Feeding habits of the White-dotted Skate, Bathyraja albomaculata (Chondrichthyes, Rajidae), on the Argentinean Continental Shelf

SHIMABUKURO, V.; L. B. SCENNA; S. A. BARBINI; D. E. FIGUEROA; J. M. DÍAZ DE ASTARLOA; M. B. COUSSEAU

St. Louis, Missouri (USA)

Congreso; 2007 Joint meeting of the American Society of Ichthyologists and Herpetologists; 2007

The white-dotted skate, Bathyraja albomaculata (Norman, 1937), is a medium size species in the Magellan region, from Uruguay in the Atlantic to central Chile in the Pacific. Diet composition, changes with sex and maturity status, and feeding strategy of this species were investigated in Argentinean waters (35°-55°S) through stomach contents analyses. Specimens were collected from research cruises carried out by Instituto Nacional de Investigación y Desarrollo Pesquero (INIDEP) between September 2003 and May 2005. Stomach contents were fixed in formalin 4%. Prey were counted, weighted, and identified to the lowest possible taxonomic level. Of a total of 184 stomachs examined, 95.1% contained food. All the sample sizes were sufficient for comparison, as the cumulative curves of diversity reached an asymptote. According to the Index of Relative Importance expressed as a percentage, polychaetes (67.97%) were the most important prey group in the diet of B . albomaculata followed by amphipods (23.78%) and isopods (8.13%). Cumaceans, crabs, euphausiids, teleosts, ophiuroids, hydrozoans and priapulids were not important in the diet (IRI<1%). The highest dietary overlap (Simplified Morisita Index) was found between mature males (n=55) and mature females (n=40) and the lowest similarity was observed between immature skates (n=80) and mature males. The graphical method of prey-specific abundance against frequency of occurrence suggested that the white-dotted skate is a polychaete specialized feeder. However, immature specimens seem to prey upon a greater proportion of amphipods than mature individuals of both sexes. These results were part of a study about ecology, biology and biodiversity of Bathyraja species on the Argentinean continental shelf. crabs, euphausiids, teleosts, ophiuroids, hydrozoans and priapulids were not important in the diet (IRI<1%). The highest dietary overlap (Simplified Morisita Index) was found between mature males (n=55) and mature females (n=40) and the lowest similarity was observed between immature skates (n=80) and mature males. The graphical method of prey-specific abundance against frequency of occurrence suggested that the white-dotted skate is a polychaete specialized feeder. However, immature specimens seem to prey upon a greater proportion of amphipods than mature individuals of both sexes. These results were part of a study about ecology, biology and biodiversity of Bathyraja species on the Argentinean continental shelf. albomaculata followed by amphipods (23.78%) and isopods (8.13%). Cumaceans, crabs, euphausiids, teleosts, ophiuroids, hydrozoans and priapulids were not important in the diet (IRI<1%). The highest dietary overlap (Simplified Morisita Index) was found between mature males (n=55) and mature females (n=40) and the lowest similarity was observed between immature skates (n=80) and mature males. The graphical method of prey-specific abundance against frequency of occurrence suggested that the white-dotted skate is a polychaete specialized feeder. However, immature specimens seem to prey upon a greater proportion of amphipods than mature individuals of both sexes. These results were part of a study about ecology, biology and biodiversity of Bathyraja species on the Argentinean continental shelf. crabs, euphausiids, teleosts, ophiuroids, hydrozoans and priapulids were not important in the diet (IRI<1%). The highest dietary overlap (Simplified Morisita Index) was found between mature males (n=55) and mature females (n=40) and the lowest similarity was observed between immature skates (n=80) and mature males. The graphical method of prey-specific abundance against frequency of occurrence suggested that the white-dotted skate is a polychaete specialized feeder. However, immature specimens seem to prey upon a greater proportion of amphipods than mature individuals of both sexes. These results were part of a study about ecology, biology and biodiversity of Bathyraja species on the Argentinean continental shelf. species in the Magellan region, from Uruguay in the Atlantic to central Chile in the Pacific. Diet composition, changes with sex and maturity status, and