Agent-based modeling and genetics reveal the Limfjorden, Denmark, as a well-connected system for mussel larvae

Abstract

Fishery of blue mussels Mytilus edulis constitutes a very important economic activity in Denmark, whereas mussel farming on long-lines or nets is a new, growing sector. Spawning from natural mussel beds takes place during early summer, and larvae disperse via water currents before settling on the bottom or on spat collectors in the farms. In the present study, we coupled a 3D physical model system (FlexSem) with an agent-based model in order to examine the connectivity of this marine system in terms of mussel larval dispersal and settling potential. To address this question, we (1) estimated the dispersal and connectivity between 17 areas in the Limfjorden, (2) identified the main donor and receiver areas of mussel larvae and (3) identified possible dispersal barriers. The results show that the central narrow strait in the Limfjorden was the main donor area in all the studied years, and that the adjacent eastern areas were the main receiver areas. Towards the inner basins of the Limfjorden, isolation increased and limited connectivity was observed. The results from the cluster analysis grouped the Limfjorden into 3 to 5 clusters, but there was still some exchange of simulated larvae observed among these clusters. Analysis of molecular markers revealed no genetic differentiation between areas and supports the model results, indicating that despite distinguishable hydrographic boundaries, the mussel populations in the Limfjorden are well connected. This study demonstrates how connectivity modeling can be used to support site selection processes in aquaculture.

Intensified Mussel Farming; Impacts on Nutrient Budgets and Ecology in a Eutrophic Semi‐Enclosed Fjord System

“…Hypoxia occurs only in bottom waters and will not affect the mortality of suspended mussels in the surface waters. Mussel spat from natural populations are not limiting for recruitment because the basins are well‐connected assuring efficient dispersal of the spat (Pastor et al., 2021).…”

Comparing life history traits and tolerance to changing environments of two oyster species (Ostrea edulis and Crassostrea gigas) through Dynamic Energy Budget theory

“…For the present study, total wet weight and shell length of an average of 130 oysters was measured seven times between 20 February 2008 and 17 November 2009. Water temperature (Gjellergraven) and salinity (both stations) were obtained from a hydrodynamic model ( Pastor et al . 2021 ).…”

Ocean Circulation Model Applications for the Estuary-Coastal-Open Sea Continuum

“…Recent measurements in different broads of the Limfjord indicated rapidly changing currents of both magnitude and direction over the course of hours to days (Pastor et al, 2020). Model simulations by Pastor et al (2021) predict the strongest time-averaged currents and highest variability of current velocities across the fjord at the western boundary in Nissum Bredning and inside narrow channels connecting the broads further east. In these areas, mean currents of up to 10 and 20 cm s −1 were reported in May/June 2010, whereas currents inside the larger broads did not exceed 5 cm s −1 during the same period (Pastor et al, 2021).…”

“…Previous modeling efforts in the Limfjord involved mechanistic models for a variety of management and research applications. The modeling studies investigated the functioning and dynamics of benthic filter feeders (e.g., Maar et al, 2010), estimated the effects of mussel fishing activities on the sediment dynamics (Holmer et al, 2003;Pastor et al, 2020), studied the species connectivity (Pastor et al, 2021) and investigated physical drivers of stratification and de-stratification (Wiles et al, 2006;Hofmeister et al, 2009). Other modeling applications were dedicated to estimate changes in the frequency and magnitude of storm surges and water levels as a consequence of climate change (Knudsen et al, 2012).…”

“…The model was applied as a standalone setup by using observed river discharges and observed sea level, water temperature and salinity as lateral boundary conditions in the North Sea and Kattegat. Pastor et al (2021) used a 3D physical model system (FlexSem; Larsen et al, 2020) coupled to an agent-based model to study dispersal and settling of mussel larvae between 17 areas in the Limfjord.…”