Table &.--Prnnary productivity, chlorophyll a concentration, and water transparency for sockeye salmoji nursery lakes of 



southwestern Alaska, 1962 



Primary Chloro- Water 



productivity phyll o transparency 



Mfan carbon Mean carbon 



fixation prr fixation per 



4-hour period 4-hour period 



per per 



square meter cubic meter Mean 



Deter- lake surface in euphotic Deter- Mean Secchi disk 



System and lake minations area zone minations concentrations Samples reading 



MAINLAND SYSTEMS }\umber Mg. Mg. Number Mg./I. Numher M. 

 Igushik system 



Amanka Lake 1 0.7 2 8.5 



Ualik Lake 9 73 2.5 2 .8 3 9.7 



Snake system 



Lake Nunavaugaluk 10 66 1.4 1 .6 1 13.0 



Wood system 



Lake Aleknagik 240 65 2.0 8 1.3 25 8.7 



Lake Nerka 659 58 1.7 22 .9 63 12.6 



Lake Beverley 118 71 1.7 8 1.0 11 12.0 



LakeKulik 108 66 1.6 7 .8 U 11.5 



Little TogiakLake-- 133 73 1.9 6 1.4 14 10.4 



Nuyakuk (Tikchik) system 



Tikchik Lake 10 52 1.6 3 .6 3 10.7 



Nuyakuk Lake 2 .2 2 10.0 



Lake Chauekuktuli 10 54 1.0 3 .5 3 15.3 



Kvichak system 



Iliamna Lake 456 54 1.5 166 .8 24 9.8 



Lake Clark 41 13 1.6 4 1.1 4 3.8 



PENINSULA SYSTEMS 



Alagnak (Branch) system 



Kukaklek Lake 18 22 1.1 4 .6 3 10.2 



Nonvianuk Lake 20 24 1.2 4 .5 4 13.2 



Naknek system 



Coville Lake 411 99 5.9 80 1.0 72 5.4 



Grosvenor Lake 553 61 2.9 85 .7 84 8.4 



Naknek Lake ' 810 59 3.4 86 .9 135 4.4 



Iliuk Arm . ^ 



Brooks Lake 832 47 1.7 73 .5 154 10.8 



Ugashik system 



Low er Ugashik Lake 20 41 1.2 4 .8 3 8.5 



Chign'k system 



Chignik Lake 311 242 13.6 41 15.3 41 1.9 



Black Lake 137 121 33.4 26 5.4 28 1.6 



Karluk system 



KarlukLake 606 131 5^_9 73 2J 105 8.6 



' Excluding Iliuk Arm. IHuk Arm is considered separately because of the large amount of suspended glacial material. 



highest photosynthetic activity and the greatest 

 standing crop of phytoplankton of all lakes 

 studied. Chignik Lake had a high average value 

 for carbon fixed in the water column, but the 

 rate per cubic meter in the euphotic zone was 

 much higher in shallow Black Lake where a high 

 rate of carbon fixation extended to the bottom. 

 Although the low transparency in these two 

 lakes was primarily due to heavy phytoplankton 

 blooms, in Chignik Lake it was partially due to 

 suspended rock flour. 



In Karluk Lake, the rate of carbon fixation 

 per cubic meter in the euphotic zone was high 

 but considerably below the rate in the Chignik 

 system. Because of the greater depth of the 

 euphotic zone at Karluk Lake, however, the rate 



of carbon fixation per square meter of surface 

 was greater than in Black Lake. The Secchi disk 

 readings were 8.6 and 1.6 m., respectively, for 

 Karluk and Black Lakes. The standing crop of 

 phytoplankton in the Karluk system was second 

 only to that of the Chignik system. 



PRODUCTIVITY MEASUREMENTS AND SALMON 

 PRODUCTION 



Studies of the size of escapements and the 

 growth of progeny indicate that in some systems 

 at least (Wood, Kvichak, and Chignik), the 

 growth of young salmon is .slower when popu- 

 lation densities are high (see later sections of 

 this paper) . This .slow growth suggests that the 

 abundance of food in the nursery lake limits 



SOCKEYE SALMON IN MAJOR RIVER SYSTEMS IN SOUTHWESTERN ALASKA 



417 



