MEPS prepress abstract  -  doi: 10.3354/meps07404

ABSTRACT: The identification of sources and sinks in open populations is difficult and constrains our ability to predict population dynamics. This paper details factors that affect population size-structure of Stenopus hispidus Olivier 1811, a popular marine ornamental, in the Upper Florida Keys, and utilizes this information to identify large-scale (inshore–offshore) patterns of source–sink population structure. Shrimp were approximately four-fold more abundant at offshore sites compared to inshore sites. Larger, reproductive shrimp dominated the inshore reefs in the Upper Florida Keys, while smaller, typically immature, shrimp dominated offshore reefs. Only 2.3% of settlement to artificial reefs occurred in the inshore region, while 97.7% occurred in offshore sites. Size-selective mortality was present but similar between the inshore and offshore reefs. Finally, growth declined with pre-molt size and was higher in the inshore reefs than offshore reefs. These results indicated that the offshore reefs were likely dominated by smaller shrimp (at high density) due to higher settlement, lower growth rates, and longer periods of susceptibility to size-selective mortality. To better understand the source-sink implications of our results, we developed a demographic model parameterized from our field estimates of size-specific molt frequency and mortality, and region-specific (inshore or offshore) settlement and growth rates. We simulated settlement, mortality, and growth in both the inshore and offshore regions and estimated reproductive output in the two regions. We found that shrimp in the inshore region exhibited higher levels of reproductive output then did shrimp in the offshore region. This suggests that the offshore region is acting as a population sink despite its higher local population size.