Abundance estimates for the Antillean manatee, Trichechus manatus manatus, in the southern Gulf of Mexico are based on interviews, mortality reports, and opportunistic sightings. The lack of quantitative data is explained by the complexity of hard-to-access fluviallake systems, low water transparency, and the elusive behavior of manatees. Side-scan sonar is a promissory tool to detect and count manatees in fluvial systems. The Pantanos de Centla Biosphere Reserve (PCBR), in the coastal plain of Tabasco (Mexico), could play a key role in the regional conservation of manatees, but it is under constant pressure, especially from the oil and gas industry, and it is important to generate quantitative data for this area. The objective of this study was to quantify the relative abundance of manatees at 4 selected sites within PCBR and at 2 reference sites outside the reserve using side-scan sonar, as a basis for the long-term monitoring of the species and to determine the importance of the reserve for regional manatee conservation. We conducted 5 to 7 boat surveys on 10-km line transects along selected water courses and recorded 63 manatee sightings. Manatees occurred at all sampling sites and abundance increased upriver. The site with the highest mean abundance (5.17 ± 1.9 manatees/10 km) was located at the southeastern end of PCBR. There was statistical difference among sites. The southeastern portion of Tabasco is a key region for manatee conservation and management in Mexico. PCBR is a key regional feature but it is necessary to define protection strategies within and beyond its southern limits.

The aim of this study was to analyze the taxonomy and distribution of the polychaetes of the family Paraonidae from a lagoon-estuarine ecosystem in the Gulf of Mexico. The samples come from 20 soft bottom stations in the Términos Lagoon during the dry and rainy seasons, of which eight included paraonids. In all, 1183 specimens belonging to two new species were identified: Aricidea (Acmira) hirsuta (1125 specimens) and Paradoneis carmelitensis (58 specimens). A. (A.) hirsuta is clearly distinguished from other members of the genus by the presence of unidentate curved spines with a dense pubescence along their medium and distal margins, and because the median antenna is short. P. carmelitensis is mainly characterized by the absence of eyes, by the presence of triangular shaped postchaetal prebranchial lobes, and the presence of branchiae and lyriform chaetae from chaetiger 4. The paraonids occurrence was mainly associated with salinities close to marine conditions (31.71 to 35.85 psu). They were almost totally collected during the rainy season (1178 specimens from both species) in the central and southern areas; during the dry season only five specimens of P. carmelitensis were recorded.