The Thames cockle fishery

The Thames cockle fishing industry

Up until the late 1960s all cockles were collected by hand raking. Following a decline in the hand-raking fishery the hydraulic cockle dredge was developed by the White Fish Authority. This proved successful although damage rates to cockles were initially high. The development of new harvesting systems saw the introduction of the solids handling pump in the early 1990s, this combined with other modifications to dredge design has meant that catch smash rates of around 20% in the 1970s have now mostly been reduced to below 5%.

As the industry modernised, new vessels were built with even greater catching capacity, which in turn triggered the need for improved monitoring and management of the fishery. In 1991 new European Shellfish Hygiene legislation came into operation, which proceeded to open up the fishery and put increased pressure upon stocks, to a level that could be detrimental to its sustainable long term production. To counteract this K&E SFC worked with the local cockle industry to develop the present day level of fishery management.

Management of the cockle stocks

To help develop and protect the cockles within the district a series of byelaws were passed which laid down the conditions by which people could remove cockles in a way that was deemed sustainable. To this end there are byelaws limiting:

· maximum vessel size

· engine power

· dredge size

· minimum cockle size

· maximum damage rate

· closure of beds/closed season

· fishing times and quantities landed

· additional fishing permit requirements

The Thames Estuary Cockle Fishery Regulating Order came into operation in 1994 and covers the major section of the fishery (picture below), only 14 vessels are licensed to fish for cockles within this area. An important part of management has been policy that closes beds to commercial exploitation once stock levels drop below set limits.

In addition to local vessels, up to 20 visiting vessels from the Wash and West coast ports have worked the outer areas not covered by the Regulating Order. Skippers are required to return catch data showing area fished, quantity taken and fishing time.

Kent and Essex Sea Fisheries District - Cockle Harvesting Areas

This chart is for illustrative purposes only, for exact details of fishing areas contact K&E SFC

These grounds are within the area covered by the Thames Estuary Cockle Fishery Order 1994. A licence granted under the Order is required in addition to a permit issued under Byelaws.

1 Marsh End and Chapman Sands

2 East of Pier

3 West of Shoebury Boom

4 East of Shoebury Boom

5a South Maplin

5b Mid Maplin

6 North Maplin and Foulness Sand

8 East Barrow and Maplin Spit

9 West Barrow

11 East Cant, Middle and Red Sand

12 Sunk Sand

13 West Cant and Scrapsgate

15 North Margate Sand and Pan Sand

16 Shingles and Long Sand

These beds are outside the area of the Thames Estuary Cockle Fishery Order. Cockles taken from within these areas are subject to K&ESFC Byelaws.

1a Inner Estuary

7 Buxey and Dengie Sands

10 Pollard, Columbine and Whitstable

14 South Margate Sands

17 South Kent Coast to Dungeness

18 Gunfleet Sand

19 Blackwater Estuary

20 Wallet and North Essex Coast

Assessing cockle stocks

It is assumed that environmental conditions are by far the largest factor governing recruitment. Due to the relatively short life cycle of cockles due to natural mortality (mean natural mortality rates have been calculated as 64% during their first winter, 28% during their second winter and third winter) there are few cockles above 5 years old found on the exposed grounds, even in areas that have not been fished. This makes long-term management difficult with high dependence on continued new recruitment into the fishery. For this reason it is vital, for the sustainable management of the fishery, to assess the spawning stock on an annual basis.

The management of the cockle stocks aims to regulate exploitation of the stock and maintain a core spawning biomass of adult cockles. To achieve this cockle socks are surveyed twice a year to assess their density and size distribution. Annual Total Allowable Catch (TAC) limits are set following completion of Spring surveys carried out during April. These assess remaining stock on the major beds and this information is combined with other stock data resulting in a TAC set at a maximum level of 33% of adult stock.

Cockle surveys on the areas Maplin and Foulness Sands have been carried out for nearly 20 years. Initially they were carried out using trials bikes, however in the last few years quad bikes have proved far easier to use in this environment. Quadrate samples are taken along the sands every quarter of a minute of latitude and longitude, and the number and age of the cockles at each location is recorded. The mean weight of cockles for each age group is also calculated for each management area. In conjunction to this the patrol vessel also uses a day grab to sample cockles in other areas within the Regulating Order.