Cromarty Seascape

Community-led marine enhancement on the east coast of Scotland

Project information
  • Status: In Progress

Cromarty Seascape is a community-led marine enhancement project in the firths around the Black Isle in the Scottish Highlands. The project works in partnership with other organizations and communities in the local area to restore biogenic habitats and the connection between people and the marine habitats around our coast.

What are the aims of Cromarty Seascape?

  • To enhance the ecosystem resilience and function of the firths by enhancing and restoring biogenic habitats, beginning with native oysters (Ostrea edulis) and seagrasses (Zostera marina and Nanozostera noltei).
  • To empower local communities to get involved and take ownership of the project.
  • To work in partnership with local organizations.
  • To generate easily accessible, open-source data and evidence for use by others.

Our core missions

  1. To reintroduce locally extinct native oysters to the Cromarty Firth and establish a self-sustaining reef.
  2. Monitor and enhance long overlooked seagrass meadows.

The Native Oyster: A Species of Cultural & Ecological Significance

Densities of the native oysters were once so great that they formed large reefs along Europe’s coastlines. In Scotland, this common bivalve mollusc would have been an integral part of people’s diet. During the 18th century, it was estimated that the oyster reef at the Firth of Forth would produce around 30 millions oysters per year! As an important source of food, oysters were cultivated and fished for thousands of years with records going back to Roman times.

More than just being culturally significant, native oysters can be ecologically valuable when they exist in healthy numbers. Forming living ‘biogenic’ reefs, they provide food and shelter for other marine wildlife. Crevices in the reef make ideal spaces for other organisms such as fish to seek shelter and reproduce. Native oysters also act as biofilters helping to improve water clarity. They filter particles from the water column which assists important light-dependent species like seagrasses. In turn, seagrasses provide ecosystem services such as oxygen production and nutrient cycling. Furthermore, where native oyster populations bounce back, there could be a positive impact on local fisheries. As a habitat for fish and the species they feed on, oyster reefs are capable of creating a ‘spill-over’ effect that could see local economies and livelihoods benefit.

A close up shot of a live European flat oyster.
Known as 'oisir/eisir' in Scottish Gaelic, native oysters and native oyster beds are a "Species and Feature of Conservation Importance” under the Marine and Coastal Access Act.

The Struggle for Survival

Today the situation is drastically different from the bountiful populations of the past. They are one of the most threatened marine habitats in Europe. From being present around most of the UK’s coastlines, the species is now considered to be on the brink of extinction, only existing in small, fragmented populations. The threats attributed to this collapse in Scotland are overexploitation for fisheries, pollution/poor water quality (particularly tributyl tin which has been found to stunt growth), parasites, diseases and historic habitat loss. Native oysters require a substrate for their young to attach to and the loss of oyster beds has therefore impacted their decline.

As populations become smaller, their ability to survive is hindered by their very own nature. Instead of using broadcast spawning to reproduce, where eggs and sperm are released into the water at once, female native oysters first draw sperm into their bodies before releasing fertilised eggs. This means where there are fewer oysters together, there is less success of fertilised eggs spreading. Being protandrous hermaphrodites, animals that are born as males but switch sexes during their life cycles, is also known to affect reproductive rates. Skewed sex ratios in favour of males has been reported and is possibly due to stress related to disease and/or anthropogenic pollutants. In addition to these factors, native oyster larvae need a surface to attach to and their favourite is the shells of older native oysters. Lower densities of native oysters mean that there are fewer places for their larvae to latch on to and grow. 

A close up shot of a native oyster in a person's hand.
Native oyster larvae spend around 8-10 days in the water column before they settle onto a suitable surface.

Our Nursery Proposal

Because of their clear benefits to the ecosystems in which they are supposed to be present, we are working to establish a native oyster nursery in the Cromarty Firth and explore whether they could be successfully reintroduced. However, the project is not without its challenges. There have been supply issues throughout the UK for young native oysters known as ‘seed’, and there are also diseases & invasive non-native species impacting the species that need to be considered with biosecurity measures put in place.

A surveyor recording native oyster remains in the Cromarty Firth.
We frequently find the dead remains of native oysters whilst out on surveys in the Cromarty, Beauly and Inverness Firths.

