Reference values for biochemical analytes in feral sheep from Socorro Island, Revillagigedo Archipelago, Mexico

ABSTRACT To establish reference values for biochemical analytes related to freshwater shortage adaptation, a total of 376 blood samples were collected from feral sheep at Socorro Island, Revillagigedo Archipelago. Year-round variation was assessed by sampling at the beginning of each season defined by the March equinox, June solstice, September equinox, and December solstice. The resulting data set was analyzed using Gaussian distribution and descriptive statistics. Confidence intervals of 95% were established. Analysis of variance was used to compare the mean values of each season. Total cholesterol, triglycerides, urea, albumin, total protein, sodium ion, anion gap, creatine kinase, arginine vasopressin, and aldosterone showed concentrations above the reference range for domestic sheep. Triglycerides, urea, albumin, sodium ion, and aldosterone showed concentrations within the reference range for domestic goats. Most biochemical analytes showed differences (P<0.05) between seasons, with the highest values occurring during winter, and the lowest during spring. Results could help improve the accuracy of metabolic profiles used as a tool for evaluating dehydration indicators, and to describe the physiological mechanisms employed by feral sheep to cope with seasonal availability of freshwater.

FISHES OF ARCHIPELAGO OF REVILLAGIGEDO ISLANDS: A SYSTEMATIC AND BIOGEOGRAPHIC UPDATE

We present a comprehensive and update checklist systematic of the icthyofauna of this insular region, which is comprised by 366 species, 241 genera, 101 families, 28 orders and tree classes. The families with the most richness specific were: Carangidae (20 spp.), Serranidae (19) and Muraenidae (18). Socorro Island was recorded 220 species, Clarion Island 179, San Benedicto Island 128; followed by Roca Partida Island 62. This diversity as well as endemic species number is relationship with the surface of each island. There is a higher similarity ictiofaunistic between Clarion Island and Socorro Island; while, the lowest similarity was between San Benedicto Island and Roca Partida Island. The ichthyogeography of the Revillagigedo Archipelago has a higher affinity with the Panamic province (42.3%), followed by the Cortes (41.5%). A higher number of species are of the wide distribution (circumglobal: 21 %; amphipacific 22.4 %). Also, endemic species are represented by 26 species (7.1%).

Shark movements in the Revillagigedo Archipelago and connectivity with the Eastern Tropical Pacific

Long-distance movements of sharks within and between islands pose substantial challenges for resource managers working with highly migratory species. When no-take zones do not cover the critical areas that sharks use as part of their lifecycle, exposure to fishing activities can be significant. Shark movements between the Marine Protected Areas (MPAs) of the Eastern Tropical Pacific (ETP) have been studied for several years, however little is known about the strength of connectivity between these islands. We analyzed the extensive MigraMar ultrasonic telemetry dataset to assess how Galapagos sharks (Carcharhinus galapagensis) and silky sharks (Carcharhinus falciformis) use different islands as stepping-stones during their migrations within the Revillagigedo National Park and other ETP islands. Of the 66 sharks monitored, 63.5% moved within the same island, 25.4% between two islands or more and only 10.1% across different MPAs. A C. falciformis tagged in Roca Partida Island, Revillagigedo, travelled to Clipperton Atoll and another one tagged in Darwin Island travelled to the atoll on two different years. The largest movement of C. galapagensis was accomplished by a shark tagged at Socorro Island, Revillagigedo, later detected at Clipperton and finally recorded in Darwin Island, Galapagos. This last path was in fact, one of the longest movements ever recorded for the species. Although long-distance dispersion was not common, our results highlight the need for co-operation between different countries to ensure adequate protection for sharks in the form of swimways and other conservation tools in the ETP.

La vegetación de Isla Socorro, Archipiélago de Revillagigedo, México

Based on physiognomic criteria and a cluster analysis based on 90 plots (14 in prairie and grassland, 35 in shrubs, 38 in forest and 3 in secondary vegetation) we classified the vegetation of Socorro Island. In addition to coastal halophytes, we found evidence supporting eight primary vegetation types: <em>Conocarpus </em> shrubby vegetation, grassland, prairie, <em>Croton masonii </em> shrubby vegetation, <em>Pteridium-Dodonaea </em> shrub, tropical dry forest, tropical rain forest and lower montane cloud forest. Prairie and grassland associations are clearly associated with altitude. Depending on the dominant tree species, three different units could be identified within the tropical rain forest of the island. Our analysis resolved differences with previous classifications of the vegetation on Socorro Island and indicated that some shrubby vegetation, sometimes considered as a different vegetation type, represented instead early succession stages of the lower montane cloud forest. The classifi cation presented constitutes a tool to aid future studies of the flora and fauna of this insular region.