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Fishery Bulletin 94(2). 1996 



cies is a warm-temperate endemic, occurring typi- 

 cally in nearshore waters of the southern part of the 

 California Current (Brinton, 1962a) and in the Gulf 

 of California (Brinton and Townsend, 1980). Other 

 abundant species of the group identified as the "Cali- 

 fornia Current's transition zone" was Nematoscelis 

 difficilis, which was even more abundant in the Gulf 

 than at the California Current stations. Euphausia 

 gibboides, Thysanoessa gregaria (transition zone), 

 and the subarctic-warm temperate E. pacifica were 

 not observed in the Gulf. 



Tropical species were scarce along both coasts of 

 the peninsula, as expected during the time of sam- 

 pling (Brinton, 1979; Brinton and Townsend, 1980). 

 In this group, E. eximia and Nematobrachion flexipes 

 were common off Point Eugenia and in Guaymas Ba- 

 sin. Euphausia lamelligera and E. distinguenda were 

 observed in Guaymas Basin only. The tropical-subtropi- 

 cal Stylocheiron affine was taken only at Point Eugenia. 



Expected trends of low abundances during daytime 

 were observed and are believed to be due to net avoid- 

 ance during the hours of light. High abundance was 

 usually accounted for by larvae of epipelagic species 

 when most of the population was in the upper 100 m 

 at night. Larvae of N. simplex accounted for 90% or 

 more of the euphausiids in the richest samples. Off 

 Point Eugenia their distribution was greater toward 

 the coast and in the upper 50 m (Fig. 3). Night occur- 

 rences of calyptopes and early furcilias (C-F :j in Fig. 3) 

 were almost exclusively at st. 120.45, with most at the 

 surface; the oldest furcilias (F 4 -F 6 ) and juveniles were 

 well represented at st. 120.50, down to 50 m. The old 

 larvae descended to 200 m during daytime. The oc- 

 currence of mature adults at the surface at the 

 nearshore station may be associated with nearshore 

 grouping to mate and spawn. Inside the Gulf few lar- 

 vae of N. simplex occurred at Salsipuedes Channel 

 (st. XI, Fig. 4). Moreover, all larval stages were found 

 at Guaymas Basin, where furcilias at st. XII were 

 restricted to the first 30 m during night; the larval 

 calyptopes were dispersed in the upper 100 m. Adults 

 were more abundant at st. XIII, peaking at 30-60 m 

 (there was no sample for 0-30 m) during night and 

 at 135-270 m in the light hours. 



Vertical distribution of Nematoscelis difficilis lar- 

 vae off Point Eugenia, as with Nyctiphanes simplex. 

 was restricted to coastal stations, with a shallower 

 range nearshore (st. 120.45) than at st. 120.50 (Fig. 

 5). In contrast to N. simplex, N. difficilis larvae 

 avoided the upper layer, and juveniles and adults 

 peaked at 100 m depth during nighttime (Fig. 5). 

 Mating and spawning may have occurred in and be- 

 low the thermocline near the coast, because most of 

 the females with spermatophore attached or carry- 

 ing external eggs were found between 75 and 200 m 



during the night (st. 120.45). In the Guaymas Basin, 

 a more extended vertical range, from 55 to 420 m, 

 was observed for adults of this species (Fig. 6). In- 

 terestingly, in Salsipuedes Channel, certain of the 

 adults were near the surface, particularly gravid fe- 

 males. These may have been shedding newly hatched 

 metanauplii in the upper layer, where many were 

 found. A progression toward more advanced larval 

 stages from north to south was observed. 



Larvae of other species were found only off Point 

 Eugenia. These were of the four most abundant spe- 

 cies of Euphausia (Fig. 7). Three (E. gibboides, E. 

 recurua, and E. eximia) included larval calyptopes 



