Aggregation dynamics in juvenile queen conch (Strombus gigas): population structure, mortality, growth, and migration

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

Section: Methodsmentioning

confidence: 99%

Section: Study Areamentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

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

Ray¹,

Stoner²

1994

“…It occurs in mammals and fish of many kinds (Pitcher 1992), and in a diversity of invertebrate groups including: squid, krill, molluscs, (Catterall & Poiner 1983, Stoner & Ray 1993, decapod crustaceans (Atema & Cobb 1980, among others), and others (Ritz 1994). Social aggregations develop because of mutual attraction among conspecifics and the evolution of cooperative group behavior that enhances individual defense, foraging, movement, or reproduction (Wilson 1975).…”

Section: Introductionmentioning

confidence: 99%

The cause and consequence of ontogenetic changes in social aggregation in New Zealand spiny lobsters

Butler¹,

MacDiarmid²,

Booth³

1999

Ontogenetic changes in the behavior, spatial distribution, or habitat use of a species are presumably adaptations to ecological forces that dlffer in their effect on various life stages. The New Zealand rock lobster Jasus edwardsii is one of several species of spiny lobster that exhibits dramatic ontogenetic shifts in sociality and spatia.1 distribution, and we tested whether such changes are adaptive. We first surveyed several natural populations of J. edwardsii to document size-speclfic differences in aggregation. To determine i f chemical cues discharged by conspecifics promote aggregation of certain ontogenetic stages, we tested the responsiveness of lobsters of 3 ontogenetic stages (early benth~c juvenile, juvenile, and subadult) to the chemical cues produced by conspecifics of different sizes. Finally, we tethered lobsters of different ontogenetic stages alone and in groups to test the effect of lobster size and aggregation on mortality. Our results offer compelling evidence that pre-reproductive J. edwardsii undergo an ontogenetic change in sociality that alters their spatial distribution and sunrival. Our field surveys show that J. edwardsii are solitary as early benthic juveniles and become social and aggregate as they grow larger. We then demonstrate, using laboratory experiments, that there is a sizespecific increase in the response of pre-reproductive J. edwardsii to the chemical cues of larger conspecifics which facilitates these ontogenet~c changes in aggregation. Finally, our tethering results confirm that this change in social condition is selectively advantageous: aggregation does not increase the survival of small lobsters, but larger lobsters survive better in groups. Thus, in this study we demonstrate the linkage between ontogenetic changes in the spatial distribution of a species, the behavioral process that creates the pattern, and the selective advantage conferred by these developmental changes.

“…SR stations tvere selected to represent the long dimension of the largest nursery (northeastsouthwest; Stns SR-I to SR-7), and to include stations distinctly outside the primary tidal flow field and juvenile population (Stns SR-8 and SR-9). Stns SR-1 and SR-7 were just outside the boundaries of the large aggregation as established for the period from 1988 to 1992 (Stoner & Ray 1993. During the same period, in the tidal flow field south of CBC.…”

Section: Methodsmentioning

confidence: 66%

Shell remains provide clues to historical distribution and abundance patterns in a large seagrass-associated gastropod (Strombus gigas)

Stoner¹,

M²

1996

Posltive correlation between the number of shells or skeletal elements of a species preserved in the sedimentary record and the abundance and distnbution of the once-living population can be an important assumption in paleoecological analysis. The assumption was tested for the large gastropod Strombus gigas (queen conch) in and around 2 nursery grounds in the central Bahamas. Concentrations of shell fragments on the surface of the sediment measured in 1990 were closely correlated (r = 0.998 and 0.928) with mean live conch abundance monitored regularly at 13 stations during the 2 previous years Projections from field experiments on shell decomposition rates indicated that the shell remains of S. gigas last for at least a decade on the sediment surface. The direct relationship between shell remains and living populations integrated over time permits interpretation of historic changes in populations. Furthermore, time-averaging qualities of the death assemblages provide an integration of distribution and abundance patterns on an ecological time scale useful in learning the relationships between the environment, the species and ~t s management.