Manta and devil ray species occurrence and distribution in Venezuela, assessed through fishery landings and citizen science data.

Manta and devil rays (collectively mobulids) belong to the monogeneric Mobulidae, which currently comprises 10 species, including a putative third manta ray species (Mobula cf. birostris). These large planktivorous rays are distributed throughout the tropical and subtropical oceans of the world. To date, six mobulid species are reported for the western Atlantic Ocean and the Caribbean Sea, three of which had previously been reported in Venezuela (Mobula birostris, Mobula tarapacana and Mobula hypostoma). A preliminary assessment of fishery landings and citizen science data was conducted to further the scientific knowledge of mobulid species in Venezuela. Fisheries landing data were collected at Margarita Island between 2006 and 2007, and again in 2014. Data mining of internet search engines and social media platforms spanning the past two decades was also conducted. A total of 117 individuals of five mobulid species were recorded: Mobula sp. (n = 27), M. birostris (n = 36), M. tarapacana (n = 3), Mobula mobular (n = 26), Mobula thurstoni (n = 14) and M. cf. birostris (n = 11). The latter three species are the first confirmation of these species in Venezuela. The authors found no records of the previously reported M. hypostoma during this study. Although the occurrence of M. hypostoma in Venezuela remains possible because of the broad regional range of this species, its current presence in Venezuela is invalidated given the repeated misidentifications which have occurred in previous publications. The results of this study increase the number of reported mobulid ray species in Venezuela to five (excluding M. hypostoma). The overall data from juvenile manta rays and pregnant M. mobular and M. thurstoni recorded in this study, combined with the occurrence of all but one species of mobulid ray found in the western Atlantic Ocean, suggest Venezuela provides important habitat for this threatened family of rays.

Variation in cownose ray Rhinoptera neglecta abundance and group size on the central east coast of Australia.

Here, we provide baseline information about the relative abundance and group size of the Australian cownose ray Rhinoptera neglecta on the central east coast of Australia. Using drone monitoring over 2 years, we completed 293 transects, each 2 km in length, at four locations distributed along c.100 km of coast. In total, 5979 R. neglecta were observed with overall relative abundance (±SE) of, 20.4 (±3.3) individuals per transect. The numbers of R. neglecta varied among locations, with the highest density found off the beach adjacent to the river mouth at Evans Head. The number of rays observed also decreased with increasing wind speed. While some of this relationship was probably associated with visibility, R. neglecta may also move offshore during strong winds. We found no evidence that R. neglecta was under significant threat. Additionally, our cost-effective surveys demonstrate the utility of aerial drones in fisheries conservation biology.

Updated taxonomic list and conservation status of chondrichthyans from the exclusive economic zone of Venezuela, with first generic and specific records.

Using the last taxonomic review of chondrichthyans of the world, we selected the species distributed in the north-western Atlantic Ocean (NWA) and compared it with the available published literature related to the class Chondrichthyes in the Venezuelan exclusive economic zone. We also revised information from worldwide databases such as: FAO (NWA-31 area), GBIF, iSpecies, IUCN and OBIS, as well as available museum collection databases. The taxonomic validity was checked using the Catalogue of Fishes of the California Academy of Sciences and recent references. The past published Venezuelan lists of chondrichthyans combined included nine orders, 30 families and 108 species. The updated list with 12 orders, 36 families and 122 species increased by three new orders, six families, three shark genera, nine shark species (one replacing another species), one chimaera genus, two chimaera species, three batoid genera and six batoid species (two replacing other species). Four holotype specimens (two sharks and two rays) are deposited in Venezuelan Museums. Most of the species have an IUCN conservation status, including four species catalogued as Critically Endangered, six as Endangered and 18 species as Vulnerable. Deep-sea fisheries, scientific exploration and taxonomic/genetic revisions might add future increments to the Venezuelan chondrichthyan list.

Invasion-mediated effects on marine trophic interactions in a changing climate: positive feedbacks favour kelp persistence.

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.

