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e 70-- 60- '* 50 CO 13 a. 40- 10 / •%! SEASONAL VARIATION IN BODY WEIGHT OF BIVALVES •83 •85 r,0.79 / p-0.02/ &A—86 so* ' y «8? I 20 I I 30 weight increment (mg) Fig. 12. Relation between highest annual body weight af Macoma in the eastern pan of the Dutch Wadden Sea (Fig. 91 and the annual weight increment of a 7-mm specimen in the western Wadden Sea (dala Irom Beukema & Cadee 1991). Tit* years concerned are indicated August (Fig. 11). There are two cohorts each year in southern areas (Hughes 1972. Bachelet 1981. Worrall ei al. 1983. Essink et al 1991). Spawning causes a 20% reduction of body weight and occurs in a period during which animals lose weight (Fig. II). The species improves its body condition during September and even October (Fig. 8). In contrast, a seasonal decrease in body weight as a consequence of spawning was not found in either Mya or Cerastoderma (Fig. 8). The reason is that, just like Macoma. but not in Scrobicularia. spawning occurs during the growing season: in June for Mya (Munch-Petersen 1973) and in May-June for Cerastoderma (Baggerman 1953. Boyden 1971, Kingston 1974, Newell & Bayne 1980, Yankson 1986). Annual differences Beukema & Cadee (1991) showed that the year-toyear variability in weight gain, and other parameters of growth rate, in Mamma depend on the food supply. i.e. the abundance of diatoms during the spring months. The annual weight gain measured in the western part of the Dutch Wadden Sea (Beukema & CadtSe 1991) and the annual variation in the peak 40 condition, measured 100 km to the east (Fig. 9). appear to be highly correlated (Fig. 12). This suggests that there is a similar common pattern of annual fluctuations in the feeding conditions for the macrozoobenthos over vast areas (see Figs. 4, 7 and 9 in de Jonge & Essink 1991). Regional differences Figures 13-16 summarize the available measurement on body weighi of the lour species from elsewhere, and compares them with the data from the study sites in the eastern part of the Dutch Wadden Sea. Since the seasonal trends and annual variations in Macoma on Balgzand, 1(X) km Io the west, closelv resemble those from our study sites (Beukema & de Bruin 1977. Beukema et al. 1985. Beukema & Desprez 1986). they are not presented to avoid cluttering Fig. 13. Several conversions had to be done in order to make the different dala sets comparable; see legends to Figs. 13- 16. In general, the seasonal variations in ihe Wadden Sea and elsewhere did not differ (very) much: the summer peak was about as high, and the winter weight was about 40 to 5096 below the summer weight There were, however, some interesting differences. The summer peak in Macoma. reached in May and June in the Wadden Sea (Fig. 13). occurred a month later in the Baltic Sea. (Pekkarinen 1983, Bonsdorfl & Wenne 1989) and Nova Scotia. Canada (Cranford et al. 1985). but a month or two earlier in S. France (Bachelet 1980). The low weight in the French population during the summer, and the subsequent increase in body weight in September, has been attributed to the occurrence of two spawning periods (Bachelet 1980, see Harvey & Vincent 1989 for a review). A detailed analysis of the regional variation in the improvement of the condition in spring has been given by Beukema & Desprez (1986). The seasonal variation in body weight of Scrobicularia in S. England (Bryan & Hummerstone 1978. Boates & Goss-Custard 1989) and the Wadden Sea is similar (Fig. 14). though Scrobicularia retain a remarkable high winter weight in N. Wales (Hughes 1970b). The great variation in the body weight in SW. France can partly be attributed to systematic differences in sites studied (Bachelet 1979. 1981). The seasonal variation of Mya in the Wadden Sea was similar to thai recorded elsewhere (Munch-
a E 400 - S. plana 35 mm 320 240 160 BO SEASONAL VARIATION IN BODY WEIGHT OF BIVALVES N-WALES »|1) S-EW31AN0 A(2) v*(3) 0(4) SWFRANCE D(5| I I I I I i ' i ' ' i J F M A M J J A S O N D .;i Ki|>. 13, Seasonal variation in Ihe AFDW of the soft parts of Macoma (15 mm) in seven studies compared with the results ohiamed at ihe study sues in the eastern pan ol ihe Duich Wadden Sea (dark: monthly range between 25 and 75 percentiles; light: ranges between 10- 25 en 75-90 percentiles). Other studies < 11 BoOBdorff/Jt Weune 11989); they give DW for specimens 13 mm long; percentages ash Irom Fig. 4 are used lo estimate AFDW these VallKS lire iiiullipliedbv 1.52 to obtain AFDW of individuals 15 mm long I Table 6). I-I I'ekkarineii (1983); concilium nuiev of DW is given; these are convened to weights, ana which ihe percentage ash given in her paper are used to estimate AFDW. (3) Madsen .v Jensen il>)S7); they prcsenl Ihe condition index of AFDW. which is transformed into the weight of an animal of 15 mm. (4i Chambers & Milne 11975a): thev relale DW to shell height; their relaiion between shell height and length is used io calculate DW ol bivalves Is mm long; percentage ash. given in Fig. 4. is used io estimate AFDW (5) tjcss-Custard ei al. (1977a). (6) Bachelet 11980). (7) Heukema & Desprez (I ••• Fi)>. 