feeding strategy of this species were investigated in Argentinean waters (35°-55°S) through stomach contents analyses. Specimens were collected from research cruises carried out by Instituto Nacional de Investigación y Desarrollo Pesquero (INIDEP) between September 2003 and May 2005. Stomach contents were fixed in formalin 4%. Prey were counted, weighted, and identified to the lowest possible taxonomic level. Of a total of 184 stomachs examined, 95.1% contained food. All the sample sizes were sufficient for comparison, as the cumulative curves of diversity reached an asymptote. According to the Index of Relative Importance expressed as a percentage, polychaetes (67.97%) were the most important prey group in the diet of B . albomaculata followed by amphipods (23.78%) and isopods (8.13%). Cumaceans, crabs, euphausiids, teleosts, ophiuroids, hydrozoans and priapulids were not important in the diet (IRI<1%). The highest dietary overlap (Simplified Morisita Index) was found between mature males (n=55) and mature females (n=40) and the lowest similarity was observed between immature skates (n=80) and mature males. The graphical method of prey-specific abundance against frequency of occurrence suggested that the white-dotted skate is a polychaete specialized feeder. However, immature specimens seem to prey upon a greater proportion of amphipods than mature individuals of both sexes. These results were part of a study about ecology, biology and biodiversity of Bathyraja species on the Argentinean continental shelf. crabs, euphausiids, teleosts, ophiuroids, hydrozoans and priapulids were not important in the diet (IRI<1%). The highest dietary overlap (Simplified Morisita Index) was found between mature males (n=55) and mature females (n=40) and the lowest similarity was observed between immature skates (n=80) and mature males. The graphical method of prey-specific abundance against frequency of occurrence suggested that the white-dotted skate is a polychaete specialized feeder. However, immature specimens seem to prey upon a greater proportion of amphipods than mature individuals of both sexes. These results were part of a study about ecology, biology and biodiversity of Bathyraja species on the Argentinean continental shelf. albomaculata followed by amphipods (23.78%) and isopods (8.13%). Cumaceans, crabs, euphausiids, teleosts, ophiuroids, hydrozoans and priapulids were not important in the diet (IRI<1%). The highest dietary overlap (Simplified Morisita Index) was found between mature males (n=55) and mature females (n=40) and the lowest similarity was observed between immature skates (n=80) and mature males. The graphical method of prey-specific abundance against frequency of occurrence suggested that the white-dotted skate is a polychaete specialized feeder. However, immature specimens seem to prey upon a greater proportion of amphipods than mature individuals of both sexes. These results were part of a study about ecology, biology and biodiversity of Bathyraja species on the Argentinean continental shelf. crabs, euphausiids, teleosts, ophiuroids, hydrozoans and priapulids were not important in the diet (IRI<1%). The highest dietary overlap (Simplified Morisita Index) was found between mature males (n=55) and mature females (n=40) and the lowest similarity was observed between immature skates (n=80) and mature males. The graphical method of prey-specific abundance against frequency of occurrence suggested that the white-dotted skate is a polychaete specialized feeder. However, immature specimens seem to prey upon a greater proportion of amphipods than mature individuals of both sexes. These results were part of a study about ecology, biology and biodiversity of Bathyraja species on the Argentinean continental shelf. The white-dotted skate, Bathyraja albomaculata (Norman, 1937), is a medium size species in the Magellan region, from Uruguay in the Atlantic to central Chile in the Pacific. Diet composition, changes with sex and maturity status, and feeding strategy of this species were investigated in Argentinean waters (35°-55°S) through stomach contents analyses. Specimens were collected from research cruises carried out by Instituto Nacional de Investigación y Desarrollo Pesquero (INIDEP) between September 2003 and May 2005. Stomach contents were fixed in formalin 4%. Prey were counted, weighted, and identified to the lowest possible taxonomic level. Of a total of 184 stomachs examined, 95.1% contained food. All the sample sizes were sufficient