A comparative evaluation of Halodule wrightii aschers, Spartina alterniflora loisel and bare sand as nursery habitats for juvenile Callinectes sapidus (Rathbun).




Thomas, J.L.

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Texas A&M University.


Habitat utilization by economically important species in estuaries has been previously examined through life history studies and faunal surveys. Recently, studies characterizing the food resource and protective functions of estuarine habitats indicate that they serve as valuable nurseries for estuarine dependent species. In this study, laboratory predation experiments were conducted that analyzed differences in food and protective functions provided to juvenile crabs by Spartine alterniflora, Halodule wrightii and bare sand habitats in Christmas Bay, Texas. Results from feeding experiments showed that small crabs fed upon Halodule epiphytes. Animal foods primarily fed on were amphipods and molluscs. Polychaetous annelids and tanaids were also eaten, but only to a minor extent. During predation experiments, the sand habitat provided the least amount of protection to juvenile blue crabs during both pinfish and subadult blue crab predation. The salt marsh habitat provided an intermediate degree of protection to juvenile blue crabs during predation by both predators. The seagrass habitat provided the greatest degree of protection to juvenile crabs. This protection varied with grass density and time of day. Mortalities sustained during pinfish predation were higher during the day than at night in the salt marsh and sand habitats and were similar and low in the seagrass habitats . During subadult blue crab predation, mortalities were higher at night in the seagrass and sand habitats and higher during the day in salt marsh habitats. These results indicate that while juvenile blue crabs are able to feed on numerous foods occurring in each habitat type, their distributions among these habitats may be regulated by the types of predators present and the time of day.


119 p., Thesis


habitat, estuaries, juveniles, Spartina alterniflora, Halodule wrightii, feeding behavior, Callinectes sapidus