14. Seasonal variation in the AFDW of the soft parts of Scrobicularia (35 mm) in live sludies. compared with ihe eastern pan of the Dutch Wadden Sea (dark: monthly range between 25 and 75 percentiles: light: ranges between 10-25 and 75-90 percentiles). Other studies; i 11 Hughes 11970b); he presents DW as a function of si/e; percentage ash. given in le 2. is used lo calculate AFDW. (2) Bryan & Itonmerstone I ITS. I j) Worrali «•• .1/ (1983); weights of a standard annual M> mm long are mulliplied by I 57 to obtain AFDW of individuals 33 mm long I this paper). (4) Boates & Goss-Custard (I9S9). (5) Bachelet (1979. 1981)
Page 1 and 2: WADERS AND THEIR ESTUARINE FOOD SUP
Page 3 and 4: plia^ohi. WADERS AND THEIR ESTUARI
Page 5 and 6: Waders and their estuarine food sup
Page 7 and 8: WADERS AND THEIR ESTUARINE FOOD SUP
Page 10 and 11: figuren: Dick Visser omslagfoto: Ja
Page 12 and 13: 15 Versatility of male curlews (Num
Page 15 and 16: That science is making progress, ma
Page 17 and 18: INTRODUCTION The remnants of brushw
Page 19 and 20: When hcnlhic bivalves extend llien
Page 21 and 22: the burrow depths and on the fracti
Page 23 and 24: INTRODUCTION Ms,i invest 409 of (he
Page 25 and 26: able lo sw itch 10 oiher prey which
Page 27 and 28: Long-term, broadly-based research c
Page 29 and 30: Chapter 1 SEASONAL VARIATION IN BOD
Page 31 and 32: SEASONAL VARIATION IN BODY WEIGHT O
Page 33 and 34: Tahle 1 Weight loss ('•- ± SE) m
Page 39 and 40: i 60 50 40 30 20 10 0 • INFESTED
Page 41 and 42: 240- SEASONAL VARIATION IN BODY WEI
Page 43: 20 10 0 -10 -20h 2 3 4 5 6 7 8 9 se
Page 49 and 50: Chapter 2 HOW THE FOOD SUPPLY HARVE
Page 51 and 52: FOOD SUPPLY HARVESTABLE BY WADERS H
Page 53 and 54: Methods The study sites were situat
Page 55 and 56: less than that of bivalves, partly
Page 57 and 58: I Fig. 3). Peak condition was reach
Page 59 and 60: total biomass since most of those t
Page 61 and 62: on the basis of the preceding and t
Page 63 and 64: However, for obvious reasons, we ma
Page 65 and 66: prey. A decrease in the prey densit
Page 67 and 68: Tahle 2. The intake rate ol < lyste
Page 69 and 70: * ' % -. . ; a X - . - * • ^ •
Page 71 and 72: (Zwarts & Wanink 1989). In quiet we
Page 73 and 74: general law relating handling time
Page 75 and 76: nearly twice as much time (0.79 s).
Page 77 and 78: 4 5 6 7 8 9 size class of Corophium
Page 79 and 80: and annually. Second, the lower siz
Page 81 and 82: Prey switching Waders feeding on ti
Page 83 and 84: autumn and spring, and the contrary
Page 85 and 86: where they switch to surface-living
Page 87 and 88: Chapter 3 BURYING DEPTH OF THE BENT
Page 89 and 90: DEPTH AND SIPHON CROPPING IN SCROBI
Page 91 and 92: I DEPTH AND SIPHON CROPPING IN SCRO
Page 93 and 94: DEPTH AND SIPHON CROPPING IN SCROBI
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Table 3. Three-Way analysis Of vari
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Chapter 4 SIPHON SIZE AND BURYING D
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15 20 size (mm) Fig. 3. Cerasioderm
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10 size (mm) SIPHON SIZE AND DEPTH
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o, 7 01 5 | * CL 5- SIPHON SIZE AND
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4 Q) Si •a a. 16- 20- A predator:
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prey risk for an animal al a depth
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Table 6. Size al which there is a m
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* ' 1 /-/ "».-^*«C
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face and so expose themselves to a
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surface in die containers was varie
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50 OOF 310.00 I 5.00 ^ 1.00 3=" 0.5
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Tahle 1. Macoma and Scrobicularia.
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siphon would not have to reach the
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known siphon weight and burying dep
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ACCESSIBLE PREY ARE OFTEN IN POOR C
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1 2 3 4 burying depth (cm) Kin. I.
