White-clawed crayfish and biosecurity on site

A white-clawed crayfish survey is a licensed activity, and the biosecurity obligations that follow it are usually more onerous than the survey itself. The species is protected under Schedule 5 of the Wildlife and Countryside Act 1981 in respect of taking and sale, so capturing one from the wild without a licence from Natural England is an offence. It is also an Annex II species, which is why some watercourses are designated as special areas of conservation partly for it.

The reason biosecurity dominates the reviewing work is crayfish plague. The pathogen travels on wet kit, and a single set of waders moved between catchments without disinfection can end a population that has survived for centuries.

Where the native crayfish survives in England

The native crayfish has been lost from most of its former range and now survives in fragmented populations, typically in upper catchments, spring-fed streams, limestone becks and some isolated ponds and reservoirs. Chalk and limestone areas hold the better remaining populations, and isolation is the main reason they persist: a population above an impassable weir or in a headwater with no angling access has a chance.

That distribution has two practical consequences for anyone reviewing an ecological submission. First, the presence of signal crayfish downstream does not mean the native species is absent upstream, and an assessment that reasons that way is defective. Second, records are patchy and often old. An absence of records in the local environmental records centre is not evidence of absence, particularly in small watercourses that nobody has surveyed.

A Preliminary Ecological Appraisal should therefore identify the potential from habitat and catchment position rather than from records alone, and PlanScope drafts one from the answers you give about the site while flagging the field data it cannot supply.

The protection and what the offences cover

The listing on Schedule 5 is partial, and the detail matters when scoping work. The species is protected in respect of section 9(1) taking and section 9(5) sale. So capturing, handling or removing an individual from the wild needs a licence, and trading in them is an offence.

It is also a species of principal importance under section 41 of the Natural Environment and Rural Communities Act 2006, which engages the duty on public authorities and gives a local planning authority a policy basis for requiring survey and mitigation even where no criminal offence is in prospect.

Separately, the release or allowing to escape of non-native crayfish is an offence, and the invasive species regime controls keeping, transport and release of the listed non-native species. That matters on development sites because moving water, silt or vegetation between catchments can move the invader as well as the pathogen.

A Protected Species Survey covering crayfish requires a suitably licensed ecologist as a matter of law, and a drafted report is a starting point for that ecologist rather than a substitute for their judgement.

Survey methods and the licences needed

Three methods, used in combination:

• Manual search, which means turning refuges, cobbles and woody debris in shallow water and examining undercut banks and tree roots. Refuges must be returned as found.
• Night-time torchlight survey from the bank or in-channel, used where the substrate is unsuitable for refuge searching.
• Trapping, used where depth prevents the other methods, and the least favoured because it is size-selective and can miss juveniles entirely.

Each carries a permission. Handling requires a Natural England licence. Trapping additionally needs consent from the Environment Agency for the traps themselves, and that consent is separate from any ecological licence. A method statement that proposes trapping without naming both permissions is incomplete, and it is the commonest gap a reviewer should pick up.

Timing is constrained by biology rather than by convenience. The workable window is the warmer, lower-flow part of the year, broadly July to October, when animals are active and females are not carrying eggs. Surveys outside that window risk disturbing berried females and are likely to under-record. High flows make manual searching both unsafe and ineffective.

Record the search effort as length of channel, time spent, number of refuges turned and water conditions. A survey that reports "no crayfish found" without effort data cannot be reviewed.

Crayfish plague and how it travels

Crayfish plague is a fungal-like pathogen carried by non-native crayfish, which are largely resistant to it, and lethal to the native species. Infected water bodies remain a source, and the spores survive in damp conditions long enough to cross a catchment in the back of a van.

The transmission routes on a construction site are mundane: waders, boots, nets, buckets, sample bottles, waterproofs, rope, survey poles, pumps, hoses, excavator buckets and tracks that have been in a watercourse elsewhere. Water itself is a route, so pumping from one watercourse and discharging to another transfers risk directly.

