The Experts below are selected from a list of 546 Experts worldwide ranked by ideXlab platform
Luis O Lucifora - One of the best experts on this subject based on the ideXlab platform.
-
Egg cases of the graytail skate Bathyraja griseocauda and the cuphead skate Bathyraja scaphiops from the south-west Atlantic Ocean.
Journal of fish biology, 2017Co-Authors: Ezequiel Mabragaña, Diego Martin Vazquez, Valeria Gabbanelli, David Ezequiel Sabadin, Santiago Aldo Barbini, Luis O LuciforaAbstract:Egg cases of Bathyraja griseocauda were larger (140-142 mm in length) than those of Bathyraja scaphiops (88-90 mm in length) and their surface was relatively smooth, without denticles, prickles or any ornamentation. Egg cases of B. scaphiops had a relative coarse surface, covered with prickles of similar size. An identification key for the all described egg cases from Bathyraja occurring in the south-west Atlantic Ocean is provided.
-
From coexistence to competitive exclusion: can overfishing change the outcome of competition in skates (Chondrichthyes, Rajidae)?
Latin American Journal of Aquatic Research, 2012Co-Authors: Natalia L. Ruocco, Juan M. Diaz De Astarloa, Luis O Lucifora, Roberto Carlos Menni, Ezequiel Mabragaña, Diego A GibertoAbstract:Competition for food could be a major force driving changes in the community structure of skates (Rajidae) subjected to fishing exploitation. Under this hypothesis, small skates are released from competition with larger skates after fishing has depleted the larger species. Here, we compare the abundance patterns of two sympatric skates with similar niches but different life histories, Bathyraja albomaculata (larger and slow-reproducing) and Bathyraja macloviana (smaller and faster-reproducing), before (1971, 1978) and after (1998-2004) a 108% increase in industrial bottom trawling on the southeastern South American shelf in order to test the prediction that B. macloviana should competitively exclude B. albomaculata after the increase in fishing mortality. In 1971 and 1978, there was no relationship between the abundance of both species, indicating that they coexisted over large scales. In 1998-2004, the relationship between the abundances of these skates was bell-shaped, indicating that both species increased in abundance at low densities until peaking, after which B. albomaculata decreased when B. macloviana became more abundant, consistent with resource competition. We tested whether food may be a potential limiting resource by comparing the diet of both species. The two species consumed mostly polychaetes, differing only in the consumption of polychaetes from the family Nephthyidae, which was much higher for B. macloviana. Bathyraja macloviana could replace B. albomaculata at high densities when food resources may become scarce. These results support the hypothesis that competition release is an important factor explaining the changes in skate communities in overexploited areas.
-
From coexistence to competitive exclusion: can overfishing change the outcome of competition in skates (Chondrichthyes, Rajidae)? De la coexistencia a la exclusión competitiva: ¿Puede la sobrepesca cambiar el resultado de la competencia en rayas (Cho
Escuela de Ciencias del Mar Facultad de Recursos Naturales Pontificia Universidad Católica de Valparaíso, 2012Co-Authors: Natalia L. Ruocco, Luis O Lucifora, Roberto Carlos Menni, Ezequiel Mabragaña, Juan Díaz M De Astarloa, Diego A GibertoAbstract:Competition for food could be a major force driving changes in the community structure of skates (Rajidae) subjected to fishing exploitation. Under this hypothesis, small skates are released from competition with larger skates after fishing has depleted the larger species. Here, we compare the abundance patterns of two sympatric skates with similar niches but different life histories, Bathyraja albomaculata (larger and slow-reproducing) and Bathyraja macloviana (smaller and faster-reproducing), before (1971, 1978) and after (1998-2004) a 108% increase in industrial bottom trawling on the southeastern South American shelf in order to test the prediction that B. macloviana should competitively exclude B. albomaculata after the increase in fishing mortality. In 1971 and 1978, there was no relationship between the abundance of both species, indicating that they coexisted over large scales. In 1998-2004, the relationship between the abundances of these skates was bell-shaped, indicating that both species increased in abundance at low densities until peaking, after