Marine Habitats
Inshore/ subtidal marine habitats
The State of Nature in Marine Habitats in Neath Port Talbot
At present we have insufficient data to give a robust assessment of the resilience and state of nature in the marine habitats of NPT. Attributes such as extent and connectivity can be assumed to be good. However, the 2018 Water Framework Directive interim assessment rated the overall and ecological status of our local coastal water to be moderate and it failed on chemical status. We conclude from this that the condition of our marine habitats is poor. Furthermore, issues such as pollution and invasive non-native species continue to threaten ecosystem resilience. At this point, we can only conclude that the state of nature in marine habitats in NPT is poor.
OVERVIEW
The marine habitats of NPT are defined in this document as the inshore, subtidal and surface seawaters of Swansea Bay off the coast of NPT to a distance of 12 nautical miles. The seabed here consists of sandstones and mudstones overlain by sand, gravel and mud. The main habitats enclosed are suitable for marine mammals, fish and invertebrates but there are no rocky subtidal areas.
Specific and detailed knowledge of the biodiversity of these habitats is lacking but surveys undertaken in 2013 found 6 infaunal groups dominated by polychaete worms and bivalves. Sabellaria alveolata reefs are formed in the bay, some of which are on man-made structures such as groynes. At least 55 species of fish and 38 species of shellfish have been recorded in the bay. These include some of international importance such as European Eel, Allis Shad, Twaite Shad and Sea Lamprey. The area is also an important nursery for flatfish and ray, while Herring are known to spawn in several places around the bay. It is possible that Sand Eel spawn here also.
The bay has a year-round presence of Harbour Porpoise with annual mother-calf sightings in late summer-autumn and near-shore foraging has been noted in several places. Common Dolphin are sighted occasionally in summer and mid-winter, perhaps a reflection of the range expansion of the Celtic Sea population which has occurred in the last 15 years, and Grey Seals have been sited occasionally. Large and significant numbers of Great Crested Grebes are counted in the bay each winter from Aberavon Beach and Crymlyn Burrows.
The marine ecosystem provides habitats for 24 of NPT’s priority species.
Actions for the recovery of
Marine Habitats in NPT
Responsibility for these actions lie with all of us and as such, we have not sought to assign actions to particular organisations or groups. Instead, it is our hope that this document will provide the guidance and inspiration for anybody, or any group or organisation, to undertake the actions that are within their capability to deliver. The Secretariat of NPT LNP (NPT Council) are providing a facilitation role to support, collate and monitor work towards these actions. If you would like to discuss your potential involvement in delivery of these actions, please get in touch with biodiversity@npt.gov.uk.
HARBOUR PORPOISE
Swansea Bay has year-round Harbour Porpoise presence, with annual mother-calf sightings in late summer-autumn. Regular near-shore foraging is also reported along the NPT Coastline. They are much smaller than native dolphin species and more difficult to spot. They do not often leave the water like dolphins but ‘breach’ with their back in a smooth arc. Porpoise have a very short beak making their head look blunt compared to a dolphin.
HERRING
Swansea Bay has several spawning sites for Herring. One of these is the sea defence area at the entrance of Port Talbot Dock. It is likely that the man-made structures provide and replicate the substrate required to allow gravel patches to form, creating the right conditions for a spawning site. Herring have different spawning points in the year; the Swansea Bay population spawns in February and March. Herring are not exploited commercially here. Due to their large numbers and fast reproductive cycle they are an important prey item within the marine ecosystem. They could be the reason for the high numbers of predators especially Great Crested Grebes we see in the winter.
CASE STUDY
GREAT CRESTED GREBE OVER-WINTERING SURVEYS
The Great Crested Grebe is the largest and most familiar of the grebes that are found in the UK. Most people associate them with large freshwater lakes where breeding birds are sometimes seen displaying to each other in an elegant, courtship water dance. There are few breeding pairs in NPT but they occur regularly on Eglwys Nunydd Reservoir near Margam and the Borrow Pits ponds near Glynneath, where adult birds can be observed with chicks, sometimes carrying the young birds, characteristically, on their backs.
Much larger numbers of these beautiful birds gather in winter feeding flocks in Swansea Bay where they often occur in 3 separate groups of birds spread across the bay from Blackpill (Swansea) to Aberavon (NPT). Two of these groups are usually located in NPT, one off Crymlyn Burrows and the other off Aberavon Beach. The numbers of wintering birds in these flocks has been counted at regular intervals for over 10 years by local enthusiasts (British Trust for Ornithology, Wetland Bird Survey (WeBS) Counts) and it is clear from these records that the bay is a very important winter feeding site with >700 individuals counted in some months. Often, the greater proportion of the bay's grebes occur in waters off NPT and those off Crymlyn Burrows, where numbers >400 have been recorded, appears to be very significant.
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Under Criterion 6 of the Ramsar Convention, wintering flocks of a waterbird species are considered to be internationally important if they contain 1% or more of the national population. This figure sets the Species Threshold Level, which for the Great Crested Grebe in UK is currently at 190. Numbers greater than this qualify a site to be of high international, conservation value. Clearly, the number of wintering Great Crested Grebe in Swansea Bay exceed this threshold by a large amount and, importantly, so does that part of the winter flock associated with NPT water. A key, limiting factor in this is the maintenance of sufficient shoals of fish on which these birds depend for food and that, in turn, is dependent on the good health and nutrient dynamics of the bay's marine ecosystem.
