Ocean–estuarine connection for ichthyoplankton through the inlet channel of a temperate choked coastal lagoon (Argentina)

Abstract

We examined the fish larvae colonising pattern of the Mar Chiquita lagoon (Argentina). We hypothesised that in this microtidal lagoon, winds could regulate fish larvae dynamics. Ichthyoplankton samples were taken in marine waters, the surf zone and the estuary. Previous studies showed no reproduction by fishes with planktonic eggs inside the lagoon. However high abundance of eggs and larvae of Brevoortia aurea collected within the estuary also suggest possible spawning activity. Throughout the study period, the cumulated richness of fish larvae was slightly higher in the estuary. However, univariate analysis revealed a higher number of species per tow in marine waters than in the estuary. The lowest average values of fish density, number of species and diversity recorded in the surf zone suggest that this area is only used as a transient corridor between the sea and the lagoon. The canonical correspondence analysis (CCA) indicated that wind direction, tidal stage, temperature and rainfall contributed significantly to the fish larvae distribution patterns observed; being ‘onshore wind’ the most important variable affecting fishes. Our results show how winds, in addition to pushing seawater into the lagoon, contribute to larvae recruitment into this estuary. Finally, we discuss the role of small lagoons in the life-history of coastal fishes.

Recruitment of juvenile fishes into a small temperate choked lagoon (Argentina) and the influence of environmental factors during the process

“…Also, fish productivity inside estuarine systems (like the Patos Lagoon Estuary, Brazil) is highly dependent on the passage of weather fronts in spring when fish eggs are more abundant in the ocean (Martins et al 2007). Moreover, previous studies have demonstrated that onshore winds are key issues in the success of fish larvae recruitment from offshore spawning grounds to inner areas of Mar Chiquita instead of tides (Bruno et al 2014).…”

“…In contrast to larvae of other clupeoids from the northern hemisphere (B. tyrannus and B. patronus) (Powell 1994) that are spawned offshore and then drift towards the coast, B. aurea larvae in the Río de la Plata estuary are spawned and retained in estuarine waters (Acha and Macchi 2000). In Mar Chiquita coastal lagoon (~350 km southward of the Río de la Plata estuary) the occurrence of few individuals of B. aurea in advanced maturation ) and the high abundances of eggs and larvae of this species over the inlet channel (Bruno et al 2014) suggest that spawning activity may also occur inside this estuarine system. Nevertheless, the bulk of the spawning must be at sea given the dominance of post-flexion larvae on ichthyoplankton surveys conducted in the area (Bruno et al 2014).…”

“…In Mar Chiquita coastal lagoon (~350 km southward of the Río de la Plata estuary) the occurrence of few individuals of B. aurea in advanced maturation ) and the high abundances of eggs and larvae of this species over the inlet channel (Bruno et al 2014) suggest that spawning activity may also occur inside this estuarine system. Nevertheless, the bulk of the spawning must be at sea given the dominance of post-flexion larvae on ichthyoplankton surveys conducted in the area (Bruno et al 2014). Therefore, similarly to O. argentinensis, the juveniles of B. aurea found in our study could be spawned inside and/or outside Mar Chiquita, showing a flexible spawning strategy for this species.…”

“…Harris et al 2001). For Mar Chiquita lagoon, a decline in fish larvae abundance and diversity in the surf zone compared with the adjacent sea and the estuary has recently been noted (Bruno et al 2014) and is mainly attributed to the comparatively high wave energy of the surf zone. Moreover, data on juveniles sampled about 1 to 2.5 km off Mar Chiquita's inlet (J.M.…”

“…Martinetto et al 2007, González-Castro et al 2009, Valiñas et al 2010, neither the temporal pattern of juvenile assemblages occupying the marine and the estuarine environments nor the factors which drive the recruitment process have been documented. Fishes enter the lagoon not only as juveniles but also as larvae; those tiny stages characterized by poor swimming abilities take advantage of wind-driven currents to recruit into the lagoon (Bruno et al 2014). Though juveniles do not necessarily require assistance of currents to move, they may use them to increase the surplus power (energy per unit time) in order to save energy that could be channeled into growth (Miller et al 1985).…”