Flapper Skate protection: NatureScot advice to the Scottish Government

Potential threats to flapper skate

The most relevant threats to skate eggs on the seabed include surface abrasion, water quality/contaminants and sedimentation, through direct mortality of eggs or indirectly by affecting the suitability of habitat. At this location, the most relevant impact is likely to be surface abrasion via mobile fishing gear and, given the nature of the seabed in this area, this will be scallop fishing by dredge.

Generic, low-resolution mapping of scallop fishing activity (e.g. as available via NMPi) shows that fishing is occurring in the vicinity of the egg site. However, a more detailed analysis of VMS data by Marine Scotland would be required to understand the nature of interaction at a scale that is relevant to informing a management decision (although noting the constraints that apply to VMS data in obtaining an understanding of fishing activity by all vessel sizes).

Understanding the risk of exposure to fishing that skate eggs may face requires this higher resolution fishing activity information (which is not directly available to NatureScot), however it is possible to give some consideration in the light of the March survey, the available bathymetry and some assumptions about fishing operations.

Firstly, the seabed in the wider area around Red Rocks in the Inner Sound has a complex topography with mixed substrates including areas of sediment, boulder/cobble and bedrock (and this area supports scallops) (see Figures 1 and 2). It is reasonable to assume that fishing will take place over some but not all of the available seabed - i.e. the precise footprint of fishing will be constrained by the ability of vessels to tow over seabed with larger boulders and bedrock.

At this point we know that eggs are present in amongst the boulders of the sizes observed in discrete areas at this location, and that these eggs have persisted there for at least a year (i.e. initial observation being in March 2019), indicating that they may not have been exposed to fishing. However, it is not yet possible to assess the size of the egg-laying area or the extent to which egg laying may be constrained by fishing activity, as this would depend on a fuller understanding of both fishing activity and potentially suitable egg-laying habitat and the overlap between them.

• - In summary, therefore, fishing by dredge is happening in the vicinity of the skate eggs.
• - This is the activity which is considered to have the greatest potential to have a negative impact on skate eggs.
• - Assessing the risk of exposure requires higher resolution fishing activity information to understand the footprint and the relationship with potential skate egg-laying habitat.
• - We also require more information on the extent of the egg-laying area (as knowledge is currently based on a limited number of survey locations).
• - It is possible that fishing activity may be constraining egg laying to those areas where fishing is not feasible.