Understanding movement patterns, habitat use and behaviour of fish is critical to determining how targeted species may respond to protection provided by “no-take” sanctuary zones within marine parks. We assessed the fine and broad scale movement patterns of an exploited herbivore, luderick (Girella tricuspidata), using acoustic telemetry to evaluate how this species may respond to protection within Jervis Bay (New South Wales, Australia). We surgically implanted fourteen fish with acoustic transmitters and actively and passively tracked individuals to determine fine and broad scale movement patterns respectively. Eight fish were actively tracked for 24 h d¯1 for 6 d (May 2011), and then intermittently over the following 30 d. Six fish were passively tracked from December 2011 to March 2012, using a fixed array of receivers deployed across rocky reefs around the perimeter of the bay. Luderick exhibited strong site fidelity on shallow subtidal reefs, tending to remain on or return consistently to the reef where they were caught and released. All eight fish actively tracked used core areas solely on their release reef, with the exception of one fish that used multiple core areas, and four of the six fish passively tracked spent between 75 to 96% of days on release reefs over the entire tracking period. Luderick did move frequently to adjacent reefs, and occasionally to more distant reefs, however consistently returned to their release reef. Luderick also exhibited predictable patterns in movement between spatially distinct daytime and night-time core use areas. Night-time core use areas were generally located in sheltered areas behind the edge of reefs. Overall, our data indicate luderick exhibit strong site fidelity on shallow subtidal reefs in Jervis Bay and suggests that this important herbivore may be likely to show a positive response to protection within the marine park.

Siliceous inclusions play an important role in deterring terrestrial herbivores, but their role in marine systems remains controversial. Sponges are ubiquitous members of marine benthic communities and represent a potentially valuable food source for many predatory species, yet they have few natural predators. An in situ method was used to assess the deterrent effects of siliceous spicules or whole sponge skeleton, which were hypothesised to act as a physical defense in temperate reef sponges. Natural concentrations of spicules from 5 species of sponge and the spongin skeleton from a sixth species were incorporated into artificial diets, which were similar in nutritional quality to the sponge tissues. These were offered to the sea urchin Centrostephanus rodgersii in feeding choice experiments including control discs containing no spicules or spongin skeleton. Spicules from 4 species, Tedania anhelans, Clathria pyramida, Chondrilla australiensis and Chondrilla sp., deterred feeding by C. rodgersii. Spicules from a fifth species, Callyspongia sp., and intact skeleton isolated from Cacospongia sp., failed to deter C. rodgersii. This is the first demonstration of antifeedant activity associated with skeletal elements against sea urchins. Importantly, unlike previous work in the tropics, very small spicules (microscleres) measuring <100 µm were effective feeding deterrents.

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