Harbour Porpoise Research Paper

Introduction
The Harbour porpoise (Phocoena phocoena) and the short beaked Common dolphin (Delphinus delphis) are two of the most common and most seen cetaceans around the coasts of the UK. The Harbour porpoise is a smallest cetacean, residing in shallow and cold waters in Northern Europe, whereas the Common dolphin prefers offshore locations and warm temperate waters (Evans, 2003). However there is a decline in both species due to various causes, with many strandings on UK beaches being surveyed each year. Identifying these causes of these strandings and moreover the main threats to these species in UK waters is therefore important for preventing further increase in mortality rates of these species which is unsustainable. Examining post-mortems

This is due to other causes needing to be ruled out in addition to sufficient evidence to diagnose bycatch. To establish the cause as bycatch, the individual needs to be in good health condition, with recent ingested food in stomach to exclude other causes of death such as disease or starvation. One of the most obvious observation of bycatch is noticeable entanglement with fishing gear, most commonly being skin lesions, particularly seen on the mouth, fin and tail with cuts being present. Also lesions can be found encircling the individual. In addition bruises are found representing a struggle for escape from the fishnets as well as if the individual is released from the net, there is often damage caused such as amputated fins, tail or flukes or incisions made into the body cavity. Furthermore hypoxia can occur when the individual has a lack of oxygen, being caused by entanglement and being trapped in fishing gear. Usually there will be a build-up of water in the lungs becoming swollen, or sometimes asphyxia with water not being present as well as froth in the airways that is persistent. (Kirkwood et al.

This includes increased concentrations of heavy metals such as Mercury (Hg) and Lead (Pb) found in the liver tissue and/or chemical toxins such as man-made Polychlorinated biphenyls (PCBs) and dichlorodiphenyltrichloroethane (e.g. DDTs) and these are found in the blubber tissue of cetaceans.(Pierce et al. 2008; Jepson et al. 1999): To investigate the high proportion of Harbour porpoises dying from infectious disease, chemical sampling was undertaken in the liver/blubber tissue of the strandings to research the effects of PCBs earlier mentioned as well as heavy metals like Mercury (Hb). The amounts of these chemicals were examined in those individuals killed by infectious disease and those that were healthy and died from physical trauma. They will then be compared to find if those who died from infectious disease had increased concentrations of heavy metals or PCBs (Bennett et al. 2001; Jepson et al.