which B. albomaculata decreased when B. macloviana became more abundant, consistent with resource competition. We tested whether food may be a potential limiting resource by comparing the diet of both species. The two species consumed mostly polychaetes, differing only in the consumption of polychaetes from the family Nephthyidae, which was much higher for B. macloviana. Bathyraja macloviana could replace B. albomaculata at high densities when food resources may become scarce. These results support the hypothesis that competition release is an important factor explaining the changes in skate communities in overexploited areas.La competencia por el alimento podría ser una fuerza importante detrás de los cambios en la estructura de las comunidades de rayas (Rajidae) bajo explotación pesquera. Según esta hipótesis, las rayas pequeñas son liberadas de la competencia por las rayas de mayor tamaño, al disminuir la abundancia de éstas últimas por la pesca. En este trabajo, se comparan los patrones de abundancia de dos rayas simpátricas con nichos similares pero con diferentes historias de vida, Bathyraja albomaculata (mayor y de reproducción lenta) y Bathyraja macloviana (más pequeña y de reproducción más rápida), antes (1971, 1978) y después (1998-2004) de un incremento del 108% en el arrastre de fondo industrial en la plataforma sudeste de América del Sur, para evaluar la predicción que B. macloviana excluiría competitivamente a B. albomaculata después del aumento en la mortalidad por pesca. En 1971 y 1978, no hubo relación entre las abundancias de ambas especies, indicando que, a escalas grandes, coexistían. En 1998-2004, la relación entre las abundancias de ambas especies tuvo forma de campana, indicando que ambas incrementaron su abundancia a densidades bajas hasta alcanzar un máximo, a partir del cual la abundancia de B. albomaculata disminuyó a medida que aumentaba la de B. macloviana, patrón consistente con la competencia por uso de recursos. Se evaluó si el alimento puede ser un recurso limitante mediante la comparación de la dieta de ambas especies. Ambas especies consumieron predominantemente poliquetos y difirieron sólo en el consumo de poliquetos Nephthyidae, mucho mayor en B. macloviana. B. macloviana remplazaría a B. albomaculata a altas densidades, cuando el alimento podría ser escaso. Estos resultados apoyan la hipótesis de que la liberación de la competencia es un factor importante en los cambios en las comunidades de rayas sobreexplotadas
-
diet of the white dotted skate Bathyraja albomaculata in waters of argentina
Journal of Applied Ichthyology, 2009Co-Authors: Natalia L. Ruocco, Luis O Lucifora, J Diaz M De Astarloa, Claudia BremecAbstract:Summary The present paper analyzes the diet, feeding strategy and niche width of Bathyraja albomaculata over the Patagonian continental shelf and upper slope. The diet comprised a variety of 14 small invertebrates, although the most important prey were polychaete worms. The opheliid polychaete Travisia sp. and the gammarid amphipod Cirolana sp. were the main prey present in stomach contents of B. albomaculata. No differences were found between the diets of males and females, however ontogenetic changes were detected. Skates 40 cm DW largely consumed polychaetes. As size increased, polychaetes became more important and the importance of amphipods decreased. B. albomaculata showed a narrow food niche and a marked specialization towards polychaetes.
-
Diet of the white‐dotted skate, Bathyraja albomaculata, in waters of Argentina
Journal of Applied Ichthyology, 2009Co-Authors: Natalia L. Ruocco, Luis O Lucifora, J. M. Díaz De Astarloa, Claudia BremecAbstract:Summary The present paper analyzes the diet, feeding strategy and niche width of Bathyraja albomaculata over the Patagonian continental shelf and upper slope. The diet comprised a variety of 14 small invertebrates, although the most important prey were polychaete worms. The opheliid polychaete Travisia sp. and the gammarid amphipod Cirolana sp. were the main prey present in stomach contents of B. albomaculata. No differences were found between the diets of males and females, however ontogenetic changes were detected. Skates 40 cm DW largely consumed polychaetes. As size increased, polychaetes became more important and the importance of amphipods decreased. B. albomaculata showed a narrow food niche and a marked specialization towards polychaetes.
Juan M. Díaz De Astarloa - One of the best experts on this subject based on the ideXlab platform.
