Mick Haywood | CSIRO - Academia.edu (original) (raw)

Papers by Mick Haywood

Oceanography and Marine Biology

The Ningaloo coast of northwestern Australia (eastern Indian Ocean) hosts one of the world's long... more The Ningaloo coast of northwestern Australia (eastern Indian Ocean) hosts one of the world's longest and most extensive fringing coral reef systems, along with globally significant abundances of large marine fauna such as whale sharks. These characteristics-which have contributed to its inscription on the World Heritage list-exist because of the unique climatic, geomorphologic and oceanographic conditions. The region is hot and arid, so runoff of water from land is low, facilitating clear water that allows corals to grow close to the shore. The polewardflowing Leeuwin Current is an important influence, bringing warm water and generally suppressing coastal upwelling. During the austral summer, strong southerly winds generate the equatorwardflowing Ningaloo Current on the inner shelf-this current facilitates sporadic upwelling events that enhance concentrations of nutrients, which in turn enhance pelagic primary productivity that supports the reef's biota. The coast has experienced several marine heatwaves since 2011 that have caused mortality of corals and probably seagrass, albeit relatively less than elsewhere along the coast. Wind-generated surface waves break over the fringing reef crest, causing cooling currents that tend to dampen warming-although this mechanism seems not to have prevented some areas from experiencing damaging heat, and corals in places that do not receive the wave-generated currents have experienced substantial mortality. Herbivores, from fish to green turtles, are abundant, and in the lagoon, extensive stands of large brown algae provide an important habitat for newly recruited fish. There has been a decline in abundance of some fish. Predictions of future pressures include a weaker but more variable Leeuwin Current and increased human use. The ability of Ningaloo's 144 MATHEW A. VANDERKLIFT ET AL. ecosystems to withstand growing pressures will depend partly on the rate and magnitude of global warming but also on actions that manage local pressures from increasing human use. These actions will rely on continued science to provide the evidence needed to identify the pressures, the changes they create and the ways that we can mitigate them.

Frontiers in Marine Science, 2021

Knowledge of the movement patterns of the lemon shark Negaprion acutidens is poor in contrast to ... more Knowledge of the movement patterns of the lemon shark Negaprion acutidens is poor in contrast to the allopatric N. brevirostis. Using acoustic telemetry, we investigated daily (diel and tidal) and seasonal patterns in residency, fidelity, home range, habitat preference, and migratory patterns along the Ningaloo coast, Australia. Thirty eight adult N. acutidens were monitored for up 6.1 years (mean 2.5 y) with 19 animals detected for more than 3 years and 5 for more than 5 y. Approximately 50% of the tagged animals remained within 10 km of their tagging location for more than 12 months (average core home range of 1.7 km2). Surprisingly, residency of adults was greater than juveniles in this known nursery area. Adults showed a strong preference for lagoon habitats and moved into shallow nearshore habitats at high tide and at night. During winter months, female sharks shifted their core home range 0.45 km further offshore into deeper lagoon areas, a shift which is likely due to behavio...

Marine and Freshwater Research, 2021

Sea urchins can play a critical ecological role in the functioning of marine benthic ecosystems, ... more Sea urchins can play a critical ecological role in the functioning of marine benthic ecosystems, mediating competitive interactions between corals and algae. Yet, little is known about factors affecting urchin distribution in intact coral reef systems. This study aims to determine the spatial distribution of two sympatric urchin species, Echinometra mathaei and Echinostrephus molaris, and potential factors contributing to this, within the intact coral reef system of Ningaloo Marine Park, north-western Western Australia. Benthic photographs and surveys were conducted on SCUBA at 126 sites across the Park to determine urchin presence, rugosity, substrate cover, water velocity, and fish predation for each site. Generalised additive models found that E. mathaei presence was positively related to algal cover, rugosity and non-sanctuary zones, suggesting that distribution may be driven by foraging behaviour, habitat complexity and predation. Echinostrephus molaris presence was positively ...

