Abstract
The trochid gastropod, Rochia nilotica is harvested in small-scale fisheries throughout Southeast Asia and the Pacific Islands, many of which were created from inter-country translocations. This species is found on structurally complex shallow reefs, but specific habitat requirements have not yet been quantified in order the maximize the success of future translocations and help future-proof the fishery in changing ocean conditions. At 28 sites around Samoa, where the species was introduced in the early 2000s, we measured a suite of habitat variables along transects in which R. nilotica were counted and the shell sizes measured in a parallel study. Boosted regression tree analyses revealed that R. nilotica were most abundant at reef locations that were shallow, with fairly consistent depth, high cover of branching coral, low cover of erect macroalgae, low wave exposure and high surface complexity. Smaller individuals were associated with wide reef flats and high cover of branching coral, whereas larger animals occurred in deeper water with high surface complexity. Multivariate analyses showed this species to be a habitat generalist, sharing much of its niche with an endemic herbivorous gastropod, Tectus pyramis. Future stocking programs should focus on sites with habitats optimal for both adults and juveniles. R. nilotica populations are likely to be especially affected by broadscale stressors that result in declines in live coral cover and substratum complexity and increasing coverage of macroalgae on coral reefs.
Highlights
Coral reefs are naturally highly complex and provide habitat for a diverse suite of marine species (Spalding et al, 2001; Hoegh-Guldberg et al, 2007)
Habitat variables differed considerably among sites, allowing for relationships with R. nilotica to be examined over a broad spectrum of conditions (Supplementary Table 1)
The present study provides a comprehensive approach to examining the relationships between benthic reef invertebrates and a range of biophysical habitat features
Summary
Coral reefs are naturally highly complex and provide habitat for a diverse suite of marine species (Spalding et al, 2001; Hoegh-Guldberg et al, 2007). Important habitat characteristics may include: substratum type, cover of benthic biota, reef surface complexity, wave exposure, and depth (McCormick, 1994; Graham and Nash, 2013; Komyakova et al, 2013). These habitat features are likely to influence key ecological processes such as recruitment, competition, foraging and predation (Luckhurst and Luckhurst, 1978; McCormick, 1994; Graham and Nash, 2013). Such knowledge can reveal habitat traits driving distributional patterns of marine invertebrates and, importantly, enhance the success of stock restoration projects by identifying optimal deployment locations (Bell et al, 2005).
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