EXPERIMENTAL DESIGN AND METHODS:
Small nekton were collected at a variety of stations throughout the Plum Island Sound Estuary. Samples were collected using a 15.2 meter length beach seine and 4.8 mm (3/16 inch) mesh. Abundance numbers are shown as the total collection from two seine hauls done at each site. Seining Method The seines were 15.2 m length and either 1.2 or 1.8 m in height with a 4.8 mm (3/16 inch) square ace mesh. The middle of the seines were fitted with a bag (1.8 x 1.8 m) of the same mesh size as the wings of the net. A lead line insured that the bottom of the net remained in contact with the substrate. At each sampling station the actually sampling loci were carefully chosen after an inspection for rocks, cobbles, and any other potential impediments. Once a locus was selected, one person held one end of the net and stood at a fixed position at the edge of the water. A second person took the other end of the net and walked out in the water perpendicular to the shoreline at the point where the first person was standing. When the net was straight, it would be checked along its length to insure that it was deployed correctly. The person at the deep water end would then move toward shore describing an arc while the person at the water's edge remained fixed. Thus each seine tow covered a quarter of a circle with a radius of 15.2 m and an area of about 181 m2. When the far end of the net was almost at the shoreline, the two people holding the ends of the net would walk toward each other and then move slowly up the beach until the net was completely out of the water. Fish and selected macroinvertebrates (decapod crustaceans) were then placed in plastic bags and stored in a cooler for later identification and enumeration back at the laboratory. Duplicate seine hauls were taken at all stations, with care taken in the second haul to avoid areas that had been impacted by the previous haul. A seine team typically consisted of three or more people. In addition to the two people holding the ends of the seine, a third person checked along its length while it was being deployed to insure that it was sampling properly, i.e. lead line down, no tangles, etc. Additional people, often volunteers, helped with collecting the samples from the net after it was hauled ashore.
KSU_Site_num 3. Horseshoe. This station was located on the northeastern side of Plum Island Sound south of the entrance to the Plum Island River and east of the entrance to Mud River. The area was a wide stretch of beach on the shore of the PRNWR. The substrate was sandy with a gentle slope that was seinable at any point during mid-low tides.
KSU_Site_num 5. Rowley Sweet Spot. This station at the southern part of the mouth of the Rowley River was a series of two sandy beaches just south of the main channel. There was a very slight gradient until the channel where it dropped off sharply. This location was sampled at mid to low tide.
KSU_Site_num 6. Rowley Upper. This station was located on the northern side of the Rowley River approximately 200 meters west of the mouth directly next to a red channel marker and west of a brown house with a dock. The substrate was sandy at the mouth and became muddy farther into the creek . The gradient was fairly steep and seine locations were picked accordingly. It was only sampled at mid tides because there was not enough water in the creek at dead low tide.
KSU_Site_num 8. Roger Island. This station was located on the south side of the Rowley River on a sandbar in between Holy Island and Roger Island. The substrate was sandy on the sandbar but muddy on either creek bank. There was a slight gradient.
KSU_Site_num 9. West Creek Sweet Spot is the same as PIE LTER Station 30(West Creek). Located on sand flat opposite/East of West Creek mouth and Law's Point.
KSU_Site_num 10. West Creek East. This station was just inside the entrance to Shad Creek. The substrate was extremely muddy and the gradient was variable depending on seine location. It was seinable at mid to low tides but because the site had to be walked to, it was usually done on the rising tide.
KSU_Site_num 11. West Creek West. This station was located just inside West Creek on the northern bank where there is a muddy bank. The substrate was difficult to walk in and the slope was fairly steep. The slope was the deciding factor for seining locations. This site was seined at low to rising tides so that it could be accessed by boat.
KSU_Site_num 14. Third Sweet Spot. This station was located on a beach on the north side of the mouth of Third Creek. The substrate was sandy and the slope was steep on the Sound-ward side but gentle on the creek side. This location could be seined only at mid tides to ensure that there was enough water in the creek side.
KSU_Site_num 15. Third Creek 1. This station was located just inside Third Creek where the creek begins to widen. The substrate was a combination of sand and mud. This location was difficult to access and had to be done on the rising tide to get the boat in and ensure there was enough water at the location. Seining had to be completed quickly because the tide flooded everything fast in this location.
KSU_Site_num 16. Third Creek 2. This station was located well inside Third Creek on a flow that connects Eagle Hill to Roger Island. There were often clammers nearby but the seine locations were not disturbed. The substrate was extremely muddy and difficult to walk in. This location was only seinied on the rising tide to ensure there was enough water and to allow for time to walk out to it. Seining had to be completed quickly because the tide flooded everything fast in this location.
KSU_Site_num18. Middle Ground. This station was located on the southwest bank of Middle Ground. The substrate was sandy and the slope was fairly extreme so locations were chosen that allowed for a proper deployment. This location could be seined at mid to low tide.
KSU_Site_num 21. Grape Sweet Spot. This station was located firhg at the mough of Grape Island Creek (also called PIne Creek on some maps) on the other side of a few house boats and just north of Ipswich Bluff. The substrate was a sandy beach and the gradient was only slight.
KSU_Site_num19. Grape In North. This station was located inside Grape Island Creek (also called Pine Creek) on a bank that was a mixture that was mostly sand with some mud. In one location there was steep gradient and then it flattened out. This location was seinable at mid to low tides as there was always enough water.
KSU_Site_num 22. Grape In South. This station was located on the creek just north and east of Ipswich Bluffs (unnamed?). The location was mostly sand with some mud. There was only a slight gradient and thus on the rising tide the area flooded quickly.
KSU_Site_num27 (Pebble Beach) is the same as PIE LTER Station 1(Great Neck, Ipswich). This station was located on a flat, very gently sloping sandy beach just north of an area of small rocks interspersed with salt marsh vegetation that seperates the site from the northern end of Pavilion Beach.
Sampling was always carried out within two hours of low tide.
Identification, enumeration, and biomass of fish and decapods
After field collection, the fish samples were brought back to the Ecosystems Center's Rowley River Laboratory for identification. Fish and decapod crustaceans from each replicate were sorted by species and counted. Fish identifications were based on Bigelow and Schroeder (1953), Robins et al. 1986), Scott and Scott (1988) and an estuarine fish key developed by the Fish Ecology Laboratory of University of Massachusetts at Amherst (Basher 1989). As described above, we routinely collected decapod crustaceans, including Crangon septemspinosa, Palaeomonetes spp. and crabs. These were identified using Smith (1964) and Gosner (1971, 1978).
Abundance data represents the sum of individual species for the combined two seine hauls.
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