Biological Conservation, 2019

While there are numerous studies that have used no-take marine reserves (NTMRs) to understand the... more While there are numerous studies that have used no-take marine reserves (NTMRs) to understand the effects of commercial fishing, much less is known about the influence of NTMRs in regions subject to recreational fishing. We used meta-analysis to synthesise data from 4,444 samples from 30 years (1987-2017) of fish 7 surveys, inside and outside a large network of NTMRs in the Ningaloo Marine Park, Western Australia, 8 where the major fishing activities are recreational. The data were collected by different agencies, using 9 varied survey designs and sampling methods. We contrasted the relative abundance and biomass of target 10 and non-target fish groups between fished and NTMR locations. We considered the influence of, and 11 possible interactions between, seven additional variables: age and size of NTMR, one of two reserve network configurations, reef habitat type, the level of recreational fishing activity, shore-based fishing regulations and survey method. Taxa responded differently: commonly targeted lethrinids had clear higher average abundance and biomass inside NTMRs, while the abundance/biomass of other targeted (and nontargeted groups) were indistinguishable inside to outside. Reef habitat was an important factor governing lethrinid response to protection, and we showed this variable can interact with reserve size, with larger NTMRs only demonstrably more effective than smaller ones in the back reef/lagoon habitats. There was little evidence of changes in relative abundance/biomass with reserve age, or before and after rezoning and expansion of the NTMR network. Our study demonstrates the complexity of fish responses to protection and fishing, and also highlights some of the key factors and interactions that likely underlie the varied results found to date in NTMR assessments, and that should thus be considered in future reserve design and 22 assessment. 23 24 Keywords 25 Marine protected area; MPA; fisheries; coral reef; Ningaloo; adaptive management; recreational fishing; Lethrinus 1. Introduction Anthropogenic activities continue to expand worldwide, particularly in the tropics, threatening natural systems and the ecosystem services they provide (Barlow et al. 2018). As a result, 'protected areas' that seek 32 to balance extractive activities with other socio-ecological values are increasingly being used to manage 33 terrestrial and marine systems (Jenkins & Joppa 2009; Sala et al. 2018). Many studies have assessed the conservation effects of no-take marine reserves (NTMR) (reviewed by Mosquera et al. 2000; Russ 2002), including quantitative syntheses of regional and global studies, with most finding higher abundance and size of targeted species within reserve boundaries (Lester et al. 2009). The large majority of these findings are from regions with commercial fisheries operating, and less is documented about the impacts of recreational fisheries, despite several studies flagging the potentially high impacts of these fisheries (McPhee et al. 2002; Coleman et al. 2004; Cowx & Cooke 2004; Lewin et al. 2006). NTMRs are a key tool for assessing the impacts of fishing (Ballantine 2014) and while there are a handful of empirical studies that have demonstrated the effects of fishing, using inside outside comparisons, on targeted invertebrates (Shears et al. 2006; Babcock et al. 2007) and finfish (Denny et al. 2004) a comprehensive assessment including NTMR with different characteristics over long time frames is lacking. The magnitude of differences inside to outside reserves has been correlated with their design, in particular size and age, with larger and older reserves typically resulting in greater abundance and/or size of targeted fishes than reserves that are smaller or newly established (Claudet et al. 2008; Edgar et al. 2014). The effects of NTMRs vary among biomes, locations and taxa of interest (Côté et al. 2005; Claudet et al. 2010; Mora & Sale 2011) and there are examples of NTMRs having negligible effects on targeted fish communities (McLaren et al. 2015). In addition to size and age of NTMRs, explanations for this variability include high levels of cross-boundary 50 movement by fishes (Pillans et al. 2014) and minimal to no difference in fishing activity across no-take and 51 2 fished areas due to accessibility and/or non-compliance by fishers (Bergseth et al. 2017), all of which make disentangling the true effects of fishing more complicated. Ideally assessments of the influence of NTMRs are based on replicated studies across multiple comparable reserves with long time series of biological data before and after reserve establishment (Underwood 1993; Russ 2002; Osenberg et al. 2011). Yet such data are typically beyond the scope of single research programs, necessitating the integration of multiple datasets. 