Seagrasses: Valuable but Threatened

Alongside our work with native oysters, we have been mapping seagrass meadows to start building a baseline of the habitat within the project area. Led by our Project Biologist Francis and with the assistance of citizen scientists from local Community Interest Company (CIC) Moray Ocean Community, there have been many walks in the (often muddy) intertidal zone.

Seagrasses might be something that you would more readily associate with the west coast of Scotland or faraway places, but we’ve sizeable meadows within the project area. Best viewed in Scotland from mid-July to the beginning of September, these mini ecological powerhouses provide habitat for juvenile trout (Salmo trutta) and food for wading birds. They also have a complex root structure that stabilizes sediments, prevents soil erosion, and they promote efficient nutrient recycling.

In the 1930s a significant proportion of seagrass in the United Kingdom are believed to have died from a wasting disease, which attacks the leaves and prevents photosynthesis, ultimately killing the plant. Since then, there have been ongoing losses to seagrass extent including since the 1980s primarily due to anthropogenic factors. These factors are known to include pollution from for example industrial, agricultural and wastewater processes.

Zostera marina on mixed sediment in the intertidal zone.
Did you know that even within individuals of the same species of seagrass there are ecotypes that have different characteristics. For example, Zostera marina has both annual and perennial varieties within the project area.

Knowledge Gaps Within the Project Area

Volunteer mapping studies undertaken by Moray Ocean Community in 2023 with our support have identified some intertidal seagrass beds in the Inner Moray Firth that have not been formally mapped for an extended period of time. From comparison between a survey carried out by Fox, Yost and Gilbert (1986) and our data, preliminary results show that there could have been losses in the past 37 years (see Figure 1). There has been limited survey work in the area since then, with the majority of publicly available records from 2008 or earlier.

Part of the challenge when it comes to promoting the recovery of seagrass meadows is that they suffer from cumulative impacts, and it can be difficult to identify why losses are happening where they occur. This is why having groups of people from our local area invested in and taking ownership of their local seagrasses is paramount, because there’s nothing quite like local knowledge! Connecting with other local people with various interests has been extremely helpful, particularly those like local shellfish farmers and others with family ties here spanning decades.

In 2024 alongside other sampling work, we are on a mission to identify and map seagrass meadows within approximately 1151 ha of potentially suitable intertidal habitat. To do this, we will be using a combination of ground truthing with drone mapping, and we are also exploring whether satellite data might come in useful. We plan to use this information to see whether it might be beneficial to reinforce the seagrass beds already present through active or passive restoration. Active being through planting, and passive being through the removal or reduction of pressures to promote recovery.

Idotea balthica on  Zostera marina
Seagrasses provide habitat for an array of species, like this Idotea balthica on Zostera marina.

Active Community Participation

Community participation is a key component of this project. From the early stages, partnerships have been developed within the local community starting with our locally based project team. Through direct participation in surveys and other opportunities, we hope to help foster people's connection with the marine environment. This engagement should also garner support for the project and contribute to the long-term sustainability of Cromarty Seascape in the area.

We are exploring the possibility of collaborating with an academic institution to monitor the project’s outcomes. This could consist of things like eDNA, acoustic habitat mapping, bathymetric surveys, benthic taxonomy and acoustic biodiversity monitoring.

Seagrass surveyors in the intertidal at Shoremill, near Cromarty.
Getting the support of the community 'onboard' is an important element of this project.

Evidence Sharing

Currently, there is a knowledge gap on native oysters and seagrasses in the project’s area. We intend to help address this by gathering data on species presence/absence, habitat mapping and other survey work. We share our findings directly with Scotland’s nature agency, NatureScot.

We thank Mossy Earth members and everyone else involved in the effort to turn the tide for this section of Scotland's coastline.

Through data collection, we aim to contribute to the knowledge of restoration in the area and further afield.

Stay tuned for updates...

At present, we are planning the busy survey season ahead and working on getting planning permission for our native oyster nursery. See the video below where Cromarty Seascape Project Manager, Isla, discusses the project in more detail. Keep in mind that this was filmed last year and the project has developed since then!

Heart Image

the team behind the project

Team Member

Isla MacLeod, Cromarty Seascape Project Manager @ Mossy Earth

Team Member

Francis Williams, Cromarty Seascape Project Biologist @ Mossy Earth

The Moray Ocean Community logo