Experimental culture of snook Centropomus undecimalis and chucumite Centropomus parallelus (Perciformes: Centropomidae) in artisanal earthen ponds

 The common snook, Centropomus undecimalis, and the locally called chucumite, Centropomus parallelus, occur naturally in the Gulf of Mexico. They are considered high value species and are regularly exploited in coastal fisheries, particularly in the state of Veracruz (Mexico). In order to study their growth in fresh-water artisanal earthen ponds, fingerlings of about 5.5 cm standard length of both species were captured in Alvarado Lagoon (Veracruz) and stocked in three 25 × 10 × 1.20 m ponds at densities of 4:1, 1:1 and 3:2 (chucumite:snook). Tilapia (Oreochromis niloticus) broodstocks were stocked at the same time to supply live food for the snook and chucumite. During the 14-month experimental period, the absolute growth rates in length and weight were recorded, obtaining maximum values of 26.43 ± 0.135 cm and 265.3 ± 0.623 g for C. undecimalis and of 12.0 ± 0.105 cm and 55.1 ± 0.191 g for C. parallelus; the daily growth rate was 0.062 cm for the former and 0.028 cm for the latter. The length-weight relationship estimated (W = aLb) was 3.01 for C. undecimalis and 2.96 for C. parallelus, presenting isometric growth. The fresh-water culture conditions were monitored throughout the experiment, including temperature (26–34°C), dissolved oxygen (4.1–6.9 mg L–1) and pH (6.9–7.5). The culture conditions used did not have any negative effect on growth, since the lengths and weights attained are within the mean values reported for both species

Drastic Vegetation Change in the Guajira Peninsula (Colombia) During the Neogene

International audienceDry biomes occupy ~35% of the landscape in the Neotropics, but these are heavily human-disturbed. In spite of their importance, we still do not fully understand their origins and how they are sustained. The Guajira Peninsula in northern Colombia is dominated by dry biomes and has a rich Neogene fossil record. Here, we have analyzed its changes in vegetation and precipitation during the Neogene using a fossil pollen and spore dataset of 20 samples taken from a well and we also dated the stratigraphic sequence using microfossils. In addition, we analyzed the pollen and spore contents of 10 Holocene samples to establish a modern baseline for comparison with the Neogene as well as a study of the modern vegetation to assess both its spatial distribution and anthropic disturbances during the initial stages of European colonization. The section was dated to span from the latest Oligocene to the early Miocene (~24.2 to 17.3 Ma), with the Oligocene/Miocene boundary being in the lower Uitpa Formation. The early Miocene vegetation is dominated by a rainforest biome with a mean annual precipitation of ~2,000 mm/yr, which strongly contrasts with Guajira's modern xerophytic vegetation and a precipitation of ~300 mm/yr. The shift to the dry modern vegetation probably occurred over the past three millions years, but the mechanism that led to this change is still uncertain. Global circulation models that include the vegetation could explain the ancient climate of Guajira, but further work is required to assess the feedbacks of vegetation, precipitation, and CO2