Dispersion of freshwater mussel larvae in a lowland river

Abstract

We examined the dispersal of larvae (glochidia) of a common unionid mussel species, Actinonaias ligamentina, which need to attach to a host fish in order to develop into juveniles, in a lowland river (Sydenham River, Ontario, Canada). Generally, the decline in the number of glochidia captured with distance from release was best described by an inverse power function. The highest proportion was found in the first net 4 m downstream (range 0.1-3.6%), but a small proportion of glochidia was captured 96 m downstream (0-0.03%). This indicates that infestation of host fish may occur several tens to hundreds of meters downstream of the adults' location, even at relatively low flow conditions (mean velocity, 15 cm s 21 ). Dispersal distances increased with velocity, but the number of glochidia sampled at a given location can vary considerably due to stochastic effects of turbulence, especially at shorter distances. Individual trials could, therefore, deviate considerably from the predictions of an existing turbulent transport model (local exchange model), but overall there was a good correlation between measured data and model prediction. However, model predictions were quantitatively much higher than measured values (i.e., . 50 fold in some cases), which could be in part due to several simplifying assumptions of the model. * Corresponding

Scale‐dependent longitudinal patterns in mussel communities

“…There are broader scale mechanistic variables that may influence mussel community composition that we were unable to include in our study, such as the distribution and assemblage structure of fishes. This variation has consequences for mussel dispersal abilities and population dynamics; thus, mussel distribution and abundance can be strongly influenced by the composition of the co-occurring fish assemblages (Haag & Warren, 1998;Vaughn & Taylor, 2000;Schwalb, Garvie & Ackerman, 2010;Schwalb et al, 2011). Mussel species vary in the type and number of suitable fish hosts, mechanisms employed in infecting the host(s), and timing of glochidial development and release (Barnhart et al 2008).…”

The effect of settling velocity on the transport of mussel larvae in a cobble‐bed river: Water column and near‐bed turbulence

“… Differences in elevation (maximum depth − measured depth) measured every 25 cm along an up to 100‐m long transect where the drift nets were placed in the Grand River and the Sydenham River (data from Schwalb et al 2010). The inset provides details of the reach between 20 and 40 m illustrating the higher bottom roughness in the Grand River compared with the Sydenham River.…”

“…Gravid females of A. ligamentina were collected from the Thames River, Ontario, and L. fasciola from the Grand River (under the Ontario Ministry of Natural Resources [OMNR] license no. 1045920 and Species at Risk Act [SARA]: SECT 08 SCI 004) and held at 10 °C in a recirculating water system (see Schwalb et al 2010 for details). Glochidia were obtained from gravid females by flushing the gills with water from a syringe.…”

“…The glochidia were stained with Rose Bengal (50 mg L − 1 ) for 48 h to facilitate identification under the microscope as drift samples had a high sediment load. Glochidia were killed by the staining process, which does not have a significant effect on their w s (Schwalb et al 2010). In addition, glochidia of A. ligamentina obtained from the Thames River were placed in ethanol after staining to ensure that no foreign glochidia were introduced alive into the watershed (required by OMNR).…”

Biota Connect Aquatic Habitats throughout Freshwater Ecosystem Mosaics

“…Pelagic‐spawning mussels create similar biological connections along stream networks, via downstream drift and upstream movement attached to host fishes (Schwalb et al. ).…”