Greg Skilleter | The University of Queensland, Australia (original) (raw)

Papers by Greg Skilleter

Plankton Biology and Ecology

Page 1. Plankton Biol. Ecol. 49(1): 17-26, 2002 plankton biology &amp;amp; ecology O The ... more Page 1. Plankton Biol. Ecol. 49(1): 17-26, 2002 plankton biology &amp;amp; ecology O The Plankton Society of Japan 2002 Comparison of demersal zooplankton in regions with differing extractive-dredging history, in the subtropical Brisbane River estuary ...

Skilleter, G.A. 2002 07 30: Structure of macrobenthic communities in relation to historical patte... more Skilleter, G.A. 2002 07 30: Structure of macrobenthic communities in relation to historical patterns of dredging in the Brisbane River estuary. Proceedings of the Royal Society of Queensland 110: 75-83. Brisbane. ISSN 0080-469X.

Effective management of estuarine and coastal fisheries resources requires detailed information o... more Effective management of estuarine and coastal fisheries resources requires detailed information on the relationships between the habitats being protected and the fisheries dependent on them. Past research of nekton has focused on comparisons of abundance and species composition between single habitats (e.g. mangroves versus seagrass or vegetated versus unvegetated habitats). These studies have provided valuable insights into the role of coastal habitats for sustaining fisheries and biodiversity but have not considered the importance of adjacent habitats to the overall value of an area. For example, fish are only able to occupy mangrove forests for a restricted amount of any high tide period. The nature of the habitats lower down the shore may be crucial to the overall value of any patch of mangrove for supporting fisheries. We are taking a new approach to assessing the value of estuarine habitats for fisheries and biodiversity that considers the spatial arrangement of different habitats within an area -or the "mosaic" of habitats within the area. The scale of the area for study is defined by the life history and biology of the species of interest. In addition to estimating the abundance, biomass and community structure of nekton (e.g. fish, crustaceans, molluscs), the functioning of mosaics will be studied by estimating growth rates and describing the food webs in different mosaics and the characteristics of the mosaics will be measured. This approach has the potential to be extended to allow much better criteria to be developed for the selection of marine reserves by managers.

There is a widely held paradigm that mangroves are critical for sustaining production in coastal ... more There is a widely held paradigm that mangroves are critical for sustaining production in coastal fisheries through their role as important nursery areas for fisheries species. This paradigm frequently forms the basis for important management decisions on habitat conservation and restoration of mangroves and other coastal wetlands. This paper reviews the current status of the paradigm and synthesises the information on the processes underlying these potential links. In the past, the paradigm has been supported by studies identifying correlations between the areal and linear extent of mangroves and fisheries catch. This paper goes beyond the correlative approach to develop a new framework on which future evaluations can be based. First, the review identifies what type of marine animals are using mangroves and at what life stages. These species can be categorised as estuarine residents, marine-estuarine species and marine stragglers. The marineestuarine category includes many commercial species that use mangrove habitats as nurseries. The second stage is to determine why these species are using mangroves as nurseries. The three main proposals are that mangroves provide a refuge from predators, high levels of nutrients and shelter from physical disturbances. The recognition of the important attributes of mangrove nurseries then allows an evaluation of how changes in mangroves will affect the associated fauna. Surprisingly few studies have addressed this question. Consequently, it is difficult to predict how changes in any of these mangrove attributes would affect the faunal communities within them and, ultimately, influence the fisheries associated with them. From the information available, it seems likely that reductions in mangrove habitat complexity would reduce the biodiversity and abundance of the associated fauna, and these changes have the potential to cause cascading effects at higher trophic levels with possible consequences for fisheries. Finally, there is a discussion of the data that are currently available on mangrove distribution and fisheries catch, the limitations of these data and how best to use the data to understand mangrove-fisheries links and, ultimately, to optimise habitat and fisheries management. Examples are drawn from two relatively data-rich regions, Moreton Bay (Australia) and Western Peninsular Malaysia, to illustrate the data needs and research requirements for investigating the mangrove-fisheries paradigm. Having reliable and accurate data at appropriate spatial and temporal scales is crucial for mangrove-fisheries investigations. Recommendations are F.J. MANSON, N.R. LONERAGAN, G.A. SKILLETER & S.R. PHINN 484

