No abstract

In March 2019, the current state of the mangrove structure in the Arroyo los Coamiles estuary (Punta Mita Bay, Nayarit) was evaluated. The method of circular plots centered on a point was used (Cottam and Curtis, 1956). The mangrove structure is made up of the species Laguncularia racemosa, Avicennia germinans, Conocarpus erectus and Rhizophora mangle. The greatest forest development is found in the second third of the estuary with a bordercontinental structure. The average height of the mangroves was 6.17 m, (SD 7.35 m), the diameter at breast height was 19.21 cm and the total basal area was 57.36 m2 . The data are associated with young trees in a good state of development and conservation. The C / N ratio was determined as an index of the quality of the soil organic substrate, the values ranged between 3.74 and 14.91 and the percentage of organic matter was from 1.45 to 8.04. The fragility of the soils reinforce the proposal to take care of the natural drainage of the property. Mangroves have been impacted by tourist developments around the world, the environmental and economic benefits that these ecosystems provide are ignored by inhabitants and authorities, which allow their destruction.

Phytoplankton biomass (Chl-a) was estimated in 7 stations of Manzanillo Bay, Colima on the surface and at the Secchi depth in the rainy and dry season (2016-2017). To evaluate the biomass, a Millipore equipment and fiberglass GF / F filters were used using the spectrophotometric technique (Lorenzen, 1967). The physicochemical parameters were estimated with a YSI 85 equipment and the nutrients using a San Plus II segmented flow autoanalyzer. The average depth of the Secchi disk ranged from 5.9 m at the Puerto station to 12.8m at the center (A1 and A2). The temperature ranged from 26.9 to 28.1 ° C, the salinity between 31.6 and 33 ups and the dissolved oxygen from 3.81 to 4.82 mg L-1. The nutrients presented high values in Puerto, A1 and Carrizales. The central part of the bay registered values greater than one mg of Chl-a and a maximum of 2.67 mg .m-3 in the Puerto station. In 2016, Chl-a decreased significantly because of a very intense Niño event, also showing high concentrations of phaeopigments, which reveal grazing conditions or degraded chlorophyll. Through an analysis of variance, it was determined that there is a significant difference between the chlorophyll-a values (p≤0.05).

ABSTRACT. The San Pedro-Mezquital River basin in Nayarit, Mexico has the majority of freshwater prawns of the genus Macrobrachium reported for the Mexican Pacific coast. Six species of freshwater shrimp are reported Macrobrachium americanum, M. occidentale, M. digueti, M. michoacanus, M. hobbsi and M. tenellum. The higher richness and diversity of freshwater prawns are found on the coastal plain. The presence of prawns in relation to the altitudinal gradient is discussed. Keywords: freshwater, crustacean, prawns, diversity, coastal plain, Nayarit, Mexico.The crustaceans of the family Palaemonidae include 36 recognized genera that are distributed in sea, brackish and/or fresh water (Holthuis, 1952). In this family, the genus Macrobrachium Bate (1868) is found, comprising about 246 species that inhabit fresh and/or brackish water environments with a wide geographical distribution in tropical and subtropical regions (De Grave & Fransen, 2011). They are distinguished from other palaemonids genera mainly for presenting the second pair of pereiopods chelate, and often in male longer than entire body (Holthius, 1952). These organisms present a behavior called amphidromy (McDowall, 2007), in which adults live in freshwater and migrate downstream near brackish water to spawn, after larval development, juveniles migrate to freshwater environments (Bauer, 2011). In Mexico, 20 species are reported (Villalobos, 1982; VillalobosHiriart et al., 1993;Wicksten & Hendrickx, 2003;Hernández et al., 2007; Alvarez & Villalobos, 2016); however, the discussion on the presence of some shrimp species on both sides (Atlantic-Pacific), or only on one of the slopes, continues among specialists. According to the region they are known as acocil, chacales, camarones, langostinos, acamayas, cauques, moyas, piguas, popotillos o gambas, are an important resource of the artisanal fishing for the people of each region (Hendrickx, 1995). The San Pedro-Mezquital River originates in the state of Durango and crosses the Sierra Madre Occidental as it passes through much of the state of Nayarit until it ends in the south of the Reserva de la Biosfera Marismas Nacionales Nayarit (DOF, 2010). The singularity of this river, is that it does not have dams in its course by Nayarit, condition that few rivers in Mexico present it. So the species move freely along the river and the basin giving great benefits to the biological diversity that sustains this lotic ecosystem. The presence of freshwater prawns in the state of Nayarit has some reports (Villalobos-Hiriart et al., 1993;Pérez-Velázquez et al., 2011); however, the San Pedro-Mezquital River is not registered to date. Therefore, the present study reports for the first time the freshwater prawns of the genus Macrobrachium in several localities of the San Pedro-Mezquital River, Nayarit River, Mexico.In January, February, May 2009 and from July to September of 2012 several localities of the San PedroMezquital River, Nayarit, were visited between 08:00 AM and 18:00 PM (Fig. 1). The sampling sites of higher altit...