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Fishery Bulletin 94(2), 1996 



air-sea fluxes, and propagation of internal waves 

 enhance mixing of the water (Roden and Groves, 

 1959; Badan-Dangon et al., 1985; Bray and Robles, 

 1991). Strongest tidal currents have been recorded 

 in the Ballenas Channel (west of Angel de la Guarda 

 Island) and Salsipuedes Channel (Fig. 1). Here the 

 water column is well mixed above 500 m during 

 spring tides (Bray and Robles, 1991) as observed in 

 May 1965 (st. XI, Fig. 2). In contrast, the Guaymas 

 Basin profiles (sts. XII and XIII) showed gradients 

 of temperature and oxygen that were particularly 

 strong above 100 m. Temperature in the top 50 m 

 showed differences of 2-4"C among the three sam- 

 pling stations. Surface salinity showed values >35.0 



ppt, characteristic of the Gulf water mass, produced 

 in the northern gulf and flowing and mixing rapidly 

 southward. 



Vertical distribution of euphausiids 



Off Point Eugenia, the greatest number of species 

 was of the Central Pacific group. These, however, had 

 relatively low abundances, <10 ind/m- per species, 

 excepting Euphausia recurva and, at one station, E. 

 hemigibba (Table 1). This group was absent in the 

 Gulf of California. 



The most abundant species in both study regions 

 was Nyctiphanes simplex (Tables 1 and 2). This spe- 



