Date of Award

Summer 2014

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Biological Sciences

Program/Concentration

Biology

Committee Director

Mark J. Butler, IV

Committee Director

Eric Walters

Committee Member

John R. McConaugha

Call Number for Print

Special Collections LD4331.B46 G88 2014

Abstract

Casitas are artificial structures placed on the seabed by fishermen to aggregate Caribbean spiny lobsters (Panulirus argus) for ease of capture. Some researchers suggest that they may also enhance lobster populations in shelter-limited environments. Conversely, aggregation of lobsters within casitas may be detrimental to the population if the nutritional condition or mortality of lobsters is poorer in casitas than in natural shelters. Small juvenile lobsters may be at particular risk because their foraging range is smaller and they are more readily preyed upon than larger lobsters. If so, then casitas placed in lobster nurseries may function as "ecological traps"; wherein under unusual circumstances, a normally beneficial instinct leads to a maladaptive outcome. I tested this hypothesis by comparing the nutritional condition and mortality of lobsters found in casitas or natural shelters in two ecologically distinct regions of the Florida Keys. Using a hepatopancreas-based nutritional condition index, I found that the nutritional condition of lobsters in casitas was similar to or better than those found in natural shelters. This was true across a range of lobster sizes and in both deeper adult habitats and shallow nursery habitats. However, small lobsters in casitas in nursery habitats were significantly less likely to survive in 24 h tethering experiments than lobsters in natural shelters; large lobsters experienced similar mortality in casitas and natural shelters. I also used accelerometry to quantify differences in activity patterns between large and small lobsters in casitas and natural shelters, and demonstrated the viability of accelerometers as a means of assessing activity on lobsters in the wild. My results indicate that casitas deployed in nursery habitats act as an ecological trap for small juvenile lobsters, but do not negatively impact large lobsters in either nursery habitats or deeper adult habitats.

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DOI

10.25777/hkry-j386

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