Shallow Water Ecology of the Rhode River
|A map of the Rhode River showing the two survey sites.
The Nearshore Survey is a long term research study (1991-present) examining the interactions between native grass shrimps (Palaemonetes pugio, P. intermedius, and P. vulgaris) and their common predators in the Rhode River, a middle Chesapeake Bay subestuary. Research is carried out at two different sites every summer from June through August, using three methods: seining, dip-net sweeps and tethering. The two research sites on the Rhode River are Canning House Bay and Fox Point. Canning House Bay is a half-moon shaped embayment characterized by sandy beaches intermingled with coarse woody debris, marsh plants, and ever-encroaching invasive Phragmites populations. Fox Point is a sheltered spit of land at the mouth of Muddy Creek characterized by forested shore line intermingled with marsh plants and coarse woody debris.
Seine Survey - Our monthly seine net survey characterizes the presence and abundance of fish and crab predators in the nearshore zone (shallow waters where shrimp seek refuge from these predators). All predator species (fish, turtles and crabs) are identified to species, measured for total body length and counted and returned to the water. Crabs are also characterized by gender, molt stage and autonomy.
|A tethered Palaemonetes pugio grass shrimp. Photo courtesy of Carl Clark.
Shrimp Tethering - Tethering the grass shrimp Palaemonetes pugio is done three days a month during the summer. Tethering involves placing shrimp tied to lines in 1 foot (30 cm) of water for several timed intervals and measuring relative predation to determine how effective this zone is as a refuge habitat. It allows us to examine the predator-prey interactions between the shrimp and its fish and crab predators. We use this information to assess the effectiveness of the nearshore zone as refuge habitat and to indirectly measure the abundance of predators. Shrimp mortality as well as predator capture rate, identification and size are recorded.
Dip-net Sweeps - Grass shrimp distribution and relative abundance is monitored at permanent transects at Canning House Bay and Fox Point each month using dip net sweeps. Ten meter long transects are sampled at four depths by pushing a long handled dip net along the river bottom. Shrimp are collected, identified, measured, examined for parasites and reproductive state, and returned to the river. These data allow us to quantify the fluctuations in grass shrimp parasite load and population dynamics.
For more information contact Stacy Havard at (443) 482-2486, Havards@si.edu.
| Seine Survey
|| Shrimp Tethering
|| Dip-net Sweeps
Clark, Kelton L., Ruiz, Gregory M. and Hines, Anson H. 2003. Diel variation in predator abundance, predation risk and prey distribution in shallow-water estuarine habitats. Journal of Experimental Marine Biology and Ecology, 287: 37-55.
Dittel, Ana I., Hines, Anson H., Ruiz, Gregory M. and Ruffin, K. Keith. 1995. Effects of shallow water refuge on behavior and density-dependent mortality of juvenile blue crabs in Chesapeake Bay. Bulletin of Marine Science, 57(3): 902-916
Hines, Anson H. and Ruiz, Gregory M. 1995. Temporal variation in juvenile blue crab mortality: Nearshore shallows and cannibalism in Chesapeake Bay. Bulletin of Marine Science, 57(3): 884-901.
Everett, Richard A. and Ruiz, Gregory M. 1993. Coarse woody debris as a refuge from predation in aquatic communities: an experimental test. Oecologia, 93: 475-486.
Ruiz, Gregory M., Hines, Anson H. and Posey, Martin H. 1993.Shallow water as a refuge habitat for fish and crustaceans in non-vegetated estuaries: an example from Chesapeake Bay. Marine Ecology Progress Series, 99: 1-16.
Updated July 2013