Habitat point records from 1984 Bishop Scilly Isles Echinus population study

Echinus esculentus is the subject of a small scale commercial fishery in the Isles of Scilly. Collection is by diving during the winter months, and during 1983/84 it is estimated that a total of 71,000 to 83,000 individuals were taken from three shallow sublittoral areas. This report presents the results of a survey of selected E esculentus populations in the Isles of Scilly during September 1984. 7 areas were sampled, 3 of which are categorised as fished, and 4 as unfished. Within these 7 sampling areas, 28 dives were made and locations recorded with a sighting compass. The mean site density of urchins ranged from 0.09/m2 to 0.56/m2, with an overall mean of 0.36/m2. There was no difference in density between fished and unfished sites. Individual diameters of E. esculentus ranged from 61 mm to 143 mm with an overall site mean of 103.98 mm. No recruitment of juveniles was noted, and all populations examined are senescent. Density and size structure of the populations of E. esculentus examined in the Isles of Scilly compare closely to results from other locations in south-west Britain. This does not necessarily suggest that there are no noticeable effects of fishing on the Scilly urchin populations, since many of these other locations have experienced collecting in the recent past. However at present there is no evidence of differing population characteristics in Scilly when comparing fished and unfished areas.