FISHERY BULLETIN: VOL. 70. NO. 1 



Specimens in the same sample frequently varied 

 from one another, and the degree of decomj^o- 

 sition in each specimen usually was not uniform. 

 Lightly digested prey were largely intact, and 

 their internal organs still visible. Moderately 

 digested prey contained obviously macerated tis- 

 sue and were often incompletely fragmented. 

 Prey in an advanced state were highly frag- 

 mented, and soft tissues were absent. Digestion 

 of foregut contents tended to be less advanced 

 in night-net than in day-net samples. However, 

 most foreguts in both categories contained ma- 

 terial in an advanced state of digestion. 



Five groups of ingested material, calanoids, 

 euphausiids, chaetognaths, fish scales, and un- 

 identifiable matter, occurred in lO^r or more of 

 at least one of the three sampling categories 

 (Figure 1). Unidentifiable material consisted 

 primarily of crustacean fragments and matted 

 aggregations of fibrous and granular debris. 

 Of identifiable groups, calanoids were usually 

 most abundant in all three categories (Table 3) . 

 The four identifiable groups of prey organisms 

 appeared in higher numbers in net samples than 

 in fish samples, diff"erences between the median 

 values, with the exception of chaetognaths, being 

 significant at P ^ 0.05. 



Frequencies, overall means, and median 

 sample means of calanoids and euphausiids in 

 day-net samples were less than were those in 

 night-net samples. However, differences be- 

 tween the day and night median values of the 

 four identifiable groups were not significant 

 (P > 0.50). Twilight-net samples do not ap- 

 pear to diflfer appreciably from day- and night- 

 net samples. 



Calanoid genera occurring in more than 10 '^r 

 of the three categories (Figure 2) were Metridia 



CALANOIDS 



EUPHAUSIIDS 



FISH SCALES 



CHAETOGNATHS 



UNIDENTIFIED 



Figure 1. — Frequencies of ingested items occurring in 

 lO'/c or more of night-net (black), day-net (open) and 

 fish (strippled) samples. 



(principally pacifica), Calaviis (principally pa- 

 cificus), Pleuromamma (principally borealis), 

 Rhincalanus (all nasutus) , Euchaeta, Eucalanus 

 (principally himgii) , Scolecithricella, and Can- 

 dacia (principally hipinnata) . These genera 

 have been found typically in the uppermost 200 

 to 300 m of the California Current region (Flem- 

 inger, unpublished data). 



The overall mean number of Calanus in day- 

 and night-set samjjles are notably diflferent 

 (Table 4) . In night-net samples Calanus ranked 

 with Metridia, the two dominating the list of 



Tablf, 3. — Median of sample means and overall mean of number of prey per foregut. 



220 



