International audienc

A research work on the planktonic copepods from La Ventosa Bay, Oaxaca, Mexico made between July 1987 and April 1993 is presented. In the zooplankton sampling Hensen nylon net was used. The behavior of the temperature and salinity showed two very marked periods: the first one was presented at the end of one year and the beginning of the next (winter-spring) and was characterized by the influence of the northern winds, the extraction of masses of water from the bottom to the surface and a decrease of temperature in the surface that oscillated between 18.5 and 29.9 ºC; the influence of the northern winds maintains the mixed water and little variation values of salinity between 33.0 and 35.0 ups; the second period were presented in the middle of the year, between June and July (Summer-Autumn), and was characterized by a greater environmental stability, the decrease of the influence of the wind and high temperatures between 28.8 and 32.0 ºC; the salinity values between 28.8 and 36 ups depending on the area.Thirty five species were identified the most important ones in presence or abundance were Canthocalanus pauper, Acrocalanus longicornis, Centropages furcatus, Acartia tonsa, Corycaeus speciosus, Labidocera acuta, Oncaea venusta and Oithona nana. Original drawings, descriptions and keys are presented for the identification of the species. The copepod abundance also showed very marked periods: at the end of one year and at the beginning of the next, the greatest average densities was detected and reached 24,265.19 cop/m³, while in middle year period the values oscillated between 4.68 and 1,130.35 cop/m³. Seven species were considered as cosmopolitans, 18 tropical-subtropical, four tropicalsubtropical-temperate, one equatorial and five tropic-equatorial; 14 species were considered as neritic, 17 oceanic, two neritic-oceanic and two neritic-coastal; 17 species were considered eurythermal and euryhaline and 18 stenothermal and estenohaline. At world level the study area is located in the region 20 and corresponds to Eastern Tropical Pacific characterized by 438 species, of which only 35 were found in this study. The cosmopolitan species found in this study were Acartia danae,

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