Connectivities of estuarine fishes to the coastal realm

European flounder Platichthys flesus life history patterns were investigated in 3 basins along a latitudinal gradient (Minho, N Portugal; Gironde, SW France; Seine, N France). We used coupled Sr:Ca and Ba:Ca otolith signatures and microstructure to retrospectively determine habitats occupied by flounder during their life, including early larval ontogeny. Flounder exhibited high life history plasticity among and even within basins, apparent by the diversity of habitats used during larval ontogeny and throughout their lives, and by the age at which flounder migrated to freshwater. Egg signatures probably had a strong maternal influence, and our interpretation suggests that flounder spawned and/or hatched predominantly in brackish waters in the Minho, while in the Gironde and Seine, flounder spawned and/or hatched either in coastal, brackish or freshwater environments. The freshwater egg signature was most frequent in the Seine. These interpretations contradict the current general assumption that flounder spawn exclusively in coastal waters. During pre-metamorphosis and metamorphosis, flounder were predominantly in brackish waters in the Minho, while in the Gironde and Seine, they were mainly in coastal and freshwater environments, respectively. The diversity of flounder life histories (LH) (i.e. sequence of habitat residence: freshwater, brackish or coastal) after metamorphosis was similar between the Minho (LH = 13), Gironde (LH = 13) and Seine (LH = 14) basins. The age at which flounder migrated to freshwater also varied among sites, at an earlier age in the Minho and Gironde (< 0.5 yr old) than in the Seine, where flounder migrating from the coast into freshwater reached maximum frequencies at age 1.3 yr old. Thus, catadromy in European flounder may be facultative, and the factors influencing flounder high LH plasticity deserve thorough research.

Section: Location Of Flounder Nursery Groundssupporting

confidence: 57%

Plasticity of European flounder life history patterns discloses alternatives to catadromy

Daverat¹,

Morais²,

Dias³

et al. 2012

“…As with other systems (Bennett et al 1985, Chabrerie et al 2001) penetration by marine fish into Fitzroy delta pools was limited by connectivity, with a direct relationship between extent of connection and presence of marine spawners. However, unlike more connected systems, the important connectivity conduits (Ray 2005) between freshwater and ocean were only available intermittently, influencing both size structures of marine spawners in isolated pools, and the likelihood of extirpation through dry down, which in turn determines the realised value of pools as nursery and feeding grounds.…”

Section: Extent To Which Variations In Connectivity Affect Fish Assemmentioning

confidence: 99%

“…individual pools, stream reaches, swamps), and between wetlands and adjacent habitats, are among the most important functional components of estuarine wetlands (Ray 2005, Sheaves 2005). The integrity of estuarine wetlands is maintained by physical connections (Chabrerie et al 2001) that are crucial in determining the extent of water level fluctuations and the temporal duration of aquatic conditions (Ruetz et al 2005), and in allowing mobile species like fish to utilise a range of different habitats often vital for proper nursery ground function (Brockmeyer et al 1997, Sheaves 2005, to enter temporal refuges from predation (Bishop et al 1995, Baker & Sheaves 2005), and to access productive feeding grounds (Shreffler et al 1992).…”

Section: Introductionmentioning

confidence: 99%

Influence of marine and freshwater connectivity on the dynamics of subtropical estuarine wetland fish metapopulations

Sheaves¹,

Johnston²

2008

Estuarine wetlands have received little study in dry tropical and subtropical areas despite the fact that unpredictable rainfall makes their temporal continuity tenuous. In fact, many of these wetlands exist for much of the time as isolated pools that are remnants of extensive areas of shallow water that occur during infrequent flooding. Among the most important functional components of estuarine wetlands are the multifaceted connections between wetland units, and between wetlands and adjacent habitats, that maintain wetland integrity and allow fish to access them as nurseries. As the principal determinants of the likelihood of recolonisation, these connections are critical to metapopulation dynamics. To understand the ways in which the unique patterns of connectivity in these wetlands influence metapopulation dynamics and the compositions of fish fauna, we investigated patterns of physical and biological connectivity among estuarine wetland pools in the Fitzroy River delta of Australia's dry subtropics. Ten wetland pools ranging in salinity from fresh to hyperhaline, and differing in periodicity of connection from weeks, through months, to years were sampled regularly from February 2004 to May 2005, using cast nets. There were 4 distinct categories of pools; isolated freshwater pools, in-stream freshwater pools, regularly connected poikilohaline pools (pools where salinity varied over time from close to fresh to hyperhaline) and infrequently connected poikilohaline pools. The catch per unit effort and size structures of fish fauna of the different pool categories reflected connectivity, which determined the extent to which both marine-and freshwaterspawned species could re-colonise pools following local extinction. Overall, factors related to recolonisation were more important than those related to extinction in determining fish assemblage structures. Moreover, in contrast to many other metapopulation situations many extinction factors were heavily influenced by connectivity rather than being independent of it.

“…Exceptions include a study that developed predictive maps of fish species richness across the seascape by integrating fish survey data collected in multiple patch types with benthic maps (patch mosaics) and surface complexity from bathymetry (continuous gradients) (Pittman et al 2007). Very few studies have directly quantified seascape connectivity, although it is in creasingly acknowledged as an important process in coastal ecology and for the design of effective management strategies (Gillanders et al 2003, Mumby et al 2004, Ray 2005, Weinstein et al 2005, Meynecke et al 2008, Grober-Dunsmore et al 2009). …”

Section: Application Of Landscape Ecology In Studies Of Organism-seasmentioning

confidence: 99%

Seascape ecology of coastal biogenic habitats: advances, gaps, and challenges

Boström¹,

Pittman²,

Simenstad³

et al. 2011

380

301

We review the progress made in the emerging field of coastal seascape ecology, i.e. the application of landscape ecology concepts and techniques to the coastal marine environment. Since the early 1990s, the landscape ecology approach has been applied in several coastal subtidal and intertidal biogenic habitats across a range of spatial scales. Emerging evidence indicates that animals in these seascapes respond to the structure of patches and patch mosaics in different ways and at different spatial scales, yet we still know very little about the ecological significance of these relationships and the consequences of change in seascape patterning for ecosystem functioning and overall biodiversity. Ecological interactions that occur within patches and among different types of patches (or seascapes) are likely to be critically important in maintaining primary and secondary production, trophic transfer, biodiversity, coastal protection, and supporting a wealth of ecosystem goods and services. We review faunal responses to patch and seascape structure, including effects of fragmentation on 5 focal habitats: seagrass meadows, salt marshes, coral reefs, mangrove forests, and oyster reefs. Extrapolating and generalizing spatial relationships between ecological patterns and processes across scales remains a significant challenge, and we show that there are major gaps in our understanding of these relationships. Filling these gaps will be crucial for managing and responding to an inevitably changing coastal environment. We show that critical ecological thresholds exist in the structural patterning of biogenic ecosystems that, when exceeded, cause abrupt shifts in the distribution and abundance of organisms. A better understanding of faunal-seascape relationships, including the identifications of threshold effects, is urgently needed to support the development of more effective and holistic management actions in restoration, site prioritization, and forecasting the impacts of environmental change.