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Table 2a. Summary of Hudson-Raritan Estuary winter flounder diet by sampling period during 1996-97, expressed as the percent frequency of occurrence of dominant prey or items (FO), and as the mean percent contribution of dominant prey or items to total stomach content volume (TV). (n = sample size; ES = percent of empty stomachs.)

Prey

Sampling Period

Jul 96
(n = 89; ES = 6.7)
Oct 96
(n = 55; ES = 14.5)
Jan 97
(n = 135; ES = 42.2)
Apr 97
(n = 209; ES = 2.9)
Aug 97
(n = 83; ES = 16.9)
Nov 97
(n = 139; ES = 15.8)
FO
TV
FO
TV
FO
TV
FO
TV
FO
TV
FO
TV
Unidentified organic matter 24.7 5.5 34.6 11.7 5.9 20.5 14.8 2.0 55.4 21.1 30.2 6.6
Northern quahog siphons 26.9 18.5 25.5 23.9 0.7 1.3 22.5 9.0 7.2 4.9 24.5 11.0
Ampelisca abdita 9.0 3.7 25.5 5.8 6.7 4.2 21.1 3.7 3.6 1.1 32.4 7.6
Atlantic surfclam siphons 11.2 2.6 25.5 9.0 0.0 0.0 45.9 31.3 2.4 1.1 22.3 21.5
Unidentified polychaetes 23.6 9.1 9.1 2.9 2.2 1.3 20.1 6.8 3.6 1.8 12.9 4.0
Neomysis americana 1.1 1.0 3.6 2.0 41.5 23.6 3.4 0.1 1.2 0.7 2.2 0.2
Unidentified clam siphons 2.2 0.9 1.8 0.3 0.7 1.3 11.5 6.9 18.1 12.7 1.4 1.7
Unciola sp. 0.0 0.0 20.0 5.8 7.4 6.8 0.5 <0.1 1.2 0.4 6.5 2.2
Blue mussel juveniles 2.2 1.4 3.6 0.6 0.0 0.0 7.3 10.5 0.0 0.0 0.0 0.0
Asabellides oculata 10.1 4.2 0.0 0.0 1.5 0.4 0.9 0.1 15.7 12.0 5.8 1.7
Corophium sp. 10.1 3.1 10.9 5.5 0.0 0.0 3.4 0.4 1.2 0.7 1.4 <0.1
Glycera sp. 14.6 11.7 1.8 1.7 0.0 0.0 3.4 1.0 2.4 6.7 2.9 2.5
Unidentified hydroids 2.2 2.1 0.0 0.0 0.0 0.0 11.9 5.1 8.4 7.8 2.9 0.9
Gammarus lawrencianus 6.7 4.5 5.5 2.6 5.9 6.3 1.0 0.3 0.0 0.0 3.6 1.2
Atlantic rock crab juveniles 19.1 10.5 0.0 0.0 0.0 0.0 1.4 1.5 1.2 3.3 1.4 0.3
Crangon septemspinosa 6.7 2.5 0.0 0.0 3.7 1.3 3.4 0.9 6.0 6.9 2.2 0.4
Nemerteans 9.0 3.9 0.0 0.0 1.5 19.8 7.7 3.7 0.0 0.0 0.0 0.0
Table 2b. Summary of Hudson-Raritan Estuary winter flounder diet by predator size group during 1996-97, expressed as the mean percent contribution of dominant prey or items to the total stomach content volume. (n = number of nonempty stomachs included.)
Prey
Winter Flounder Size Group (cm TL)
6.0 - 9.9
(n = 44)
 10.0 - 19.9
(n = 291) 		20.0 - 29.9
(n = 158) 		30.0 - 45.0
(n = 85)
Neomysis americana 40.81 6.20 0.01 0.00
Detritus 14.47 11.80 3.40 1.70
Ampelisca vadorum 8.75 5.90 3.30 0.20
Unciola sp. 6.75 0.70 0.05 0.10
Unidentified polychaetes 5.34 5.85 3.70 1.40
Hydroids 5.34 2.32 1.90 3.50
Blue mussel spat 3.69 0.63 0.46 0.65
Northern quahog siphons 1.86 14.20 19.60 4.40
Atlantic surfclam siphons 1.80 8.10 32.30 69.50
Bivalve mollusk remains 0.85 3.01 0.74 12.50
Glycera sp. 0.00 5.26 4.32 1.00
Crangon septemspinosa 3.39 2.55 0.67 0.31
Ensis directus 0.00 0.27 5.10 0.02
Table 2c. Summary of Hudson-Raritan Estuary juvenile winter flounder (less than 20 cm TL) diet by sampling period during 1996-97, expressed as the mean percent contribution of dominant prey or items to total stomach content volume. (n = number of nonempty stomachs included.)
Prey
Sampling Period
Jul 96
(n = 63)		 Oct 96
(n = 39)		 Jan 97
(n = 65)		 Apr 97
(n = 65)		 Aug 97
(n = 47)		 Nov 97
(n = 56)
Northern quahog siphons 10.50 23.77 0.01 7.68 3.59 22.15
Atlantic surfclam siphons 7.36 21.49 0.00 8.63 1.53 7.82
Ampelisca vadorum 3.98 11.20 4.28 7.03 0.93 8.62
Gammarus lawrencianus 7.42 1.68 13.06 0.00 0.00 0.65
Sabellaria vulgaris 3.34 3.20 0.39 0.00 19.52 0.00
Neomysis americana 0.11 0.00 62.47 5.80 0.00 0.17
Crangon septemspinosa 3.98 0.00 2.53 3.53 4.05 1.30
Unciola sp. 0.00 8.00 4.46 0.06 1.29 0.07
Detritus 6.64 17.68 2.96 5.14 26.10 22.15
Table 2d. Summary of Hudson-Raritan Estuary adult winter flounder (greater than or equal to 20 cm TL) diet by sampling period during 1996-97, expressed as the mean percent contribution of dominant prey or items to total stomach content volume. (n = number of nonempty stomachs included.)
Prey
Sampling Period
Jul 96
(n = 18)		 Oct 96
(n = 4)		 Jan 97
(n = 7)		 Apr 97
(n = 137)		 Aug 97
(n = 16)		 Nov 97
(n = 61)
Northern quahog siphons 30.73 74.77 0.00 11.71 15.41 16.82
Atlantic surfclam siphons 2.74 0.00 0.00 49.95 0.00 47.79
Glycera sp. 20.25 0.00 0.00 2.42 37.25 0.65
Atlantic rock crab juveniles 10.93 0.00 0.00 3.55 1.28 0.11
Table 2e. Summary of Hudson-Raritan Estuary juvenile winter flounder (6.0 - 19.9 cm TL) diet by sampling stratum during 1996-97, expressed as mean percent contribution of dominant prey or items to total stomach content volume. (n = number of nonempty stomachs included.)
Prey
Stratum
1
(n = 31)
2
(n = 46)
3
(n = 71)
4
(n = 51)
5
(n = 13)
6
(n = 70)
7
(n = 17)
8
(n = 18)
9
(n = 16)
Glycera sp. 15.8 9.1 5.2 0.0 0.0 2.5 0.0 0.0 0.0
Sabellaria vulgaris 15.8 0.0 <1.0 <1.0 0.0 1.6 0.0 0.0 0.0
Pherusa affinis 0.0 0.0 7.8 1.8 0.0 1.1 6.2 0.0 0.0
Asabellides oculata 1.3 0.0 0.0 0.0 2.7 12.8 0.0 0.0 0.0
Ampelisca sp. 12.0 6.2 8.3 1.4 0.0 7.0 0.0 20.8 4.9
Gammarus sp. <1.0 0.0 1.4 1.2 0.0 6.8 28.0 <1.0 0.0
Neomysis americana 0.0 2.2 13.3 20.5 51.1 4.1 3.5 20.0 18.8
Crangon septemspinosa <1.0 0.0 4.0 5.1 9.8 2.9 0.0 0.0 0.0
Cancer sp. juveniles 0.0 0.0 <1.0 15.1 0.0 1.1 2.3 0.0 0.0
Northern quahog siphons 11.0 42.0 14.8 1.6 0.0 11.1 0.0 0.0 1.0
Atlantic surfclam siphons 0.0 7.2 2.0 20.7 0.0 10.5 2.4 7.9 0.0
Detritus 6.2 12.0 12.7 3.4 0.0 9.5 13.9 12.1 44.2

