Estuarine production of resident and nursery fish species: Conditioning by drought events?

Abstract

The production of resident (Pomatoschistus minutus and Pomatoschistus microps) and marine juvenile fish species using the Mondego estuary (central Portugal) as nursery grounds (Dicentrarchus labrax, Platichthys flesus, Solea solea), was assessed in order to: (1) understand the potential of the estuary for fish production; (2) know the production of nursery fish species likely to be exported to the coastal stocks; and (3) how anthropogenic and natural stress could influence the estimated production. C, night temperatures). The secondary production was estimated using the increment summation method, after recognition of the cohorts. Production was in general lower in the Mondego estuary when compared to other systems, which was associated to the estuary's small area (only 3.4 km 2 , less than 1/4 of area compared to other studied systems). Dicentrarchus labrax was among the most productive species. Production decreased in the drought year for all species, especially evident for D. labrax, P. minutus and P. flesus. No direct effects could be attributable to the salinity and temperature variations and to the low freshwater discharges (resulting from the drought and high temperatures), yet these were pointed as probable major reasons for the decreased production. A significant reduction (15e45% reduction in the estuarine production) was also concluded for the potential production to be exported for coastal areas by the nursery species in the drought conditions.

Effects of local and large-scale climate patterns on estuarine resident fishes: The example of Pomatoschistus microps and Pomatoschistus minutus

“…This pattern confirms the important role of freshwater flow that has both direct and indirect effects on fish abundance (Costa et al, 2007;Martinho et al, 2007) and production (Dolbeth et al, 2008a(Dolbeth et al, ,b, 2010. For Pomatoschistus microps, mean annual production and biomass were relatively constant along the study period, confirming the higher resilience of this species to temperature and salinity variations (Riley, 2003;Dolbeth et al, 2007).…”

“…In particular, fish dynamics, growth and production of estuarine ecosystems seem to be strongly affected by altered hydrology patterns, which can be regulated by floods and drought events (Whitfield, 2005;Dolbeth et al, 2008aDolbeth et al, , 2010Baptista et al, 2010). Fish recruitment, growth and production can also be influenced directly by changes in physico-chemical parameters, such as salinity, turbidity and dissolved oxygen (Pampoulie et al, 2001;Selleslagh and Amara, 2008) or indirectly, through changes in food availability (Whitfield, 2005).…”

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

“…Eggs and larvae appear to be flushed out as a result of the excessive amount of river flow that will potentially contribute to the loss of larvae from the estuary into the marine environment. Moderate freshwater discharge increases the overall primary production of estuarine systems that are vital for the nursery function of the lower reaches of estuaries (Dolbeth et al 2008) and promotes the emergence of chemical cues used by larvae for orientation in estuarine zones (Costa et al 2007). However, excessive supply can effectively alter the larval composition of estuarine resident and estuarine dependent marine fish species (Strydom et al 2002).…”

Use of stable isotope ratios of fish larvae as indicators to assess diets and patterns of anthropogenic nitrogen pollution in estuarine ecosystems

“…Estuarine ecosystems constitute transition zones where freshwater from land drainage and river basins mixes with seawater, creating some of the most biologically productive areas on Earth (Levin et al, 2001). Such environments are effective nurseries for several marine fish species, and provide shelter and food for several other resident ones that complete their entire life cycle within the estuarine system (Dolbeth et al, 2007(Dolbeth et al, , 2008. Resident species are quite relevant in estuarine food webs as intermediate predators, being consumers of plankton and benthos, and prey of several larger fishes, decapods, and birds, playing a crucial role in the overall dynamics and functioning of the estuarine ecosystem.…”