The only reliable controls are drying, disinfection and separation. Drying works because the spores do not survive desiccation, but it needs everything to be dry through, including seams, boot treads and the inside of hoses, and that takes longer than a shift.

Biosecurity for plant, boots and nets

Build the protocol around the recognised check, clean and dry approach and make each step specific:

1. Dedicate equipment to a single catchment where the programme allows. Two sets of waders is cheaper than one incident.
2. Check and remove all mud, silt, vegetation and animals on site before leaving the water. Silt in a boot tread is the item most often missed.
3. Clean with a disinfectant approved for aquatic biosecurity, at the manufacturer's concentration and contact time, in a container large enough to immerse the item. A quick spray does not achieve the contact time.
4. Dry fully before reuse in another catchment, for a period stated in the method statement rather than left to judgement.
5. Never transfer water, silt or vegetation between water bodies, including in pumps, tanks and bowsers.
6. Site the wash-down station away from the watercourse, on an impermeable surface, with the used disinfectant collected and disposed of correctly rather than allowed to drain to the channel.

The generic biosecurity method statement approach for development sites applies here with one difference: for crayfish, the consequences of a failure are irreversible within that population, so the protocol should be written as a set of hard requirements rather than as best endeavours.

Working in and near the watercourse

Consents stack up quickly and they are easy to miss in a review.

Works in, over, under or within eight metres of the bank of a main river generally need a flood risk activity permit, and the distance is greater for tidal main rivers and sea defences. Works affecting an ordinary watercourse need land drainage consent from the lead local flood authority, under the Land Drainage Act 1991, which is a separate application with its own timescale.

Then there is pollution prevention. Silt is the routine problem, and a crayfish population downstream of an unmanaged excavation can be smothered without anyone breaching a wildlife offence at all. Specify silt fencing, settlement, a clean water diversion where the works are in-channel, and a stop-work trigger for turbidity.

Where the scheme includes channel works, sequence them so any in-channel activity happens inside the low-flow window and after the survey, not before it.

The method statement an authority expects

A crayfish method statement that will survive review contains:

The survey findings, with effort data, dates, water conditions and the licence numbers under which the work was done. The catchment context, including the known distribution of both native and non-native crayfish upstream and downstream. A clear statement of whether any taking or handling is proposed, and under which licence. The biosecurity protocol, with named products, concentrations, contact times and drying periods. The consents obtained for the in-channel works. A named responsible person on site. A toolbox talk schedule and the content of that talk. And a stop-work procedure for an unexpected find.

Two omissions recur. Method statements written for the survey team, which say nothing about the groundworkers who will actually be in the water six months later. And protocols that name a disinfectant without a concentration, which are unauditable.

Where the scheme also relies on habitat enhancement to deliver biodiversity units, check the metric entries against the watercourse condition assessment. Several of the metric errors councils find most often involve watercourse condition scored optimistically against a channel that the ecological report describes as degraded.

Recording compliance

Biosecurity fails quietly, so the record is the control.

Keep a dated log of every disinfection event, with the item, the product, the concentration, the contact time and the person who did it. Keep an equipment register showing which kit is assigned to which catchment. Photograph the wash-down station in use. Have the ecological clerk of works audit the log at each visit and report to the local planning authority at an interval set by condition, monthly during in-channel works being a reasonable default.

Then write the condition wording yourself and offer it. A condition requiring compliance with an approved biosecurity method statement, with a monthly compliance report during works affecting the watercourse, is enforceable. One requiring "appropriate biosecurity measures" is not.

Enter your postcode on PlanScope to see which ecology documents a watercourse site is likely to need.

This is general guidance, not legal advice. Check the position with your local planning authority, Natural England or a qualified professional before relying on it. PlanScope provides AI-assisted draft reports for planning applications. Reports should be reviewed before submission. We do not guarantee planning approval. For specialist technical reports, qualified professional input may be required.