The age and growth determination and population dynamics of greenback mullet, Liza subviridis collected from Parangipettai (latitude 11°29′25.55″N, longitude 79°45′ 38.62″E) waters during May 2011-April 2012 were studied using the length frequency data. The estimated L∞ and K values were 267.75 mm and 1.10 year −1 for males and 278.25 mm and 1.00 year −1 for females, respectively. The 't 0 ' values obtained from the von Bertalanffy plot estimated for males and females of L. subviridis were −0.5396 and −0.4493 year, respectively. The estimated growth performance index (Ø′) for males and females were 4.725 and 4.708, respectively. The estimated life span, longevity (t max) values for males and females were 4.054 and 4.545 years, respectively. Total mortality, natural mortality and fishing mortality for males were 0.653, 0.7953 and 0.03, and for females were 0.558, 0.730 and 0.30, respectively. The predicted E max values for male was 0.530 and for female 0.521 Whereas the current exploitation ratio (E) was on the lower side (0.0346 for males and 0.3240 for females) for L. subviridis which implies that both the males and females are under-exploited. Thus the fishing pressure on the stock is under control for both the sexes in Parangipettai waters.
The present study aims to apply a DNA barcoding tool through amplifying two mitochondrial candidate genes i.e., COI and 16S rRNA for accurate identification of fish, aquatic molluscs and crustaceans of Sundarbans mangrove wetland, to build a reference library of fish and shellfishes of this unique ecosystems. A total of 185 mitochondrial COI barcode sequences and 59 partial sequences of the 16S rRNA gene were obtained from 120 genera, 65 families and 21 orders of fish, crustaceans and molluscs. The collected samples were first identified by examining morphometric characteristics and then assessed by DNA barcoding. The COI and 16S rRNA sequences of fishes and crustaceans were clearly discriminated among genera in their phylogenies. The average Kimura two-parameter (K2P) distances of COI barcode sequences within species, genera, and families of fishes are 1.57±0.06%, 15.16±0.23%, and 17.79±0.02%, respectively, and for 16S rRNA sequences, these values are 1.74±.8%, 0.97±.8%, and 4.29±1.3%, respectively. The minimum and maximum K2P distance based divergences in COI sequences of fishes are 0.19% and 36.27%, respectively. In crustaceans, the K2P distances within genera, families, and orders are 1.4±0.03%, 17.73±0.15%, and 22.81±0.02%, respectively and the minimum and maximum divergences are 0.2% and 33.93%, respectively. Additionally, the present study resolves the misidentification of the mud crab species of the Sundarbans as Scylla olivacea which was previously stated as Scylla serrata. In case of molluscs, values of interspecific divergence ranges from 17.43% to 66.3% in the barcoded species. The present study describes the development of a molecular and morphometric cross-referenced inventory of fish and shellfish of the Sundarbans. This inventory will be useful in future biodiversity studies and in forming future conservation plan.
The feeding ecology and prey preference of greenback grey mullet Liza subviridis (Valenciennes, 1836) were investigated in Parangipettai waters (11°29′25.55″N; 79°45′38.62″E) from May 2011 to April 2012. A total of 328 male and 360 female specimens of L. subviridis were analysed. Detritus and sand particles formed the major food item of L. subviridis in both sexes besides, diatoms, dinoflagellates, algae, zooplankton, foraminiferans, polychaetes and larval forms were also noticed and ranked respectively based on the quantities.
Morphometric characters of two species of lizardfishes viz.,Saurida pseudotumbil Dutt and Sagar, 1981 and Saurida tumbil (Bloch, 1795), were studied to delineate the species using multivariate techniques. Specimens were collected from Parangipettai and Cochin waters, southern India, for recording data on 21 morphometric characters. Principal component analysis (PCA) was done after log transformation and the first three components explained 93.36% of the total variation. The most important morphometric characters determined using the eigenvectors (coefficients) of these components were post-orbital length, snout to pectoral, snout to pelvic, snout to anal, anal fin base and dorsal fin base, which showed high loading (≥0.8) in the three components. The overlapping ratio between these species ranged from 42.59 to 89.28%. The PCA data cloud of S. pseudotumbil and S. tumbil also reflected the same trend. Therefore, canonical analysis of principal coordinates (CAP) was done which clearly separated the species with maximum case allocation success (100%) for both S. pseudotumbil and S. tumbil, which clearly showed that both the species are different.
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