Oceanography and Marine Biology - An Annual Review, 2005

There is a widely-held paradigm that mangroves are critical for sustaining production in coastal ... more There is a widely-held paradigm that mangroves are critical for sustaining production in coastal fisheries through their role as important nursery areas for fisheries species. This paradigm frequently forms the basis for important management decisions on habitat conservation and restoration of mangroves and other coastal wetlands. This paper reviews the current status of the paradigm and synthesises the information on the processes underlying these potential links. In the past, the paradigm has been supported by studies identifying correlations between the areal and linear extent of mangroves and fisheries catch. This paper goes beyond the correlative approach to develop a new framework on which future evaluations can be based. First, the review identifies what type of marine animals are using mangroves and at what life stages. These species can be categorised as estuarine residents, marine-estuarine species and marine stragglers. The marineestuarine category includes many commercial species that use mangrove habitats as nurseries. The second stage is to determine why these species are using mangroves as nurseries. The three main proposals are that mangroves provide a refuge from predators, high levels of nutrients and shelter from physical disturbances. The recognition of the important attributes of mangrove nurseries then allows an evaluation of how changes in mangroves will affect the associated fauna. Surprisingly few studies have addressed this question. Consequently, it is difficult to predict how changes in any of these mangrove attributes would affect the faunal communities within them, and, ultimately, influence the fisheries associated with them. From the information available, it seems likely that reductions in mangrove habitat complexity would reduce the biodiversity and abundance of the associated fauna, and these changes have the potential to cause cascading effects at higher trophic levels with possible consequences for fisheries. Finally, there is a discussion of the data that are currently available on mangrove distribution and fisheries catch, the limitations of these data and how best to use the data to understand mangrove-fisheries links and, ultimately, to optimise habitat and fisheries management. Examples are drawn from two relatively data-rich regions, Moreton Bay (Australia) and Western Peninsular Malaysia, to illustrate the data needs and research requirements for investigating the mangrove-fisheries paradigm. Having reliable and accurate data at appropriate spatial and temporal scales is crucial for mangrove-fisheries investigations. Recommendations are 486 made for improvements to data collection methods that would meet these important criteria. This review provides a framework on which to base future investigations of mangrove-fisheries links, based on an understanding of the underlying processes and the need for rigorous data collection. Without this information, the understanding of the relationship between mangroves and fisheries will remain limited. Future investigations of mangrove-fisheries links must take this into account in order to have a good ecological basis and to provide better information and understanding to both fisheries and conservation managers.

ICES Journal of Marine Science, 2015

ABSTRACT Reducing otter-board angle of attack (AOA) has been proposed as a way to limit the habit... more ABSTRACT Reducing otter-board angle of attack (AOA) has been proposed as a way to limit the habitat impacts of demersal trawls, but there are few quantitative assessments. This study tested the hypothesis that a novel otter-board design, termed the “batwing” (comprising a 0.1-m wide sled with an offset sail at 20° AOA) would have relatively fewer bottom impacts than a conventional flat-rectangular otter board (35° AOA, with a similar hydrodynamic spreading force). Pairs of each otter board were suspended beneath a purpose-built rig comprising a beam and posterior semi-pelagic collection net and repeatedly deployed across established trawl grounds in an Australian estuary. Compared with the conventional otter boards, the batwings displaced significantly fewer empty shells (Anadara trapezia and Spisula trigonella) by 89% and school prawns (Metapenaeus macleayi) by up to 78%. These rates were similar to the difference in base-plate bottom contact (87%). Further, the batwing damaged proportionally fewer damaged shells, attributed to their displacement away from the board's surface area. Other debris (lighter pieces of wood) and benthic fish (bridled gobies, Arenigobius bifrenatus) were not as greatly mobilised (i.e. reduced by 50 and 25%, respectively); possibly due to their position on or slightly off the bottom, and a similar influence of hydrodynamic displacement by the hydro-vane surface areas. Although the consequences of reducing otter-board bottom contact largely remain unknown, low AOA designs like the batwing may represent a practical option for fisheries where trawling is perceived to be hazardous to sensitive habitats.

2002 07 30: Harvesting of intertidal animals for bait for use in a recreational fishing competiti... more 2002 07 30: Harvesting of intertidal animals for bait for use in a recreational fishing competition. Proceedings of the Royal Society of Queensland 110: 93-101. Brisbane. ISSN 0080-469X.

Journal of the Marine Biological Association of the United Kingdom, 1996

Six mangrove forests in the urban region of Sydney, Australia, were examined to determine whether... more Six mangrove forests in the urban region of Sydney, Australia, were examined to determine whether there were relationships between levels of human-induced damage and the structure of molluscan assemblages, the first stage in the validation of a technique for rapid assessment of the impacts of anthropogenic disturbance in urban mangroves. All six mangrove forests showed some damage but the amount varied considerably among and within each forest. Significant correlations between the levels of damage and abundance of different taxa, and changes in the structure of the molluscan assemblage along gradients of damage, suggest that indices based on measures of damage have the potential to provide a means for the rapid, wide scale evaluation of mangroves affected by impacts associated with human activities in urban areas.

