Flapper Skate protection: NatureScot advice to the Scottish Government

Importance of the location for flapper skate

As set out above, our advice is that the density and extent of flapper skate egg cases at the Red Rocks site is important in a Scottish context. The results of the recent survey work provide valuable information, not just about this location, but also more generally about egg-laying habitat

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used by flapper skate. The information about habitat type (predominantly boulders and cobbles) will help to inform future habitat modelling. In turn, this will enable future survey effort to be better focussed, not just in the Inner Sound, but elsewhere in Scotland.

There are two specific knowledge gaps in our understanding of the life history of flapper skate. One gap concerns the behaviour and ecology of the juvenile skate, which we do not discuss further in this advice. The other being their reproductive biology including egg laying (i.e. locations, preferred habitat, numbers of eggs, gestation period).

Consequently, attempts to identify egg-laying locations has been part of the research undertaken in the Loch Sunart to Sound of Jura MPA, including citizen science diving surveys and drop-down video camera surveys. Skate eggs have also been one of the targets for analysis of the drop-down video camera surveys conducted in the EMFF project "Engaging Fishermen in Marine Environmental Monitoring".

The locations where skate eggs have been positively identified recently on the seabed include Red Rocks, the Sound of Jura (including at the mouth of Loch Craignish) and near Lunna Ness in Shetland. However, these latter records are for single or low numbers of eggs. There is also evidence of egg-laying activity by flapper skate to the west of Orkney, from robust records of flapper skate eggs coming ashore there. Unfortunately, there is not as yet corresponding observations of where on the seabed the eggs found in Orkney are being laid. We are aware of some other reports of egg cases but these are subject to confirmation.

Assessing the relative importance of the Red Rocks location is subject to a number of uncertainties including those relating to: artefacts of the survey methodology including recent improvements in technology which affect the likelihood of observing egg cases; whether changes in skate abundance/range are leading to changes in reproductive activity; and our understanding of the extent to which skate exhibit site-fidelity to egg-nursery habitats.

The information collected in the March survey provides information that helps address these questions. The number of eggs present indicates use by multiple animals and the range in egg condition is an indication of use over at least two years (i.e. bearing in mind the initial observation of eggs in March 2019 during the EMFF video survey, and that egg gestation period is thought to be well over a year).