'Adaptive management,' involving changes to the number, size or boundaries of reserves in response to new scientific information, changes in fishing pressure or changing social attitudes (McCook et al. 2010) further complicates long-term assessments. Ongoing improvement of ecological sampling methods and technologies has resulted in new survey methods being introduced to monitoring (Goetze et al. 2015): video based methods (baited remote underwater video (BRUV) and diver operated video (DOV)) are now commonly used alongside or in place of the previously more common underwater visual census (UVC) (Mallet & Pelletier 2014). Therefore, evaluations of NTMRs must have the capacity to incorporate and evolve with changes in reserve design and survey methods (Claudet & Guidetti 2010). Other factors, including differences in habitat and benthic structure, have been shown to affect outcomes of NTMR evaluation (Miller & Russ 2014; Rees et al. 2018b) and while these factors have been studied independently, few assessments consider multiple factors simultaneously, including possible interactions (Edgar et al. 2014). Differences in fishing pressure outside of 69 reserves will also directly impact inside to outside comparisons, yet data that quantify localised variation in 70 fishing activity at the scale of marine parks and typical NTMR networks are rarely available (Lewin et al. 71 2006). 72 73 Here, we synthesise a unique 30 year dataset from within a multiple-use marine park at Ningaloo Reef, 74 Western Australia. The type of fishing activity at Ningaloo Reef (almost exclusively recreational) in 75 combination with a highly regulated network of NTMRs that have undergone significant expansion during 76 the study period, offers the opportunity to advance on previous studies and inform on the potential impacts 77 of recreational fisheries. We integrate data from numerous agencies with varied survey designs and methods, 78 and therefore use a meta-analytical approach to compare the abundance and biomass of select targeted and 79 non-targeted tropical reef fish inside NTMRs with adjacent fished areas. We tested two hypotheses: (1) the 80 relative abundance/biomass of targeted fish taxa will be greater inside NTMRs than outside due to 81 recreational fishing activity; and (2) the observed relative abundance/biomass will vary with survey method, 82 age and size of NTMR, spatial variability in fishing activity (including shore-based fishing) and/or habitat. 83 Our study offers four main novelties. First, the effect of recreational fishing on targeted species is assessed in isolation from commercial fishing. Second, we explicitly consider potential interactions between variables. Third, the influence of changes in the NTMR network are considered in the context of the increasingly common adaptive management. Fourth, we consider the influence of shore-based fishing, which has rarely been investigated. We therefore provide advances on previous work that are of importance for future planning and assessment of protected areas. 2. Material and methods 2.1 Study region Data for this study are from the Ningaloo Marine Park (NMP) on the western Australian coastline (22°S, 113°E). The Park covers the majority of Ningaloo Reef (a World Heritage site) which is a fringing coral reef almost 300 km in length. The reef encompasses a sheltered lagoon that is highly accessible by shore-based fishers and those operating recreational vessels (Smallwood & Beckley 2012). Despite a relatively small permanent human population, this area is a popular tourism destination for recreational fishers (Sumner et al. 2002; Smallwood & Beckley 2012; Mitchell et al. 2018). There have not been any major commercial fishing activities within the marine park since the 1970s, (for summary see pg. 78, CALM (2005) and pg. 70, DPIRD (2017)). Recreational spearfishing has additional restrictions of varying degrees outside of the NTMRs, with spearfishing prohibited along a 70km stretch of coast between Tantabiddi Well and Winderabandi Point, and spear fishing for Labridae and Serranidae prohibited throughout the Park (DPIRD 2018) (Fig. 1).