-
Exploring nursery sites for oviparous chondrichthyans in the Southwest Atlantic (36°S–41°S)
Marine Biology Research, 2016Co-Authors: Diego Martin Vazquez, Ezequiel Mabragaña, Valeria Gabbanelli, Juan M. Díaz De AstarloaAbstract:ABSTRACTThe aim of this paper was to explore egg-laying areas of oviparous chondrichthyans occurring in the northern part of the Southwest Atlantic Ocean (36°S–41°S) at between 50 and 200 metres depth and the Mar del Plata Canyon (from 200 to 3447 m). A total of 515 capsules were collected corresponding to 10 species. Four species accounted for 87.6% of the total catch: Psammobatis normani, Bathyraja macloviana, Amblyraja doellojuradoi and Bathyraja brachyurops. The remaining corresponded to Schroederichthys bivius, Psammobatis rudis, Zearaja chilensis, Bathyraja albomaculata, Psammobatis lentiginosa and Bathyraja sp. Most hauls were monospecific and relatively few hauls contained four or five species (southern part of the area, in sites located at 75 and 94–105 m depth). No egg capsules were recorded between 1712 m and 3447 m. Highest densities (>3000 capsules/km2) were mainly found between 39°46.2′ and 40°29.9′S from 85 to 105 m and they were also recorded near the Mar del Plata Canyon at 37°59.7′S and ...
-
Food habits of the broad nose skate, Bathyraja brachyurops (Chondrichthyes, Rajidae), in the south-west Atlantic
Scientia Marina, 2008Co-Authors: Mauro Belleggia, Ezequiel Mabragaña, Santiago Aldo Barbini, Daniel E. Figueroa, Lorena B. Scenna, Juan M. Díaz De AstarloaAbstract:Food habits of Bathyraja brachyurops were studied based on stomach content analyses of 346 specimens collected from research cruises carried out from 2003 to 2005 on the Argentinean continental shelf (36oS-55oS). A total of 265 stomachs (76.6%) contained food, and thirty-five taxonomic levels of prey were identified. The most important prey were fishes followed by isopods. Trophic level analysis revealed that B. brachyurops is a tertiary consumer throughout its life history. There were no differences between sexes and regions in the diet composition, but dietary shifts with ontogeny were found. The Levins’ standardized index indicated wider niche breadth for small skates, whereas larger skate specimens showed a narrow niche breadth with a specialization in fishes.
-
Reproductive biology and abundance of the white-dotted skate, Bathyraja albomaculata, in the Southwest Atlantic
ICES Journal of Marine Science, 2006Co-Authors: Natalia L. Ruocco, Luis O Lucifora, Juan M. Díaz De Astarloa, Otto WöhlerAbstract:Size at maturity, sexual dimorphism, gonad development, and abundance of white-dotted skate, Bathyraja albomaculata, were assessed along its geographic range in the Southwest Atlantic, from Uruguay to Tierra del Fuego (Argentina). In all, 291 specimens from eight research cruises conducted between 1998 and 2003 were examined. Lengthemass relationships were sexually dimorphic, adult females being significantly heavier than males of the same length. The largest female observed was 762 mm total length (LT), and 50% maturity (LT50) was attained at 653 mm LT. The largest male was 732 mm LT, and male LT50 was 628 mm LT. Female and male LT50 were not significantly different and were about 86% of observed maximum size, similar to other Bathyraja species. The lack of sexual dimorphism in size at maturity and the slight difference in maximum size between sexes support the hypothesis of relaxation of selection for large female size in oviparous elasmobranchs. Liver size was not sexually dimorphic. Mature female gonads were symmetrical in terms of mass, and similar in ovarian follicle number and size. Females carried egg cases in April, September, and October, consistent with previous observations around the Islas Malvinas and suggesting year-round egg laying. Bathyraja albomaculata was most abundant on the outer continental shelf and slope between 36(30#S and 45(S (northern area). In contrast, it was generally absent between 48(S and 52(S (southern area), a region where it was formerly reported as abundant. These differences are coincident with the development of a fishery targeting skates in the southern area, whereas in the north B. albomaculata taken as bycatch are mostly discarded alive.