Biología de Rhizoprionodon lalandii (Elasmobranchii: Carcharhinidae) capturado en la pesca artesanal de Isla de Margarita, Venezuela

Rhizoprionodon lalandii es un pequeño tiburón ( 57 cm de LT), prohibir por completo el desembarque de hembras grávidas y decretar un periodo de veda de al menos cuatro meses al año, para preservar los beneficios económicos de la pesquería.

Rhizoprionodon lalandii is a small shark ( 57 cm de LT), ban the catches of pregnant females and the application of a banned season of at least four months per year, to preserve the economic benefits of this fishery.

[Fishery and biology of Rhinobatospercellens (Rajiformes: Rhinobatidae) caught by the artisanal fishery at La Pared beach, Venezuela]. / Pesquería y biologia de Rhinobatos percellens (Rajiformes: Rhinobatidae) capturados por la pesquería artesanal de playa La Pared, Venezuela.

R. percellens is incidentally caught in Venezuela by the artisanal fishery using bottom gillnets. This species was classified by the IUCN as being "near threatened", and there is poor knowledge about its biology and fishery in Venezuela. For this reason, we analyzed the specimens caught by the artisanal fleet in playa La Pared, once a week, from January to December 2007. We determined total length, sex and maturity for each captured specimen. A total of 210 specimens were analyzed, 159 females and 51 males. The 81% of all specimens caught were adults, but within this group 27% were pregnant. The average size of sexual maturity was found between 51 and 52cm for females and males, respectively. Adult females were found all year round, and pregnant females in seven of the months sampled; highest numbers were found between February-March and September. The analyzed females had a total of 96 embryos with a size range between 2 and 19cm, with a maximum fertility of four embryos per litter. February and June-July showed the maximum breeding time, and considering the broad range of embryos sizes and the frequency of pregnant females along the different months, allow us to believe that they reproduce throughout the year. Fishing regulation including minimum catch size in relation to maturity length and release of pregnant females in water is recommended.

[Composition and structure of the macrofauna associated with beds of two bivalve species in Cubagua Island, Venezuela]. / Composición y estructura de la macrofauna asociada con agregaciones de dos especies de bivalvos en Isla de Cubagua, Venezuela.

Bivalve aggregations constitute a microhabitat for a wide variety of organisms in intertidal, subtidal and deep-water marine benthic habitats. Increase in density of bivalve beds could offer more crevices and substratum for the associated fauna, affecting community composition. Beds of the Atlantic Pearl Oyster (Pinctada imbricata) and the Turkey Wing (Arca zebra) of contrasting population densities were evaluated to determine the composition and structure of the associated macrofauna of three taxa (Crustacea Decapoda, Mollusca and Echinodermata). We evaluated plots of three levels of bed density in both species, the associated fauna were identified and counted. Other species were collected by qualitative samples. Univariate and multivariate descriptors were tested comparing the associated fauna between the beds of two species at three levels of density. In these beds a total of 104 species belonging to 58 families were recorded. Mithraculus forceps (Majidae), Crucibulum auricula (Calyptraeidae) and Ophiotrix angulata (Ophiothrichidae) were the most common species found in these assemblages. The medium and high-density bivalve beds exhibited greater species number, abundance, Shannon diversity, evenness, taxonomic diversity, and taxonomic distinctness of associated fauna, than low-density bivalve beds. Moreover, multivariate analysis detected different assemblages of associated fauna between beds with different densities. Additionally, similarities were found in the communities of macrofauna in both beds of P imbricata and Area zebra. Our results suggest that bivalve aggregations at Cubagua Island provide additional habitat for macrofauna living in other shallow habitats such as Thalassia beds, corals and rocky environments. Bed density, associated with topographic complexity, represents an important factor for the composition and complexity of the associated fauna.

