Ichthyoplankton dynamics in the Guadiana estuary and adjacent coastal area, South-East Portugal

Abstract

The species composition, abundance and distribution of the ichthyoplankton of the Guadiana estuary and adjacent coastal area were studied in relation to several environmental parameters. Sampling occurred during new moon Spring tides, at the ebb and flood, at nine stations, from March 2002 to February 2003. Temperature, salinity, dissolved inorganic macronutrients, seston and organic matter and chlorophyll a were determined at each station. A total of 22 and 34 fish eggs and larvae taxa were identified, respectively. The highest abundances were registered in the lower and middle part of the estuary, probably due to the presence of species that use the estuary as a preferential spawning ground, mainly Pomatoschistus spp. and Engraulis encrasicolus sensu lato. Temporal patterns of occurrence of ichthyoplankton allowed each species' spawning season to be determined. Two taxa dominated the ichthyoplanktonic community during spring and summer (Pomatoschistus spp. and E. encrasicolus), whereas Sardina pilchardus was particularly abundant during autumn and winter. The forcing variables responsible for community structure were chlorophyll a and seston for eggs, while temperature, salinity and nitrite explained the larval component. Comparisons of the results with previous ichthyoplankton studies of the Guadiana estuary conducted before the Alqueva dam was built also indicate that river flow has an important impact on the distribution and abundance of ichthyoplankton in the estuary.

Environmental factors affecting larval fish community in the salt marsh area of Guadiana estuary (Algarve, Portugal)

“…Despite the higher abundance of the three species (D. sargus, S. pilchardus and P. microps), we found lower diversity and abundance of the overall fish larvae community compared with previous surveys carried out in adjacent areas of the Guadiana estuary (Chícharo et al 2000 andFaria et al 2006). However, in these studies, captures exclusively near our sampling area had diversity and abundance values much closer to our observations.…”

“…Chícharo et al (2000) reported for the sampling point "Carrasqueira creek" (a marsh creek a few meters from our sampling site) the presence of 5 different species and an abundance peak of 143 larvae/100 m 3 in March 2000. Values observed by Faria et al (2006) for the lower estuary were slightly higher, with 19 different species and a maximum abundance of 285 larvae/100 m 3 in June 2002. Diversity in the salt marsh creek agreed well with descriptions in the literature for other European marshes, where few species were found.…”

“…Veiga et al (2006) analysed the Castro Marim salt marsh area in order to characterize communities of adult and juvenile fish. Other studies focusing on the population dynamics of fish larvae were only conducted in the main channel of the Guadiana estuary (Chícharo et al 2000, Faria et al 2006. This is a crucial first step for determining the sustainable carrying capacity of these ecosystems.…”

Is <em>Fundulus heteroclitus</em> Intrusion Depleting Winter Marsh Pools of Native Fish Species?

“…In the Guadiana estuary, a community shift has been already documented, including plankton and fish [9,11,12]. In addition, first occurrences of several marine invasive species have also been recorded, with potentially detrimental effects on native biota [13].…”

Response of Gilthead Seabream (Sparus aurata L., 1758) Larvae to Nursery Odor Cues as Described by a New Set of Behavioral Indexes

“…The larvae of Sparidae were among the most abundant in this lagoon, and most of these larvae were post-flexion larvae collected during flood tides (Chícharo and Teodósio, 1991). So, the absence of a meaningful number of pre-flexion larvae and the presence of post-flexion larvae during flood tides suggests that spawning does not occur inside the lagoon, as observed for other species in an estuary located nearby (Faria et al, 2006;Morais et al, 2009). Larvae's ingress mechanisms were never evaluated, so larvae's ingress could result from purely stochastic events (e.g., winds, tides) (Hare et al, 2005;Schieler et al, 2014) or due to active ingress strategies (e.g., selective tidal stream transport, bottom-inflow ingress, or ingress near the bottom or margins where water velocity is slower) which include ingress during flood tides (Hare et al, 2005).…”