Rajids ovipositing on marine litter: A potential threat to their survival.

Marine litter is a complex environmental issue threatening the well-being of multiple organisms. In the present study, we present an overlooked pathway by which marine litter interaction with certain ovigerous skates (Family: Rajidae) communities could compromise their survival. We propose that skates from the genus Sympterygia deposit their egg capsules on marine litter substrates by accident, which are then washed ashore still unhatched. We conducted 10 monitoring surveys on three beaches of La Libertad Region, on the north coast of Peru, looking for marine litter conglomerates to determine the presence of egg capsules. We registered a total of 75 marine litter conglomerates, containing 1595 egg capsules, out of which only 15.9 % were presumably hatched, and 15.8 % were still fresh. Fishing materials were identified as the main item in marine litter conglomerates. We conclude that this behavior could contribute to the decline of Sympterygia communities, although further research is needed.

Relationship between over-crowding within egg capsules of the marine gastropod Acanthina monodon and prospects for juvenile success.

Encapsulated development with extraembryonic yolk may lead to competition for nutrients within egg capsules. In this research, different degrees of competition among embryos in subtidal egg capsules of Acanthina monodon resulted in considerable differences in hatching size. For newly hatched juveniles, individuals hatching from less crowded egg capsules showed better survival, larger SL, higher rates of oxygen consumption, and higher rates of food consumption. However, by 28 days after hatching, the largest surviving juveniles were the best-performing individuals, regardless of the initial embryo density within the capsules. In summary, more crowded egg capsules resulted in poorer survival. These findings may help to explain the variability seen in juvenile success in some field populations; much of that variation may reflect stressful experiences that the new recruits have had during the early stages of their encapsulated development.

First observations on captive hatching and incubation period of the yellow-nose skate Dipturus chilensis (Rajiformes: Rajidae), from the South-Eastern Pacific Ocean.

Twelve egg capsules laid in captivity by three females of Dipturus chilensis were incubated in the laboratory. After 252 ± 9.4 days, 10 skates successfully hatched, with a mean total length, disc length, and disc width of 17.2, 7.4, and 11.4 cm, respectively. This is the first report of captive hatching of D. chilensis and its corresponding incubation period.

Comparación de la abundancia, estructura de tallas y fecundidad de Voluta musica (Caenogastropoda: Volutidae) en tres sitios de la costa norte de la Península de Araya, Venezuela / Abundance, size structure and fecundity of Voluta musica (Caenogastropoda: Volutidae) in three sites of the north coast of Araya Peninsula, Venezuela

Abundance, size structure and fecundity of Voluta musica (Caenogastropoda: Volutidae) in three sites of the north coast of Araya Peninsula, Venezuela. Considering the intensive artisanal fishing activity and the consequent carrion discard found at Isla Caribe, in relation to other two sites with no intensive artisanal fishing activity, we expect different effects on some features of V. musica life history (larger egg capsules, larger organisms, higher abundance of adult organisms). In this paper we compare some population parameters of Voluta musica at three localities in the north coast of the Araya Peninsula in Venezuela under different fishing exploitation regimes. The samples were taken monthly during 2008 and 2009 at Isla Caribe, Isla Lobos and Bajo Cuspe. At each site, samples were taken within three areas of 40m². The abundance of V. musica ranged between 5 ind/120m² to 30 ind/120m² with significant differences between sites (F=7.77; p<0,01). Organisms from Isla Caribe were larger in size (p=0,045), than those in the other two sites. There is a significant differences in the number of egg capsules between sites and between months, and there is clear evidence that Isla Caribe has the largest abundance of egg capsules (p<0,01) suggesting that the extra feeding source (carrion) found at Isla Caribe could have a positive effect on the reproductive potential of the V. musica population at this site.

Teniendo en cuenta la intensa actividad pesquera artesanal y subsecuente fuente adicional de alimento como carroña en Isla Caribe, se esperaría un efecto sobre algunos parámetros poblacionales de V. musica como: mayor número de ovicápsulas, individuos de tallas mayores y densidades de caracoles adultos mayores. Con el presente trabajo se desea conocer la abundancia, estructura de talla y fecundidad de Voluta musica en tres sitios de la costa norte de la Península de Araya en las que existen actividades de pesca diferenciales. Se realizaron muestreos mensuales entre 2008 y 2009 en Isla Caribe, Isla Lobos y Bajo Cuspe, en cada uno con 3 áreas de 40m². La abundancia varió de 5ind/120m² a 30ind/120m², con diferencias significativas entre los sitios (F= .77; p<0,01), siendo igual para Bajo Cuspe e Isla Caribe (p=0,39) pero distinta y menor en Isla Lobos, (p=0,008; 0,0149). Los individuos de Isla Caribe demostraron ser más grandes (p=0,045). Existen diferencias significativas entre sitios y entre meses en el número de ovicápsulas (p<0,01), siendo Isla Caribe el sitio con mayor abundancia de ovicápsulas (p<0,01). Esto sugiere que el alimento suplementario en forma de carroña podría incrementar el potencial reproductivo de la población en Isla Caribe.