striped bass, the Atlantic sturgeon, and the Atlantic tomcod. However, a project of the Petitcodiac Riverkeeper, funded by the Government of Canada's Environmental Damage Fund in 2005, noted that the removal of the causeway would result in a "good" chance of bringing back the eliminated species, and an "excellent" chance of increasing the numbers of species deemed to have been reduced in numbers. No data has been released for the Atlantic salmon or the striped bass. Various insects and arachnids reside around the Petitcodiac River. Among them is the stonefly, the mayfly, the caddisfly, the simulium, the subfamily of tanypodinae, and the Hydracarina. Non-native species, such as the black-footed spider, the beech scale, the white-marked tussock moth, and the mountain ash sawfly have also made their home in the Petitcodiac River watershed. At the southern extremities of the watershed, 50 to 90 percent of the world's semipalmated sandpipers feed on the mud shrimp at Shepody Bay. Around 269,445 stop there before migrating to South America, a number which accounts for at least 7.7 percent of the total population. Among others, the semipalmated plover (around 2 percent of the North American population), the short-billed dowitcher, the red knot, the sanderling, and the least sandpiper are also known for migrating through the Important Bird Area. A diverse number of plant species reside in the watershed as well. Red, white, and black spruce, red maple, white birch, and trembling aspen are the most common. Jack pine is commonly found in regions that fires have repeatedly ravished, while cedar is found in bogs and areas where gypsum and limestone are present. Higher altitude slopes and ridgetops house sugar maple, beech, and yellow birch trees. Zelazny et al. note that "[the] high frequency of disturbed sites dominated by aspen stands reveals the degree of historical and recent human disturbance along the Petitcodiac River." The Petitcodiac River's riparian zone houses a number of trees, including willows, white spruce, white pine, and speckled alder. Other trees, such as the tamarack and white pine, can also be found in the watershed. Plants such as the rufous bulrush tend to grow near calcareous areas, and hemlock can be found in small, pure stands. Alien plant species include the mother-of-thyme, the Japanese barberry, the Scotch broom, the yellow flag, and Canada bluegrass. In 1937, the 37,000-year-old skeleton of a mastodon was discovered by workers near Hillsborough. It was in near