FISHERY BULLETIN: VOL. 74, NO. 3 



Figure 4.-Collecting plankton at 

 middepths. 



area: a pair at night, under a full moon (when there 

 was enough light to maneuver among the kelp 

 columns), and a pair the following midday. 



Because diving lights probably influence organ- 

 isms in the water column, we turned them off when 

 collecting with the plankton net at night. At these 

 times the moon provided ample light to navigate 

 when it was present, but on dark nights we 

 depended on the luminous dials of our compasses 

 and depth gauges. 



Collecting Fishes 



To determine the food habits of the fishes, we 

 speared 521 specimens of the eight species and 

 then examined their gut contents. All specimens 

 were taken in the study area between September 

 1973 and May 1974— the same period over which we 

 sampled the zooplankton. Most of these specimens 

 were collected either at night, within the 2 h 

 before sunrise, or during the afternoon— times 

 that best show differential day or night feeding. 

 All measurements of fish size noted in this report 

 are of standard length. 



Sample Analysis 



Zooplankton Samples 



Generally the samples were analyzed within 2 

 wk after collection. Sample volumes, which ranged 

 from 0.2 to 36.0 ml (x = 8.3), were determined 



after they had settled for 5 min in a graduated 

 cylinder. The entire sample was analyzed when its 

 volume was less than 5 ml. When the sample 

 was larger, 5-ml aliquots were analyzed, and 

 numbers for the entire sample then extrapolated. 

 Whenever less than the entire sample was an- 

 alyzed, the balance was searched for forms miss- 

 ing from the aliquot; when found-always in small 

 numbers— these were counted and added to the 

 list. 



Fish Gut-Content Samples 



The digestive tract of each fish specimen was 

 removed immediately after collection, and pre- 

 served in a 10% Formalin-^ solution. For analysis, 

 the contents were examined under a binocular 

 dissecting microscope, and, when necessary, a 

 binocular compound microscope. A note was made 

 of the position in the digestive tract of the various 

 items. A list was then composed of the items in the 

 gut, with the species identified when feasible. The 

 following data were then noted for the items in 

 each listed category: 1) their number; 2) their size 

 range; 3) the extent they had been digested (sub- 

 jectively assessed on a scale of five, from fresh to 

 well-digested); and 4) an estimate of their repre- 

 sentation in the gut as percent by volume of the 

 contents. 



^Reference to trade names does not imply endorsement by 

 the National Marine Fisheries Service, NOAA. 



570 



