Biometric conversion factors as a unifying platform for comparative assessment of invasive freshwater bivalves

1. Invasive bivalves continue to spread and negatively impact freshwater
ecosystems worldwide. As different metrics for body size and biomass are
frequently used within the literature to standardise bivalve related
ecological impacts (e.g. respiration and filtration rates), the lack of
broadly applicable conversion equations currently hinders reliable
comparison across bivalve populations. To facilitate improved comparative
assessment amongst studies originating from disparate geographic
locations, we report body size and biomass conversion equations for six
invasive freshwater bivalves (or species complex members) worldwide:
Corbicula fluminea, C. largillierti, Dreissena bugensis, D. polymorpha,
Limnoperna fortunei and Sinanodonta woodiana, and tested the reliability
(i.e. precision and accuracy) of these equations. 2. Body size (length,
width, height) and biomass metrics of living-weight (LW), wet-weight (WW),
dry-weight (DW), dry shell-weight (SW), shell free dry-weight (SFDW) and
ash-free dry-weight (AFDW) were collected from a total of 44 bivalve
populations located in Asia, the Americas and Europe. Relationships
between body size and individual biomass metrics, as well as proportional
weight-to-weight conversion factors, were determined. 3. For most species,
although inherent variation existed between sampled populations, body size
directional measurements were found to be good predictors of all biomass
metrics (e.g. length to LW, WW, SW or DW: R2 = 0.82–0.96), with moderate
to high accuracy for mean absolute error (MAE): ±9.14–24.19%. Similarly,
narrow 95%–confidence limits and low MAE were observed for most
proportional biomass relationships, indicating high reliability for the
calculated conversion factors (e.g. LW to AFDW; CI range: 0.7–2.0, MAE:
±0.7–2.0%). 4. Synthesis and applications. Our derived biomass prediction
equations can be used to rapidly estimate the biologically active biomass
of the assessed species, based on simpler biomass or body size
measurements for a wide range of situations globally. This allows for the
calculation of approximate average indicators that, when combined with
density data, can be used to estimate biomass per geographic unit-area and
contribute to quantification of population-level effects. These general
equations will support meta-analyses, and allow for comparative assessment
of historic and contemporary data. Overall, these equations will enable
conservation managers to better understand and predict ecological impacts
of these bivalves.02-Jun-2021 --