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Feeding and substrate preferences of the Japanese shore crab, hemigrapsus sanguineus / Scott R....

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Feeding and substrate preferences of the Japanese shore crab, hemigrapsus sanguineus / Scott R. Percival

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Identifier	Thesis 1662
Author	Percival, Scott R
Title	Feeding and substrate preferences of the Japanese shore crab, hemigrapsus sanguineus / Scott R. Percival
Publisher	Central Connecticut State University
Resource Type	Master's Thesis
Abstract	Hemigrapsus sanguineus, the Japanese shore crab, is native to the western Pacific Ocean and was first reported in Long Island Sound in 1992. Since then, it has become firmly established and, in many locations, is the most common crab in the rocky intertidal zone. H. sanguineus commonly feeds on a variety of prey including the northern rock barnacle (Semibalanus balanoides) and is found in large numbers in cobble size substrate. This study tested the hypothesis that substrate preference and the ability to consume a wide range of barnacle sizes by Hemigrapsus sanguineus may lead to competition with the native mud crab (Eurypanopeus depressus) and the established introduced green crab (Carcinus maenas). Based on field observations, experiments were designed to determine substrate preference and aspects of the diet of the crab. Crabs were collected from Connecticut rocky shores, sexed, and measured across the widest portion of the carapace. Three size grouping were created based on carapace width (6-12 mm, 13-19 mm, and 20-26 mm) in the lab. Experiments were conducted to determine the influence or crab sex or size on 1) preference of cobble-size substrate and 2) preference for specific size ranges of the northern rock barnacle, Semibalanus balanoides, for food. Individual crabs from each size class were simultaneously offered three different substrate sizes based (diameter sizes of <1 cm, 2 cm, and 5 cm). In the feeding experiments, crabs were allowed to feed individually on a range of sizes of barnacles for 24 hours. In the barnacle feeding experiment all sizes of barnacle were consumed by the three crab size classes. Analysis of variance showed statistically significant differences among crab size classes in the mean size barnacle eaten but no difference between the sexes. A post-hoc Scheffe' analysis of the average size eaten / average size offered ratio identified statistically significant differences in barnacle size eaten between crab size class 1 and 3 and 2 and 3. Smaller crabs were eating barnacles smaller than the average size offered whereas larger crabs were eating barnacles larger than the average size offered. The largest size substrate was chosen by 63% of the crabs and chosen the most often by crabs in each size class. Males and females showed similar substrate selection with 63% of the males and 62% of the females choosing the largest substrate. The presence or absence of light does not appear to affect the substrate choice. Analysis of the results (chi-square) revealed a statistical significance relationship between substrate class and crab size class in 5 of 6 trials. The largest substrate (5 cm) was chosen most often across the three crab classes during experiments with and without light. The substrate experiments clearly show a preference by H. sanguineus for largersized particles. These results are consistent with several reports of crabs observed in the field that H. sanguineus shows a preference for the cobble size substrate. H. sanguineus demonstrated a feeding preference with regards to the mean barnacle size offered. In all three classes there were several occasions where all barnacles, of various sizes, were consumed. This ability to clear entire rocks of barnacles, regardless of size, in such a short period of time, may mean that H. sanguineus could influence barnacle recruitment and population size. Based on substrate preference and the ability to consume a wide range of barnacle sizes by Hemigrapsus sanguineus, I predict that H. sanguineus will successfully compete with and potentially alter the current distribution of crab species in the rocky intertidal zone in southern New England.
Subject	Crabs -- Long Island Sound (N.Y. and Conn.) Introduced animals -- Long Island Sound (N.Y. and Conn.)
Department	Department of Biological Sciences
Advisor	Wilson, Kim A.
Type	Text
Digital Format	application/pdf
Language	eng
Date of Publication	2002
OCLC number	50658143
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Feeding and substrate preferences of the Japanese shore crab, hemigrapsus sanguineus / Scott R. Percival

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