Transforming mussel surveys with multispectral drone data

• North Western Inshore Fisheries and Conservation Authority (NWIFCA) is conducting mussel surveys with the DJI Mavic 3 Multispectral;

• Drones are helping to enhance survey accuracy, providing standardised and consistent metrics, as well as increasing the efficiency of gathering data - especially crucial in tide-restricted areas;

• Multispectral data enables the team to distinguish mussel beds from surrounding substrates based on their unique spectral signatures;

• NWIFCA plans to extend aerial surveys to other scientific work beyond mussel classification. NWIFCA also deploys the DJI M30T for fisheries enforcement;

• heliguy™ has helped NWIFCA integrate drones through product supply, pilot training, and hardware servicing, while the in-house survey department built a dedicated multispectral post-processing course.

An Inshore Fisheries and Conservation Authority (IFCA) is exploring how multispectral drone data can bolster vital environmental management along the coast.

North Western IFCA is conducting mussel bed surveys with the DJI Mavic 3 Multispectral.

While work to develop a drone-based methodology is in its infancy, the early results look promising.

Aerial mapping is set to enhance precision, collect data quickly during short tidal windows, standardise metrics, and enable non-invasive surveys.

Monitoring mussel beds is important to support sustainable fishing, protect ecosystems, and ensure compliance in sensitive, biodiversity-rich marine areas.

“From the science team’s perspective, using drones is a developing area and we are first concentrating on mussel, with a view to improving the accuracy of the surveys,” said Jon Haines, NWIFCA Senior Science Officer.

“It looks like the data gathered will improve our ability to map mussel areas and classify the mussel, which will feed into the management of the intertidal hand-gathered and boat-based dredge fishery within the NWIFCA district,” he added.

The plan is to extend aerial surveys to other scientific work within Marine Protected Areas (MPAs) and European Marine Sites, to help shape management measures.

NWIFCA is also deploying the DJI M30T drone for fisheries enforcement operations.

“From an enforcement perspective, the drone allows for more effective monitoring,” said Jon.

heliguy™ has supported NWIFCA through product supply, pilot training, and hardware servicing, while the in-house survey department built a dedicated post-processing course to help the NWIFCA team interpret the multispectral survey data.

Transforming mussel monitoring with drones

Before using drones, the NWIFCA team accessed mussel beds by quadbike, or by drying a boat out at low water and walking the bed.

The composition and extent of the mussel would be recorded using handheld GPS, or taking samples and recording percentage coverage to obtain a biomass estimate.

These methods were bound by limitations: Labour-intensive, tide-restricted, and opinion-based.

From the early tests, drones have the potential to combat these challenges.

Jon said: “It is hoped to improve the accuracy of our data, particularly in areas where time is severely restricted by tides.

“Some areas are only exposed for a couple of tides each month for around an hour and involve drying a vessel out on them.

“It is also hoped it will provide standardised metrics to our analysis of mussel beds.

“Currently, visual inspections are undertaken with officers providing percentage cover estimates. This can be subjective.

“The drone imagery and analysis will be able to provide an estimate of coverage and density that is independent, consistent, and comparable between years.”

The methodology is being developed in Morecambe Bay, with a view to extend it throughout the district, with a particular focus on the Dee and Wyre Estuaries, Fleetwood, and the Solway Firth.

Multispectral imaging for mussel surveys

The drone’s ability to capture accurate and efficient data brings obvious benefits.

But, the fact it collects multispectral data helps to provide even deeper insights.

Jon said: “The ability to capture data across multiple wavelengths allows us to distinguish mussel beds from surrounding substrates based on their unique spectral signatures.

“It also allows us to map the spatial extent of mussel beds more consistently over time, especially in shallow coastal or intertidal areas."

The images above demonstrate mussel categorisation with multispectral (NDVI) data.

The DJI Mavic 3M is equipped with four 5MP multispectral cameras, allowing data collection in the Green, Red, Red Edge, and Near-infrared bands. The drone also has a built-in 20MP RGB camera.

While initial surveys are looking promising, the NWIFCA scientists want to refine their approach to gather even greater and more accurate mapping data.

Further testing includes looking at how the presence of algae growth interspersed with mussel affects the imagery, testing NDVI scores across different beds with different characteristics, and exploring a methodology for calculating biomass with combined sampling.

The importance of mussel surveys

Having accurate data is vital for NWIFCA’s survey work.

Explaining the importance of monitoring mussel, Jon said: “Mussel is an important fishery within the North West, for size mussel, which goes for human consumption, and for seed mussel, for aquaculture, which is grown before going for human consumption.

“NWIFCA is responsible for the sustainability of the fishery, and as nearly all the mussel beds are within Marine Protected Areas, we need to ensure that the fishery does not impact any of the protected features.

“As such, it is important that we have the stock information to inform the management decision.

“In addition, mussels form an essential food resource for the many protected bird species in the region.

“The ability to accurately calculate their biomass and coverage is an essential part in determining fisheries management measures that protect this resource.

“For example, understanding the amount of mussel available contributes to the understanding of the overall shellfish biomass to birds in the District, and how we may allocate stock quotas to fishers in the future.”

Additional scientific research with drones

While NWIFCA’s initial focus is mussel surveys, the plan is to extend drone deployment to other environmental work throughout the district.

Jon said: “We plan to use the drone for other science activities.

“For instance, mapping the location of fishers on the cockle beds over the duration of a fishery. This data can then be overlaid with our stock assessment data to identify patterns of fishing and how these relate to the density and distribution of stocks on the bed.”

Drones for fisheries enforcement

NWIFCA is deploying the DJI M30T to assist with offence detection and evidence gathering.

The drone offers a fast response to monitor, record, and document illegal activity that may not otherwise be seen, as well as being used for routine observations and checks.

The M30T is equipped with thermal, RGB, and zoom cameras, plus a laser rangefinder, while its IP55 design is ideal for handling coastal environments.

Joe Moulton Head of Enforcement at NWIFCA said: “The drone allows for more effective monitoring of closed fishing areas, (particularly at night with the use of the thermal camera), and fishing gear restrictions. It also helps with collecting more accurate and robust fishing activity information.”

heliguy™: NWIFCA’s drone partner

NWIFCA started using drones in 2024. The team currently has three pilots, and another going through GVC training.

“The aim is to always have four pilots in total with two from the Enforcement team and two from the Science team,” said Jon.

NWIFCA has leveraged the support of heliguy™ to start and scale its drone programme, through supply, training, servicing, and data-processing support.

Jon said: “We completed our GVC training with heliguy™, with their instructors coming to us in the Northwest to complete the training. We have also discussed the potential for assistance with a future BVLOS application to the CAA.

“heliguy™ also developed a tailored post-processing training session, using data collected by us, to analyse the multispectral image data.”