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I—1 • • : : : : ! - ! -|-r 0
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Chapter 7 DOES AN OPTIMALLY FORAGIN
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OPTIMAL FORAGING AND THE FUNCTIONAL
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100 200 300 prey density (n-m-2) Fi
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Table I. Results of five one way an
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Table 2. Results of eight iwo-wav a
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prey density II III Fig. 12. Freque
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PREY SIZE SELECTION AND INTAKE RATE
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Predicted 'passive size selection'
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lig. 2. Larger Mussels are less ava
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Fig. 5. Scrobicularia plana. Size c
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and maiiv are too thick-shelled to
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The measurements of handling time i
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1 2 3 4 5 6 7 probing depth (cm PRE
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valves may vary by a factor of two
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optimal foraging model, the minimum
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their gut is full? Do they reduce t
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PREY PROFITABILITY AND INTAKE RATE
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catchers to take only certain prey
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licult error of estimate arose if p
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Counts of feeding and non-feeding b
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20 30 40 50 shell length (mm) PREY
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Nereis Arenicola tipuia earthwo'm M
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take rate. We might therefore expec
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prey species, using parallel slopes
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5.0 4.0 1-3.0 a & • % * • * •
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time during the feeding period. As
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winter. Similarly, handling time in
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5.0 - f-4.0 S 3.0 in I 20 a 2 a | 1
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situation arrived in the western pa
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• ' • 14 PREY PROFITABILITY AND
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Notes lo appendix: PREY PROFITABILI
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Chapter 10 WHY OYSTERCATCHERS HAEMA
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2 4 6 8 10 time on feeding area (h)
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80- 60- o 80 60- 40- 20- INTAKE RAT
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est of bod\ behind: an estimated 22
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INTAKE RATE AND PROCESSING RATE IN
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Wanink 1993). The energy content of
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(7) Age All studies dealt with adul
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irds over long periods. As an examp
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Discussion There is no difference i
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comparison between the weight of ih
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. 1', L ! •
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Introduction PREDICTING SEASONAL AN
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PREDICTING SEASONAL AND ANNUAL FLUC
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1000 r 1 II" 1 - r^Jan'80 PREDICTIN
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Page 248 and 249:
Page 250 and 251:
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IOO BO 60 40 20 0 PREDICTING SEASON
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WHY KNOT TAKE MEDIUM-SIZED MACOMA W
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in Zwarts & Esselink 1989). The len
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shell length (mm) FIR. 3. Peringia.
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fused, specimens larger than this w
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50 100- s s I — f = S. plana, n=2
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area is twice as large as the touch
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10 15 lower size threshold (mm) Fig
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lime (Hughes 1979). This would furt
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WHY KNOT TAKE MEDIUM-SIZED MACOMA T
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Chapter 13 ANNUAL AND SEASONAL VARI
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VARIATION IN FOOD SUPPLY OF KNOT AN
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Two sites (N and M in Fig. 2) were
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20 30 VARIATION IN FOOD SUPPLY OF K
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20 l i r'l ' i •o j^y^T n ^ ' " ^
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July ' Aug ' Sept Fig. 9. Proportio
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available. There must, however, be
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Chapter 14 SEASONAL TREND IN BURROW
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BURROWING AND FEEDING IN NEREIS SEA
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Table 2. Results of a 2-way analysi
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June 1981 June 1982 is * N.MUD •
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8 10 I 12 JZ 5. -g 1*» •e o i 16
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6 - n=!080 5 • g 4 CP > i 3 CO CD
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1985) and Curlew (/wails ,v, Lsseli
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Chapter 15 VERSATILITY OF MALE CURL
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Smid! 1951. Muus 1967, Wolff 1973,
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0.6 0.8 1.0 1.2 1.4 1.6 jaw lengih
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Na oi both Nrieck Fig. 7. Numenius
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6 8 10 12 14 16 18 worm length (cm)
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too (Fig. 11 A). Indeed, the averag
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VERSATILITY OF CURLEWS FEEDING ON N
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total time spent al the surface. Th
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2 4 . • 2.2 • 30 .-.2.0 to Q. 1
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PREY DEPLETION BY OYSTERCATCHER AND
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the rule: the observed lower limit
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to locate the clams after they had
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Curlew, by bury ing some hundreds o
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PREY DEPLETION BY OYSTERCATCHER AND
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SAMENVATTING 345
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Voorgeschiedenis In 1960 verscheen
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maken. Als gebied A een grotere voe
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omdat ze nog vrijwel niets wegen. l
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kunnen opzuigen. of diep leven en z
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van de uitgerekte sifo over het wad
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het toen niet gemakkelijk hebben ge
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doende nonnetjes van 10 tot 15 mm l
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aangevoerde voedsel en de wulp past
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zijn dan twee jaar en wulpen geen s
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was dan ook dank/ij de inzet van al
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REFERENCES 367
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Allen RL. 1983. Feeding behaviour o
Page 367 and 368:
BreyT. 1989. Der Einfluss physikali
Page 369 and 370:
latie tol chironoiiiiilen en de wai
Page 371 and 372:
huch der Vogel Milteleuropas, Band
Page 373 and 374:
llolmann II. & H. Huerschelmann 196
Page 375 and 376:
l-cndrem D.W. 1984. Flocking, feedi
Page 377 and 378:
Pekkarinen M. 1984. Regeneration of
Page 379 and 380:
lion of Mussels Mytilus edulis hy O
Page 381 and 382:
lulal Dal esiuanes: a comparison of
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