Relationships between estuarine habitats and coastal fisheries in Queensland, Australia

Worldwide, estuaries have been recognized as critical habitats for nearshore fish productivity through their capacity as nursery grounds and nutrient sources. The purpose of this study was to demonstrate the importance of the habitat characteristics of estuaries to commercial fish catch in Queensland, Australia, with particular focus on the role of mangrove, saltmarsh, and seagrass habitats, and their connectivity. Traditionally, such analyses have taken the single-habitat approach, i.e., assessing the value of individual habitat types. Combined occurrence of these habitats and their collective accessibility may better explain the importance of estuaries to nekton. A literature review identifies the role of estuaries as integrated systems for fisheries. Our study provides strong supportive evidence for habitat-based, not species-based, management of fisheries in Queensland. Outcomes from preliminary analyses in Queensland suggest that collective spatial characteristics of estuarine habitats such as size and structural connectivity significantly correlate with fish catch data with r(2) values > 0.7 for 17 commercial species groups. The catch of one quarter of the investigated species was best explained by the presence of mud- and sandflats. An exploration of currently available data on habitat distribution and fisheries catch shows the need to scrutinise their spatial and temporal accuracy, and how best to use them to understand estuarine-fisheries links. We conclude that structural connectivity of estuarine habitats is fundamental to the size of fish stocks and to optimizing the sustainable yield for commercial and recreational fishers

Linking spatial metrics and fish catch reveals the importance of coastal wetland connectivity to inshore fisheries in Queensland, Australia

Many commercially important fish species use coastal marine environments such as mangroves, tidal flats and seagrass beds as nurseries or breeding grounds. The ecological importance of spatially connected habitats to conservation is well established for terrestrial environments. However, few studies have applied spatial metrics, including measures of structural connectivity to marine environments. We examined the relationship between catch-per-unit-effort for commercially caught species and the spatial patterning of mapped benthic habitat types along the coast of Queensland, Australia in their dominant fisheries (trawl, line, net or pot fisheries). We quantified the composition and spatial configuration of seascapes and calculated coastline length, number of estuaries, river length and geographical latitude using 12 metrics within ninety 30-nautical-mile grid cells, which supported inshore fish catch data from 21 species groups. Multiple regression analysis and non-metric multidimensional scaling plots indicated that ecological linkages may exist between geomorphic coastal features and nearshore fisheries production for a number of species groups. Connectivity indices for mangroves, salt marsh and channels explained the largest proportion (30–70%), suggesting the importance of connected tidal wetlands for fisheries. Barramundi (Lates calcarifer) catch-per-unit-effort was best explained by the number of wetland patches, mangrove connectivity and wetland connectivity (r2 = 0.38, n = 28). Catch-per-unit-effort for the Gulf of Carpentaria was highly correlated with wetland connectivity, the number of estuaries and seagrass patch density (r = 0.57, n = 29). The findings could guide the spatial design of marine protected area networks to maintain ecosystem services and avoid potential disruption to connectivity caused by habitat removal or modification. Application of the same approach to analyses of finer spatial scales would enable catch information to be related to particular estuarine habitats and provide better understanding of the importance of habitat connectivity for fisheries

Rainfall and its possible hysteresis effect on the proportional cover of tropical tidal-wetland mangroves and saltmarsh-saltpans

© 2019 CSIRO. Mangrove-saltmarsh tidal wetlands are highly dynamic ecosystems, responding and adapting to climate and physical conditions at all spatial and temporal scales. Knowledge of the large-scale ecosystem processes involved and how they might be influenced by climate variables is highly relevant today. For tidal-wetland sites well within the latitudinal range of the mostly tropical mangrove communities, we confirm that average annual rainfall influences vegetative cover, as well as species composition and biomass of tidal wetlands. On the basis of 205 largely unmodified, tropical and subtropical estuaries of northern Australia, a sigmoidal relationship, with a centroid inflection point ∼1368 mm, was derived between rainfall and the relative amounts of high-biomass mangroves and low-biomass saltmarsh-saltpan vegetation. The presence and probability of observed combinations of these community types were quantified using the wetland cover index, which is the ratio of total mangrove area to that of mangroves plus intertidal saltmarsh and saltpans. Accordingly, periodic changes in rainfall trends are likely manifest as either encroachment or dieback of mangroves along the ecotones separating them from tidal saltmarsh-saltpans. Presented is a new conceptual framework and model that describes how such ecosystem-scale processes take place in tropical and subtropical tidal wetlands

Effect of rainfall as a component of climate change on estuarine fish production in Queensland, Australia

The speculation that climate change may impact on sustainable fish production suggests a need to understand how these effects influence fish catch on a broad scale. With a gross annual value of A$ 2.2 billion, the fishing industry is a significant primary industry in Australia. Many commercially important fish species use estuarine habitats such as mangroves, tidal flats and seagrass beds as nurseries or breeding grounds and have lifecycles correlated to rainfall and temperature patterns. Correlation of catches of mullet (e.g. Mugil cephalus) and barramundi (Lates calcarifer) with rainfall suggests that fisheries may be sensitive to effects of climate change. This work reviews key commercial fish and crustacean species and their link to estuaries and climate parameters. A conceptual model demonstrates ecological and biophysical links of estuarine habitats that influences capture fisheries production. The difficulty involved in explaining the effect of climate change on fisheries arising from the lack of ecological knowledge may be overcome by relating climate parameters with long-term fish catch data. Catch per unit effort (CPUE), rainfall, the Southern Oscillation Index (SOI) and catch time series for specific combinations of climate seasons and regions have been explored and surplus production models applied to Queensland's commercial fish catch data with the program CLIMPROD. Results indicate that up to 30% of Queensland's total fish catch and up to 80% of the barramundi catch variation for specific regions can be explained by rainfall often with a lagged response to rainfall events. Our approach allows an evaluation of the economic consequences of climate parameters on estuarine fisheries. thus highlighting the need to develop forecast models and manage estuaries for future climate chan e impact by adjusting the quota for climate change sensitive species. Different modelling approaches are discussed with respect to their forecast ability. (c) 2006 Elsevier Ltd. All rights reserved

Mangroves: unusual forests at the seas edge

Mangroves form distinct sea-edge forested habitat of dense, undulating canopies in both wet and arid tropic regions of the world. These highly adapted, forest wetland ecosystems have many remarkable features, making them a constant source of wonder and inquiry. This chapter introduces mangrove forests, the factors that influence them, and some of their key benefits and functions. This knowledge is considered essential for those who propose to manage them sustainably. We describe key and currently recommended strategies in an accompanying article on mangrove forest management (Schmitt and Duke 2015)

A world without mangroves? [1]

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A world without mangroves?

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