Definition of a new unbiased gonad index for aquatic invertebrates and fish: its application to the sea urchin Paracentrotus lividus

Reproductive output of two benthic resources (Fissurella latimarginata and Loxechinus albus) under different management regimes along the coast of central Chile

“…Since individual body dry weight (IDW) and the gonadosomatic index (GSI) were highly correlated with body size (r > 0.45 in all cases), we used body size as a covariate in our analyses to assess the effects of fisheries management regime and upwelling. Following the method of residuals analysis proposed by Ouréns et al (2012), we first computed the individual linear regression model between each log-transformed response variable (IDW and GSI) and mean individual body size for each combination of levels of both factors. Then, for each significant linear model we removed the effect of the covariable (body size) on the response variable (IDW and GSI) extracting the residuals for each linear regression, and used the residuals as the new response variable in subsequent analyses.…”

Spatial and Temporal Variability of Spawning in the Green Sea UrchinStrongylocentrotus droebachiensisalong the Coast of Maine

“…Comparison of GI, both temporally and spatially, assumes that GI is independent of urchin body size (diameter) (Gonor 1972, Ebert et al 2011, Our ens et al 2012. Because it was unfeasible to sort underwater all urchins at or above 40 mm TD on each sampling date, this assumption was tested using regression analysis with GI (dependent variable) and TD (independent variable).…”

“…35%) used both GI and histology, whereas after 2000, the rate was 33 of 61 papers (54%) ( Table 7). Recently there has been an emphasis on the need to standardize the methodology for calculating GI (Ebert et al 2011, Our ens et al 2012, 2013.…”

“…Because GI is a relative measure of reproduction (timing and effort), it is readily subject to differing views and interpretations (Ebert et al 2011, Our ens et al 2012. It would be desirable to standardize the measure of GI so that researchers, resource managers, and commercial enterprises have a common reference and understanding of what the results mean.…”

“…Recently, there has been a renewed interest in what induces spawning and the means of assessing it (Ebert et al 2011, Our ens et al 2012. Here, data are provided to assess spawning in Strongylocentrotus droebachiensis.…”