show- 

 ing relative areal zooplankton abundance by month 

 are included. 



582. The Japanese Atlantic longline fishery, 

 1965, and the status of the yellowfin tuna and 

 albacore stocks, by John P. Wise and William 

 W. Fox, Jr. April 1969, 7 pp., 2 figs., 7 tables. 



ABSTRACT 

 Fishing effort reached nearly 100 million hooks 

 in 1965, a level which is more than the yellowfin tuna 

 stocks can support and remain commercially pro- 

 ductive. As catch rates for yellowfin tuna decrease, 

 more and more fishing will be directed toward al- 

 bacore. 



583. Electrical installation for control of the 

 northe)n squawfish, by Galen H. Maxfield, 

 Gerald E. Monan, and Holbrook L. Garrett. 

 February 1969, iii + 14 pp., 8 figs., 4 tables. 



ABSTRACT 



Electricity was used e.xperimentally to divert and 

 trap squawfish during their spawning migration 

 in 1958 at Cascade Reservoir, Idaho. Electrical 

 fields, created by sequentially energizing a V-shaped 

 array of vertically suspended round electrodes with 

 square-wave, d.c. pulses, were evaluated as a means 

 of diverting squawfish into traps. 



Three test conditions of varied pulse frequency, 

 pulse duration, and voltage were tested. Two sets 

 had a pulse frequency of 10 pulses per second (2 per 

 field per second when five fields were pulsed in se- 

 quence), a pulse duration of 50 msec, and voltages 

 of 140 and 180 v.; one set had a pulse frequency of 

 15 pulses per second (3 per field), a pulse duration 

 of 25 msec, and a voltage of 180 v. One set (pul.se 

 frequency, 10 pulses per second; pulse duration, 

 50 msec; and voltage, 180 v.) was repeated. 



The electrical fields of the electrode array were 

 effective in diverting squawfish into traps. The test 

 condition with pulse frequency of 15 pulses per sec- 

 ond, pulse duration of 25 msec, and voltage of 180 v. 

 was less effective than the other test conditions. 



584. Fur seal investigations, 1966, by BCF, 

 Marine Mammal Biological Laboratory. June 

 1969, vii + 123 pp., 33 figs., 6 app. C figs., 

 52 tables, 27 app. A tables, 15 app. C tables. 



ABSTRACT 



In 1966, 52,497 male and 391 female fur seals 

 (Callorhinus insinus) were killed on the Pribilof 

 Islands. 



Counts of dead fur seals included 27,392 pups, 

 222 adult males, and 227 adult females. 



Malnutrition, hookworm disease, infections, and 

 bite wounds were the major causes of death of 164 

 pups examined in 1966. 



On the Pribilof Islands 9,948 harem and 6,856 

 idle males were counted in 1966. 



Of the 51 4-year-old females examined, one was 

 primiparous and post partum; none of the 65 3- 

 year-old females had been gravid. 



Handling apparently causes pups to lose weight 

 or slows their rate of weight gain. 



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