FISHERY BULLETIN: VOL. 79, NO. 1 



proved to be betv^een 34 and 40, x = 37.3, min after 

 sunset. Once there, its behavior was much like 

 that described above for nocturnally feeding olive 

 rockfish. Its diet, too, proved similar to that of the 

 rockfish. All 13 individuals (163-170 mm SL, x = 

 173.7) collected more than 3 h after sunset were 

 full of food, much of it fresh. Prey were organisms 

 that are in the nearshore water column only at 

 night, with major forms being the gammarids 

 Batea transversa (2-4 mm) and Ampelisca cristata 

 (3-8 mm), the caprellid Caprella pilidigita (6-12 

 mm), the cumacean Cyclaspis nubila (2-4 mm), 

 the mysid Siriella pacifica (4-10 mm), and epitok- 

 ous nereid polychaetes (15 mm). 



Sciaenidae: Seriphus politus 



The queenfish schools in relatively inactive as- 

 semblages near shore during the day and dis- 

 perses to feed in the water column at night after 

 moving away from its daytime schooling sites 

 (Hobson and Chess 1976). Thus, its diel activity 

 pattern is similar to that of subadult Sebastes ser- 

 ranoides and X. californiensis, described above. 

 The first Seriphus politus appeared at a nocturnal 

 feeding site on four occasions at 38-60, x = 44, min 

 after sunset. Food and feeding behavior of S. 

 politus also are similar to the other two species. All 

 31 individuals (114-193 mm SL, x = 151) sampled 

 later than 3 h after sunset contained prey, much of 

 it fresh. All were larger zooplankton that are in 

 the water column only at night, wdth major forms 

 being mysids (Siriella pacifica, 3-11 mm, and 

 Acanthomysis sculpta, 6-11 mm), a gammarid 

 (Batea transversa, 2-4 mm), and an isopod 

 (Paracercies sp., 2-7 mm). 



Sciaenidae: Umbrina roncador 



The yellowfin croaker schools close to sandy 

 beaches during the day, and at nightfall disperses 

 here and also to the regions immediately offshore. 

 It feeds on organisms in the sediment, often prob- 

 ing with its snout to make the capture. Most of its 

 foraging seems to occur at night. Of 20 individuals 

 (191-255 mm SL, x - 210.8) collected more than 

 3 h after sunset, all but 1 contained prey, much 

 of it fresh. Major items were sand-dwelling 

 polychaetes, many of them tubicolous, with 

 Onuphis sp. (15-40 mm) and Nothria stigmaeus 

 (10-20 mm) predominating; other important prey 

 were sand-dwelling gammarids, especially Am- 

 pelisca cristata (2-12 mm), Acuminodeutopus 



heteruropus (2-3 mm), and Paraphoxus heterocus- 

 pidatus (2-3 mm). Only limited feeding occurs by 

 day, as attested by eight individuals (210-239 mm 

 SL, X = 222.5) collected during the afternoon. Of 

 these, only two contained fresh material (sand- 

 dwelling amphipods, most of them Ampelisca 

 cristata). These same two, and two others, also con- 

 tained extensively digested polychaetes that obvi- 

 ously had been in the guts for some time; the other 

 four (50% of the sample) were empty. 



Embiotocidae: Hyperprosopon argenteum 



The walleye surfperch is the only predomi- 

 nantly nocturnal species among the five em- 

 biotocids considered in this paper. It schools inac- 

 tively by day, often close to shore, then disperses at 

 nightfall and moves to feeding grounds some dis- 

 tance away (Hobson and Chess 1976; Ebeling and 

 Bray 1976). It forages in the water column, where 

 it takes the larger zooplankton that are numerous 

 there only after dark. Thus, H. argenteum has 

 habits similar to those of the other nocturnal 

 planktivores described above. Although it usually 

 forages lower in the water column than these 

 others, its diet and feeding behavior also are simi- 

 lar: of 29 individuals (100-157 mm SL, x = 126) 

 collected over nocturnal feeding grounds at night, 

 or from recently formed schools before sunrise, 28 

 (97%) contained food, much of it fresh. Major prey 

 items were the gammarids Batea transversa (2-4 

 mm), Ampelisca cristata (3-4 mm), and Ampithoe 

 sp. (4-6 mm); the cumacean Cyclaspis nubila (2-4 

 mm); the isopod Paracercies sp. (2-5 mm); and the 

 caprellid Caprella pilidigita (4-10 mm). 



Fishes That Feed Day and Night 



Only two of the species studied resist classifica- 

 tion as being either primarily diurnal or primarily 

 nocturnal in their feeding activities. Both seem 

 equipped to exploit circumstances that permit ef- 

 fective feeding during all hours of day and night. 

 They are listed in Table 3, along with certain of 

 their visual characteristics. The following ac- 

 counts of their diel foraging activities puts their 

 diurnal and nocturnal habits in perspective. 



Cottidae: Leiocottus hirundo 



The lavender sculpin rests immobile in exposed 

 locations on sandy substrata, usually near rocks 

 and algae, at all hours of day and night. On the 



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