Length-mass relationships for macroinvertebrates in the Choghakhor international wetland, Iran

This study investigates length-mass relationships for 17 families of freshwater macroinvertebrates collected in the Choghakhor Wetland (Central Iran). Body length, head width, distance between eyes and mass (dry weight and wet weight) were used to estimate biomass with linear, log-linear and exponential models. The results show better performance of the log-linear model (ANOVA, p = 0.03), as compared to the other two (ANOVA, p > 0.05). A cross-validation test demonstrated that all three models performed reasonably well, in terms of both statistics and the accuracy of prediction. However, for more than 60% of the relationships the p value for the log-linear model was greater than for the other two, suggesting that the accuracy of this model is in general superior. Body length was generally demonstrated to be a good indicator to estimate biomass. However, for some taxa, the measurement of sclerotized structures (i.e., the distance between the eyes and the head width) were also found to be suitable biomass indicators. The latter is beneficial for the estimation of biomass with individuals that have been kept for a long time under laboratory conditions and/or those that show damaged parts of their bodies. The present study provides the first set of length-mass relationships for macroinvertebrates in the Middle-East region, and its findings are expected to contribute to the estimation of biomass in aquatic environments that are affected by semi-arid conditions and different degrees of anthropogenic stress.