6. IMPLEMENTATION OF 'TURTLE GUARDS' BY INDUSTRY

 

Given their endangered/critically endangered species status, the issue of turtle entrapment in seismic equipment should be acknowledged and addressed by offshore industry. In addition to potentially reducing turtle mortality, the implementation of turtle guards confers several further advantages to industry (Box 2), and it is recommended that their implementation is adopted worldwide as HSE 'best practice'. The use of turtle guards is particularly important in tropical and subtropical waters, and in/adjacent to documented feeding and breeding habitat for marine turtles.   The implementation of 'turtle guards' or the use of 'turtle friendly' tail buoys (meaning those buoys with designs where there is no possibility of turtles becoming trapped, i.e. no subsurface gaps and appropriately positioned tow chains, see Figure 11) should occur at three levels:   (1) Regional licensing bodies The issuing of licences for seismic surveys in areas known to be inhabited by turtles should include the requirement for turtle guards or 'turtle friendly' tail buoys and reporting on any turtle fatalities in towed equipment should be a mandatory requirement   (2) Seismic contractors Contractors who operate seismic vessels should voluntarily adopt turtle guards or 'turtle friendly' tail buoys   (3) Oil and gas companies Companies that charter seismic vessels to conduct surveys should include the requirement for turtle guards or 'turtle friendly' tail buoys in the tender process. It should be a requirement of survey mobilisation that the survey does not commence until all tail buoys are appropriately fitted to minimise turtle mortality

Box 2. Why choose to implement turtle guards or 'turtle-friendly' tail buoy designs?     1. Conservation relevance: Six of the seven marine turtle species are endangered or critically endangered and avoidable mortality should be eliminated 2. Environmental credibility   3. Cost-effectiveness: The problem is very simple and cheap to solve 4. Health and Safety: Workboat operations are required to remove entrapped turtles, thus subjecting seismic personnel to increased risk exposure 5. Seismic survey production: The entrapment of turtles within a tail buoy structure can cause the buoy to tow/track to one side, risking taking the survey out of spec The faulty tracking caused by turtle entrapment could potentially lead to tail buoy tangles, causing streamer damage and streamer fluid leaks into the sea and potentially causing increased tension on streamers causing them to break. Such events can result in several days of lost production

7. IMPLEMENTATION OF 'TURTLE FRIENDLY' TAIL BUOYS BY MANUFACTURERS

A further form of implementation is via the tail buoy manufacturers who should be encouraged by industry to consider turtle entrapment during future tail buoy design. Tail buoy manufacturers should consider the possibility of turtle entrapment when designing new buoys, and particularly consider reducing the occurrence of gaps at the front of the buoy, the necessity for the undercarriage and the positioning of tow chains in relation to the buoy undercarriage. Some possibilities that have been suggested include:

• Removing or reducing the subsurface undercarriage. This would be the most obvious solution to prevent turtle entrapment. However, it is recognised that some subsurface structure is needed to counter-balance the otherwise top-heavy design of tail buoys. The possibility of designing a buoy with a single keel should be explored, particularly since the presence of solar panels on most buoys now reduces the need for the underwater propeller unit (at least in the sub-tropical and tropical waters where the highest turtle densities occur). The advantage that the twin-fin design offers for upright storage is considered surplus since it is not utilised on many ships (see Figure 6)

• Re-locating the towing chains to the front of the buoy undercarriage to remove the tight angle between the chains and the undercarriage where turtles are known to get caught (Section 2.4). Ideally, the use of a single tow chain would greatly reduce the potential for turtle entrapment and is already used in some tail buoy designs (Section 4.2)

• Removing surplus parts of the tail buoy undercarriage (e.g. the horizontal joining stiffener, Figure 9) which have no obvious role and create extra gaps where turtles could become trapped

• Incorporating effective 'turtle guards' as an integral part of new tail buoy designs when an undercarriage and/or twin-fin design is necessitated