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.

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.

Summary:Mustelus higmani is categorized as "least concern" according to the red list of the International Union for Conservation of Nature, but gaps in population trends occur in most of its distribution range. In Venezuela, this species has local importance because it is part of typical dishes. The aim of this work is to analyse the population structure, reproduction and feeding of M. higmani from Margarita Island's artisanal fishery landings for management purposes. Between 2006 and 2008, 2223 specimens were analysed: 1156 females (24.8-88.4 cm total length [TL]) and 1067 males (20-69.2 cm TL). Temporal variations in sex ratio and length class structure were detected. Changes in body size were detected throughout different years of sampling. A decrease in TL and an increase in immature specimens in the catch were observed in 2008. Mean length at maturity (L 50 ) was estimated at 46.7 cm TL for females and 47.6 cm TL for males. Female fecundity was 4±1.8 embryos (n=388). Length at birth was between 20 and 29 cm TL, and no differences in sex ratio were detected for embryos. Feeding analyses (n=266 stomachs) showed a diet mainly based on decapod crustaceans, small fish, stomatopods and cephalopods. The trophic level was 3.3, which shows feeding based on benthic and demersal species of the continental shelf, especially crustaceans.Keywords: shark fishery; elasmobranch; Chondrichthyes; artisanal fishery; Caribbean.Longitud de captura, reproducción y alimentación de la viuda amarilla, Mustelus higmani (Carcharhiniformes: Triakidae), en isla de Margarita, Venezuela Resumen: Mustelus higmani está catalogada con "preocupación menor" en la lista roja de la IUCN, sin embargo existen vacíos de información sobre la tendencia poblacional en la mayoría de su rango de distribución. En Venezuela, esta especie tiene gran importancia local porque es parte de platos típicos tradicionales. El objetivo del presente trabajo es analizar la estructura poblacional, reproducción y alimentación de los ejemplares de M. higmani provenientes de los desembarques de la pesca artesanal de isla de Margarita, para contribuir con el manejo de la especie. Durante 2006Durante -2008Durante , fueron analizados 2223Durante ejemplares: 1156.4 cm LT) y 1067 machos (20-69.2 cm). Fueron detectadas variaciones temporales en la proporción sexual y estructura de longitudes. Una disminución de la longitud total y un incremento de organismos inmaduros fueron observados durante el 2008. La longitud media de madurez sexual (L 50 ) fue estimada en 46.7 cm LT para las hembras y 47.6 cm LT para machos. La fecundidad uterina fue estimada en 4±1.8 embriones (n=388). Longitud cercana al nacimiento entre 20-29 cm LT, sin diferencias en la proporción sexual de embriones. Los análisis de alimentación (n=266 estómagos) muestran una dieta basada principalmente en crustáceos decápodos, peces pequeños, estomatópodos y cefalópodos. El nivel trófico calculado fue 3.3. La especie muestra una alimentación basada en especies demersales y del bentos habitantes de la plataform...