for comparison, as the cumulative curves of diversity reached an asymptote. According to the Index of Relative Importance expressed as a percentage, polychaetes (67.97%) were the most important prey group in the diet of B . albomaculata followed by amphipods (23.78%) and isopods (8.13%). Cumaceans, crabs, euphausiids, teleosts, ophiuroids, hydrozoans and priapulids were not important in the diet (IRI<1%). The highest dietary overlap (Simplified Morisita Index) was found between mature males (n=55) and mature females (n=40) and the lowest similarity was observed between immature skates (n=80) and mature males. The graphical method of prey-specific abundance against frequency of occurrence suggested that the white-dotted skate is a polychaete specialized feeder. However, immature specimens seem to prey upon a greater proportion of amphipods than mature individuals of both sexes. These results were part of a study about ecology, biology and biodiversity of Bathyraja species on the Argentinean continental shelf. crabs, euphausiids, teleosts, ophiuroids, hydrozoans and priapulids were not important in the diet (IRI<1%). The highest dietary overlap (Simplified Morisita Index) was found between mature males (n=55) and mature females (n=40) and the lowest similarity was observed between immature skates (n=80) and mature males. The graphical method of prey-specific abundance against frequency of occurrence suggested that the white-dotted skate is a polychaete specialized feeder. However, immature specimens seem to prey upon a greater proportion of amphipods than mature individuals of both sexes. These results were part of a study about ecology, biology and biodiversity of Bathyraja species on the Argentinean continental shelf. albomaculata followed by amphipods (23.78%) and isopods (8.13%). Cumaceans, crabs, euphausiids, teleosts, ophiuroids, hydrozoans and priapulids were not important in the diet (IRI<1%). The highest dietary overlap (Simplified Morisita Index) was found between mature males (n=55) and mature females (n=40) and the lowest similarity was observed between immature skates (n=80) and mature males. The graphical method of prey-specific abundance against frequency of occurrence suggested that the white-dotted skate is a polychaete specialized feeder. However, immature specimens seem to prey upon a greater proportion of amphipods than mature individuals of both sexes. These results were part of a study about ecology, biology and biodiversity of Bathyraja species on the Argentinean continental shelf. crabs, euphausiids, teleosts, ophiuroids, hydrozoans and priapulids were not important in the diet (IRI<1%). The highest dietary overlap (Simplified Morisita Index) was found between mature males (n=55) and mature females (n=40) and the lowest similarity was observed between immature skates (n=80) and mature males. The graphical method of prey-specific abundance against frequency of occurrence suggested that the white-dotted skate is a polychaete specialized feeder. However, immature specimens seem to prey upon a greater proportion of amphipods than mature individuals of both sexes. These results were part of a study about ecology, biology and biodiversity of Bathyraja species on the Argentinean continental shelf. species in the Magellan region, from Uruguay in the Atlantic to central Chile in the Pacific. Diet composition, changes with sex and maturity status, and feeding strategy of this species were investigated in Argentinean waters (35°-55°S) through stomach contents analyses. Specimens were collected from research cruises carried out by Instituto Nacional de Investigación y Desarrollo Pesquero (INIDEP) between September 2003 and May 2005. Stomach contents were fixed in formalin 4%. Prey were counted, weighted, and identified to the lowest possible taxonomic level. Of a total of 184 stomachs examined, 95.1% contained food. All the sample sizes were sufficient for comparison, as the cumulative curves of diversity reached an asymptote. According to the Index of Relative Importance expressed as a percentage, polychaetes (67.97%) were the most important prey group in the diet of B . albomaculata followed by amphipods (23.78%) and isopods (8.13%). Cumaceans, crabs, euphausiids, teleosts, ophiuroids, hydrozoans and priapulids were not important in the diet (IRI<1%). The highest dietary overlap (Simplified Morisita Index) was found between mature males (n=55) and mature females (n=40) and the lowest similarity was observed between immature