Using age to evaluate reproduction in Caribbean spiny lobster, Panulirus argus, in the Florida Keys and Dry Tortugas, United States

Abstract

For many species of lobsters, size at sexual maturity varies across spatially separated populations. This is so for two populations of Caribbean spiny lobster, Panulirus argus, in southern Florida, where females from open‐fishing areas around the Dry Tortugas mature at a larger size than females from open‐fishing areas in the Florida Keys. Variations in onset of maturity between populations of lobsters have been attributed to different environmental conditions, lobster density, and/or fishing pressure. We used age as estimated by histologically expressed neurolipofuscin to examine differences in size at maturity in P. argus. Neurolipofuscin content measured in known‐age, laboratory‐reared animals in a previous study was used to estimate age in wild‐caught P. argus. We show that lobsters from the Florida Keys are significantly smaller than lobsters of the same age from the Dry Tortugas. This difference in growth rates between lobsters from the two locations likely explains the differences in size at onset of maturation. High rates of injury from fishery practices in the Florida Keys and differential predation on slow‐growing lobsters in the Dry Tortugas may account for these differences in growth rates. Additionally, we compared the ages of reproductive females collected from breeding grounds of the Florida Keys to same‐sized non‐reproductive females from an area in the Florida Keys where there was no evidence of breeding. We found that females possessing eggs early in the breeding season were significantly older than females that bore eggs later in the breeding season or that did not produce eggs. Older females also produced more clutches of eggs. Our research indicates that reproduction is related to age in P. argus. The intense fishery and the methods used to fish lobsters are the most likely causes of the reduction in spiny lobster population size structure and size at maturity.