FISHERY BULLETIN: VOL. 70, NO. 4 



types of algae among which two species of 

 Caiderpa, C. prolifera and C. paspaloides, were 

 most conspicuous. Collections of fishes were 

 made near low tide at which time the depth at 

 the sampling sites was 3 to 4 ft. Specimens an- 

 alyzed for this report were collected from April 

 3 to August 25, 1971. Water temperatures at 

 the sampling sites during this period ranged 

 from 17.3° to 33.1 °C whereas salinities ranged 

 from 16.4 to 24.1 ^/ic. All sampling sites were 

 greater than a mile from the zone of influence 

 of thermal discharge from the electric station. 

 The majority of juvenile fishes used in this 

 study were collected with a bag seine (50 ft X 

 6 ft) constructed of %-inch stretched mesh net- 

 ting. A few specimens were collected in a 5-ft 

 cast net constructed of i/^-inch stretched mesh 

 netting. Specimens were preserved immediately 

 in 20% Formalin-seawater. In the laboratory, 

 fish were washed in tap water, sorted to species, 

 and stored in 75% isopropyl alcohol. High con- 

 centrations of preservative were used to assure 

 adequate preservation of stomach contents. 

 Specimens of adult D. holbrooki were collected 

 with hook and line, injected immediately with 

 Formalin, and treated as above. 



ANALYSIS OF STOMACH CONTENTS 



Juvenile fishes were measured to the nearest 

 1.0 mm standard length and sorted into size 

 classes of 5-, 10-, or 20-mm increments depend- 

 ing on the number of fish available. All refer- 

 ences to fish length are in terms of standard 

 length. After removal of stomachs, food items 

 were removed in alcohol with the aid of a dissect- 

 ing microscope. Stomach contents from similar 

 size classes were pooled and analyzed as to per- 

 cent composition using a modified gravimetric 

 procedure which employed a preliminary frac- 

 tionation of food items with a series of sieves. 

 This procedure is outlined below: 



1. Large food items of similar types easily 

 recognizable to the naked eye were removed 

 onto pre weighed filter pads (Whatman^ 



* Reference to trade names in this publication does 

 not imply endorsement of commercial products by the 

 National Marine Fisheries Service. 



No. 42, 2.5-inch diameter). This initial 

 step was used only for certain food items 

 (i.e., shrimp, crabs, larval fish, etc.) ob- 

 tained from fish in the larger size classes. 



2. The remaining stomach contents were 

 poured into a series of 3-inch diameter 

 sieves (U.S. Standard Nos. 10, 20, 30, 60, 

 120, 200) arranged and clamped together 

 in order of decreasing mesh size. Sieves 

 Nos. 10 and 20 were frequently not needed 

 for fractionations of material from fish in 

 very small size classes. 



3. The series of sieves was secured to a Bur- 

 rell "Wrist Action" shaker and shaken 

 gently for 10 to 15 min while washing 

 continuously under slowly flowing water. 



4. The contents of each sieve (comprising a 

 sieve fraction) was washed into a finger 

 bowl for detailed analysis beneath a dissect- 

 ing microscope. Analysis involved adding 

 five large drops of the sieve fraction to a 

 gridded petri dish (13 squares per inch) 

 and recording the frequency of occurrence 

 of each type of food item in each drop. The 

 accuracy of this method is good because 

 all food items in a particular sieve fraction 

 are of comparable size. The portion of the 

 contents of each sieve fraction attributable 

 to each type of food item was recorded. 



5. After analysis of all sieve fractions, each 

 fraction was vacuum-filtered onto a sep- 

 ate preweighed filter pad using a Millipore 

 filter holder and a vacuum flask. 



6. Filter pads were dried overnight in a dry- 

 ing oven (ca. 70°C) and dry weights of 

 food items were calculated after weighing 

 the pads to the nearest 0.0001 g on a micro- 

 balance. 



Further comments on the eflficacy of this pro- 

 cedure for analyzing the stomach contents of 

 small fish are given in the following section on 

 Results. 



RESULTS 



OLIGOPLITES SAURUS 



Figure 1 shows the results of analyses of 

 stomach contents of juvenile O. saurus belonging 



1112 