Physiological and Biochemical Zoology, 2003

The possibility of premigratory modulation in gastric digestive performance was investigated in a... more The possibility of premigratory modulation in gastric digestive performance was investigated in a long-distance migrant, the eastern curlew (Numenius madagascariensis), in eastern Australia. The rate of intake in the curlews was limited by the rate of digestion but not by food availability. It was hypothesized that before migration, eastern curlews would meet the increased energy demand by increasing energy consumption. It was predicted that (1) an increase in the rate of intake and the corresponding rate of gastric throughput would occur or (2) the gastric digestive efficiency would increase between the midnonbreeding and premigratory periods. Neither crude intake rate (the rate of intake calculated including inactive pauses; 0.22 g DM [grams dry mass] or 3.09 kJ min Ϫ1 ) nor the rate of gastric throughput (0.15 g DM or 2.85 kJ min Ϫ1 ) changed over time. Gastric digestive efficiency did not improve between the periods (91%) nor did the estimated overall energy assimilation efficiency (63% and 58%, respectively). It was concluded that the crustacean-dominated diet of the birds is processed at its highest rate and efficiency throughout a season. It appears that without a qualitative shift in diet, no increase in intake rate is possible. Accepting these findings at their face value poses the question of how and over what time period the eastern curlews store the nutrients necessary for the ensuing long, northward nonstop flight.

Oecologia, 1994

Macoma balthica (L.) is a common clam of the estuarine seafloor, belonging to an important group ... more Macoma balthica (L.) is a common clam of the estuarine seafloor, belonging to an important group of invertebrates possessing the capacity to choose between the two fundamental modes of feeding available, using its siphon to inhale either suspended food particles from the water or food particles deposited on the sediment surface. Field experiments demonstrate that intraspecific competition, effects of other

Marine Policy, 2010

Marine reserve networks are an essential and effective tool for conserving marine biodiversity. T... more Marine reserve networks are an essential and effective tool for conserving marine biodiversity. They also have an important role in the governance of oceans and the sustainable management of marine resources. The translation of marine reserve network theory into practice is a challenge for conservation practitioners. Barriers to implementing marine reserves include varying levels of political will and agency support and leadership, poorly coordinated marine conservation policy, inconsistencies with the use of legislation, polarised views and opposition from some stakeholders, and difficulties with defining and mapping conservation features. The future success of marine reserve network implementation will become increasingly dependent on: increasing political commitment and agency leadership; greater involvement and collaboration with stakeholders; and the provision of resources to define and map conservation features. Key elements of translating marine reserve theory into implementation of a network of marine reserves are discussed based on approaches used successfully in New Zealand and New South Wales (Australia).

Marine Ecology Progress Series, 2004

An understanding of how habitat structure influences physical environmental processes that are im... more An understanding of how habitat structure influences physical environmental processes that are important to organisms utilizing the habitat is a necessary basis for predicting biological responses to habitat variation. Seagrass meadows represent an important coastal nursery habitat that modifies the local flow environment. We used basic fluid-dynamic balances to construct a simple model of the effects of seagrass habitat structure on mean flow within and above the canopy, and tested quantitative predictions of the model against published flume observations and our own field measurements. In the field, flow reduction was detected in 10 of 13 cases inside the canopies of 5 seagrass beds varying in vegetation density (11 to 52 m 2 m -3 ) and upstream flow (5 to 14 cm s -1 ). The field data demonstrated greater flow reductions inside the canopy with increasing vegetation density. Flume data further confirmed a quantitative prediction of our model that the vertically integrated flow velocity inside the canopy would vary inversely with the square root of vegetation density. The model also predicted that the width of the 'seagrass-edge zone', in which flow decelerates, is a declining function of vegetation density, indicating that 'edge effects' (and by inference variation among patches of differing sizes) change predictably with seagrass bed structure. Empirical observations and simplified theory relating mean flow reduction to seagrass vegetation density can now be used to generate predictions of dependent biological responses such as variation in gamete fertilization, larval and spore settlement, and growth rates of organisms responsive to fluxes.