Composición y estructura de la macrofauna asociada con agregaciones de dos especies de bivalvos en Isla de Cubagua, Venezuela / Composition and structure of the macrofauna associated with beds of two bivalve species in Cubagua Island, Venezuela

Bivalve aggregations constitute a microhabitat for a wide variety of organisms in intertidal, subtidal and deep-water marine benthic habitats. Increase in density of bivalve beds could offer more crevices and substratum for the associated fauna, affecting community composition. Beds of the Atlantic Pearl Oyster (Pinctada imbricata) and the Turkey Wing (Arca zebra) of contrasting population densities were evaluated to determine the composition and structure of the associated macrofauna of three taxa (Crustacea Decapoda, Mollusca and Echinodermata). We evaluated plots of three levels of bed density in both species, the associated fauna were identified and counted. Other species were collected by qualitative samples. Univariate and multivariate descriptors were tested comparing the associated fauna between the beds of two species at three levels of density. In these beds a total of 104 species belonging to 58 families were recorded. Mithraculus forceps (Majidae), Crucibulum auricula (Calyptraeidae) and Ophiotrix angulata (Ophiothrichidae) were the most common species found in these assemblages. The medium and high-density bivalve beds exhibited greater species number, abundance, Shannon diversity, evenness, taxonomic diversity, and taxonomic distinctness of associated fauna, than low-density bivalve beds. Moreover, multivariate analysis detected different assemblages of associated fauna between beds with different densities. Additionally, similarities were found in the communities of macrofauna in both beds of P. imbricata and Arca zebra. Our results suggest that bivalve aggregations at Cubagua Island provide additional habitat for macrofauna living in other shallow habitats such as Thalassia beds, corals and rocky environments. Bed density, associated with topographic complexity, represents an important factor for the composition and complexity of the associated fauna.

Las agregaciones de bivalvos constituyen un microhábitat para una gran variedad de organismos en el ambiente intermareal, submareal y en aguas profundas. Agregaciones de la ostra perla (Pinctada imbricata) y pepitona (Arca zebra) a diferentes densidades poblacionales se evaluaron para determinar la composición y estructura comunitaria de la macrofauna asociada en tres taxa (Crustacea Decapoda, Mollusca y Echinodermata). La hipótesis nula de no diferencias en descriptores univariados y multivariados fue probada comparando la fauna asociada entre las agregaciones de las dos especies a tres niveles de densidad. En estas agregaciones se identificaron 102 especies de 55 familias. Mithraculus forceps (Majidae), Crucibulum auricula (Calyptraeidae) y Ophiotrix angulata (Ophiothrichidae) fueron las especies más comunes encontradas en estas asociaciones. Las densidades medias y altas de las agregaciones de bivalvos presentaron mayor número de especies, abundancia, diversidad de Shannon, equidad, diversidad taxonómica y distinción taxonómica de la fauna asociada que las agregaciones de baja densidad poblacional. Análisis multivariados detectaron diferentes estructuras de los ensambles de la fauna asociada en agregaciones de bivalvos con densidad baja en comparación con los de densidad media y alta. Adicionalmente no se detectaron diferencias en la fauna asociada entre las especies. La densidad de las agregaciones de bivalvos, asociada a la complejidad topográfica, es un factor importante para la composición de la fauna asociada.

Pesquería y biología de Rhinobatos percellens (Rajiformes: Rhinobatidae) capturados por la pesquería artesanal de playa La Pared, Venezuela / Fishery and biology of Rhinobatos percellens (Rajiformes: Rhinobatidae) caught by the artisanal fishery at La Pared beach, Venezuela

R. percellens is incidentally caught in Venezuela by the artisanal fishery using bottom gillnets. This species was classified by the IUCN as being near threatened, and there is poor knowledge about its biology and fishery in Venezuela. For this reason, we analyzed the specimens caught by the artisanal fleet in playa La Pared, once a week, from January to December 2007. We determined total length, sex and maturity for each captured specimen. A total of 210 specimens were analyzed, 159 females and 51 males. The 81% of all specimens caught were adults, but within this group 27% were pregnant. The average size of sexual maturity was found between 51 and 52cm for females and males, respectively. Adult females were found all year round, and pregnant females in seven of the months sampled; highest numbers were found between February-March and September. The analyzed females had a total of 96 embryos with a size range between 2 and 19cm, with a maximum fertility of four embryos per litter. February and June-July showed the maximum breeding time, and considering the broad range of embryos sizes and the frequency of pregnant females along the different months, allow us to believe that they reproduce throughout the year. Fishing regulation including minimum catch size in relation to maturity length and release of pregnant females in water is recommended.

