Resumen.-En Venezuela, las rayas Dasyatis guttata y D. americana son consideradas comunes y con importancia comercial. A pesar de existir pesquerías dirigidas a capturarlas, existen pocos estudios sobre su biología, siendo ambas catalogadas en la IUCN con datos deficientes. Por esto, el presente estudio planteó analizar las capturas de la pesquería artesanal de la Isla de Margarita, con la finalidad de aportar datos biológicos que contribuyan a su manejo pesquero. Para ello entre enero 2006 y diciembre 2007, se visitaron una vez por semana 3 comunidades pesqueras y 2 mercados de venta de pescado. A cada ejemplar se le midió la longitud del ancho del disco, se determinó el sexo y estadio de madurez. Un total de 355 ejemplares de D. guttata demostraron que las hembras (32-173 cm) alcanzan longitudes superiores que los machos (28,6-113 cm); el 35% de las capturas correspondió a individuos inmaduros; se encontraron diferencias en la proporción sexual pero no en las tallas de madurez (L 50 para ambos sexos: 56 cm); todos los individuos se encontraron maduros a partir de 78 cm; sólo se observó una hembra grávida (junio 2007), con fecundidad de 5 embriones. Para D. americana se analizaron 224 ejemplares, de los cuales el 40% eran inmaduros; las hembras mostraron longitudes superiores (21,2-164 cm) que los machos (35-147 cm), y maduran a mayores longitudes (L 50 : H: 64 cm; M: 56 cm); todos los individuos se encontraron maduros a partir de 70 cm; hubo diferencias en la proporción sexual y sólo se observaron hembras grávidas para agosto 2006 y marzo 2007, siendo la fecundidad máxima uterina de 5 embriones. Se recomienda establecer longitudes mínimas de captura y periodos de veda.

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The interactive effects of ocean warming and invasive species are complex and remain a source of uncertainty for projecting future ecological change. Climate-mediated change to trophic interactions can have pervasive ecological consequences, but the role of invasion in mediating trophic effects is largely unstudied. Using manipulative experiments in replicated outdoor mesocosms, we reveal how near-future ocean warming and macrophyte invasion scenarios interactively impact gastropod grazing intensity and preference for consumption of foundation macroalgae ( Ecklonia radiata and Sargassum vestitum ). Elevated water temperature increased the consumption of both macroalgae through greater grazing intensity. Given the documented decline of kelp ( E. radiata ) growth at higher water temperatures, enhanced grazing could contribute to the shift from kelp-dominated to Sargassum -dominated reefs that is occurring at the low-latitude margins of kelp distribution. However, the presence of a native invader ( Caulerpa filiformis ) was related to low consumption by the herbivores on dominant kelp at warmer temperatures. Thus, antagonistic effects between climate change and a range expanding species can favour kelp persistence in a warmer future. Introduction of species should, therefore, not automatically be considered unfavourable under climate change scenarios. Climatic changes are increasing the need for effective management actions to address the interactive effects of multiple stressors and their ecological consequences, rather than single threats in isolation.

Abstract-Species of the genus Myliobatis have been poorly assessed because of a lack of available information regarding their capture and life history. We provide valuable data based on the commercial landings of the bullnose ray (Myliobatis freminvillei), which we studied during 2 separate time periods (October 2005-December 2007 and JanuaryDecember 2013. A total of 187 individuals were analyzed: 85 females (24.0-96.0 cm in disc width [DW]) and 102 males (22.8-118.0 cm DW). There was no difference in the overall sex ratio (females to males: 4:5); however, differences were found between the annual sex ratio in 2005, 2006, and 2013. Estimated capture per unit of effort for this species was 0.8 individuals/trip (standard deviation [SD] 1.3) or 2.9 kg/trip (SD 5.5), showing an increase in effort through time and significant differences between years. Approximately 25% of both sexes were shorter than the estimated median DW at maturity. No pattern in the reproductive cycle was identified because of the lack of landings during several months; however, mature individuals were observed frequently throughout the study period; gravid females were observed on only 2 occasions. This study provides baseline biological information on the life history of the bullnose ray for necessary fishery management.

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Distribution and density of two holothurian species in Cubagua Island, Venezuela. Holothurian populations in the Caribbean have been significantly depleted in some areas, and others are still in danger to satisfy international markets. In Venezuela, this marine resource has been illegally exploited since the early 1990s. To contribute with their management and protection, this work analyzed the distribution, abundance and population structure of two commercial holothurians Isostichopus badionotus and Holothuria mexicana in Cubagua Island shores. A total of 52 stations were studied around the island during the year 2008. Surveys included visits to each station, for which a band transect of 50m 2 with four replicates were carried out. The results show that I. badionotus has a higher distribution on the East coast of the island, and is found over Thalassia testudinum beds or bivalve molluscs aggregations, with an average density of 0.011ind/m 2 , C.I. 95%=0.005-0.017, n=122, and a general abundance estimated in 117ind/ha. H. mexicana has been practically depleted (0.001 ind/m 2 C.I. 95%=0.0002-0.0013, 7.7 ind/ha, n=8). We recommend the maintenance of the total ban adopted in 1997 to assure the protection of these species, mainly because no previous data supported the start of the fishery, and also, because the current densities are still very low when compared to other areas in Venezuela and the Caribbean. These are animals easy to catch, susceptible to overfishing, and with a very low recovery rate; thus, more control is required from the local authorities. Rev. Biol. Trop. 59 (2): 843-852. Epub 2011 June 01.

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