-
Bathyraja cousseauae sp.n.: A New Softnose Skate from the Southwestern Atlantic (Rajiformes, Rajidae)
Copeia, 2004Co-Authors: Juan M. Díaz De Astarloa, Ezequiel MabragañaAbstract:Abstract A new species of softnose skate, Bathyraja cousseauae, is described from two adult and 19 juvenile specimens collected from different localities of the southwestern Atlantic. Bathyraja cousseauae is distinguished from all other southwestern Atlantic softnose skate species by its color pattern, squamation pattern of dorsal surface, lack of interspace between dorsal fins, and clasper morphology. The new species has a round pale area ocellus-like, margined with dark brown on posterior part of each pectoral base of dorsal surface, paler and dark spots over the disk, a continuous row of 21–27 median thorns from nuchal region to first dorsal fin and upper side of disc densely covered with dermal denticles. Males have rod-shaped claspers not expanded at proximal section of glans as it does in Bathyraja brachyurops. Besides the external morphological features, skeletal characteristics (neurocranium, scapulocoracoids, and claspers) are also described and illustrated here.
Ezequiel Mabragaña - One of the best experts on this subject based on the ideXlab platform.
-
Egg cases of the graytail skate Bathyraja griseocauda and the cuphead skate Bathyraja scaphiops from the south-west Atlantic Ocean.
Journal of fish biology, 2017Co-Authors: Ezequiel Mabragaña, Diego Martin Vazquez, Valeria Gabbanelli, David Ezequiel Sabadin, Santiago Aldo Barbini, Luis O LuciforaAbstract:Egg cases of Bathyraja griseocauda were larger (140-142 mm in length) than those of Bathyraja scaphiops (88-90 mm in length) and their surface was relatively smooth, without denticles, prickles or any ornamentation. Egg cases of B. scaphiops had a relative coarse surface, covered with prickles of similar size. An identification key for the all described egg cases from Bathyraja occurring in the south-west Atlantic Ocean is provided.
-
Exploring nursery sites for oviparous chondrichthyans in the Southwest Atlantic (36°S–41°S)
Marine Biology Research, 2016Co-Authors: Diego Martin Vazquez, Ezequiel Mabragaña, Valeria Gabbanelli, Juan M. Díaz De AstarloaAbstract:ABSTRACTThe aim of this paper was to explore egg-laying areas of oviparous chondrichthyans occurring in the northern part of the Southwest Atlantic Ocean (36°S–41°S) at between 50 and 200 metres depth and the Mar del Plata Canyon (from 200 to 3447 m). A total of 515 capsules were collected corresponding to 10 species. Four species accounted for 87.6% of the total catch: Psammobatis normani, Bathyraja macloviana, Amblyraja doellojuradoi and Bathyraja brachyurops. The remaining corresponded to Schroederichthys bivius, Psammobatis rudis, Zearaja chilensis, Bathyraja albomaculata, Psammobatis lentiginosa and Bathyraja sp. Most hauls were monospecific and relatively few hauls contained four or five species (southern part of the area, in sites located at 75 and 94–105 m depth). No egg capsules were recorded between 1712 m and 3447 m. Highest densities (>3000 capsules/km2) were mainly found between 39°46.2′ and 40°29.9′S from 85 to 105 m and they were also recorded near the Mar del Plata Canyon at 37°59.7′S and ...
-
From coexistence to competitive exclusion: can overfishing change the outcome of competition in skates (Chondrichthyes, Rajidae)?
Latin American Journal of Aquatic Research, 2012Co-Authors: Natalia L. Ruocco, Juan M. Diaz De Astarloa, Luis O Lucifora, Roberto Carlos Menni, Ezequiel Mabragaña, Diego A GibertoAbstract:Competition for food could be a major force driving changes in the community structure of skates (Rajidae) subjected to fishing exploitation. Under this hypothesis, small skates are released from competition with larger skates after fishing has depleted the larger species. Here, we compare the abundance patterns of two sympatric skates with similar niches but different life histories, Bathyraja albomaculata (larger and slow-reproducing) and Bathyraja macloviana (smaller and faster-reproducing), before (1971, 1978) and after (1998-2004) a 108% increase in industrial bottom trawling on the southeastern South American shelf in order to test the prediction that B. macloviana should competitively exclude B. albomaculata after the increase in fishing mortality. In 1971 and 1978, there was no relationship between the abundance of both species, indicating that they coexisted over large scales. In 1998-2004, the relationship between the abundances of these skates was bell-shaped, indicating that both species increased in abundance at low densities until peaking, after which B. albomaculata decreased when B. macloviana became more abundant, consistent with resource competition. We tested whether food may be a potential limiting resource by comparing the diet of both species. The two species consumed mostly polychaetes, differing only in the consumption of polychaetes from the family Nephthyidae, which was much higher for B. macloviana. Bathyraja macloviana could replace B. albomaculata at high densities when food resources may become scarce. These results support the hypothesis that competition release is an important factor explaining the changes in skate communities in overexploited areas.
