Age and Growth of Spotted Snakehead, Channa punctata from the Ganga River

Comparison of ages determined by using an Eberbach projector and a microscope to read scales from Atlantic menhaden (Brevoortia tyrannus) and Gulf menhaden (B. patronus)

“…An exchange of 100 fishery independent scales between reader 1 and an aging technician at the University of Southern Mississippi, aged on the same Eberbach projector, yielded a PA of 79.0% (Leaf 7 ). The PA values from our study were also similar to or higher than those from studies for other species, with PA values of 39.8-100.0% when precision of estimates for multiple aging structures were compared (Khan and Khan, 2009;Khan et al, 2015;Kumbar and Lad, 2016) and of 68.1-92.4% when estimated precision was compared between readers (Goldman and Musick, 2006; Khan et al, 2019).…”

“…The workshop participants com puted an ACV of 2.1% (ASMFC 6 ), a value that is similar to the ACV of 2.2% computed in this study for the same reference collection. Values of ACV for age data for both Atlantic and Gulf menhaden across all comparisons are similar to the values of 1.0-22.8% from other studies across aging structures and between readers (Khan and Khan, 2009;Herbst and Marsden, 2011;Khan et al, 2015;Khan et al, 2019). Values of ACV from this study indicate that the use of the microscope and the use of the Eberbach projector are comparable in providing ages for Atlantic and Gulf menhaden.…”

“…Overall, comparisons of age estimates made with the microscope and the Eberbach projector resulted in APEs under 4.4%, which is similar to or less than published APEs of about 8.0% (Campana, 2001;McBride, 2015), including the mean APEs for estimates from a simula tion by McBride (2015) that indicated no bias and that decreased with increasing precision. Average percent errors from other studies have ranged from 0.7% to 16.1% when age estimates were compared among multiple aging structures or between readers (Gürsoy et al, 2005;Khan and Khan, 2009;Khan et al, 2015;Khan et al, 2019). Average percent errors in age readings were best for the reference collections, which had better quality, more leg ible scales than the scales taken from fish sampled for this study.…”

“…McBride (2015) used a sample size of 5 fish to produce 5 age estimates per age class, a sample size that like those in most studies is much smaller than the sample sizes used in our study. For example, other studies have used sample sizes of 85-180 per species when comparing aging struc tures (Khan and Khan, 2009;Khan et al, 2015;Baudouin et al, 2016;Kumbar and Lad, 2016), 14-390 per species when comparing ages between readers (Wakefield et al, 2017;Khan et al, 2019), and 30-182 per species when comparing both aging methods and ages between readers (Gürsoy et al, 2005;Goldman and Musick, 2006;Herbst and Marsden, 2011). Given these smaller sample sizes, comparing age estimates from our study to those from the other studies has been difficult.…”