Vertical patterns of ichthyoplankton at the interface between a temperate estuary and adjacent coastal waters: Seasonal relation to diel and tidal cycles

Abstract

Vertical distribution and migration pattern of ichthyoplankton assemblage in the Mondego estuary were investigated in relation to diel and tidal cycle. Summer and winter communities were sampled, at surface and bottom, over a diel cycle during spring and neap tides at a fixed station at the mouth of the estuary. Summer presented higher larvae density mainly of Pomatoschistus spp., Gobius niger and Parablennius pilicornis. Main species in winter assemblages were Pomatoschistus spp. and Sardina pilchardus. There were no differences between depth stratums across diel or tide cycle. Nevertheless, main species larval densities showed significant periodic variation associated with tide (M2) and diel (K1) cycles presenting generally, higher density at night and around low tide. Conversely, vertical patterns observed could not be related with diel or tidal cycle. Tough, main species presented some extent of vertical migration. Vertical patterns observed appear to be related to seasonal stratification and river flow, increasing amplitude during periods of less stratification and lower water currents. Present study provides a better understanding of ichthyoplankton vertical movement patterns and of small scale dynamics at the interface of two coastal European systems.

Mesozooplankton biomass and copepod estimated production in a temperate estuary (Mondego estuary): effects of processes operating at different timescales

“…Additionally, spring copepod production rates seem to show a vertical variation associated with depth (changes in depth according to diel phase); a strong evidence of diel vertical migrations. It is generally accepted that the daily sunlight cycle plays an important role in the diel vertical migration (DVM) behavior of zooplankton, which has been observed in coastal regions (e.g., Zhu et al 2000, Devreker et al 2008, Primo et al 2012. Nocturnal vertical movements in the water column have commonly been reported for different taxa, including copepods (Rawlinson et al 2005).…”

Winds vs. tides: factors ruling the recruitment of larval and juvenile fishes into a micro-tidal and shallow choked lagoon (Argentina)

“…Such variations have also been attributed to the combination of the variability in seawater volume entrance according to lunar-tide cycles with the seasonal variation in river flows due to seasonality in rainfall (e.g. Primo et al 2012). The scarce variation in water parameters (temperature, salinity and transparency) between spring and neap tides in Mar Chiquita may be due to the combination of the shallowness of the system (1.5-3 m) with the major contribution of seawater input compared to the freshwater contribution (a single stream discharges into the inlet channel, Reta et al 2001).…”

“…Therefore, studies regarding on the mechanisms of young fishes ingress and retention in nursery areas have caught much attention (e.g. Jager 1999; Epifanio and Garvine 2001;Islam et al 2007;Primo et al 2012). …”

“…Also, tidal phase-related factors such as salinity, temperature, chemical substances, current velocity and hydrostatic pressure have been reported to be important to ichthyoplankton distribution (e.g. Primo et al 2012). Particularly in the case of juveniles, the lunar-tide cycle (spring, neap) can have a strong impact on species distribution because it determines the temporal and spatial availability of coastal habitats like estuaries, saltmarshes and coastal lagoons (Hampel et al 2003).…”

“…In order to do so, we explored spatial and temporal patterns in larval and juvenile fishes abundance related to neap/spring tides, winds and also water properties (temperature, salinity and transparency) that may vary according to tidal cycles (e.g. Primo et al 2012). We hypothesize that the abundance of young fishes is higher during spring tides combined with strong onshore winds.…”