Mitigation is the act of reducing the severity, or seriousness of an event. For marine mammals the event could be, for example: sound exposure (e.g. military sonar, underwater blasting, seismic exploration), entanglement (fishing) or collision (vessels). Different levels of risk mitigation are used depending on the type, location and duration of the activity, as well as the species present in the region. When it comes to marine mammals, the consequences can be disturbance, discomfort or in extreme cases, even injury.
Marine mammal risk mitigation has become a critical part of maritime operations across most of the world’s oceans. For mitigation against risks due to noise exposure, various governing bodies have written guidelines that form a condition of consent to carry out offshore noise producing operations. Such governing bodies include, but are not limited to: Joint Nature Conservation Committee (JNCC) for the UK, Bureau of Ocean Energy Management (BOEM) for the Gulf of Mexico, and the National Parks and Wildlife Service (NPWS) for Ireland. These guidelines form the basis of a Marine Mammal Mitigation Plan (MMMP) which sets out what marine mammal risk mitigation will be used for a specific operation. For more details on what is included in a MMMP see www.marinemammalmitigationplan.co.uk.
A research project carried out in 1998 looked at the mitigation of harbour porpoise (Phocoena phocoena) by-catch in the gillnet fishery in the lower Bay of Fundy. This study shows an 85% reduction in harbour porpoise by-catch after simple marine mammal risk mitigation (such as the use of pingers on nets) had been implemented.
Components of marine mammal risk mitigation
A very simple and effective form of marine mammal risk mitigation is the use of dedicated Marine Mammal Observers (MMOs; www.marinemammalobserver.co.uk), working in shifts to cover all hours of daylight, from sun-rise to sun-set, armed only with binoculars, keen-eyes and a passion for their work. Marine Mammal Observers are, quite often, at the heart of marine mammal risk mitigation. Marine Mammal Observers reduce the risks to marine mammals by making sure no marine mammals are in the immediate vicinity of the risky event.
In areas of high marine mammal sensitivity or Special Areas of Conservation (SAC), up to two or three Marine Mammal Observers may be required as well as Passive Acoustic Monitoring (PAM; www.passiveacousticmonitoring.com). Marine Mammal Observers are very effective, but cannot provide dependable risk mitigation during times of reduced visibility, such as at night, in poor weather conditions or in heavy fog. This is where Passive Acoustic Monitoring comes into force. Passive Acoustic Monitoring works in a similar way to Marine Mammal Observers, but instead of looking visually for marine mammals operators listen for marine mammal vocalisations.
Marine mammal risk mitigation will vary depending on the activity that is being conducted. To minimise the risk of marine mammal and vessel collisions, speed limits are often enforced in areas where marine mammals are particularly susceptible to vessel collisions. Passive Acoustic Monitoring has also been used to localise marine mammals in order to inform vessel captains of when and where they need to reduce their speed. To reduce the risk of marine mammal by-catch, fishing nets can be modified to allow marine mammals to see the nets better, either acoustically or visually, or to escape.
Ocean Science Consulting Ltd. (OSC) has been providing marine mammal risk mitigation services since their formation in 2004, thus making them one of the most experienced companies in their field. Ocean Science Consulting is renowned for their highly qualified scientists trained to monitor marine mammals, seabirds, turtles and other marine wildlife of interest (e.g. sharks) during offshore industrial projects. Using Marine Mammal Observers (www.marinemammalobserver.com) and Passive Acoustic Monitoring (PAM; www.passiveacousticmonitoring.co.uk) techniques, OSC have contributed to the protection of marine mammals for years, passionately and professionally. When it comes to pioneering marine mammal risk mitigation, OSC are at the forefront. Ocean Science Consulting have supplied marine mammal risk mitigation for seismic surveys, dredging, piling, seabed mapping during site-surveys for pipe-laying, rock trenching and dumping, VSP surveys, and oil rig decommissioning, just to name a few.
For more information about our other services and areas of research, please see our main website (www.osc.co.uk).