M. Afzal Khan

Precision of aging structures for Indian major carp, Cirrhinus mrigala, from the River Ganga

Scales, opercular bones, otoliths, vertebrae, and dorsal fin rays were compared to ascertain the best aging structure of Cirrhinus mrigala. All structures showed alternating opaque and translucent bands that were interpreted as annuli; however, structures differed greatly in the clarity of their presumed annual marks. Age estimates were compared by calculating the percentage of agreement (PA), average percentage of error (APE), and coefficient of variation (CV) and by constructing age bias plots. Age estimates were evaluated between readers and between the pairs of aging structures. Among all structures, scales showed the clearest annual rings and had highest (94.6%) PA between readers, followed by opercular bones (88.6%), otoliths (83.9%), vertebrae (79.9%), and dorsal fin rays (62.4%). Due to highest PA and lower minimal aging error, the scales were considered the most reliable bony structure for aging C. mrigala. When scale ages were compared with those of the other structures, the highest PA and lowest APE and CV values were found between scale and opercular bone estimates. Mean values of age estimate from scales were comparable (p > 0.05) to the values obtained from opercular bones, otoliths, and vertebrae and were significantly (p < 0.05) different with the dorsal fin ray age estimates. Scales were the most suitable structures for age estimation in C. mrigala.

Evaluation of ageing precision from different structures of three threatened freshwater fish species, Clarias batrachus, Heteropneustes fossilis and Wallago attu

Abstract. Ageing precision from otoliths, vertebrae and pectoral spines was studied in Clarias batrachus, Heteropneustes fossilis and Wallago attu. In C. batrachus, otoliths showed the highest (92.9 %) agreement between readers followed by vertebrae (87 %) and pectoral spines (83.8 %). The highest percentage of agreement (87 %) and lowest average percentage of error (1.89 %) and coefficient of variation (3.81 %) values were observed between otoliths and vertebrae age estimates. In H. fossilis, vertebrae showed the clearest annual rings and had highest (90.8 %) PA values between readers, followed by otoliths (80.3 %) and pectoral spines (73.7 %). The highest PA and lowest APE and CV values were found between vertebrae and otoliths estimates. In W. attu, otoliths showed the highest PA (86.7 %) values between readers followed by pectoral spines (70.3 %) and vertebrae (67.9 %). The highest PA and lowest APE and CV values were found between otoliths and pectoral spines. On account of the highest PA, lowest APE and CV values, the most suitable ageing structure was otolith in C. batrachus and W. attu, while vertebrae in H. fossilis. If mean age estimates are considered then in the absence of the most suitable ageing structure, alternatively, vertebrae can be used in C. batrachus, otoliths in H. fossilis and pectoral spines in W. attu.

Impact of Polyhouse Culture During Winter on Ovarian Maturity, Growth, Muscle, and Egg Composition of Carps

Abstract Impact of polyhouse culture was examined on ovarian maturity, growth, muscle and egg composition in two Indian major carps: rohu, Labeo rohitaand catla, Catla catla; and two Chinese carps: grass carp, Ctenopharyngodon idellaand silver carp, Hypophthalmichthys molitrixduring winter. Eight females (2+ years age group) of each species, were stocked in polyhouse and outdoor concrete tanks (250 m2), in duplicate. Results of the study revealed that polyhouse-cutured fishes, in general, exhibited better (P < 0.05) values for weight increment, gonadosomatic index, total number of eggs/fish, number of eggs/g body weight, and egg diameter. Proximate composition of muscle and eggs in fishes varied significantly with culture conditions. It was seen that Chinese carps attained maturity about two weeks earlier than the Indian major carps. The stage of oocyte maturation varied between fishes reared in the two culture systems. Polyhousecultured fishes possessed most oocytes (> 70%) at migrating germinal vesicle stage, while those reared in outdoor tanks exhibited these at the central germinal vesicle stage. An advancement in attainment of maturity was evident in these carps when grown in polyhouse during winter.

Stock delineation of the long-whiskered catfish, Sperata aor (Hamilton 1822), from River Ganga by using morphometrics

Long-term isolation of populations and interbreeding can lead to morphometric variations among fish populations. This study was conducted with the objective to delineate stock structure of Sperata aor on the basis of morphometric characters, using truss network of the fish body. In total, 407 S. aor samples were collected from the four sampling locations of the Ganga River, viz. Narora, Kanpur, Varanasi and Bhagalpur. In total, 28 truss distance measurements were created by joining 13 morphometric landmarks on the fish body. MANCOVA showed significant (P<0.001) morphological variance among the sampling locations for the target fish species. Univariate ANOVA showed significant (P<0.001) differences in each of the morphometric measurements among the fish from different sampling locations. Wilk’s lambda test of canonical discriminant function analysis showed significant (P<0.001) differences in morphometric measurements of the fish from all sampling locations. Discriminant function analysis using Jackknife (leave-one-out) cross-validation classification showed 87.5% correct classification of the individuals into their original populations. Mantel test showed an overall good correlation between the genetic and morphometric datasets in the selected fish species. The results of this study can be employed in formulating stock-specific management strategies for S. aor from River Ganga.