Date Awarded

1991

Document Type

Dissertation

Degree Name

Doctor of Philosophy (Ph.D.)

Department

Virginia Institute of Marine Science

Advisor

Romuald N. Lipcius

Abstract

Field tethering experiments in seagrass beds of Bahia de la Ascension, Mexico examined the impact of different-sized artificial shelters upon survival of three juvenile size-classes of the Caribbean spiny lobster, Panulirus argus. The artificial shelters were concrete structures (casitas) that simulate lobster dens. In the tethering experiments, spiny lobster survival was generally higher in smaller than larger casitas, though the effect depended upon the relationship between lobster and shelter size. Thus, spiny lobster survival depends not only upon the availability of shelter, but also on the scaling between shelter size and lobster size. These results suggest that placement of appropriately-scaled artificial shelters in nursery habitats where natural shelter is scarce is likely to augement habitat carrying capacity and therefore lobster production by increasing protection from predators. Field enclosure experiments examined the effects of spiny lobster size, social condition (i.e. presence or absence of conspecifics), shelter size, and predation risk (i.e. presence or absence of a major predator, the nurse shark Ginglyostoma cirratum) upon den choice by juvenile and adult P. argus. to corroborate the findings of the enclosure experiments, seasonal, size-specific abundance patterns of P. argus were quantified in the field by deploying artificial lobster shelters (casitas) of different sizes in two habitats that differed primarily in the potential for gregarious interactions. The experimental and observational field results were strikingly similar. Social condition and the scaling of lobster size to shelter size jointly regulated den choice patterns of adult and juvenile Panulirus argus in the field experiments and observations; lobsters also displayed marked size-specific behavioral flexibility in den choice according to social condition and predation risk. When conspecific densities and predation risk were low, lobsters resided primarily in smaller shelters; when conspecific densities were high and predation risk was low, lobsters resided predominantly in large shelters offering the highest potential for gregariousness; and, when predation risk was high, irrespective of conspecific densities, lobsters shifted to gregarious habitation in smaller, safer shelters. Hence, this study provides an empirical and conceptual framework for identifying how variations in the availability of resources, such as conspecifics and appropriately scaled refuges, influence the distribution and abundance of social, shelter-dwelling species.

DOI

https://dx.doi.org/doi:10.25773/v5-neek-pq28

Rights

© The Author

Download

Share Feedback

Share

COinS