Effect of Water Flow on Grazing by the Sea Urchin (<i>Strongylocentrotus Nudus</i>) in the Presence of Refuge Habitat

Abstract

Effect of water disturbance on grazing by the sea urchin with the refuge habitat was estimated. We tested the hypothesis that sea urchins ceased feeding and remained in refuge habitat for protection against disturbance even though water flows were not high to inhibit their grazing. Fecal density from sea urchins was positively related to their residence time under the undisturbed condition. This result suggested that the fecal density is a useful criterion for understanding the residence time of sea urchins in the calm condition. Five types of structure (L-shaped, cave shaped, crack-shaped, smaller and larger rectangular structure) as refuge habitats were deployed in the undisturbed tank with sea urchins and the fecal densities at each structure were measured to examine the habitat forms which sea urchins prefer. This experiment indicated that the crack-shaped form was used for sea urchins as the refuge habitat. Feeding rate of sea urchins inversely corresponded to water flow. Feeding rates with the refuge habitat were lower than in the absence of habitat, although water disturbances were almost the same. The presence of refuge habitat seemed to be a factor responsible for the reduction of their grazing, because sea urchins sheltered to avoid water disturbances.

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

“…These results indicate that small M. nudus could be reseeded in areas with a flow velocity below 30 cm s −1 . This is because movement is the basis for the other fitness-related behaviours such as foraging (Agatsuma, 2013) and sheltering (Tamaki et al, 2018) of sea urchins (Santos & Flammang, 2008;Morse & Hunt, 2013).…”

“…Sea urchins use their tube feet to attach to the sea bottom, effectively resisting the dislodgement risk in water flow (Morse & Hunt, 2013). The adhesion of tube feet regulates the movement of sea urchins and thus plays an important role in their foraging and risk avoidance (Cohen-Rengifo et al ., 2017; Tamaki et al ., 2018). Further, righting behaviour is essential to maintain activity in water flow (Lawrence, 1975; Hagen, 1994).…”

Long-term study of behaviors of two cohabiting sea urchin species, Mesocentrotus nudus and Strongylocentrotus intermedius, under conditions of high food quantity and predation risk in situ

“…It is known that with increasing water velocity (higher than approximately 15 cm s -1 ), sea urchins decrease their displacement and cease feeding both under laboratory (Kawamata, 1998; Frey & Gagnon, 2016; Cohen-Rengifo et al, 2018; Tamaki, Muraoka & Inoue, 2018) and field (Lissner, 1980; Dance, 1987; Siddon & Witman, 2003; Dumont, Himmelman & Russell, 2006; Dumont, Himmelman & Robinson, 2007) conditions. Escape behavior was also observed in laboratory flume experiments: at flow velocity ≤30 cm s −1 , sea urchins moved in a downstream direction whereas at 35–45 cm s −1 , individuals moved in an upstream direction (Morse & Hunt, 2013; Cohen-Rengifo et al, 2018).…”

Peer Review #1 of "Long-term study of behaviors of two cohabiting sea urchin species, Mesocentrotus nudus and Strongylocentrotus intermedius, under conditions of high food quantity and predation risk in situ (v0.1)"

“…It is known that with increasing water velocity (higher than approximately 15 cm s -1 ), sea urchins decrease their displacement and cease feeding both under laboratory (Kawamata, 1998;Frey & Gagnon, 2016;Cohen-Rengifo et al, 2018;Tamaki et al, 2018) and field (Lissner, 1980;Dance, 1987;Siddon & Witman, 2003;Dumont et al, 2006Dumont et al, , 2007 conditions. Escape behavior was also observed in laboratory flume experiments: at flow velocity ≤ 30 cm s -1 , sea urchins moved in a downstream direction whereas at 35-45 cm s -1 , individuals moved in an upstream direction (Morse & Hunt, 2013;Cohen-Rengifo et al, 2018).…”