Table 2f. Summary of Hudson-Raritan Estuary adult winter flounder (20.0 - 45.0 cm TL) diet by sampling stratum during 1996-97, expressed as mean percent contribution of dominant prey or items to total stomach content volume. (n = number of nonempty stomachs included.)
Prey
Stratum
 
1
(n = 29)
2
(n = 30)
3
(n = 45)
4
(n = 39)
5
(n = 48)
6
(n = 18)
7
(n = 18)
8
(n = 5)
9
(n = 11)
Maldanopsis 20.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0
Glycera sp. 12.3 11.1 3.3 0.0 0.0 <1.0 17.5 0.0 0.0
Ampelisca sp. 6.9 14.5 1.0 0.0 0.0 <1.0 1.1 4.4 8.0
Cancer sp. juveniles <1.0 0.0 4.0 <1.0 <1.0 20.8 1.3 0.0 0.0
Northern quahog siphons 14.5 31.6 47.1 0.0 <1.0 29.2 0.0 0.0 0.0
Atlantic surfclam siphons 6.0 6.8 16.3 77.3 78.8 1.3 42.1 11.8 0.0
Ensis directus <1.0 1.1 0.0 13.4 0.0 0.0 0.0 0.0 0.0
Softshell siphons 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 50.3
Mulinia lateralis <1.0 1.1 <1.0 0.0 0.0 <1.0 0.0 10.0 3.3
Detritus 2.0 4.9 3.5 0.0 <1.0 8.2 7.5 10.7 24.1

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 (Modified Jun. 13 2008)