Marine Ecology Progress Series, 2003

This study (1) investigated functional (capture rate, foraging success) and numerical (density) r... more This study (1) investigated functional (capture rate, foraging success) and numerical (density) responses of bar-tailed godwits Limosa lapponica to an experimental decrease in densities of their prey, and (2) estimated seasonal depletion of the stock of their main prey, the mictyrid crab Mictyris longicarpus, in a subtropical estuary. It was predicted that if intake rates of the godwits are in the vicinity of the gradient section of a functional response curve, i.e. are directly determined by prey density, they will respond rapidly to experimental reduction in the density of their prey. Bartailed godwits did respond rapidly, both functionally and numerically, to a decrease in the density of M. longicarpus, indicating that their intake rate was limited by food availability. The estimated seasonal depletion of the stocks of Mictyris by the godwits was 88% of the initial standing stock. Despite the virtual disappearance of Mictyris from sediment samples through the course of a non-breeding season, local densities of godwits did not change between October and March, implying that adequate rates of intake could be maintained throughout their residence period.

Marine Ecology Progress Series, 2007

The effects of grazing by the dugong Dugong dugon on benthic invertebrate assemblages in seagrass... more The effects of grazing by the dugong Dugong dugon on benthic invertebrate assemblages in seagrass beds were examined in subtropical Moreton Bay, southeast Queensland, Australia. During feeding, dugongs leave distinct trails through seagrass beds where vegetation has been removed and sediments disturbed. The abundance of benthic fauna was examined along 3 recently created feeding trails and compared to 3 nearby patches of ungrazed seagrass within the same bed. A controlled, manipulative field experiment was then conducted, simulating the effects of dugong grazing, but distinguishing between the effect of removal of vegetation and the disturbance of the sediment during feeding. Dugong grazing was associated with declines in the abundance of benthic animals by up to 85% along trails, with the most noticeable impacts on amphipods and polychaete worms. Simulated dugong grazing caused a significant decline in the biomass of seagrass, through the removal of the vegetation but also from the physical disturbance during feeding. The combined and separate effects on the vegetation and from disturbance were associated with: (1) significant effects of grazing but not of physical disturbance for amphipods, capitellid and opheliid polychaetes;

Marine Ecology Progress Series, 2005

The abundance and community composition of the endofauna in 2 species of sponge, Haliclona sp. 1 ... more The abundance and community composition of the endofauna in 2 species of sponge, Haliclona sp. 1 and Haliclona sp. 2 (phylum Porifera: order Haplosclerida), were examined at different sites on the slope at Heron Island Reef, in the southern Great Barrier Reef, on 2 separate occasions. Both species of Haliclona occupy similar habitats on the reef slope and are often found living adjacent to each other, but the major groups of secondary metabolites and the gross external morphology in the 2 species of sponge are different. The 2 species of sponge supported significantly different endofaunal communities, with Haliclona sp. 2 supporting 3 to 4 times more individuals than Haliclona sp. 1. Fewer demersal zooplankton (copepods), nematodes and some peracarid crustaceans were found in Haliclona sp. 1 compared with Haliclona sp. 2. There were also differences in the numbers of spionid, nereidid and syllid polychaetes living in the 2 species of sponge. The only taxon that was more abundant in Haliclona sp. 1 than Haliclona sp. 2 was the spionid Polydorella prolifera, and this difference was only evident on 1 of the 2 occasions. The amount of free space (pores, channels, cavities) for a given weight of sponge was only 19% greater in Haliclona sp. 2 than in Haliclona sp. 1, suggesting other factors, such as the differences in the allelochemicals, may have a role in determining the numbers and types of animals living in these 2 species of sponge.

Marine Ecology Progress Series, 1994

Densities of adult infaunal clams Macorna balth~ca and Mya arenana in mesohaline sections of Paml... more Densities of adult infaunal clams Macorna balth~ca and Mya arenana in mesohaline sections of Pamlico Sound, North Carolina, USA, declined rapldly between April and June 1991 and 1992, except in places where there was abundant shell material on the sediment or large densities of the mactrid bivalve Rangia cuneata. Survivorship of M. balthica and M. arenarja was examined experimentally in 1 m2 plots containing different types of habitat: widgeon grass Ruppia maritima, live R. cuneata, 'artificial' R. cuneata, shell valves of R. cuneata and clean sediments to determine whether these structures provided a refuge from predation for the clams. M. balthjca and M. arenaria obtained a substantial refuge from predation by crabs when living in patches containing R. cuneata. Neither species obtained a refuge from predation when in beds of widgeon grass. There were 2 surprising results in these experiments. First, survivorship of the clams was significantly reduced in patches containing both seagrass and R. cuneata compared with patches of only R. cuneata. Second, survivorship was significantly less in patches of live R. cuneata than in patches of 'sham' (artificial) clams or equal numbers of shell valves. Two alternative, but not necessarily exclusive, explanations are offered for these results. (1) Subsurface rhizomes of widgeon grass may reduce the depth to which clams are able to burrow into the substratum leaving them more susceptible to predation by digging crabs.