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Leon-Chavez C.A.,National Autonomous University of Mexico | Leon-Chavez C.A.,Ave Institute Polytechnic Nacional S N | Sanchez-Velasco L.,Ave Institute Polytechnic Nacional S N | Beier E.,Research Center Cientifica Educacion Superior Of Ensenada | And 3 more authors.
Journal of Plankton Research | Year: 2010

In this work, we linked larval fish assemblages with water masses and circulation in the Eastern Tropical Pacific off Mexico, during autumn 2005 and winter 2007. Four assemblages were defined. (i) The "Transitional" assemblage, with the lowest mean larval abundance and dominated by tropical mesopelagic Vinciguerria lucetia and Diogenicthys laternatus. It was associated with modified California Current Water in winter and with modified Tropical Surface Water in autumn. (ii) The "Coastal-oceanic" assemblage was found off Cabo Corrientes, with high larval abundance, and dominated by Bregmaceros bathymaster; part of this assemblage was trapped by coastal cyclonic eddies. (iii) The "Tropical A" assemblage was associated with Tropical Surface Water. It had the highest abundance and richness, and the largest number of dominant species (e.g. D. laternatus, Auxis spp.); it covered a wider area in winter than in autumn. (iv) The "Tropical B" assemblage, distinguished by the highest abundance of V. lucetia, was present only in autumn; it was associated with overall anticyclonic circulation of warm Tropical Surface Water. The agreement between larval fish assemblage distributions, water masses and mesoscale dynamics indicates that the formation and permanence of assemblages depends on the interaction of spawning strategies of different species with large-scale and mesoscale processes.

Sanchez-Velasco L.,Ave Institute Polytechnic Nacional S N | Lavin M.F.,CICESE | Jimenez-Rosenberg S.P.A.,Ave Institute Polytechnic Nacional S N | Montes J.M.,CICESE | Turk-Boyer P.J.,Centro Intercultural Para El Estudio Of Desiertos Y Oceanos Cedo
Continental Shelf Research | Year: 2012

The Upper Gulf of California (UGC) is a Biosphere Reserve that despite its extreme environmental conditions (macrotidal inverse estuary) houses a high fish species richness. An intensive sampling of fish larvae and hydrography was carried out during June 2008 in the UGC. From 56 zooplankton sampling stations with a maximum of three sampling strata (each 5. m deep, from 0 to 15. m), a total of 29,505 fish larvae were collected, included in 99 taxa and 32 families. The Bray-Curtis Index defined three main larval fish habitats that varied in composition. (i) The "Mixed" larval habitat was mostly defined in the vertically mixed western sector of the UGC; the coastal pelagic Anchoa spp. presented high abundance in this habitat, associated with demersal species such as Gobulus crescentalis and Scianidae type 1. The lowest diversity and abundance, and the highest salinity, temperature and chlorophyll distinguished this larval habitat. (ii) The "Front" habitat was located mostly on the physical-chemical frontal zone between the UGC and the Northern Gulf; it had the highest specific richness and larval abundance. The dominant species were the coastal pelagics Anchoa spp. and Opisthonema sp. 1; the latter was almost limited to the north by the frontal zone. (iii) The "Shelf" habitat, found over the shelf off the mainland, was the deepest and less salty, and was also dominated by Opisthonema sp. 1, but included epipelagic species such as Scombridae (e.g., Scomber japonicus, Auxis spp., Scomberomerus sierra), probably from the adjacent deeper zone. These larval fish habitats had well-defined limits that coincided with marked environmental gradients, with the lowest larval diversity in the saltiest environment; this suggests that the human-induced shift to hypersaline conditions may have reduced the preferred larval habitat for some species. The habitats most likely change with the seasons, with implications for the management of the reserve. © 2011 Elsevier Ltd.

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