318
J. van der Meer et al.
made above are warranted, one may wonder how relevant the results actually are.
Preferably, production is directly estimated by, for example, the mortalitysummation method (Crisp 1984). This method, however, requires knowledge
of the age-structure of the population and the changes therein. As this knowledge is rarely available, in most cases published species-specific production/biomass ratios (P /B ratio) were used instead, in combination with species
biomass estimates. Only in one study (Baird and Milne 1981) were estimates
based on direct methods and then only for one or two species (Table 15.1). Predation causes mortality of the prey and may thus enhance production and
turnover rate. Thus, predation itself may increase the P/B ratio, and a certain
amount of circularity occurs when consumption/production ratios are used
to study the impact of predation assuming constant P /B ratios.
Table 15.1. Annual consumption by shorebirds C (g AFDM m- 2 ), macrozoobenthos
biomass B (g AFDM m- 2 ) and annual zoobenthic production P (g AFDM m- 2 ) for various
intertidal areas
Area
Region a C
B
P
Method b
Source(s)
Ythan
W
39.7 59.8 111.4 ms;PIB
Baird and Milne (1981)
Tees
W
17.1
44.4 38.7
PIB
Evans et al. (1979)
Wadden Sea
W
5.0
26.6 29.6
PIB
Beukema (1976, 1981);
Smit (1981); De Wilde
and Beukema (1984)
Grevelingen C
W
8.3
46.8 56.1
PIB
Wolff et al. (1976);
Wolff and De Wolf
(1977)
Oosterschelde W
12.3
74.3
Meire et al. (1994)
Westerschelde W
4.5
14.6
Meire et al. (1989);
Stuart et al. (1989)
Tagus
S
4.9
40.8
guess
Moreira (1997)
Banc d' Arguin A
14.0
14.5 27.0
guess
Wolff and Smit (1990);
Wolff (1991); Wolff et
al. (1993)
Maputo
A
2.1
De Boer and
Longamane (1996)
Berg River
A
26.7
19.4 87.6
PIB
Summers (1977); Baird
et al. (1985)
Langebaan
A
6.4
9.3
32.0
PIB
Velasquez et al. (1991);
Kalej ta (1992)
a W, Western Europe; S, southern Europe; A, Africa.
b Production is estimated by the mortality-summation method (ms), through published
PIB ratios (PIB) or guessed.
C The figures presented here refer specifically to the intertidal area and can be derived
from the original published figures.
J. van der Meer et al.
made above are warranted, one may wonder how relevant the results actually are.
Preferably, production is directly estimated by, for example, the mortalitysummation method (Crisp 1984). This method, however, requires knowledge
of the age-structure of the population and the changes therein. As this knowledge is rarely available, in most cases published species-specific production/biomass ratios (P /B ratio) were used instead, in combination with species
biomass estimates. Only in one study (Baird and Milne 1981) were estimates
based on direct methods and then only for one or two species (Table 15.1). Predation causes mortality of the prey and may thus enhance production and
turnover rate. Thus, predation itself may increase the P/B ratio, and a certain
amount of circularity occurs when consumption/production ratios are used
to study the impact of predation assuming constant P /B ratios.
Table 15.1. Annual consumption by shorebirds C (g AFDM m- 2 ), macrozoobenthos
biomass B (g AFDM m- 2 ) and annual zoobenthic production P (g AFDM m- 2 ) for various
intertidal areas
Area
Region a C
B
P
Method b
Source(s)
Ythan
W
39.7 59.8 111.4 ms;PIB
Baird and Milne (1981)
Tees
W
17.1
44.4 38.7
PIB
Evans et al. (1979)
Wadden Sea
W
5.0
26.6 29.6
PIB
Beukema (1976, 1981);
Smit (1981); De Wilde
and Beukema (1984)
Grevelingen C
W
8.3
46.8 56.1
PIB
Wolff et al. (1976);
Wolff and De Wolf
(1977)
Oosterschelde W
12.3
74.3
Meire et al. (1994)
Westerschelde W
4.5
14.6
Meire et al. (1989);
Stuart et al. (1989)
Tagus
S
4.9
40.8
guess
Moreira (1997)
Banc d' Arguin A
14.0
14.5 27.0
guess
Wolff and Smit (1990);
Wolff (1991); Wolff et
al. (1993)
Maputo
A
2.1
De Boer and
Longamane (1996)
Berg River
A
26.7
19.4 87.6
PIB
Summers (1977); Baird
et al. (1985)
Langebaan
A
6.4
9.3
32.0
PIB
Velasquez et al. (1991);
Kalej ta (1992)
a W, Western Europe; S, southern Europe; A, Africa.
b Production is estimated by the mortality-summation method (ms), through published
PIB ratios (PIB) or guessed.
C The figures presented here refer specifically to the intertidal area and can be derived
from the original published figures.