Fishes, 2021

Bolbometopon muricatum (bumphead parrotfish, Valenciennes, 1839) is a conspicuous, iconic and eco... more Bolbometopon muricatum (bumphead parrotfish, Valenciennes, 1839) is a conspicuous, iconic and ecologically important coral reef fish species. B. muricatum plays an important role in the bioerosion of the reef framework and as a result has been described as both an ecosystem engineer and keystone species. Despite the complete absence of B. muricatum from 32 years of scientific surveys across the Ningaloo Reef World Heritage Area, we recorded a total of 155 individuals of B. muricatum across 63.2 ha of reef crest surveys, equating to mean density of 2.38 ind/ha. Our observations represent the first record of this iconic species in scientific surveys at Ningaloo and in combination with qualitative observations of B. muricatum by expert witnesses, indicate B. muricatum is likely to have been present in ecologically relevant densities since 2006. The densities of B. muricatum observed at northern Ningaloo in 2021 suggest this species is removing an estimated 13.42 tonnes/ha or 1.34 kg/m2...

Marine Ecology Progress Series, 1996

It is accepted that mangroves are important nursery areas for prawns and fish, including some of ... more It is accepted that mangroves are important nursery areas for prawns and fish, including some of major commercial importance, but little is known about how these mobilc animals use the mangrove forests. \Me recorded the dlstnbution of juvenile banana prd\-\,ns Penaeus nierguiensis and of f~s h in an intertidal mangrove forest adjacent to a small creek In northern Australia in November 1992 and In h4arch 1993. Four discrete areas of the forest were enclosed w~t h a 100 m long, 2 mm mesh stake net 2 at the creek mangrove 11-inge and 2 at further distances into the mangroves. The mean distance of each sanlpling s~t e inland from the creek mangrove frlnge ranged from 13 to 59 m and the area of the sites ranged from 480 to 640 m< Two mangrove communities, one dominated by the structurally complex Rhlzophora stylosd, the other b? the more open Ceriops tagal were sampled. A large size range of juvenile prawns and small flsh moved at least 43 m Into the mangroves at high tide, and the density of prawns near the creek mangrove fringe was inversely related to the maximum tide height. The highest density of juvenile P. merguiensis recorded in the mangroves in November was 18.3 prawns 100 m-' and in hlarch was 334.5 prawns 100 m-'. Mean fish density over all samples was 83.0 fish 100 ni-' and mean fish biomass was 3.9 g m 2 ; 55 species of f~s h were caught during the sampling. P. merguiensis showed no apparent preference for either of the 2 mangrove communities sampled; however, more fish (101 fish 100 m-2) and more fish species (26) were caught a t the creek mangrove fringe site than a t the other more inland sites; the lowest numbers of fish (27 fish m-2) and species (13) were caught at the inland site (Ceriops). On average, fish caught a t the fringe site were also longer and heavier than fish caught at the other sites. By moving well into the mangrove forest, prawns and small fish are probably less vulnerable to predat~on by larger fish.

Journal of Applied Ecology, Dec 17, 2015

1. Understanding biodiversity patterns depends on data collection, which in marine environments c... more 1. Understanding biodiversity patterns depends on data collection, which in marine environments can be prohibitively expensive. Transferable predictive models could therefore provide time-and cost-effective tools for understanding biodiversity-environment relationships. 2. We used fish species counts and spatial and environmental predictors to develop predictive models of fish species richness (S) for two major coral reefs located in separate ocean basins: Australia's Great Barrier Reef (GBR; Queensland) and Ningaloo Reef (NR; Western Australia). We tested the ability of the GBR model to predict S at NR (its transferability) under various scenarios using different sampling durations, years sampled and transect sizes. 3. Based on R 2 , the GBR model poorly predicted S at NR (R 2 < 16%) with few predicted values strongly correlated with observations. However, comparable spatial patterns in S across NR were predicted by both the NR and the GBR models when calibrated at similar spatio-temporal scales. 4. This result suggests that poor validation of the transferred models may indicate low deviance explained by the predictors in the new system (where other predictors not included might have a more direct effect on the response) and that in some situations, model transferability may be considerably improved by using data sets of similar spatio-temporal scales. Therefore, data filtering by time and space may be required prior to transferring models. 5. Policy implications. Transferable models can provide initial estimates of fish species richness patterns in poorly sampled systems, and thereby guide the design of better and more efficient sampling programs. Further improvements in model transferability will increase their predictive power and utility in conservation planning and management.

Journal of Experimental Marine Biology and Ecology, Sep 1, 2020

A variety of techniques for measuring coral growth, a fundamental biological trait, have been use... more A variety of techniques for measuring coral growth, a fundamental biological trait, have been used to improve our understanding of coral demographics. Remaining gaps and biases in this information, in combination with technological advances, led to the present study. We assessed the capacity of structure-from-motion (SfM) technology to build image mosaics (orthophotos) of~6 × 8 m reef plots from which individual coral colonies could be identified in repeated annual surveys and colony planar area measured. We monitored Acropora, Pocilloporidae (specifically from the genera Stylophora and Seriatopora) and Platygyra colonies over 2 years. We compared growth measurements, as change in radius, from SfM orthophotos to the more traditional method of tagging and photographing individual coral colonies. We conclude that planar coral growth can be measured from SfM orthophotos, with clear advantages over tagging including large sample sizes, and speed and ease of surveying, albeit with some bias in the SfM method (growth estimates were 15% greater (~0.5 cm/year) from standard photos than from the SfM orthophotos). We documented mortality and growth rates in a high wave energy environment on the reef slope at Ningaloo Reef, Western Australia, where there were no existing coral growth or mortality estimates. The mean change in radial extension of Acropora colonies with no mortality was 2.92 ± 0.06 (SE, n = 572) cm year −1 across the pooled data set of standard and orthophotos, substantially lower than previous estimates on similar species from the region. The growth rate of Pocilloporidae was 3.54 ± 0.52 (SE, n = 12) cm year −1 for colonies with no mortality. Robust planar growth estimates were not obtained for Platygyra due to its morphology, but we report high survivorship of the colonies: 94% with no mortality as compared with 79% for Acropora and only 53% for Pocilloporidae. High sample sizes from the novel SfM methodology allowed us to demonstrate that Acropora growth rate was inversely linked to wave energy and coral size.

