MEPS 360:135-145 (2008)  -  DOI: https://doi.org/10.3354/meps07404

Population sinks in the Upper Florida Keys: the importance of demographic variation in population dynamics of the marine shrimp Stenopus hispidus

Brandon R. Chockley1,2,*, Colette M. St. Mary1, Craig W. Osenberg1

1Department of Zoology, 223 Bartram Hall, University of Florida, Gainesville, Florida 32611, USA
2Fish Passage Center, 1827 NE 44th Avenue, Portland, Oregon 97213, USA

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 ca. 4 times 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 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 both inshore and offshore and estimated reproductive output in the 2 regions. We found that shrimp in the inshore region exhibited higher levels of reproductive output than did shrimp in the offshore region. This suggests that the offshore region is acting as a population sink despite its higher local population size.


KEY WORDS: Demographic modeling · Marine reserves · Size-selective mortality · Source–sink theory · Stenopus hispidus


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Cite this article as: Chockley BR, St. Mary CM, Osenberg CW (2008) Population sinks in the Upper Florida Keys: the importance of demographic variation in population dynamics of the marine shrimp Stenopus hispidus. Mar Ecol Prog Ser 360:135-145. https://doi.org/10.3354/meps07404

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