Vertical migration behavior and larval transport in brachyuran crabs

Abstract

documented the patterns of vertical distribution and abundance of zoeae from 3 families of brachyuran crabs in the York River, a sub-estuary in southern Chesapeake Bay (USA). The family groups included species from Ocypodidae. Pinnotheridae, and Panopeidae. I assessed the effects of light and tidal current stage on the abundance and vertical distribution of zoeae using analysis of variance (ANOVA) and logistic regression Clear behavioral patterns were evident in the logistic regression. Ocypodid larvae exhibited t~dally timed behavior with larvae nearest the surface during ebb tides. Pinnotherid larval behaviors were correlated with both light and tidal current phase. Larvae were nearest the surface at night and during ebb tides. Panopeid larvae were near the bottom durlng early flood tldes, near mid-depths during late flood and early ebb tides, and nearest the surface during late ebb tides. These behavioral patterns should result in horizontal distributions that are consistent with those observed in previous studies. The ANOVA reflected similar results; however, high variablllty between replicates weakened the significance of these patterns. The different analyses reflect processes on different spatial and temporal scales. The samples were replicated on short time scales (5 to 10 min). The logistic regression, a categorical analysis, largely ignores the variation between replicates and reflects average behaviors on the scale of several tidal cycles. In contrast, the ANOVA is highly sensitive to the variation between replicates and reflects patterns on scales of minutes. This high variation reflects turbulent vertical mixing and fine-scale horizontal patchiness In larval distribution. Small-scale physical processes that redistribute larvae both vertically and horizontally may have a strong influence on the variability in dispersal and recruitment success.