Effects of flow velocity on fitness-related behaviours of the sea urchin Mesocentrotus nudus: new information on stock enhancement

Abstract

The effects of flow velocity on the fitness-related behaviours of Mesocentrotus nudus remain largely unknown, greatly hampering the efficiency of stock enhancement. To explore the appropriate velocities for stock enhancement, we investigated dislodgement and immobilization velocities up to 90 cm s−1. The experimental results showed that M. nudus (test diameter of ~30 mm) were dislodged at 73.50 ± 7.7 cm s−1 and that M. nudus movement occurred only when the flow velocity was less than 33.40 ± 2.7 cm s−1. Three flow velocities less than 33.40 ± 2.7 cm s−1 (2, 10 and 20 cm s−1) were subsequently used to study the effects of flow velocities on covering behaviour and the righting response time of M. nudus. The downstream movement velocity of M. nudus was significantly larger than that upstream at 2 cm s−1 (P = 0.016) and 10 cm s−1 (P = 0.008), but not at 20 cm s−1 (P = 0.222). The righting response time of M. nudus was significantly longer at 20 cm s−1 than that at 2 cm s−1 (P = 0.015). The present study indicates that a flow velocity less than 20 cm s−1, preferably 2–10 cm s−1, is probably appropriate for the stock enhancement of M. nudus. Notably, the current study is a laboratory investigation without considering the hydrographic complexity in the field. Further studies should be carried out to investigate the long-term effects of water flow on feeding and growth of M. nudus both in the laboratory and the field.

Transcriptomes reveal the involved genes in the sea urchin Mesocentrotus nudus exposed to high flow velocities

“…For example, it greatly increases the energy consumption of the fish Rhynchocypris lagowskii 34 and reduces the fat content of the flounder Paralichthys olivaceus 35 . Consistently, our previous studies found that high flow velocity displays negative effects on the growth and development of sea urchins 18 , 28 . Here, we further found three metabolism pathways through KEGG analysis, including arachidonic acid metabolism, linoleic acid metabolism, and arginine and proline metabolism.…”

“…Our previous study found that test diameter and body weight of M . nudus increased significantly slower at a high flow velocity 18 . Tube feet of sea urchins are highly sensory 19 .…”