Major survey of skate is under way

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This week sees a major survey in the Loch Sunart to the Sound of Jura Marine Protected Area (MPA).

The Loch Sunart to the Sound of Jura MPS was designated to conserve a nationally important population of common skate, the largest remaining coastal population of the species.

Common skate display an unusually high level of residency in the area. This has been confirmed by an analysis of angler mark-and-recapture data and an acoustic tagging project that continuously monitored the movements of tagged skate in the Sound of Jura. These tagging projects showed the skate either stay within or repeatedly return to the area covered by the MPA.

As the marine environment does not always respond as we might anticipate, further marine science is needed if we are to ascertain if the status and condition of habitats and species is improving in response to MPAs.

To understand if juvenile skate use the MPS, in addition to adults, Marine Scotland Science, in collaboration with St Andrews University and Scottish Natural Heritage, is undertaking the survey on the research vessel Alba na Mara between September 23 and 30.

Various methods have been tried previously, such as cameras and fish traps, but juvenile skate have proven elusive. Therefore, for this survey, trawl gear will be used at locations within the MPA where such activity can take place year round and in areas where it is restricted on a seasonal basis (a scientific permit has been issued for the latter).

The seasonal restriction also maximises the chance of finding juveniles as the area has been undisturbed over the closure. The duration of each haul will be limited, typically to 15 minutes, to minimise disturbance to the skate.

Skate caught in this survey will be tagged and released and genetic samples will be taken to enable scientists to relate data on juveniles to the adult data.

Elasmobranchs (shark, skate and ray) are important components of marine ecosystems, but globally many species have suffered major declines due to fishing and habitat loss.

Elasmobranchs are typically slow growing, have a late age of sexual maturity, often in their teenage years, and produce a low number of large and well-developed young.

The common skate is considered to be two separate species: the flapper skate (Dipturus intermedius) and the blue skate (Dipturus batis).

The flapper skate is the largest species of skate in Europe, measuring more than two metres from wing tip to wing tip and weighing over 100kg. It has a similar life cycle to humans, reaching ages in excess of 60 and maturing at around 15-16. Like other species of skate, the flapper lays eggs, approximately 30-60 each year.