Demographic structure suggests migration of the sea urchin Paracentrotus lividus in a coastal lagoon

Abstract

To cite this version:C. Fernandez, A. Caltagirone, M. Johnson. Demographic structure suggests migration of the sea urchin Paracentrotus lividus in a coastal lagoon.

How effective are MPAs? Predation control and ‘spill-in effects’ in seagrass–coral reef lagoons under contrasting fishery management

“…This pattern, almost identical to those previously found in the study area (McClanahan & Muthiga 1989, McClanahan & Shafir 1990, indicates that T. gratilla are controlled by highly abundant reef predators and, consequently, that overfishing reduces predation control (see also Alcoverro & Mariani 2004). As many urchins, including T. gratilla, show ontogenetic migrations from hard-bottom reefs to seagrass beds in search of food (Ogden et al 1973, Dafni & Tobol 1987, Fernandez et al 2001, it is possible that overfishing of coral reef-associated urchin predators could induce overgrazing of adjacent seagrass beds. Such 'cross-system' cascades have been previously observed in linked oceanic-nearshore systems (Estes et al 1998), but must be studied in closer detail before taken as a fact (e.g.…”

“…Sala & Zabala 1996, Guidetti 2006. Dominance of one age cohort (as reported here) is common and can be caused by sporadic extreme recruitment success and/ or ontogenetic habitat shifts (Fernandez et al 2001). However, while Kenyan T. gratilla populations seem to have continuous reproduction (Muthiga 2005) they appear to have been dominated by adults for the past decade (Alcoverro & Mariani 2002, Muthiga 2005.…”

Population Dynamics of Edible Sea Urchins Associated with Variability of Seaweed Beds in Northern Japan

“…Formation of grazing front is initiated from an increase in the population size of sea urchins due to successful recruitment, migration, decrease of predators (Lawrence 1975) and reduction in the availability of drift algae, which cause sedentary urchins to graze actively (Dean et al 1984;Ebeling et al 1985). Unlike grazing activity, for the sea urchin Loxechinus albus, Sphaerechinus granularis and Paracentrotus lividus, the movement to feed kelps, seagrasses or macro algae is caused by changes in food habit with urchin's growth (Guisad and Castilla 1987;Guillou and Michel 1993;Fernandez et al 2001). But these studies gave little thought in the context of annual grazing activities, reproductive cycles and seasonal growth of sea urchins.…”

Effect of an exceptional rainfall event on the sea urchin (Paracentrotus lividus) stock and seagrass distribution in a Mediterranean coastal lagoon

“…In Urbinu lagoon, sea urchins occur, in variable densities, in four habitats: pebble bottoms (recruitment area), seagrass beds (growth area) but also in silt and sandy habitats. These last two habitats seem to be principally traversed during migrations which take place between the recruitment and growth areas (Fernandez et al, 2001).…”

“…The consumption of C. nodosa by grazing could reach 45%, and the role of herbivores in controlling seagrass production increases notably from exposed to sheltered meadows (Cebrian et al, 1996). In coastal lagoons, where C. nodosa beds are particularly extensive (Pasqualini et al, 2006), surprisingly little is known about sea urchin populations living in these environments (Fernandez and Boudouresque, 1997;Fernandez et al, 2001) whereas they are the main consumers of C. nodosa beds. This sea urchin is assumed to consume, when density is around 0.5 ind/m 2 , about 1e7% of the C. nodosa production (Fernandez, unpublished data); for density around 10e30 ind/m 2 (which has already been observed in coastal lagoons: Fernandez and Caltagirone, 1990), consumption reaches 100% of the C. nodosa production and induces overgrazing.…”