Continental Shelf Research, Sep 1, 2008

A comprehensive survey of the benthic assemblages of the Torres Strait was conducted in order to ... more A comprehensive survey of the benthic assemblages of the Torres Strait was conducted in order to provide critical baseline information for regional marine planning, assessing the environmental sustainability of fisheries and understanding the ecosystems of the region. Over 150 sites throughout the region were sampled with a modified prawn trawl, towed underwater video, pipe dredge and epibenthic sled. This manuscript provides a broad overview of the activities undertaken and data collected. Two thousand three hundred and seventy-two different nominal species were sampled by the trawl and sled; only 728 by both gears. The towed video was not able to provide the same level of taxonomic resolution of epibenthic taxa but was particularly useful in areas where the seabed was too rough to be sampled. Data from the trawl, sled and video were combined to characterise the epibenthic assemblages of the region. Data from the towed video was also used to provide a characterisation of the inter-reefal benthic habitats which was then analysed in combination with physical covariate data to examine relationships between the two. Levels of mud and gravel in the sediments, trawling effort and seabed current stress were the covariates most significant correlated with the nature of the seabed habitats.

Coral Reefs, Nov 2, 2018

Outbreaks of coral predators are defined as increases (often rapid) in their abundance above thre... more Outbreaks of coral predators are defined as increases (often rapid) in their abundance above threshold densities that can be sustained by local coral assemblages, which in turn depends on the abundance and turnover of coral prey. To investigate the outbreak densities of the corallivorous gastropod Drupella cornus, we conducted both in situ feeding and coral growth experiments at Mandu reef within the Ningaloo Marine Park, Western Australia. Over two 10-day periods, we tagged and photographed feeding scars on colonies of the tabulate coral Acropora spicifera that harboured Drupella feeding aggregations. We calculated a mean in situ Drupella consumption rate of 1.16 ± 1.1 cm 2 coral area individual-1d-1. We also determined coral growth rates by tagging and photographing 24 colonies of Acropora spicifera at time zero and then again 1 year later. We calculated a mean linear extension rate of 7.9 ± 3.7 cm yr-1 for actively growing Acropora spicifera, which we then used to estimate A. spicifera growth rates over a range of coral cover values. This combination allowed us to determine the maximum number of Drupella that could be sustained across a range of coral cover. Our data suggest that the outbreak density of Drupella at the average level of coral cover for back reef sites at Mandu reef (17.6 ± 13.7%) is approximately 0.95 individuals m-2 reef area. At the maximum coral cover observed at Mandu reef (60%), the outbreak density of Drupella is estimated to be approximately 2.83 individuals m-2 reef area. Establishing Drupella outbreak densities assists managers in predicting possible outbreak abundances and in monitoring coral reef health.

Frontiers in Marine Science, Jul 24, 2019

Babcock et al. ECEs Affect 45% Australian Coastline abrupt ecological changes that are caused by ... more Babcock et al. ECEs Affect 45% Australian Coastline abrupt ecological changes that are caused by ECEs could have greater long-term impacts than slower warming that leads to gradual reorganization and possible evolution and adaptation. ECEs are an emerging threat to marine ecosystems, and will require better seasonal prediction and mitigation strategies.

