t~, William F. ~e r r n k i n d~, Michael J. childress3, Rodney ~e r t e l s e n~, William sharp2, Thomas ~a t t h e w s~, J e n n i f e r M. Field4, Harold G. ~a r s h a l l ' is experiencing an unprecedented series of ecological disturbances. In 1991, following reports of other ecosystem perturbations, we observed widespread and persistent blooms of cyanobacteria that coincided with the decimation of sponge communities over hundreds of square kilometers. Juvenile Caribbean spiny lobsters Panulirus argus, among other animals, rely on sponges for shelter; the impact of sponge loss on the abundance of lobsters and their use of shelter, in particular, has been dramatic. The loss of sponges on 27 experimental sites in hard bottom habitat in central Florida Bay resulted in the redistribution of juvenile lobsters among the remaining shelters, an influx of lobsters into sites where artificial shelters were present, and a decline in lobster abundances on sites without artificial shelters. Diver surveys of sponge damage at additional sites in central Florida Bay confirmed that the sponge die-off was widespread and its occurrence coincided with areas that had been exposed to the cyanobacteria bloom. This cascade of disturbances has dramatically altered the community structure of affected hard bottom areas and demonstrates the coupled dynamics of this shallow marine ecosystem.

Accurate age estimates for Panulirus argus, the commercially important Caribbean spiny lobster, would greatly enhance life history and population analyses. Most age approximations of P. argus are based on size and growth data, but size is generally considered a poor proxy for age of crustaceans in the field because of numerous environmental, density-dependent, and fishery-related factors. An established technique for aging crustaceans, employing histologically determined lipofuscin content in the nervous system, was investigated using known-age lobsters reared in the laboratory at ambient temperatures. We verified the presence of lipofuscin in eyestalk neural tissue by using autofluorescence and Sudan black staining and described its distribution in cell cluster A of the hemiellipsoid body. Neurolipofuscin accumulated with age; the overall trend was linear with indications of seasonal oscillation, whereas growth began to approach an asymptote after 3 years. Differences in the neurolipofuscin concentrations in the two eyestalks from the same animal were statistically insignificant. There was also no difference in the neurolipofuscin concentrations of males and females of the same age. The present data suggest a maximum potential lifespan for P. argus of about 20 years. These results also suggest that the neurolipofuscin technique will be valuable for estimating age of wild-caught specimens of P. argus.

No abstract

We used acoustic telemetry to study the movements of spiny lobster (Panulirus argus) during the spring and summer of 2003 and 2004 in Hawk Channel in the Western Sambo Ecological Reserve near Key West, Florida, United States. Overall, lobsters generally showed greatest movement after sunset and before sunrise with relatively less movement between midnight and 0200 h, however, there was great variability in movement patterns between individual lobsters and these variations were related to size or sex. Little or no movement occurred during daytime. Patterns of movement, as revealed by acoustic telemetry revealed that some lobsters repeatedly travelled to the same foraging area at the same time and then returned to the same patch reef (homing ability). Female lobsters that were reproductively active, exhibited movement patterns consistent with reproductive migrations to the forereef. These migrations lasted approximately 1 week and the lobster returned to the same patch reef presumably using the same homing ability used during daily activities. Although not statistically significant, the greatest overall daily total movement (total distance travelled) was found in small females. Small females also showed the greatest net daily movement (distance between denning locations) which suggests they had the highest rate of changing dens. The greater daily movement of small females did not convert to greater home ranges. There was no pattern in home range size with respect to the size and sex of lobsters.

Using diver surveys, we compared the size structure, fecundity, and reproductive season of spiny lobsters ( Panulirus argus ) in the Dry Tortugas National Park lobster sanctuary with those of spiny lobsters in the south Florida fishery. The number of lobsters of both sexes larger than the legal size limit declined sharply in the fishery but not in the sanctuary. Clutch sizes were larger in the Dry Tortugas sanctuary, averaging 0.8 million, than in the fishery, averaging 0.3 million. The reproductive season was shorter and more intense in the sanctuary than in the fishery. In addition, lobsters in the sanctuary begin producing eggs at a larger size and produce more eggs per gram of body mass than lobsters in the fishery. Peak egg production occurs earlier in larger lobsters than in small ones. Establishing a fundamental reason for the differences between lobster reproduction in the sanctuary and that in the fishery is not possible until the chronological age of lobsters can be determined, but one hypothesis consistent with these differences is that, if lobsters reproduce at a certain chronological age, then sublethal fishery practices may account for slower growth for some lobsters resulting in some smaller but older reproductively active lobsters.