Rhinobatos percellens es capturada en Venezuela por la flota artesanal que opera con redes de fondo. Está clasificada por la IUCN como casi amenazada, y no existen estudios sobre su biología o pesquería en el país. Por ello, se analizaron desembarques de la pesca artesanal de playa la Pared (isla de Margarita) durante enero-diciembre 2007. A cada ejemplar capturado se le determinó la longitud total, sexo y madurez. Fueron analizados 210 ejemplares, 159 hembras y 51 machos. El 81% de los ejemplares se encontraban maduros y un 27% de este grupo correspondió a hembras grávidas. La talla media de madurez sexual quedó ubicada en 51 y 52cm para hembras y machos, respectivamente. Se detectaron hembras maduras todo el año, y hembras grávidas en siete meses. Fueron analizados 96 embriones con tallas entre 2-19cm, siendo la fecundidad máxima cuatro embriones. La variación de las longitudes de los embriones entre los meses del año indican dos picos máximos de alumbramiento al año pero no existe una sincronía en la cópula ya que la especie se reproduce prácticamente todo el año. Se recomienda elaborar regulaciones pesqueras que incluyan una talla mínima de captura en función de la talla de madurez señalada y liberar las hembras grávidas al agua.

[Distribution, density and size structure of Oreaster reticulatus and Luidia senegalensis (Echinodermata: Asteroidea) in Cubagua Island, Venezuela]. / Distribución, densidad y estructura de talla de Oreaster reticulatus y Luidia senegalensis (Echinodermata: Asteroidea) en isla de Cubagua, Venezuela.

There is limited biological information about the starfish Oreaster reticulatus and the nine-armed starfish Luidia senegalensis in Venezuelan waters. These species are currently considered threatened in many localities of the Caribbean, Brazil and Colombia. Therefore, the aim of this study was to describe their population density, size distribution and population structure in Cubagua Island. During 2008, 52 stations located around the island were evaluated using band transects of 50m2. Each organism was counted and measured (maximum radius), and its size was compared to the maturity length reported in the literature. The results for O. reticulatus include: 167.3ind./ha; 33% juveniles and 67% adults; average size of 10.7 +/- 5cm (range: 2.2-21cm); a wide distribution around the island, with higher densities in the Eastern and Southwest areas. The 50% of the specimens were found in seagrass beds, 25% in sand, 16% in areas covered by decomposed seaweeds, 9% in oyster beds and 1% coralline patches. The densities of O. reticulatus were higher than those reported in the Caribbean, Panama and Puerto Rico, but lower than Venezuelan National Parks: Mochima and Morrocoy; as well as in the Virgin Islands and Belize. For L. senegalensis we found an average density of 40ind./ha; 95% exceeded the reported size at maturity, with mean length of 12cm +/- 3.5cm (range: 3.5-22.3cm); they were found only in 15% of the stations of which 92.5% were sandy bottoms and the other 7.5% oyster beds. The degree of aggregation of L. senegalensis was greater than O. reticulatus, with an estimated k of 0.06. However, it was not possible to compare the densities of L. senegalensis with any other study. For both species is recommended to carry out reproductive studies and to monitor their population densities to infer temporal variations.

Distribución, densidad y estructura de talla de Oreaster reticulatus y Luidia senegalensis (Echinodermata: Asteroidea) en isla de Cubagua, Venezuela / Distribution, density an size structure of Oreaster reticulatus and Luidia senegalensis (Echinodermata: Asteroidea) in Cubagua Island, Venezuela