-
From coexistence to competitive exclusion: can overfishing change the outcome of competition in skates (Chondrichthyes, Rajidae)? De la coexistencia a la exclusión competitiva: ¿Puede la sobrepesca cambiar el resultado de la competencia en rayas (Cho
Escuela de Ciencias del Mar Facultad de Recursos Naturales Pontificia Universidad Católica de Valparaíso, 2012Co-Authors: Natalia L. Ruocco, Luis O Lucifora, Roberto Carlos Menni, Ezequiel Mabragaña, Juan Díaz M De Astarloa, Diego A GibertoAbstract:Competition for food could be a major force driving changes in the community structure of skates (Rajidae) subjected to fishing exploitation. Under this hypothesis, small skates are released from competition with larger skates after fishing has depleted the larger species. Here, we compare the abundance patterns of two sympatric skates with similar niches but different life histories, Bathyraja albomaculata (larger and slow-reproducing) and Bathyraja macloviana (smaller and faster-reproducing), before (1971, 1978) and after (1998-2004) a 108% increase in industrial bottom trawling on the southeastern South American shelf in order to test the prediction that B. macloviana should competitively exclude B. albomaculata after the increase in fishing mortality. In 1971 and 1978, there was no relationship between the abundance of both species, indicating that they coexisted over large scales. In 1998-2004, the relationship between the abundances of these skates was bell-shaped, indicating that both species increased in abundance at low densities until peaking, after which B. albomaculata decreased when B. macloviana became more abundant, consistent with resource competition. We tested whether food may be a potential limiting resource by comparing the diet of both species. The two species consumed mostly polychaetes, differing only in the consumption of polychaetes from the family Nephthyidae, which was much higher for B. macloviana. Bathyraja macloviana could replace B. albomaculata at high densities when food resources may become scarce. These results support the hypothesis that competition release is an important factor explaining the changes in skate communities in overexploited areas.La competencia por el alimento podría ser una fuerza importante detrás de los cambios en la estructura de las comunidades de rayas (Rajidae) bajo explotación pesquera. Según esta hipótesis, las rayas pequeñas son liberadas de la competencia por las rayas de mayor tamaño, al disminuir la abundancia de éstas últimas por la pesca. En este trabajo, se comparan los patrones de abundancia de dos rayas simpátricas con nichos similares pero con diferentes historias de vida, Bathyraja albomaculata (mayor y de reproducción lenta) y Bathyraja macloviana (más pequeña y de reproducción más rápida), antes (1971, 1978) y después (1998-2004) de un incremento del 108% en el arrastre de fondo industrial en la plataforma sudeste de América del Sur, para evaluar la predicción que B. macloviana excluiría competitivamente a B. albomaculata después del aumento en la mortalidad por pesca. En 1971 y 1978, no hubo relación entre las abundancias de ambas especies, indicando que, a escalas grandes, coexistían. En 1998-2004, la relación entre las abundancias de ambas especies tuvo forma de campana, indicando que ambas incrementaron su abundancia a densidades bajas hasta alcanzar un máximo, a partir del cual la abundancia de B. albomaculata disminuyó a medida que aumentaba la de B. macloviana, patrón consistente con la competencia por uso de recursos. Se evaluó si el alimento puede ser un recurso limitante mediante la comparación de la dieta de ambas especies. Ambas especies consumieron predominantemente poliquetos y difirieron sólo en el consumo de poliquetos Nephthyidae, mucho mayor en B. macloviana. B. macloviana remplazaría a B. albomaculata a altas densidades, cuando el alimento podría ser escaso. Estos resultados apoyan la hipótesis de que la liberación de la competencia es un factor importante en los cambios en las comunidades de rayas sobreexplotadas
-
Food habits of the broad nose skate, Bathyraja brachyurops (Chondrichthyes, Rajidae), in the south-west Atlantic
Scientia Marina, 2008Co-Authors: Mauro Belleggia, Ezequiel Mabragaña, Santiago Aldo Barbini, Daniel E. Figueroa, Lorena B. Scenna, Juan M. Díaz De AstarloaAbstract:Food habits of Bathyraja brachyurops were studied based on stomach content analyses of 346 specimens collected from research cruises carried out from 2003 to 2005 on the Argentinean continental shelf (36oS-55oS). A total of 265 stomachs (76.6%) contained food, and thirty-five taxonomic levels of prey were identified. The most important prey were fishes followed by isopods. Trophic level analysis revealed that B. brachyurops is a tertiary consumer throughout its life history. There were no differences between sexes and regions in the diet composition, but dietary shifts with ontogeny were found. The Levins’ standardized index indicated wider niche breadth for small skates, whereas larger skate specimens showed a narrow niche breadth with a specialization in fishes.
