food items. As a result, the animals are more susceptible to diseases and have fewer offspring. Harbour porpoises from the English Channel were found to have accumulated heavy metals. The military and geologists employ strong sonar and produce an increases in noise in the oceans. Marine mammals that make use of biosonar for orientation and communication are not only hindered by the extra noise, but may race to the surface in panic. This may lead to a bubbling out of blood gases, and the animal then dies because the blood vessels become blocked, so-called decompression sickness. This effect, of course, only occurs in porpoises that dive to great depths, such as Dall's porpoise. Additionally, civilian vessels produce sonar waves to measure the depth of the body of water in which they are. Similar to the navy, some boats produce waves that attract porpoises, while others may repel them. The problem with the waves that attract is that the animal may be injured or even killed by being hit by the vessel or its propeller. Conservation The harbour porpoise, spectacled porpoise, Burmeister's porpoise, and Dall's porpoise are all listed on Appendix II of the Convention on the Conservation of Migratory Species of Wild Animals (CMS). In addition, the Harbour porpoise is covered by the Agreement on the Conservation of Small Cetaceans of the Baltic, North East Atlantic, Irish and North Seas (ASCOBANS), the Agreement on the Conservation of Cetaceans in the Black Sea, Mediterranean Sea and Contiguous Atlantic Area (ACCOBAMS) and the Memorandum of Understanding Concerning the Conservation of the Manatee and Small Cetaceans of Western Africa and Macaronesia. Their conservation statuses are either at least concern or data deficient. As of 2014, only 505 Yangtze finless porpoises remained in the main section of the Yangtze, with an alarming population density in Ezhou and Zhenjiang. While many threatened species decline rate slows after their classification, population decline rates of the porpoise are actually accelerating. While population decline tracked from 1994 to 2008 has been pegged at a rate of 6.06% annually, from 2006 to 2012, the porpoise population decreased by more than half. Finless porpoise population decrease of 69.8% in just a 22-year span from 1976 to 2000. 5.3%. A majority of factors of this population decline are being driven by the massive growth in Chinese industry since 1990 which caused increased shipping and pollution and ultimately environmental degradation. Some of