(2015) revealed that the southernmost population of P. Recent study by Hidalgo-de-la-Toba et al.
#GEO DUCK NEAR ME SERIES#
generosa fishery led to a series of studies that characterized geographical distribution ( González-Peláez et al., 2013), reproduction ( Calderon-Aguilera et al., 2014), phylogenetic relationships ( Leyva-Valencia et al., 2015), and individual growth ( Calderon-Aguilera et al., 2010). In Mexico, the recent development of the P. Despite this general observation, estimates of asymptotic length reveal it to be a highly variable parameter among geographically close areas, ranging from 135.2–161.0 mm for British Columbia ( Bureau et al., 2002 Campbell and Ming, 2003) to 130–173 mm in Washington ( Hoffman et al., 2000). generosa are in accord that during the first 10 years the highest growth rate occurs, and subsequently the rate decreases drastically until the organism ultimately reaches maximum size. Thus, results of individual growth models based on SLTA data sets are frequently unclear for the first years of development, precisely when the accelerated growth phase occurs. This bias has been frequently observed in individual growth analyses in populations of geoducks, a group of long-lived species where early age classes are frequently absent in biological samples. Due to the selectivity of the fishing gear used, there exists a certain propensity to bias for certain lengths ( Shaul and Goodwin, 1982 Kilada et al., 2007a Kilada, 2010). As such, the analysis derived from this information represents only the terminal length and age structures of the individuals captured during sampling. Individual growth in bivalves is typically characterized via measurements of the shell length (SL) and estimations of age at the moment of capture, which, in most cases, has been done through the counting of growth marks periodically deposited in the shell ( Thompson et al., 1980 Cerrato, 2000). The results demonstrate that IGP yields reliable information from relatively few organisms, improves the biological knowledge of the population, and increases the accuracy of parameter estimates for better fishery management. In terms of performance, the IGP and IGP + SLTA data sets informed individual growth models with stronger relationships ( r 2 > 0.9) and higher modelling efficiency ( ME > 0.9) than those fitted to SLTA alone ( r 2 = 0.51 ME = 0.51). For SLTA data alone, the most parsimonious was the Johnson model, with L ∞ = 161.6 mm reaching the asymptotic phase at >25 years. The most parsimonious model for both IGP and IGP + SLTA data sets was the Schnute model, with L ∞ = 127.9 and 122.5 mm, respectively, with the asymptotic phase attained at ∼15 years. We compared IGP against SLTA and a combination of both IGP + SLTA data through a multi-model approach for the southernmost known P. To increase early age representation and improve growth modelling, we implemented an approach that used individual growth profile (IGP) data recorded in shells of the Pacific geoduck ( Panopea generosa).
Contemporary modelling of growth based on shell-length to terminal age (SLTA) in long-lived clams is subject to inaccuracies as a consequence of low representation of early age classes in population samplings.
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