Browsing by Author "Siegenthaler, Andjin"
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- Outlanders in an unusual habitat: holothuria mammata (Grube, 1840) behaviour on seagrass meadows from Ria Formosa (S Portugal)Publication . Siegenthaler, Andjin; Canovas, Fernando; Gonzalez-Wanguemert, MercedesHolothuria mammata is one of the new target species from the Mediterranean and Atlantic. Usually, it inhabits rocky bottoms, staying in crevices and holes during the day and leaving them in the night for feeding on sandy bottoms. However, it can be found in unusual habitats such as seagrass with diurnal and nocturnal feeding. This study provides information for the first time on the behaviour, density and small scale distribution of H. mammata in a seagrass habitat from Ria Formosa (S Portugal). To reach these aims, a mark/recapture methodology was used. Abundance was estimated through R statistical software v.2.15.3 (package "Rcapture"). The minimum area method was applied in GRASS GIS v.6.4.2 for home range. Size distribution was estimated applying a Shapiro-Wilk test. Rayleigh test for randomness was applied to study the directionality of movements. A circular one-way ANOVA was used to test for differences in movement direction. Capture probability was higher on seagrass than sand and the total length of the individuals ranged from 13 to 25 cm. Movement speed was between 4.7 and 14.7 m day(-1). Movements were not directional. H. mammata differs in its behaviour from the related Holothuria arguinensis occurring in the same habitat.
- Spatial distribution patterns and movements of Holothuria arguinensis in the Ria Formosa (Portugal)Publication . Siegenthaler, Andjin; Canovas, Fernando; Gonzalez-Wangueemert, MercedesHolothurian populations are under pressure worldwide because of increasing demand for beche-de-mer, mainly for Asian consumption. Importations to this area from new temperate fishing grounds provide economic opportunities but also raise concerns regarding future over-exploitation. Studies on the habitat preferences and movements of sea cucumbers are important for the management of sea cucumber stocks and sizing of no-take zones, but information on the ecology and behavior of temperate sea cucumbers is scarce. This study describes the small-scale distribution and movement patterns of Holothuria arguinensis in the intertidal zone of the Ria Formosa national park (Portugal).Mark/recapture studieswere performed to record theirmovements over time on different habitats (sand and seagrass). H. arguinensis preferred seagrass habitats and did not show a size or life stage-related spatial segregation. Its density was 563 ind. ha−1 and mean movement speed was 10 m per day. Movement speed did not differ between habitats and the direction of movement was offshore during the day and shoreward during the night. Median home range size was 35 m2 and overlap among home ranges was 84%. H. arguinensis' high abundance, close association with seagrass and easy catchability in the intertidal zone, indicate the importance of including intertidal lagoons in future studies on temperate sea cucumber ecology since those systems might require different management strategies than fully submerged habitats.