Three-dimensional distribution of larval fish habitats in the shallow oxygen minimum zone in the eastern tropical Pacific Ocean off Mexico. (July 2015)

• Record Type: Journal Article
• Authors: Davies, S.M.; Sánchez-Velasco, L.; Beier, E.; Godínez, Victor M.; Barton, Eric D.; Tamayo, A.
• Is Part Of: Deep sea research. Volume 101(2015)
• Page Start: 118
• Page End: 129
• Publication Date: 2015-07
• Subjects: Shallow oxygen minimum zone -- Larval fish habitats -- Bregmaceros bathymaster -- Eastern tropical Pacific Ocean off Mexico; Oceanography -- Periodicals; Océanographie -- Périodiques; 551.4605
• DOI: 10.1016/j.dsr.2015.04.003
• Languages: English
• ISSNs: 0967-0637

Abstract

Abstract: Three-dimensional distribution of larval fish habitats was analyzed, from the upper limit of the shallow oxygen minimum zone (~0.2 mL/L) to the sea surface, in the eastern tropical Pacific Ocean off Mexico in February 2010. The upper limit rises from ~250 m depth in the entrance of the Gulf of California to ~80 m depth off Cabo Corrientes. Three larval fish habitats were defined statistically: (i) a Gulf of California habitat dominated by Anchoa spp. larvae (epipelagic species), constrained to the oxygenated surface layer (>3.5 mL/L) in and above the thermocline (~60 m depth), and separated by a salinity front from the Tropical Pacific habitat; (ii) a Tropical Pacific habitat, dominated by Vinciguerria lucetia larvae (mesopelagic species), located throughout the sampled water column, but with the highest abundance in the oxygenated upper layer above the thermocline; (iii) an Oxygen Minimum habitat defined mostly below the thermocline in hypoxic (<1 mL/L; ~70 m depth) and anoxic (<0.2 mL/L; ~80 m depth) water off Cabo Corrientes. This subsurface hypoxic habitat had the highest species richness and larval abundance, with dominance of Bregmaceros bathymaster, an endemic neritic pelagic species; which was an unexpected result. This may be associated with the shoaling of the upper limit of the shallow oxygen minimum zone near the coast, a result of the strong costal upwelling detected by the Bakun Index. In this region of strong and semi-continuous coastal upwelling in the eastern tropical Pacific off Mexico, the shallow hypoxic water does not have dramatic effects on the total larval fish abundance but appears to affect species composition. Highlights: The largest hypoxic region of the world is the eastern tropical Pacific off Mexico. Three larval fish habitats were defined with different affinities to dissolved oxygen. A larval fish habitat was defined in hypoxic and anoxic water off Cabo Corrientes. This habitat was the most abundant of the study dominated by Bregmaceros bathymaster. No dramatic effect of growth of hypoxic water on larval fish abundance was apparent.