Séret Bernard - One of the best experts on this subject based on the ideXlab platform.
-
FIGURE 4 in A new temperate deepwater skate of the genus Bathyraja (Rajoidei: Arhynchobatidae) from the South-West Pacific
2016Co-Authors: Last, Peter R., Stewart, Andrew L., Séret BernardAbstract:FIGURE 4. Radiograph of the head of Bathyraja pacifica sp. nov., adult male holotype (NMNZ P39707, 1224 mm TL)
-
FIGURE 6 in A new temperate deepwater skate of the genus Bathyraja (Rajoidei: Arhynchobatidae) from the South-West Pacific
2016Co-Authors: Last, Peter R., Stewart, Andrew L., Séret BernardAbstract:FIGURE 6. Lateral view of the dorsal and caudal fins of Bathyraja pacifica sp. nov., adult male holotype (NMNZ P39707, 1224 mm TL)
-
FIGURE 3 in A new temperate deepwater skate of the genus Bathyraja (Rajoidei: Arhynchobatidae) from the South-West Pacific
2016Co-Authors: Last, Peter R., Stewart, Andrew L., Séret BernardAbstract:FIGURE 3. Bathyraja pacifica sp. nov., adult male holotype (NMNZ P39707, 1224 mm TL, preserved coloration) showing the oronasal region and tooth bands
-
FIGURE 7 in A new temperate deepwater skate of the genus Bathyraja (Rajoidei: Arhynchobatidae) from the South-West Pacific
2016Co-Authors: Last, Peter R., Stewart, Andrew L., Séret BernardAbstract:FIGURE 7. Map of the New Zealand Exclusive Economic Zone showing the collection location of the holotype of Bathyraja pacifica sp. nov., in the northern Tasman Sea
-
A new temperate deepwater skate of the genus Bathyraja (Rajoidei: Arhynchobatidae) from the South-West Pacific
2016Co-Authors: Last, Peter R., Stewart, Andrew L., Séret BernardAbstract:Last, Peter R., Stewart, Andrew L., Séret, Bernard (2016): A new temperate deepwater skate of the genus Bathyraja (Rajoidei: Arhynchobatidae) from the South-West Pacific. Zootaxa 4132 (1): 107-117, DOI: http://doi.org/10.11646/zootaxa.4132.1.
Natalia L. Ruocco - One of the best experts on this subject based on the ideXlab platform.
-
From coexistence to competitive exclusion: can overfishing change the outcome of competition in skates (Chondrichthyes, Rajidae)?
