A comparison of the effect of different types of clam rakes on non‐target, subtidal benthic fauna

Figures & data

Figure 1 The hydraulic rake. In the foreground a fisherman shows how to rake clams; in the back the motor pump that, when connected trough the rubber hose to the rake, is used to expel water through the rake jets.

Figure 2 The hydraulic rake: particular of jets from which water is expelled under pressure.

Table I. Two‐way ANOVA for treatments (MR, HR, C) and time relative to macrofaunal community descriptors at the muddy site (T×T: interaction term).

Factor	F	P	1−β
Number of species
Treatment	6.85	0.003
Time	1.46	0.24	0.55
T×T	0.49	0.81
Abundance
Treatment	5.12	0.01
Time	1.04	0.38	0.50
T×T	0.38	0.88
Evenness
Treatment	4.36	0.02
Time	2.47	0.07	0.60
T×T	0.19	0.98
Diversity
Treatment	3.04	0.04
Time	1.08	0.37	0.48
T×T	0.32	0.93

Table II. Abundance (ind m⁻²) for control (C) and treatments (MR, HR) at time 0, and similarity percentage (SIMPER) analysis at the muddy site (cut‐off: 70%). MR, manual rake; HR, hydraulic rake; C, control.

Species	Control	Treatment	Contribution (%)	Cumulative (%)
C vs MR: average dissimilarity = 28.6
Polydora ciliata	548.0	362.2	18.63	18.63
Corophium orientale	431.1	300.0	16.99	35.62
Streblospio shrubsolii	381.1	354.5	10.70	46.32
Melita palmata	101.0	55.1	6.94	53.26
Corophium insidiosum	100.1	51.8	6.63	59.89
Neanthes succinea	247.2	193.5	6.56	66.45
Oligochaeta sp.	143.2	121.0	4.69	71.14
C vs HR: average dissimilarity = 34.07
Polydora ciliata	548.0	391.9	18.50	18.50
Corophium orientale	431.1	266.0	16.73	35.23
Streblospio shrubsolii	381.1	222.0	11.87	47.10
Neanthes succinea	247.2	158.0	6.59	53.69
Corophium insidiosum	100.1	69.6	4.51	58.20
Gammarus aequicauda	0.0	50.0	3.98	62.18
Melita palmata	101.0	84.0	3.73	65.90
Oligochaeta sp.	143.2	106.9	3.70	69.60
Gammarus insensibilis	24.4	42.6	3.26	72.86
MR vs HR: average dissimilarity = 34.56
Polydora ciliata	362.2	391.9	17.24	17.24
Corophium orientale	300.0	266.0	14.97	32.21
Streblospio shrubsolii	354.5	222.0	12.68	44.90
Melita palmata	55.1	84.0	5.96	50.85
Neanthes succinea	193.5	158.0	4.91	55.76
Gammarus aequicauda	0.0	50.0	4.90	60.67
Oligochaeta sp.	121.0	106.9	4.83	65.50
Ruditapes philippinarum	19.6	60.7	4.17	69.66
Corophium insidiosum	51.8	69.6	4.08	73.74

Table III. Two‐way ANOVA for treatments (MR, HR, C) and time relative to macrofaunal community descriptors at the shallow sandy site (T×T: interaction term).

Factor	F	P	1−β
Number of species
Treatment	7.90	0.003
Time	3.08	0.051	0.45
T×T	0.49	0.81
Abundance
Treatment	34.74	<0.001
Time	3.01	0.054	0.50
T×T	1.02	0.41
Evenness
Treatment	11.07	<0.001
Time	5.15	0.008
T×T	2.84	0.036
Diversity
Treatment	25.93	<0.001
Time	4.78	0.011
T×T	7.79	0.001

Table IV. Abundance (ind m⁻²) for control (C) and treatments (MR, HR) at time 0, and similarity percentage (SIMPER) analysis at the shallow sandy site (cut‐off: 70%). C, control; MR, manual rake; HR, hydraulic rake.

Species	Control	Treatment	Contribution (%)	Cumulative (%)
C vs MR: average dissimilarity = 42.98
Ampelisca sarsi	242.0	72.2	17.70	17.70
Streblospio shrubsolii	203.5	52.2	15.02	32.72
Spio decoratus	431.4	300.4	14.44	47.16
Capitella capitata	186.1	88.4	10.59	57.75
Oligochaeta sp.	58.1	45.1	7.46	65.22
Polydora ciliata	78.1	14.4	5.98	71.19
C vs HR: average dissimilarity = 31.69
Ampelisca sarsi	242.0	136.2	16.84	16.84
Streblospio shrubsolii	203.5	153.2	13.47	30.31
Spio decoratus	431.4	405.2	11.81	42.12
Oligochaeta sp.	58.1	120.3	11.52	53.64
Capitella capitata	186.1	184.3	10.64	64.28
Polydora ciliata	78.1	81.0	7.85	72.13
MR vs HR: average dissimilarity = 38.81
Spio decoratus	300.4	405.2	14.15	14.15
Streblospio shrubsolii	52.2	153.2	12.43	26.58
Capitella capitata	88.4	184.3	11.66	38.24
Oligochaeta sp.	45.1	120.3	11.53	49.77
Ruditapes philippinarum	31.8	108.0	9.67	59.44
Polydora ciliata	14.4	81.0	8.46	67.90
Ampelisca sarsi	72.2	136.2	8.14	76.04

Table V. Two‐way ANOVA for treatments (MR, HR, C) and time relative to macrofaunal community descriptors at the deeper sandy site (T×T: interaction term).

Factor	F	P	1−β
Number of species
Treatment	1.75	0.21	0.20
Time	13.42	0.001
T×T	6.49	0.01
Abundance
Treatment	1.03	0.33	0.12
Time	5.31	0.02
T×T	2.54	0.11
Evenness
Treatment	13.74	0.003
Time	2.76	0.09	0.25
T×T	2.83	0.08
Diversity
Treatment	51.07	<0.001
Time	23.21	<0.001
T×T	15.48	<0.001

Table VI. Abundance (ind m⁻²) for control (C) and treatment (CR) at time 0, and similarity percentage (SIMPER) analysis at the deeper sandy site (cut‐off: 70%). C, control; CR, conveyor rake.

Species	Control	Treatment	Contribution (%)	Cumulative (%)
C vs CR: average dissimilarity = 37.16
Heteromastus filiformis	141.0	203.5	10.19	10.19
Melita palmata	81.4	9.3	9.62	19.81
Polydora ciliata	68.1	119.5	9.22	29.03
Streblospio shrubsolii	102.1	116.2	7.57	36.60
Ruditapes philippinarum	125.1	111.0	7.17	43.77
Neanthes succinea	101.0	85.1	6.42	50.19
Ampelisca sarsi	32.6	37.7	6.33	56.53
Capitella capitata	60.3	29.6	6.06	62.58
Spio decoratus	131.0	117.7	5.81	68.39
Oligochaeta sp.	67.7	74.7	4.42	72.81