Environ Biol Fish (2010) 89:505–512 DOI 10.1007/s10641-010-9685-y
Otolith retrieval from faeces and reconstruction of prey-fish size for Great Cormorant (Phalacrocorax carbo) wintering at the East Dongting Lake National Nature Reserve, China K. V. Radhakrishnan & Ming Liu & Wenping He & Brian R. Murphy & Songguang Xie
Received: 1 October 2009 / Accepted: 27 June 2010 / Published online: 14 July 2010 # Springer Science+Business Media B.V. 2010
Abstract The food composition of Great Cormorant (Phalacrocorax carbo) was studied by analyzing 360 faecal samples collected from their roosting sites at the East Dongting Lake National Nature Reserve in south-central China during November 2008 and January 2009. A total of 223 fish otoliths were retrieved. Only sagittal otoliths (N=74) with intact margins, good medial relief, and well-defined sulcus were used to identify the prey-fish species and to reconstruct prey-fish size. Through shape indices and elliptical Fourier analyses, these otoliths were identified as belonging to two cyprinid fish species, crucian carp Carassius auratus (72%) and white amur bream Parabramis pekinensis (28%). The otolith size (maximum length, Lo)—prey-fish size K. V. Radhakrishnan : M. Liu : W. He : S. Xie (*) Key Laboratory of Biodiversity and Conservation of Aquatic Organisms, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan, Hubei 430072, China e-mail:
[email protected]
(standard length, Ls) relationships determined for the two fish species were Ls=−19. 5+37.1 Lo (N=74; R2 =0.95; P0.05 for both species, Table 2). The average otolith shapes reconstructed from FDs of crucian carp reference otoliths highly overlapped those of otoliths recovered from faeces and tentatively identified as this species. This situation was similar for white amur bream as well (Fig. 2). Eleven species in 2 orders and 3 families were collected by the experimental fishing at the reserve (Table 3). Family Cyprinidae had the highest number
Environ Biol Fish (2010) 89:505–512
509
Table 2 Comparison of the shape indices for otoliths of crucian carp Carassius carbo (N=53) auratus, andtaken whitefrom amurfish bream collected Parabramis in the wild pekinensis, (N=62) and carp from Carassius faecesauratus, of Greattaken Cormorant from fish Phalacrocorax collected incarbo the wild (N=53) and takenwhite fromamur fish collected bream Parabramis in the wild pekinensis, (N=31) andtaken from from faecesfish of (N=62) collected and in the from wildfaeces (N=31) of and Great from Cormorant faeces ofPhalacrocorax Great Cormorant Phalacrocorax Great Cormorant carbo Phalacrocorax (N=21) carbo (N=21) Species Crucian carp
White amur bream
Shape indices
Otoliths from fish
Otoliths from faeces
Df
F
t-test
P
Form factor
0.760±0.347
0.751±0.889
113
0.051
0.262
Roundness
0.777±0.356
0.722±0.054
113
0.102
1.106
0.79 0.27
Circularity
17.495±2.645
17.380±2.129
113
0
0.959
0.34
Rectangularity
0.687±0.274
0.653±0.027
113
0.024
0.878
0.91
Ellipticity
0.073±0.030
0.071±0.030
113
0.051
0.822
0.79
Form factor
0.364±0.050
0.481±0.176
50
0.001
−0.051
0.96
Roundness
0.720±0.080
0.814±0.107
50
1.523
−1.743
0.07
Circularity
35.098±4.811
29.349±9.558
50
0.007
0.054
0.91
Rectangularity
0.651±0.033
0.695±0.514
50
0.014
−1.736
0.10
Ellipticity
0.073±0.034
0.066±0.032
50
0.041
−0.848
0.41
of fish species with 9 members whereas the other two families (Osphronemidae and Odontobutidae) were represented by single species each. The crucian carp was the most abundant species, with 27% of the catch, followed by white amur bream with 16%. The Ls of crucian carp collected ranged from 32.8 to 131.9 mm (mean 81.5±28.7 mm), while Ls for white amur bream ranged from 33.3 to 125.5 mm (mean 77.2±30.3 mm) (Fig. 3). The Lo-Ls relationships were fitted to linear functions as Ls=−19.5+37.1 Lo (N=74; R2 =0.95; P