Latin American Journal of Aquatic Research, 2012Co-Authors: Natalia L. Ruocco, Juan M. Diaz De Astarloa, Luis O Lucifora, Roberto Carlos Menni, Ezequiel Mabragaña, Diego A GibertoAbstract:Competition for food could be a major force driving changes in the community structure of skates (Rajidae) subjected to fishing exploitation. Under this hypothesis, small skates are released from competition with larger skates after fishing has depleted the larger species. Here, we compare the abundance patterns of two sympatric skates with similar niches but different life histories, Bathyraja albomaculata (larger and slow-reproducing) and Bathyraja macloviana (smaller and faster-reproducing), before (1971, 1978) and after (1998-2004) a 108% increase in industrial bottom trawling on the southeastern South American shelf in order to test the prediction that B. macloviana should competitively exclude B. albomaculata after the increase in fishing mortality. In 1971 and 1978, there was no relationship between the abundance of both species, indicating that they coexisted over large scales. In 1998-2004, the relationship between the abundances of these skates was bell-shaped, indicating that both species increased in abundance at low densities until peaking, after which B. albomaculata decreased when B. macloviana became more abundant, consistent with resource competition. We tested whether food may be a potential limiting resource by comparing the diet of both species. The two species consumed mostly polychaetes, differing only in the consumption of polychaetes from the family Nephthyidae, which was much higher for B. macloviana. Bathyraja macloviana could replace B. albomaculata at high densities when food resources may become scarce. These results support the hypothesis that competition release is an important factor explaining the changes in skate communities in overexploited areas.
-
From coexistence to competitive exclusion: can overfishing change the outcome of competition in skates (Chondrichthyes, Rajidae)? De la coexistencia a la exclusión competitiva: ¿Puede la sobrepesca cambiar el resultado de la competencia en rayas (Cho
Escuela de Ciencias del Mar Facultad de Recursos Naturales Pontificia Universidad Católica de Valparaíso, 2012Co-Authors: Natalia L. Ruocco, Luis O Lucifora, Roberto Carlos Menni, Ezequiel Mabragaña, Juan Díaz M De Astarloa, Diego A GibertoAbstract:Competition for food could be a major force driving changes in the community structure of skates (Rajidae) subjected to fishing exploitation. Under this hypothesis, small skates are released from competition with larger skates after fishing has depleted the larger species. Here, we compare the abundance patterns of two sympatric skates with similar niches but different life histories, Bathyraja albomaculata (larger and slow-reproducing) and Bathyraja macloviana (smaller and faster-reproducing), before (1971, 1978) and after (1998-2004) a 108% increase in industrial bottom trawling on the southeastern South American shelf in order to test the prediction that B. macloviana should competitively exclude B. albomaculata after the increase in fishing mortality. In 1971 and 1978, there was no relationship between the abundance of both species, indicating that they coexisted over large scales. In 1998-2004, the relationship between the abundances of these skates was bell-shaped, indicating that both species increased in abundance at low densities until peaking, after which B. albomaculata decreased when B. macloviana became more abundant, consistent with resource competition. We tested whether food may be a potential limiting resource by comparing the diet of both species. The two species consumed mostly polychaetes, differing only in the consumption of polychaetes from the family Nephthyidae, which was much higher for B. macloviana. Bathyraja macloviana could replace B. albomaculata at high densities when food resources may become scarce. These results support the hypothesis that competition release is an important factor explaining the changes in skate communities in overexploited areas.La competencia por el alimento podría ser una fuerza importante detrás de los cambios en la estructura de las comunidades de rayas (Rajidae) bajo explotación pesquera. Según esta hipótesis, las rayas pequeñas son liberadas de la competencia por las rayas de mayor tamaño, al disminuir la abundancia de éstas últimas por la pesca. En este trabajo, se comparan los patrones de abundancia de dos rayas simpátricas con nichos similares pero con diferentes historias de vida, Bathyraja albomaculata (mayor y de reproducción lenta) y Bathyraja macloviana (más pequeña y de reproducción más rápida), antes (1971, 1978) y después (1998-2004) de un incremento del 108% en el arrastre de fondo industrial en la plataforma sudeste de América del Sur, para evaluar la predicción que B. macloviana excluiría competitivamente a