skates (n=80) and mature males. The graphical method of prey-specific abundance against frequency of occurrence suggested that the white-dotted skate is a polychaete specialized feeder. However, immature specimens seem to prey upon a greater proportion of amphipods than mature individuals of both sexes. These results were part of a study about ecology, biology and biodiversity of Bathyraja species on the Argentinean continental shelf. crabs, euphausiids, teleosts, ophiuroids, hydrozoans and priapulids were not important in the diet (IRI<1%). The highest dietary overlap (Simplified Morisita Index) was found between mature males (n=55) and mature females (n=40) and the lowest similarity was observed between immature skates (n=80) and mature males. The graphical method of prey-specific abundance against frequency of occurrence suggested that the white-dotted skate is a polychaete specialized feeder. However, immature specimens seem to prey upon a greater proportion of amphipods than mature individuals of both sexes. These results were part of a study about ecology, biology and biodiversity of Bathyraja species on the Argentinean continental shelf. albomaculata followed by amphipods (23.78%) and isopods (8.13%). Cumaceans, crabs, euphausiids, teleosts, ophiuroids, hydrozoans and priapulids were not important in the diet (IRI<1%). The highest dietary overlap (Simplified Morisita Index) was found between mature males (n=55) and mature females (n=40) and the lowest similarity was observed between immature skates (n=80) and mature males. The graphical method of prey-specific abundance against frequency of occurrence suggested that the white-dotted skate is a polychaete specialized feeder. However, immature specimens seem to prey upon a greater proportion of amphipods than mature individuals of both sexes. These results were part of a study about ecology, biology and biodiversity of Bathyraja species on the Argentinean continental shelf. crabs, euphausiids, teleosts, ophiuroids, hydrozoans and priapulids were not important in the diet (IRI<1%). The highest dietary overlap (Simplified Morisita Index) was found between mature males (n=55) and mature females (n=40) and the lowest similarity was observed between immature skates (n=80) and mature males. The graphical method of prey-specific abundance against frequency of occurrence suggested that the white-dotted skate is a polychaete specialized feeder. However, immature specimens seem to prey upon a greater proportion of amphipods than mature individuals of both sexes. These results were part of a study about ecology, biology and biodiversity of Bathyraja species on the Argentinean continental shelf. Bathyraja albomaculata (Norman, 1937), is a medium size species in the Magellan region, from Uruguay in the Atlantic to central Chile in the Pacific. Diet composition, changes with sex and maturity status, and feeding strategy of this species were investigated in Argentinean waters (35°-55°S) through stomach contents analyses. Specimens were collected from research cruises carried out by Instituto Nacional de Investigación y Desarrollo Pesquero (INIDEP) between September 2003 and May 2005. Stomach contents were fixed in formalin 4%. Prey were counted, weighted, and identified to the lowest possible taxonomic level. Of a total of 184 stomachs examined, 95.1% contained food. All the sample sizes were sufficient for comparison, as the cumulative curves of diversity reached an asymptote. According to the Index of Relative Importance expressed as a percentage, polychaetes (67.97%) were the most important prey group in the diet of B . albomaculata followed by amphipods (23.78%) and isopods (8.13%). Cumaceans, crabs, euphausiids, teleosts, ophiuroids, hydrozoans and priapulids were not important in the diet (IRI<1%). The highest dietary overlap (Simplified Morisita Index) was found between mature males (n=55) and mature females (n=40) and the lowest similarity was observed between immature skates (n=80) and mature males. The graphical method of prey-specific abundance against frequency of occurrence suggested that the white-dotted skate is a polychaete specialized feeder. However, immature specimens seem to prey upon a greater proportion of amphipods than mature individuals of both sexes. These results were part of a study about ecology, biology and biodiversity of Bathyraja species on the Argentinean continental shelf. crabs, euphausiids, teleosts, ophiuroids, hydrozoans and priapulids were not important in the