This report provides the results of a terrestrial invertebrate survey which was conducted at the Tilbury intertidal zone, between Coalhouse Fort and Tilbury Fort. The survey aims to inform Natural England’s proposal to enlarge the Mucking Flats and Marshes Site of Special Scientific Interest (SSSI), notified (in part) for its invertebrate interest. The survey area was split into five sub-compartments and the work was carried out in 2024 based on two survey visits in July and a further two in September using active sampling methods only.
The survey targeted Species Assemblage Type (SAT) M311 ‘Saltmarsh and Transitional Brackish Marsh’. In addition, a key objective of the survey was to assess the local abundance of the Nationally Scarce Sea Aster Mining Bee Colletes halophilus and its main forage resource Sea Aster Aster tripolium. Data was collected by sweep-netting, grubbing/hand searching and suction sampling.
A total of 389 species were recorded across the five compartments. Over half of the species recorded by the survey were found in compartment F1. This compartment also produced the highest proportion of unique species which were not found elsewhere (36%). Of the recorded species, 62 had a conservation status; eight Section 41 species and 54 which are Nationally Rare or Nationally Scarce. Four SATs were reported as being in a favourable condition including; ‘Saltmarsh and Transitional Brackish Marsh’ (M311), ‘Rich Flower Resource’ (F002), ‘Bare Sand and Chalk’ (F111) and ‘Scrub Edge’ (F001). The Sea Aster Mining Bee Colletes halophilus, an important saltmarsh indicator species, was present in three of the survey sub-compartments and while just a single nesting aggregation was located, suitable foraging areas were mapped in all five.
A simple benchmark for any survey is the proportion of the recorded fauna composed of species with Nationally Rare or Nationally Scarce status. Sites where this exceeds 10% indicate exceptional quality. The overall figure for the areas surveyed here, stands at almost 16% suggesting that they may qualify as nationally important.