Bradford M.,CSIRO |
Kroon F.J.,CSIRO |
Russell D.J.,Northern Fisheries Center
Marine and Freshwater Research | Year: 2011
Tilapia mariae (Cichlidae) is a tropical teleost, native to West African coastal drainages in the Gulf of Guinea and naturalised in the USA, Australia and possibly Russia. This paper reviews published information on the species from its native and introduced range to improve the effective management of fisheries as well as manage current infestations, reduce further spread and promote research on control measures outside its natural range. Within its natural range, the species is abundant and contributes to the local subsistence and artisanal fisheries; however, it is not extensively utilised for aquaculture. Outside its native range, it has proliferated, particularly in disturbed aquatic ecosystems. Tilapia mariae has several characteristics that make it successful in both its natural and introduced range. These include plasticity in reproductive behaviour (particularly parental care of the brood), a variety of feeding behaviours and dietary components, tolerance of a wide range of environmental conditions and aggressive behaviour to other fish species. Although tilapiine species are considered to be amongst the world's worst invasive alien species, surprisingly little information is available on potential impacts of T. mariae on native species and aquatic ecosystems outside its native range. © CSIRO 2011.
Peel D.,CSIRO |
Good N.M.,Northern Fisheries Center |
Canadian Journal of Fisheries and Aquatic Sciences | Year: 2011
Many fisheries worldwide have adopted vessel monitoring systems (VMS) for compliance purposes. An added benefit of these systems is that they collect a large amount of data on vessel locations at very fine spatial and temporal scales. This data can provide a wealth of information for stock assessment, research, and management. However, since most VMS implementations record vessel location at set time intervals with no regard to vessel activity, some methodology is required to determine which data records correspond to fishing activity. This paper describes a probabilistic approach, based on hidden Markov models (HMMs), to determine vessel activity. A HMM provides a natural framework for the problem and, by definition, models the intrinsic temporal correlation of the data. The paper describes the general approach that was developed and presents an example of this approach applied to the Queensland trawl fishery off the coast of eastern Australia. Finally, a simulation experiment is presented that compares the misallocation rates of the HMM approach with other approaches.
Unsworth R.K.,Northern Fisheries Center |
Cullen L.C.,James Cook University
Conservation Letters | Year: 2010
Seagrass meadows are declining globally at an unprecedented rate, yet these valuable ecosystem service providers remain marginalized within many conservation agendas. In the Indo-Pacific, this is principally because marine conservation priorities do not recognize the economic and ecological value of the goods and services that seagrasses provide. Dependency on coastal marine resources in the Indo-Pacific for daily protein needs is high relative to other regions and has been found in some places to be up to 100%. Habitat loss therefore may have negative consequences for food security in the region. Whether seagrass resources comprise an important contribution to this dependency remains largely untested. Here, we assemble information sources from throughout the Indo-Pacific region that discuss shallow water fisheries, and examine the role of seagrass meadows in supporting production, both directly, and indirectly through process of habitat connectivity (e.g., nursery function and foraging areas). We find information to support the premise that seagrass meadows are important for fisheries production. They are important fishery areas, and they support the productivity and biodiversity of coral reefs. We argue the value of a different paradigm to the current consensus on marine conservation priorities within the Indo-Pacific that places seagrass conservation as a priority. ©2010 Wiley Periodicals, Inc.
Collier C.J.,James Cook University |
Waycott M.,James Cook University |
Waycott M.,University of Adelaide |
McKenzie L.J.,Northern Fisheries Center
Ecological Indicators | Year: 2012
There is a world-wide trend for deteriorating water quality and light levels in the coastal zone, and this has been linked to declines in seagrass abundance. Localized management of seagrass meadow health requires that water quality guidelines for meeting seagrass growth requirements are available. Tropical seagrass meadows are diverse and can be highly dynamic and we have used this dynamism to identify light thresholds in multi-specific meadows dominated by Halodule uninervis in the northern Great Barrier Reef, Australia. Seagrass cover was measured at ∼3 month intervals from 2008 to 2011 at three sites: Magnetic Island (MI) Dunk Island (DI) and Green Island (GI). Photosynthetically active radiation was continuously measured within the seagrass canopy, and three light metrics were derived. Complete seagrass loss occurred at MI and DI and at these sites changes in seagrass cover were correlated with the three light metrics. Mean daily irradiance (I d) above 5 and 8.4 mol m -2 d -1 was associated with gains in seagrass at MI and DI, however a significant correlation (R = 0.649, p < 0.05) only occurred at MI. The second metric, percent of days below 3 mol m -2 d -1, correlated the most strongly (MI, R = -0.714, p < 0.01 and DI, R = -0.859, p = <0.001) with change in seagrass cover with 16-18% of days below 3 mol m -2 d -1 being associated with more than 50% seagrass loss. The third metric, the number of hours of light saturated irradiance (H sat) was calculated using literature-derived data on saturating irradiance (E k). H sat correlated well (R = 0.686, p < 0.01; and DI, R = 0.704, p < 0.05) with change in seagrass abundance, and was very consistent between the two sites as 4 H sat was associated with increases in seagrass abundance at both sites, and less than 4 H sat with more than 50% loss. At the third site (GI), small seasonal losses of seagrass quickly recovered during the growth season and the light metrics did not correlate (p > 0.05) with change in percent cover, except for I d which was always high, but correlated with change in seagrass cover. Although distinct light thresholds were observed, the departure from threshold values was also important. For example, light levels that are well below the thresholds resulted in more severe loss of seagrass than those just below the threshold. Environmental managers aiming to achieve optimal seagrass growth conditions can use these threshold light metrics as guidelines; however, other environmental conditions, including seasonally varying temperature and nutrient availability, will influence seagrass responses above and below these thresholds. © 2012 Elsevier Ltd. All rights reserved.
Unsworth R.K.F.,University of Swansea |
Collier C.J.,James Cook University |
Henderson G.M.,University of Oxford |
McKenzie L.J.,Northern Fisheries Center
Environmental Research Letters | Year: 2012
Highly productive tropical seagrasses often live adjacent to or among coral reefs and utilize large amounts of inorganic carbon. In this study, the effect of seagrass productivity on seawater carbonate chemistry and coral calcification was modelled on the basis of an analysis of published data. Published data (11 studies, 64 records) reveal that seagrass meadows in the Indo-Pacific have an 83% chance of being net autotrophic, resulting in an average net sink of 155gCm2yr1. The capacities for seagrass productivity were analysed using an empirical model to examine the effect on seawater carbonate chemistry. Our analyses indicate that increases in pH of up to 0.38 units, and Ωarag increases of 2.9 are possible in the presence of seagrass meadows (compared to their absence) with the precise values of these increases dependent on water residence time (tidal flushing) and water depth. In shallow water reef environments, Scleractinian coral calcification downstream of seagrass has the potential to be 18% greater than in an environment without seagrass. If this potential benefit to reef calcifiers is supported by further study it offers a potential tool in marine park management at a local scale. The applicability of this will depend upon local physical conditions as well as the spatial configuration of habitats, and the factors that influence their productivity. This novel study suggests that, in addition to their importance to fisheries, sediment stabilization and primary production, seagrass meadows may enhance coral reef resilience to future ocean acidification. © 2012 IOP Publishing Ltd.