There is limited biological information about the starfish Oreaster reticulatus and the nine-armed starfish Luidia senegalensis in Venezuelan waters. These species are currently considered threatened in many localities of the Caribbean, Brazil and Colombia. Therefore, the aim of this study was to describe their population density, size distribution and population structure in Cubagua Island. During 2008, 52 stations located around the island were evaluated using band transects of 50m2. Each organism was counted and measured (maximum radius), and its size was compared to the maturity length reported in the literature. The results for O. reticulatus include: 167.3ind./ha; 33% juveniles and 67% adults; average size of 10.7±5cm (range: 2.2-21cm); a wide distribution around the island, with higher densities in the Eastern and Southwest areas. The 50% of the specimens were found in seagrass beds, 25% in sand, 16% in areas covered by decomposed seaweeds, 9% in oyster beds and 1% coralline patches. The densities of O. reticulatus were higher than those reported in the Caribbean, Panama and Puerto Rico, but lower than Venezuelan National Parks: Mochima and Morrocoy; as well as in the Virgin Islands and Belize. For L. senegalensis we found an average density of 40ind./ha; 95% exceeded the reported size at maturity, with mean length of 12cm±3.5cm (range: 3.5-22.3cm); they were found only in 15% of the stations of which 92.5% were sandy bottoms and the other 7.5% oyster beds. The degree of aggregation of L. senegalensis was greater than O. reticulatus, with an estimated k of 0.06. However, it was not possible to compare the densities of L. senegalensis with any other study. For both species is recommended to carry out reproductive studies and to monitor their population densities to infer temporal variations.

Las estrellas de mar: Oreaster reticulatus y Luidia senegalensis, han sido objeto de escasos estudios en aguas venezolanas. Actualmente son consideradas especies amenazadas en diversas zonas del Caribe, Brasil y Colombia. Por esto, se planteó como objetivo generar información sobre su densidad poblacional, distribución y estructura de talla en los alrededores de la isla de Cubagua. Para ello, durante el año 2008, se realizaron cuatro transectas bandas de 50m2 cada una, en 52 estaciones ubicadas alrededor de la isla. Entre los resultados obtenidos para O. reticulatus destacan: 167.3ind/ha, un 33% inmaduros y 67% adultos con un promedio de tallas de 10.7±5cm (rango: 2.2-21cm); una amplia distribución en los alrededores de la isla, con mayores densidades en la zona este y suroeste. Luidia senegalensis mostró una densidad promedio de 40ind/ha, 95% superaba la talla de madurez reportada, con talla promedio de 12cm±3.5cm (rango: 3.5-22.3cm). Se recomienda realizar estudios de reproducción, así como monitoreos de sus densidades poblacionales que permitan inferir sus variaciones temporales.

[Distribution and density of two holothurian species in Cubagua Island, Venezuela]. / Distribución y densidad de dos especies de holoturoideos en la isla de Cubagua, 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 50 m2 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 0.011 ind/m2, C.I. 95% = 0.005-0.017, n = 122, and a general abundance estimated in 117 ind/ha. H. mexicana has been practically depleted (0.001 ind/m2 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.

Distribución y densidad de dos especies de holoturoideos en la isla de Cubagua, Venezuela

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 50m² 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/m², 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/m2 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.

En algunas zonas del Caribe, poblaciones enteras de holoturias han sido agotadas. En Venezuela, éste recurso ha sido explotado ilegalmente desde inicios de 1990. Por esta razón, se planteó estimar la distribución, abundancia y estructura poblacional de las holoturias comerciales Isostichopus badionotus y Holothuria mexicana en la isla Cubagua. Para ello, durante el año 2008, se realizaron cuatro transectas bandas de 50m² cada una en 52 estaciones ubicadas alrededor de la isla. Entre los resultados obtenidos destacan: I. badionotus presenta mayor distribución en el lado este de la isla, sobre fondos de Thalassia testudinum o bancos de moluscos bivalvos; con una densidad promedio de 0.011±0.022ind/m² (n=122), y una abundancia general estimada en 117ind/ha. Se identificaron cinco posibles zonas de crianza para esta última especie. H. mexicana ha sido prácticamente agotada (0.001±0.002ind/m², 7.7ind/ ha, n=8). Se recomienda mantener la veda total implantada en 1997, principalmente por no tener conocimiento de las densidades previas al inicio de la pesquería; por considerar que la densidad actual sigue siendo muy baja en comparación con otras zonas de Venezuela, y por ser animales de fácil captura, rápidamente sobreexplotables y de recuperación lenta.