Experimental analysis of growth and survivorship in a marine gastropod aggregation: balancing growth with safety in numbers

Abstract

The relatlve roles of habltat quallty and predation were examined to test the hypothes~s that surv~vorshlp In a manne gastropod, Strombus glgas, IS enhanced by livlng In a g g r e g a t~o n s when young Enclosure and tether experiments were conducted In and around a juven~le aggregatlon located In the m~d d l e of a tidal flow field in the Bahamas whlch occupied ca 21 ha Elght s t a t~o n s were selected to represent a gradient from bare sand to h~g h seagrass blomass and a transect through the aggregatlon (~n s i d e density = 0 40 to 0 56 )uveniles m-' outside denslty SO 08 )uveniles m-2) Seagrass characteristics proved to be poor pred~ctors of habltat sultab~lity in terms of S glgas growth and compared w~t h the presence of conspecifics relatively unimportant predictors In terms of shelter from predation Although growth was > 0 1 mm d.' at all but 2 stations, juveniles (60 to 80 mm shell length) suffered higher proport~onal mortal~ty when tethered outside the aggregatlon (48 to 100%) than inside (18 to 20%) Mortal~ty showed a strong negatlve correlat~on w~t h wild S glgas density, suggesting that small-scale distnbut~on is greatly influenced by denslty-dependent phenomena Presence of conspecifics proved to be a n important factor affect~ng survivorshlp In seagrass meadows of the Bahamas KEY WORDS. Strombus gigas. Habitat quality Predat~on . Seagrass . T e t h e r~n g . Bahamas

Growth and population assessment of the queen conch <i>Strombus gigas</i> (Mesogastropoda: Strombidae) by capture mark-recapture sampling in a natural protected area of the Mexican Caribbean

“…m -2 . In other areas of the Caribbean similar increases were observed (Randall 1964, Alcolado 1976, Brownell 1977, Ray & Stoner 1994. Growth rates measured during this study were comparable to other studies conducted under natural conditions using mark-recapture methods.…”

“…Alcolado (1976) showed that growth may vary according to environmental variability between sites; however, the study area of the Cueva is a relatively small area, making it more likely that all organisms have been exposed to the same conditions. Ray & Stoner (1994) suggested that juvenile conch are vulnerable to predation and may choose lower quality habitat in terms of resources, compromising maximum ingestion and growth, by aggregating or sheltering in dense vegetation, to reduce the risk of predation and increase survival probabilities. The high growth rate of juvenile conch in Xel-Ha and the large variations in individuals likely reflects the natural conditions of foraging and aggregation.…”

A groundwater-fed coastal inlet as habitat for the Caribbean queen conch Lobatus gigas—an acoustic telemetry and space use analysis

“…In general, the use of lower-quality marginal habitats in order to reduce exposure to predators has been documented for large marine herbivores (green and loggerhead turtles, Heithaus et al 2002;dugong, Wirsing et al 2007). Ray & Stoner (1994) noted that juvenile conches may also choose lower-quality habitat in terms of resources, compromising growth in favour of reduction of predation pressure. However, due to a lack of data on predator abundance inside and outside the inlet, more investigations are required to determine whether the absence of predators is a key factor explaining the use of the inlet by queen conches.…”

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

“…This unexplained variation might reflect autonomous biological characteristics of L. lambis such as their propensity to aggregate, unmeasured environmental variables that are important descriptors of L. lambis habitat, or patterns in the settlement of the recruits. Aggregation in strombids is well known, although the causes and advantages are not fully understood (Catterall & Poiner 1983, Stoner & Ray 1993, Ray & Stoner 1994. Aggregation of Strombus gigas is a common phenomenon in important nursery areas (Stoner & Ray 1993), while S. luhuanus frequently occurs in local aggregations with discrete boundaries (Catterall & Poiner 1983).…”