Mark L. Tasker

INFLUENCES OF HUMAN ACTIVITIES ON SEABIRD POPULATIONS IN THE NORTH SEA

This paper describes the North Seas seabird resource, which is of great international importance. It reviews the significance of human activities on seabirds; these are persecution, fishing, eutrophication, chemical pollution, introduction of alien predators, rising sea level, and oil pollution. The paper speculates on future trends. Some suggestions to reduce human pressures, to use seabirds as monitors of the marine environment and to conserve their populations more effectively are made.

What Caused the UK's Largest Common Dolphin (Delphinus delphis) Mass Stranding Event?

On 9 June 2008, the UKs largest mass stranding event (MSE) of short-beaked common dolphins (Delphinus delphis) occurred in Falmouth Bay, Cornwall. At least 26 dolphins died, and a similar number was refloated/herded back to sea. On necropsy, all dolphins were in good nutritive status with empty stomachs and no evidence of known infectious disease or acute physical injury. Auditory tissues were grossly normal (26/26) but had microscopic haemorrhages (5/5) and mild otitis media (1/5) in the freshest cases. Five lactating adult dolphins, one immature male, and one immature female tested were free of harmful algal toxins and had low chemical pollutant levels. Pathological evidence of mud/seawater inhalation (11/26), local tide cycle, and the relative lack of renal myoglobinuria (26/26) suggested MSE onset on a rising tide between 06∶30 and 08∶21 hrs (9 June). Potential causes excluded or considered highly unlikely included infectious disease, gas/fat embolism, boat strike, by-catch, predator attack, foraging unusually close to shore, chemical or algal toxin exposure, abnormal weather/climatic conditions, and high-intensity acoustic inputs from seismic airgun arrays or natural sources (e.g., earthquakes). International naval exercises did occur in close proximity to the MSE with the most intense part of the exercises (including mid-frequency sonars) occurring four days before the MSE and resuming with helicopter exercises on the morning of the MSE. The MSE may therefore have been a “two-stage process” where a group of normally pelagic dolphins entered Falmouth Bay and, after 3–4 days in/around the Bay, a second acoustic/disturbance event occurred causing them to strand en masse. This spatial and temporal association with the MSE, previous associations between naval activities and cetacean MSEs, and an absence of other identifiable factors known to cause cetacean MSEs, indicates naval activity to be the most probable cause of the Falmouth Bay MSE.

The distribution of auks and Procellariiformes in north-west European waters in relation to depth of sea

The distribution of 5 species of auks and 3 species of Procellariiformes in northwest European waters was analysed in relation to 5 depth zones. Auks and Manx Shearwaters were restricted mainly to the continental shelf. Fulmars and British Storm Petrels were found mostly in waters of greater than 100 m depth. Interspecific variation in distribution may be related to dietary differences. The presence of fishing vessels was considered to be of secondary importance for Fulmars.

The distribution of Manx Shearwaters Puffinus puffinus in north-west European waters

Seabirds in north-west European waters were surveyed offshore throughout the year from 1979 to 1993. During the breeding season the distribution of Manx Shearwaters centred around the main colonies of Rhum, Skomer and Skokholm. Densities were low in the North Sea, where birds were mainly restricted to waters off the north-east coasts of England and Scotland, in particular the Moray Firth, the Firth of Forth and Flamborough Head. Manx Shearwaters can forage at long distances from the colonies, but highest densities were observed in the Irish Sea, south-west Wales, south-west Ireland and the inshore waters of West Scotland during the chick-rearing period when parent birds visit the colony more frequently. The area of the Irish Sea front was important, particularly in the autumn, and feeding occurred here in preference to other areas of the Irish Sea. From November to February Manx Shearwaters were virtually absent from north-west European waters.

How Might We Assess and Manage the Effects of Underwater Noise on Populations of Marine Animals

The European Union Marine Strategy Framework Directive (MSFD) aims to achieve good environmental status (GES) in European seas by 2020. One of the features of GES is that underwater sound should not adversely affect the marine environment. Direct injury of marine life may occur, but a more pervasive effect is likely to be through the cumulative indirect effects on behavior. Assessing the significance of these effects on an ecosystem scale is difficult. If subsequent management of these effects is required, complex and challenging international decisions will be required.

Regulation of Sound in the Ocean: Recent and Future Possible Changes

The regulation of sound in the ocean has proved difficult to achieve globally. Broadly, attempts have been made to ensure that sound does not harm marine life, but this has proved difficult to achieve primarily because there is very limited knowledge of which sounds or which features of sound can cause adverse effects. In some jurisdictions, the focus has been to avoid effects on animals that are particularly protected (e.g., cetaceans or some fish). Although this may be useful in regulating some sounds, there are limits to regulatory effectiveness because not all biota are considered and, additionally, key aspects of the biology of some protected biota (e.g., special and temporal distribution in the oceans) are not well known. In addition, regulation tends to be based around peak sound pressures or, more recently, around a total sound level over a period of time (sound exposure level), whereas adverse effects may derive from some other aspect of noise such as rise time or cumulative behavioral effects over a long period of time.

Managing Underwater Noise in European Waters: Implementing the Marine Strategy Framework Directive

The European Union’s (EU) Marine Strategy Framework Directive (2008/56/EC) aims to improve the condition of all Europe’s seas and ensure that human usage of these seas is sustainable. The directive will work by requiring EU member states to set a series of objectives for 11 Descriptors of Environmental Status. One of these descriptors, Introduction of Energy, Including Underwater Noise, Is at Levels That Do Not Adversely Affect the Marine Environment, concerns underwater noise. A task group consisting of the authors was established to recommend to the European Commission indicators that might be used by member states to define good environmental status (GES) under this descriptor. The task group focused on sounds that affect relatively broad areas of the marine environment and developed three possible indicators of underwater sound.

Oil and Gas Development in the North Sea

The rise in offshore oil developments led to considerable concerns about the potential environmental impacts of the developments, but little was known of some aspects of the offshore environment. As a consequence, several research projects were established to address these limitations. This paper details the above process and draws some wider lessons for managing potential environmental consequences of oil and gas development in the marine environment.