B. albomaculata después del aumento en la mortalidad por pesca. En 1971 y 1978, no hubo relación entre las abundancias de ambas especies, indicando que, a escalas grandes, coexistían. En 1998-2004, la relación entre las abundancias de ambas especies tuvo forma de campana, indicando que ambas incrementaron su abundancia a densidades bajas hasta alcanzar un máximo, a partir del cual la abundancia de B. albomaculata disminuyó a medida que aumentaba la de B. macloviana, patrón consistente con la competencia por uso de recursos. Se evaluó si el alimento puede ser un recurso limitante mediante la comparación de la dieta de ambas especies. Ambas especies consumieron predominantemente poliquetos y difirieron sólo en el consumo de poliquetos Nephthyidae, mucho mayor en B. macloviana. B. macloviana remplazaría a B. albomaculata a altas densidades, cuando el alimento podría ser escaso. Estos resultados apoyan la hipótesis de que la liberación de la competencia es un factor importante en los cambios en las comunidades de rayas sobreexplotadas
-
diet of the white dotted skate Bathyraja albomaculata in waters of argentina
Journal of Applied Ichthyology, 2009Co-Authors: Natalia L. Ruocco, Luis O Lucifora, J Diaz M De Astarloa, Claudia BremecAbstract:Summary The present paper analyzes the diet, feeding strategy and niche width of Bathyraja albomaculata over the Patagonian continental shelf and upper slope. The diet comprised a variety of 14 small invertebrates, although the most important prey were polychaete worms. The opheliid polychaete Travisia sp. and the gammarid amphipod Cirolana sp. were the main prey present in stomach contents of B. albomaculata. No differences were found between the diets of males and females, however ontogenetic changes were detected. Skates 40 cm DW largely consumed polychaetes. As size increased, polychaetes became more important and the importance of amphipods decreased. B. albomaculata showed a narrow food niche and a marked specialization towards polychaetes.
-
Diet of the white‐dotted skate, Bathyraja albomaculata, in waters of Argentina
Journal of Applied Ichthyology, 2009Co-Authors: Natalia L. Ruocco, Luis O Lucifora, J. M. Díaz De Astarloa, Claudia BremecAbstract:Summary The present paper analyzes the diet, feeding strategy and niche width of Bathyraja albomaculata over the Patagonian continental shelf and upper slope. The diet comprised a variety of 14 small invertebrates, although the most important prey were polychaete worms. The opheliid polychaete Travisia sp. and the gammarid amphipod Cirolana sp. were the main prey present in stomach contents of B. albomaculata. No differences were found between the diets of males and females, however ontogenetic changes were detected. Skates 40 cm DW largely consumed polychaetes. As size increased, polychaetes became more important and the importance of amphipods decreased. B. albomaculata showed a narrow food niche and a marked specialization towards polychaetes.
-
Reproductive biology and abundance of the white-dotted skate, Bathyraja albomaculata, in the Southwest Atlantic
ICES Journal of Marine Science, 2006Co-Authors: Natalia L. Ruocco, Luis O Lucifora, Juan M. Díaz De Astarloa, Otto WöhlerAbstract:Size at maturity, sexual dimorphism, gonad development, and abundance of white-dotted skate, Bathyraja albomaculata, were assessed along its geographic range in the Southwest Atlantic, from Uruguay to Tierra del Fuego (Argentina). In all, 291 specimens from eight research cruises conducted between 1998 and 2003 were examined. Lengthemass relationships were sexually dimorphic, adult females being significantly heavier than males of the same length. The largest female observed was 762 mm total length (LT), and 50% maturity (LT50) was attained at 653 mm LT. The largest male was 732 mm LT, and male LT50 was 628 mm LT. Female and male LT50 were not significantly different and were about 86% of observed maximum size, similar to other Bathyraja species. The lack of sexual dimorphism in size at maturity and the slight difference in maximum size between sexes support the hypothesis of relaxation of selection for large female size in oviparous elasmobranchs. Liver size was not sexually dimorphic. Mature female gonads were symmetrical in terms of mass, and similar in ovarian follicle number and size. Females carried egg cases in April, September, and October, consistent with previous observations around the Islas Malvinas and suggesting year-round egg laying. Bathyraja albomaculata was most abundant on the outer continental shelf and slope between 36(30#S and 45(S (northern area). In contrast, it was generally absent between 48(S and 52(S (southern area), a region where it was formerly reported as abundant. These differences are coincident with the development of a fishery targeting skates in the southern area, whereas in the north B. albomaculata taken as bycatch are mostly discarded alive.
