Spatial distribution patterns and movements of Holothuria arguinensis in the Ria Formosa (Portugal)

Abstract

Holothurian populations are under pressure worldwide because of increasing demand 3 for beche-de-mer, mainly for Asian consumption. Importations to this area from new 4 temperate fishing grounds provide economic opportunities but also raise concerns 5 regarding future over-exploitation. Studies on the habitat preferences and movements 6 of sea cucumbers are important for the management of sea cucumber stocks and 7 sizing of no-take zones, but information on the ecology and behaviour of temperate 8 sea cucumbers is scarce. This study describes the small-scale distribution and 9 movement patterns of Holothuria arguinensis in the intertidal zone of the Ria 10 Formosa national park (Portugal). Mark/recapture studies were performed to record 11 their movements over time on different habitats (sand and seagrass). H. arguinensis 12 preferred seagrass habitats and did not show a size or life stage-related spatial 13 segregation. Its density was 563 ind ha-1 and mean movement speed was 10 m per 14 day. Movement speed did not differ between habitats and the direction of movement 15 was offshore during the day and shoreward during the night. Median home range size 16 was 35 m 2 and overlap among home ranges was 84 %. Holothuria arguinensis' high 17 abundance, close association with seagrass and easy catchability in the intertidal zone, 18 indicate the importance of including intertidal lagoons in future studies on temperate 19 sea cucumber ecology since those systems might require different management 20 strategies than fully submerged habitats.

Untitled

“…It consists of a sandy habitat (44.5 % coverage) and a seagrass habitat (35.6 % coverage). More details about the study area can be found in Siegenthaler et al (2015).…”

“…Tidal height at low tide was between 0.57 and 0.70 m during the first period and 0.36 and 0.60 m during the second one (source Instituto Hidrográfico). The whole study area was searched during each period of exposure (between 2 hours before low tide and 1 hour after it) and all holothurians found were marked in situ by means of scratching a code on their dorsal side (Reichenbach, 1999;Mercier, Battaglene, & Hamel, 2000;Navarro, García-Sanz, Barrio, & Tuya, 2013b;Siegenthaler et al, 2015) and released them at the same spot where captured. Although stress caused by marking and handling could result in increased initial activity (Shiell, 2006), scratching is considered as less invasive than other tagging methods (Conand, 1990;Kirshenbaum, Feindel, & Chen, 2006;Navarro, García-Sanz, & Tuya, 2014;Purcell, Agudo, & Gossuin, 2008;Schiell, 2006) and does not result in major behavioural changes (Mercier et al, 2000).…”

“…Although stress caused by marking and handling could result in increased initial activity (Shiell, 2006), scratching is considered as less invasive than other tagging methods (Conand, 1990;Kirshenbaum, Feindel, & Chen, 2006;Navarro, García-Sanz, & Tuya, 2014;Purcell, Agudo, & Gossuin, 2008;Schiell, 2006) and does not result in major behavioural changes (Mercier et al, 2000). Relative position (see Siegenthaler et al (2015) for the methodology used), total length (by means of metric tape), time and type of substrate were recorded for each sea cucumber sampled. Temperature, salinity and weather information for the duration of the study can be also found in Siegenthaler et al (2015).…”

“…Relative position (see Siegenthaler et al (2015) for the methodology used), total length (by means of metric tape), time and type of substrate were recorded for each sea cucumber sampled. Temperature, salinity and weather information for the duration of the study can be also found in Siegenthaler et al (2015).…”

“…This study aims to provide data on the population parameters (density, length, weight, spatial distribution), and behaviour characteristics of H. mammata in the Ria Formosa National Park (S Portugal), an unusual distribution area characterized by seagrass communities mixed with sandy bottoms (González-Wangüemert, & Borrero-Pérez, 2012;González-Wangüemert, Braga, Silva, Valente, Rodrigues, & Serrao, 2013;Siegenthaler, Cánovas, & González-Wangüemert, 2015). This information will be of value for future management of sea cucumber stocks in the Ria Formosa National Park.…”