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2. Methodology

The modern cockles were obtained from areas of the widest possible type of collection practices: a commercially exploited site in Wales, an undisturbed cockle population in Scotland and two recovering populations in Essex and Lincolnshire. It was thought that the differences in collection methods at the modern sites would provide contrasting age curves that may help to highlight changes in cockle exploitation through time. The result of the age curve analysis is given in section 3.2 (see Figures 11, 12, 13 and 14).

Each collector was asked to provide at least 25 cockle shells collected once per month for 24 consecutive months. A two-year period of collection was chosen in order to highlight any inter-year variability in growth patterns. Receipt of samples from all sites did not cover the full 24 months (see Table 1); however, enough months were covered to provide a good record of cockle size, age and growth patterns.

Table 1: The dates and number of cockle valves received from the modern British collection sites

Lincolnshire Collection dateNumber of valves received
Left Right
Friskney 17/02/2003 20 19
Butterwick and Wrangle 16/06/2003 33 32
Butterwick 11/08/2003 38 46
Butterwick and Wrangle 10/11/2003 39 40
Butterwick 08/12/2003 25 25
Total Number of Samples 155 162
Essex Date of receipt Number of valves received
Left Right
Buxey Sands 15/09/2003 25 25
30/09/2003 25 25
13/11/2003 28 28
12/02/2004 21 21
10/05/2004 25 25
16/11/2004 26 26
Total number of samples 150 150
WalesDate of receiptNumber of valves extracted
Left Right
Burry Inlet 14/02/2003 50 50
19/03/2003 53 53
12/05/2003 50 50
25/07/2003 50 50
18/09/2003 39 50
03/10/2003 26 50
08/11/2003 21 25
10/12/2003 32 32
12/01/2004 25 25
02/02/2004 30 25
08/03/2004 25 25
06/04/2004 30 30
25/06/2004 39 40
20/07/2004 54 54
Total number of samples 524 559
ScotlandCollection dateNumber of valves received
Left Right
Mill Sand 28/02/2003 24 25
24/03/2003 27 28
30/04/2003 28 23
31/05/2003 33 31
30/06/2003 33 33
31/07/2003 30 30
31/08/2003 29 29
28/09/2003 31 29
28/10/2003 41 41
26/11/2003 25 25
07/12/2003 30 30
07/03/2004 30 30
25/04/2004 25 25
30/05/2004 30 30
30/06/2004 25 25
21/08/2004 30 30
15/09/2004 31 31
17/10/2004 29 29
Total number of samples 531 524

Archaeological cockles were collected from the two Danish shell midden sites of Krabbesholm and Norsminde; see Figure 3 for the locations.

On receipt of the archaeological unsorted midden samples, they were dried in the laboratory and then sorted into mollusc species and other materials such as bone and pottery. The mollusc species were counted to provide a minimum number of individuals (MNI) using the undamaged apices of the gastropods and the undamaged hinges of the bivalves. All whole cockle valves were extracted and measured for height, width and length dimensions. The cockles were also aged using the external annual growth lines.

The modern cockles were also measured and aged. Suitable valves were then selected from both archaeological and modern collections for dissection and acetate peel manufacture; for numbers of valves used at each stage of analysis see Table 2.

Figure 3: Map showing the location of Krabbesholm and Norsminde midden sites in Denmark.
Figure 3: Map showing the location of Krabbesholm and Norsminde midden sites in Denmark

Table 2: The number of modern and archaeological cockle valves used at different stages of analysis

Modern locations Total number of samples Number of valves measured and aged Number of valves selected for acetate peels Number of successful peels
Essex 300 300 60 27
Lincolnshire 317 317 50 34
Scotland 1055 1055 180 119
Wales 1073 1073 140 101
Totals 2745 2745 430 281
Archaeological locations Total number of samples Number of valves aged Number of valves measured Number of valves selected for acetate peels Number of successful peels
Norsminde 2521 2511 2521 100 57
Krabbesholm 7737 432 372 432 69 42
Krabbesholm 7738 419 405 419 55 31
Totals 3372 3288 3372 224 130

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Last updated: Tues Oct 2 2007