Dataset: scallop_spat

The first trial was short-term, and conducted from May to June 2007. Two approximately 1 km2 bottom areas were closed to all dragging and diving activities. Bottom plots (15 m x 15 m; n = 8) within each area were seeded at a density of 2.5 individuals/m2 using legal and sub-legal size scallops dragged from an area in Englishman Bay, in Jonesport. One-half of the plots in each area received scallops that had been stored for ca. 7 hours in commercial fish totes (black, plastic units measuring 70 cm x 40 cm x 28 cm deep with holes in the bottom) on board two commercial draggers, while the other half of the plots received scallops that had been held in flow-through containers (modified Xactic box) for the same period of time. The fate of these scallops was followed for thirty days by SCUBA divers. Scallop recovery and survival in all plots in both areas was excellent and independent of handling treatment. In one of the two areas, mean number of scallops recovered on Day 30 from both handling treatments was not significantly different from the initial seeding density. Final recovery was lower at the other area where faster tidal currents occurred that tended to push scallops out of the marked bottom plots.

The second (2007-2008) and third (2008-2009) field trials involved collecting wild scallop spat (juveniles < 20 mm in shell height) using fine-mesh bags similar to those used successfully to collect small scallops of the same species in nearby Passamaquoddy Bay during the 1990's, and in the Northumberland Strait and surrounding areas of the Canadian Maritimes in the past decade. In addition, materials and methods of deploying spat bags were similar to those used successfully in Japan, Chile, and Northern Europe. The reason for attempting to collect wild spat was for the purposes of enhancing the bottom plots in both closed areas. A total of 1200 bags were deployed in late summer 2007 and 2008, and these were retrieved in the spring of 2008 and 2009, respectively. Each year, one half of the bags were placed on the eastern and western side of Great Wass Island, in the town of Beals. On each side of the island, one-half of the bags were deployed in shallow (< 20 m) and deep (> 30 m) water. Less than 40% of the gear was retrieved in both years. In May 2008, number of spat per bag averaged 2.8 ± 0.43 individuals (n = 460 bags). Recruitment was approximately 6.5x higher in May 2009 (18.6 ± 2.04 individuals per bag; n = 383 bags). In May 2008, scallop density per bag was significantly higher and scallop size was significantly greater on the western vs. eastern side of Great Wass Island. In May 2009, no significant difference in scallop density was observed between sides of the island, but scallop size remained higher on the western vs. eastern side. In both years, more scallops settled into bags deployed in deep vs. shallow water. These results are in stark comparison to the work of others in the Canadian Maritimes where > 3,000 spat have been collected in similar size bags.

On 8-9 September 2007, we deployed 240 lines -- 120 on the east and west side of Great Wass Island (Beals, Maine; Lat. 44o 28.83'N; Long. 67o 35.90'W). Each line was anchored to the bottom using a typical cement block filled with cement. Five spat bags (0.75 m long x 0.45 m wide with 3 mm aperture and stuffed with a single piece of Netron® ca. 0.70 m long x 0.5 m wide) were arrayed on each line approximately 1.5 m apart. The bottommost spat bag was placed 3 m from the anchor, and the remaining four bags were each space 1.5 m apart from each other. That is, the uppermost bag was approximately 9 m from the cement anchor. A buoy was placed 1 m above the uppermost bag to ensure that the line remained upright during the time when bags were in the water. A surface buoy marked each line. Bags were deployed in early September, because we have found that this is approximately one month after gonad indices fall significantly (Beal 2004), which signals reproduction. One half of the lines and bags on each side of Great Wass Island were deployed in both shallow (< 20 m) and deep (>30) locations. These locations were chosen by collaborating fishermen, and in the analysis, location is considered a "fixed factor," whereas "lines within each location" were considered a "random" factor. Specific locations of each line were recorded using GIS.