diet (IRI<1%). The highest dietary overlap (Simplified Morisita Index) was found between mature males (n=55) and mature females (n=40) and the lowest similarity was observed between immature skates (n=80) and mature males. The graphical method of prey-specific abundance against frequency of occurrence suggested that the white-dotted skate is a polychaete specialized feeder. However, immature specimens seem to prey upon a greater proportion of amphipods than mature individuals of both sexes. These results were part of a study about ecology, biology and biodiversity of Bathyraja species on the Argentinean continental shelf. albomaculata followed by amphipods (23.78%) and isopods (8.13%). Cumaceans, crabs, euphausiids, teleosts, ophiuroids, hydrozoans and priapulids were not important in the diet (IRI<1%). The highest dietary overlap (Simplified Morisita Index) was found between mature males (n=55) and mature females (n=40) and the lowest similarity was observed between immature skates (n=80) and mature males. The graphical method of prey-specific abundance against frequency of occurrence suggested that the white-dotted skate is a polychaete specialized feeder. However, immature specimens seem to prey upon a greater proportion of amphipods than mature individuals of both sexes. These results were part of a study about ecology, biology and biodiversity of Bathyraja species on the Argentinean continental shelf. crabs, euphausiids, teleosts, ophiuroids, hydrozoans and priapulids were not important in the diet (IRI<1%). The highest dietary overlap (Simplified Morisita Index) was found between mature males (n=55) and mature females (n=40) and the lowest similarity was observed between immature skates (n=80) and mature males. The graphical method of prey-specific abundance against frequency of occurrence suggested that the white-dotted skate is a polychaete specialized feeder. However, immature specimens seem to prey upon a greater proportion of amphipods than mature individuals of both sexes. These results were part of a study about ecology, biology and biodiversity of Bathyraja species on the Argentinean continental shelf. B . albomaculata followed by amphipods (23.78%) and isopods (8.13%). Cumaceans, crabs, euphausiids, teleosts, ophiuroids, hydrozoans and priapulids were not important in the diet (IRI<1%). The highest dietary overlap (Simplified Morisita Index) was found between mature males (n=55) and mature females (n=40) and the lowest similarity was observed between immature skates (n=80) and mature males. The graphical method of prey-specific abundance against frequency of occurrence suggested that the white-dotted skate is a polychaete specialized feeder. However, immature specimens seem to prey upon a greater proportion of amphipods than mature individuals of both sexes. These results were part of a study about ecology, biology and biodiversity of Bathyraja species on the Argentinean continental shelf. crabs, euphausiids, teleosts, ophiuroids, hydrozoans and priapulids were not important in the diet (IRI<1%). The highest dietary overlap (Simplified Morisita Index) was found between mature males (n=55) and mature females (n=40) and the lowest similarity was observed between immature skates (n=80) and mature males. The graphical method of prey-specific abundance against frequency of occurrence suggested that the white-dotted skate is a polychaete specialized feeder. However, immature specimens seem to prey upon a greater proportion of amphipods than mature individuals of both sexes. These results were part of a study about ecology, biology and biodiversity of Bathyraja species on the Argentinean continental shelf. followed by amphipods (23.78%) and isopods (8.13%). Cumaceans, crabs, euphausiids, teleosts, ophiuroids, hydrozoans and priapulids were not important in the diet (IRI<1%). The highest dietary overlap (Simplified Morisita Index) was found between mature males (n=55) and mature females (n=40) and the lowest similarity was observed between immature skates (n=80) and mature males. The graphical method of prey-specific abundance against frequency of occurrence suggested that the white-dotted skate is a polychaete specialized feeder. However, immature specimens seem to prey upon a greater proportion of amphipods than mature individuals of both sexes. These results were part of a study about ecology, biology and biodiversity of Bathyraja species on the Argentinean continental shelf.Bathyraja species on the Argentinean continental shelf.