PeerJ, Apr 17, 2018

Reliable abundance estimates for species are fundamental in ecology, fisheries, and conservation.... more Reliable abundance estimates for species are fundamental in ecology, fisheries, and conservation. Consequently, predictive models able to provide reliable estimates for un-or poorly-surveyed locations would prove a valuable tool for management. Based on commonly used environmental and physical predictors, we developed predictive models of total fish abundance and of abundance by fish family for ten representative taxonomic families for the Great Barrier Reef (GBR) using multiple temporal scenarios. We then tested if models developed for the GBR (reference system) could predict fish abundances at Ningaloo Reef (NR; target system), i.e., if these GBR models could be successfully transferred to NR. Models of abundance by fish family resulted in improved performance (e.g., 44.1% < R 2 < 50.6% for Acanthuridae) compared to total fish abundance (9% < R 2 < 18.6%). However, in contrast with previous transferability obtained for similar models for fish species richness from the GBR to NR, transferability for these fish abundance models was poor. When compared with observations of fish abundance collected in NR, our transferability results had low validation scores (R 2 < 6%, p > 0.05). High spatio-temporal variability of patterns in fish abundance at the family and population levels in both reef systems likely affected the transferability of these models. Inclusion of additional predictors with potential direct effects on abundance, such as local fishing effort or topographic complexity, may improve transferability of fish abundance models. However, observations of these local-scale predictors are often not available, and might thereby hinder studies on model transferability and its usefulness for conservation planning and management.

Scientific Reports, Oct 29, 2019

One of the most robust metrics for assessing the effectiveness of protected areas is the temporal... more One of the most robust metrics for assessing the effectiveness of protected areas is the temporal trend in the abundance of the species they are designed to protect. We surveyed coral-reef fish and living hard coral in and adjacent to a sanctuary zone (SZ: where all forms of fishing are prohibited) in the World Heritage-listed Ningaloo Marine Park during a 10-year period. There were generally more individuals and greater biomass of many fish taxa (especially emperors and parrotfish) in the SZ than the adjacent recreation zone (RZ: where recreational fishing is allowed)-so log response ratios of abundance were usually positive in each year. However, despite this, there was an overall decrease in both SZ and RZ in absolute abundance of some taxa by up to 22% per year, including taxa that are explicitly targeted (emperors) by fishers and taxa that are neither targeted nor frequently captured (most wrasses and butterflyfish). A concomitant decline in the abundance (measured as percentage cover) of living hard coral of 1-7% per year is a plausible explanation for the declining abundance of butterflyfish, but declines in emperors might be more plausibly due to fishing. Our study highlights that information on temporal trends in absolute abundance is needed to assess whether the goals of protected areas are being met: in our study, patterns in absolute abundance across ten years of surveys revealed trends that simple ratios of abundance did not.

Springer eBooks, 2009

... Page 4. 232 MDE Haywood and RA Kenyon ... More commonly, however, tropical decapods undergo a... more ... Page 4. 232 MDE Haywood and RA Kenyon ... More commonly, however, tropical decapods undergo a number of habitat shifts as they develop. Pittman and McAlpine (2003) characterized coastal fish and decapods as having a tri-phasic life cycle involving: ...

Marine and Freshwater Research, 2017

Large mobile herbivorous fish that specialise in browsing large brown algae are particularly impo... more Large mobile herbivorous fish that specialise in browsing large brown algae are particularly important on coral reefs because their activities mediate algal-coral competition. Despite this important ecological role, we have a poor understanding of the movement patterns of such large herbivorous fish, including Kyphosus bigibbus. Nineteen K. bigibbus captured near adjacent but distinct patch reefs were tagged with internal acoustic tags and their movements monitored for up to 20 months by an array of 60 acoustic receivers. Home-range estimates showed that movements of individuals from each patch reef encompassed different spatial extents and resulted in differences in habitat used by the two groups of fish. The average 50 and 95% kernel utilisation distribution for long-term resident fish was 0.27 AE 0.03 and 1.61 AE 0.30 km 2 respectively, ranges that represent the largest values for a herbivorous coral reef fish recorded to date. There was a significantly higher degree of fidelity among fish from the same school, and to particular patch reefs, despite the proximity of the reefs and substantial overlap between schools of conspecifics. A coefficient of sociality was used on pairs of fish and showed that there was no evidence that individuals were consistently detected together when they were detected by receivers away from their home reef. The variability of movement patterns among individuals of K. bigibbus results in an increased niche footprint for this important browser, potentially increasing reef resilience.

