Movement and effectiveness of shelters for restocking of the sea cucumber Isostichopus badionotus

Abstract

The sea cucumber Isostichopus badionotus has been overfished along its Mexican distribution, but no abundance recovery has been observed despite management efforts. Restocking and sea ranching strategies can use releasing individuals, and magnitude of protected areas be related on species dispersion knowledge. We measured the short-term movement paths on I. badionotus and their relation with environmental variables. In addition, the influence of biofilm presence/absence on artificial shelters surfaces and the use for animals were compared. Data was obtained through time-lapse cameras in experiments performed in outer aquaria under the natural fluctuation of temperature and sunlight. We observed that larger (Le) individuals exhibited greater daily movement distances (D) (D=0.89*Le −2.533 cm); furthermore, the sea cucumbers move faster in bare aquaria than aquaria with sand. The mean daily movement without sand was 518 cm for small sizes, 615 cm for medium, and 688 cm for large sizes. In the presence of sand, was 127, 196, and 315 cm, respectively. Movement was minimal in the morning/early afternoon (07:00–15:00), a maximum in the afternoon/evening (15:00–23:00), and an intermediate at night/early morning (23:00–07:00). The movement of the small sea cucumbers (>5.96−10.75 cm), was linked to light. Medium-sized and large sea cucumbers (>10.6−19.69 cm) respond to changes in temperature. We observed a higher rate of shelter use by small sea cucumbers (53 % of the day) and a greater affinity for pre-conditioned shelters (80 % of shelter use). Medium-sized and large animals did not show any shelter preferences. Results indicate low dispersion of I. badionotus on daily timescale. The affinity found in small animals towards shelters with biofilm, and their use only in this size class, makes them essential for survival in restoration strategies.