Modelling habitat associations of the common spider conch in the Cocos (Keeling) Islands

Abstract

The type and configuration of benthic habitats can influence community structure of marine fauna and the effectiveness of management actions, such as spatial closures. We quantified the relationship between the distribution and density of Lambis lambis, an exploited marine gastropod, and available benthic habitats at the Cocos (Keeling) Islands. We used 3 modelling approaches to develop a model of the density of L. lambis as a function of habitat: conventional polynomial regression, Moran's eigenvector maps (MEM) and variance partitioning. Distribution and abundance of L. lambis was not uniform throughout the lagoon. Both the amount and configuration of habitat influenced L. lambis density; the highest densities were associated with moderate levels of hard macroalgae and submassive corals, and the lowest densities with seagrass and relict coral. These results illustrate that incorporating information on the distribution and patchiness of preferred habitats is essential to ensure that appropriate habitats are included in the design and implementation of long-term monitoring programs and management tools such as spatial closures. KEY WORDS: Lambis lambis · Habitat associations · Spatial ecology Resale or republication not permitted without written consent of the publisherMar Ecol Prog Ser 432: [83][84][85][86][87][88][89][90] 2011 been collecting L. lambis is not known, surveys indicate that collecting only became popular in the last 2 decades (Lincoln-Smith et al. 1993). The fishery is currently unregulated, but new fishing guidelines are being introduced. Whether these new guidelines will ensure the sustainability of the Cocos (Keeling) Islands L. lambis fishery remains uncertain.Lambis lambis shares similarities with Strombus gigas, which has been severely overfished throughout the tropical and subtropical waters of the Caribbean; diverse stock management regulations have been in place in Caribbean nations since the 1970s (Theile 2003). Factors that contribute to the sensitivity of L. lambis to over-fishing include probable late maturation, shallow water habitat, slow movement, and tendency to aggregate in shallow water for spawning. Previous studies have suggested that the distribution and abundance of S. gigas are dependent on the distribution of the habitats used by the species, as well as on the processes that are inherent to their life cycle such as recruitment, migration and mortality (Stoner & Waite 1990, Stoner 2003. Assessing the sustainability of fishing and management practises on L. lambis at the Cocos (Keeling) Islands requires an understanding of its distribution and density in relation to available habitats. The extent and location of these habitats in relation to the fishing community can also provide information on patterns of exploitation and assist in implementing management strategies such as temporal and spatial closures.In this study, we used several modelling approaches to explore the relationships of Lambis lambis density within the lagoon at the Cocos (Keeling) Islands with...

eDNA metabarcoding survey reveals fine‐scale coral reef community variation across a remote, tropical island ecosystem

“…Preferring algal‐dominated lagoon flats, the southeast area of the lagoon once supported a high density of L. lambis . However, recent surveys indicate a change in their distribution, which may be due to macroalgal habitat declines (Bellchambers, Meeuwig, Evans, & Legendre, 2011) and an overall reduction in stock abundance between 2008–2014 (Evans et al, 2016). Not many of the sites surveyed overlapped with those of Evans et al (2016); nonetheless we only detected L. lambis at one site (20), in the medium complexity lagoon area.…”

Examining the Movement of the Common Spider Conch Lambis lambis in Shallow Water of a Northeastern Indian Ocean Atoll Using Passive Acoustic Tracking

“…1C). The site contained a high abundance of L. lambis and a mix of preferred benthic habitats (see Bellchambers et al 2011) including macro-algae (e.g., Caulerpa spp. ), coral rubble, and isolated outcrops of scleractinian coral and sand.…”

“…Management and trade regulations have been introduced for some conch fisheries (Jagadis et al 2012, Annamary & Mohanraj 2014; however, there are many that would benefit from increased management attention (Allen & McKenna 2001, Mazo et al 2013, Wagey et al 2017. The data-poor nature of these fisheries and the paucity of knowledge surrounding the biology and ecology of the target species make determination of the most effective fishery management techniques problematic (Pilling et al 2009, Bellchambers et al 2011.…”

“…A recreational fishery for L. lambis occurs at the Australian Indian Ocean External Territory of the Cocos (Keeling) Islands (CKI) and is an example of a data-limited conch resource that has been shown to have concerns for sustainability (Hourston 2010, Evans et al 2016. At CKI, L. lambis are found in the shallow waters of the southern atoll lagoon where they are highly associated with areas of macro-algae and coral outcrops (Bellchambers et al 2011). Fishing occurs by hand while wading or snorkeling and is thought to have become popular in the 1970s (Lincoln-Smith et al 1993).…”

“…Fishing occurs by hand while wading or snorkeling and is thought to have become popular in the 1970s (Lincoln-Smith et al 1993). Anecdotal evidence suggests that the typical catch of L. lambis is between 200 and 1,000 individuals each fishing trip and that several thousand can be harvested for community events multiple times per year (Bellchambers et al 2011). Relative abundance assessments of L. lambis at CKI have shown a general declining trend since the first recorded assessment in 1992 (Lincoln-Smith et al 1993, Konzewitsch & Evans 2019.…”