Marine Ecology Progress Series, 1998

We studied the fortnightly, seasonal and annual variation in abundance of postlarval and juvenile... more We studied the fortnightly, seasonal and annual variation in abundance of postlarval and juvenile Penaeus merguiensis in the Embley and Mission River estuaries (northeastern Australia) and of juveniles emigrating from the rivers between September 1986 and March 1992. The climate is tropical with distinct wet and dry seasons, and the pattern of salinity and temperature changes in the estuaries closely reflects this seasonal variation Postlarval and juvenile prawns were caught for up to 8 rno of the year, from before the wet season to just after the wet season (October to May). There was a weak bimodal distribution of catches during this period but the pattern of variation was quite variable from year to year. There were also subtle differences in the seasonal patterns of abundance between the Embley and Mission Rivers, probably due to different impacts of wet season rainfall on the 2 estuaries. In the nvers, environmental variation explained very little of the variation in catches of planktonic postlarvae, benthic postlarvae and juveniles, but increased emigration of juverdes from the rivers was significantly correlated with increased rainfall. The main factor determining the abundance of juvenile P. merguiensis in the estuaries was the supply and successful settlement of postlarvae from offshore areas. The highest densities of prawns caught within the estuaries were near the upper reaches of small creeks rather than in the main rivers. It is likely that these differences are due to differential settlement patterns of postlarvae between the creek and the main nver. Although the largest emigration of juvenile prawns from the estuaries occurred during the wet season, lower levels of migration of prawns from the creeks to the main rivers occurred throughout the year. Over the 6 yr of this project, the annual offshore commercial catch of adult P. merguiensis was significantly correlated with catches of prawns emigrating from the Embley River during the wet season.

Marine Biology, May 9, 2019

Successive, extensive bleaching events have reduced coral cover and altered species assemblages s... more Successive, extensive bleaching events have reduced coral cover and altered species assemblages significantly in the Montebello and Barrow Islands in northwestern Australia. In particular, acroporid and pocilloporid populations were dramatically reduced, while poritid and faviid corals were less impacted and now dominate coral assemblages. Subsequent to this perturbation, there have been changes in the abundance and distribution of the coral eating crown-of-thorns starfish, Acanthaster cf. solaris (to densities of up to 320 ha −1) that have had a further impact on coral communities selectively targeting the coral taxa most susceptible to bleaching, often referred to as climate change "losers". The feeding selectivity of A. cf. solaris under post-bleaching conditions was studied to determine its likely impact on coral communities and coral recovery. We found that even when Acropora and Pocillopora were extremely rare, A. cf. solaris demonstrated a high level of selectivity for these genera, although they consumed non-preferred taxa such as poritid, faviid, and merulinid corals in greater numbers. The consumption of non-preferred genera and families of corals differed between sites and was influenced by their local abundance. This study demonstrates that where crown-of-thorns starfish populations greatly exceed outbreak threshold densities of 10-15 ha −1 , they are likely to impact recovery of coral communities from bleaching events and exacerbate bleaching induced changes in assemblage structure.

Oceanography and Marine Biology, Dec 6, 2016

Tidal range is a master factor governing the differences in physico-chemical and biological chara... more Tidal range is a master factor governing the differences in physico-chemical and biological characteristics between microtidal ( 2 m) estuaries, which, for convenience, thus include mesotidal estuaries (2–4 m). Microtidal estuaries differ from macrotidal estuaries in geomorphology, tidal water movements, salinity regimes, residence times, turbidity, sedimentology and intertidal area. Consequently, their phytoplankton, microphytobenthos and macrophytes communities differ in biomass and production, areal extent, distribution patterns and composition. Mesozooplankton comprise predominantly autochthonous species in microtidal estuaries and allochthonous species in macrotidal estuaries. Meiobenthos in microtidal estuaries have greater densities in subtidal than intertidal areas and species persist along the estuary. Macrobenthos is dominated by small deposit-feeding species in microtidal estuaries, whereas macrotidal estuaries contain some larger species and suspension feeders. Species richness and abundance of estuarine-resident fish species and the contributions of diving piscivorous birds and wading invertebrate-feeding birds are greater in microtidal estuaries. As paradigms regarding estuarine ecology have been based mainly on northern hemisphere macrotidal systems, this review has redressed this imbalance by detailing the extent of differences between microtidal and macrotidal estuaries. In particular, it uses data and case studies for southern hemisphere microtidal systems to demonstrate that the physico-chemical characteristics and ecology of the main flora and fauna of microtidal estuaries are frequently not consistent with those paradigms.

Bulletin of Marine Science, Jul 1, 2018