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To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.anbehav.2006.11.008 Byline: Clement P. Dumont, David Drolet, Isabelle DeschA*nes, John H. Himmelman Abstract: Although numerous species of sea urchins often cover themselves with small rocks, shells and algal fragments, the function of this covering behaviour is poorly understood. Diving observations showed that the degree to which the sea urchin Strongylocentrotus droebachiensis covers itself in the field decreases with size. We performed laboratory experiments to examine how the sea urchin's covering behaviour is affected by the presence of predators, sea urchin size, wave surge, contact with moving algae blades and sunlight. The presence of two common sea urchin predators did not influence the degree to which sea urchins covered themselves. Covering responses of sea urchins that were exposed to a strong wave surge and sweeping algal blades were significantly greater than those of individuals that were maintained under still water conditions. The degree to which sea urchins covered themselves in the laboratory also tended to decrease with increasing size. Juveniles showed stronger covering responses than adults, possibly because they are more vulnerable to dislodgement and predation. We found that UV light stimulated a covering response, whereas UV-filtered sunlight and darkness did not, although the response to UV light was much weaker than that to waves and algal movement. Our observations suggest that the covering behaviour of S. droebachiensis has evolved as an adaptation to protect it from mechanical injuries associated with abrasion and dislodgement, and to a lesser extent as a defence against UV radiation. The covering behaviour may reduce the sea urchin's ability to move and this would limit its ability to forage and to flee from predators. In this case, the covering behaviour may have evolved as a trade-off between locomotion and limiting environmental stresses. Author Affiliation: (a) Departement de Biologie, Quebec-Ocean, Universite Laval, Canada (a ) CEAZA, Departamento de Biologia Marina, Universidad Catolica del Norte, Chile Article History: Received 26 March 2006; Revised 29 August 2006; Accepted 13 November 2006 Article Note: (miscellaneous) MS. number: A10403

Population outbreaks of the coral-eating predator crown of thorns starfish (COTS), Acanthaster planci are responsible for large-scale disturbance of coral reefs throughout the Indo-Pacific. In response, attempts are often made to control COTS outbreaks in protected areas. For instance, volunteers remove thousands of sea stars every year in Malaysia. This study reports the status of the COTS population in the Pulau Tioman Marine Park and examines the effectiveness of the seasonal sea star removal programme. After the 2009 removal season, we monitored COTS densities and coral assemblages before and after a 6-month no-removal season at sites with and without COTS removal efforts. We recorded high COTS densities up to 330 ind. ha−1 at a few sites independent of removal effort. In fact, removal only temporarily reduced large individuals from local populations. Moreover, after the no-removal season, sites with COTS removal had increased live coral cover, but sites without COTS removal had a drastic decrease in live coral cover, with Acropora spp. being most affected. Therefore, this study suggests that the current seasonal removals could promote coral health, despite the high density of COTS. [ABSTRACT FROM PUBLISHER]

This is the first systematic assessment conducted on fouling communities to determine the current status of six non-native marine invertebrates that were first recorded in Hong Kong three decades ago. They include the solitary ascidian, Ciona intestinalis; the slipper limpet, Crepidula onyx; the bryozoan, Bugula californica; the Caribbean bivalve, Mytilopsis sallei; the Mediterranean mussel, Mytilus galloprovincialis; and the boring isopod, Sphaeroma walkeri. Field surveys were conducted at 31 locations during wet (2011) and dry (2012) seasons and included fouling communities on piers and mariculture zones from estuarine to oceanic zones. The sampling was conducted by using photo-quadrats, destructive quadrats and field observations. To detect temporal changes in the abundance and recruitment of the sedentary non-native species, three piers were monitored with permanent photo-quadrats and recruitment panels for a one year period. We examined the relationship between seawater quality data available for Hong Kong and the abundances of fouling and non-native species. Only four of the six target non-native species were recorded in this survey. The isopod Sphaeroma walkeri was common and widely distributed in fouling communities in Hong Kong, while Ciona intestinalis, Crepidula onyx, and Mytilopsis sallei were uncommon and mainly restricted to areas with intensive human activities and poor seawater quality. These findings suggest that near shore human activities and poor water quality could increase the risk of establishment of non-native species in Hong Kong's marine fouling communities. [ABSTRACT FROM AUTHOR]

Many studies have applied fluorochrome tagging to examine the growth of animals with calcified skeletons, but most of them have used only a single tag to determine the annual growth rate. We used sequential fluorochrome tagging to study the seasonal growth of the purple sea urchin Heliocidaris crassispina in Hong Kong waters from February 2012 to February 2013. Sea urchins ranging from 18.9 to 42.7 mm in test diameter had a yearly growth from 0.6 to 13.0 mm. During that year, the sea urchins grew from 0.6 to 5.0 mm in test diameter during the first six months, and from 0.4 to 10.2 mm in test diameter in the second six months. The seasonal differences in growth were confirmed using the von Bertalanffy model. The growth was clear for young sea urchins, especially for individuals less than 5 years old, but was not evident for sea urchins older than 7 years. The seasonal differences in growth were probably related to the reproductive cycle and the seasonal differences in environmental conditions. Our empirical results provide the first evidence of seasonal changes in growth for H. crassispina , demonstrating the usefulness of sequential fluorochrome tagging in studying the growth of sea urchins in the field. We also identify the problem of low recovery of tagged individuals and provide recommendations to improve the tagging procedure.